I. Flashcards

Question

Ground substance of the cornea?

Answer 1

- consists of proteoglycans that run along and between the collagen fibrils. - Their glycosaminoglycan components (eg, keratan sulfate) are highly charged and account for the swelling property of the stroma.

Answer 2

In the stroma, they lie between the corneal lamellae

Answer 3

- they synthesize both collagen and proteoglycans.

Answer 4

- highly active cells rich in mitochondria, rough endoplasmic reticula, and Golgi apparatuses - have attachment structures, communicate by gap junctions, and have unusual fenestrations in their plasma membranes

Answer 5

- Their flat profile and even distribution in the coronal plane ensure a minimum disturbance of light transmission

Answer 6

Studies with vital dyes suggest that there may be at least 3 different types

Answer 7

- at birth 3-4 µm - in adulthood 10-12 µm Thickness increases with age

Answer 8

- anterior banded zone that develops in utero - and a posterior nonbanded zone that is laid down by the corneal endothelium throughout life ( These zones provide a historical record of the synthetic function of the endothelium. )

Answer 9

It is rich in type IV collagen | like other basal laminae

Answer 10

- Peripheral excrescences of the Descemet membrane | - they are common, especially among elderly people

Answer 11

corneal guttae appear with increasing age?!

Answer 12

a single layer of mostly hexagonal cells derived from the neural crest

Answer 13

neuroectodermal

Answer 14

- ~ 500,000 cells | - ~ 3000/mm2

Answer 15

by specular microscopy at the slit lamp

Answer 16

The apical surfaces of these cells face the anterior chamber; their basal surfaces abut the Descemet membrane

Answer 17

- Typically, young endothelial cells have large nuclei and abundant mitochondria. - The active transport of ions by these cells leads to the transfer of water from the corneal stroma and the maintenance of stromal deturgescence and transparency - Mitosis of the endothelium is rare in humans, and the overall number of endothelial cells decreases with age

Answer 18

- in a complex way and form a variety of adherent junctions, but desmosomes are never observed between normal cells - In cross section, pinocytotic vesicles and a terminal web (a meshwork of fine fibrils that increases the density of the cytoplasm) can be observed toward the apical surface of the cells. - Junctional complexes are present at the overlapping apicolateral boundaries of contiguous cells. - They form a significant but lesser barrier to ion and water flow than do the tight junctions of the epithelium.

Answer 19

It may cause endothelial decompensation, stromal edema, and vision failure In humans, endothelial mitosis is limited, and destruction of cells causes cell density to decrease and residual cells to spread and enlarge.

Answer 20

- surgical injury, - inflammation, - inherited disease (eg, Fuchs endothelial dystrophy

Answer 21

occlusion of the zonular fibers (sometimes referred to as zonules). These zonular fibers confer the properties of a semipermeable membrane to the epithelium

Answer 22

desmosomes

Answer 23

by gap juctions

Answer 24

posterior 4/5

Answer 25

superficial scleral collagen

Answer 26

- thinnest (0.3 mm) just behind the insertions of the rectus muscles - thickest (1.0 mm) at the posterior pole around the optic nerve head. - 0.4-0.5 mm thick at the equator - 0.6 mm thick anterior to the muscle insertion

Answer 27

- in a circumferential arc parallel to the corneal limbus opposite the site of impact - at the insertion of the rectus muscles - at the equator of the globe The most common site is the superonasal quadrant near the limbus

Answer 28

the sclera is essentially avascular except for the superficial vessels of the episclera and the intrascleral vascular plexus located just posterior to the limbus.

Answer 29

Numerous channels that penetrate the sclera, allowing for the passage of arteries, veins, and nerves. Extraocular extension of malignant melanoma of the choroid often occurs by way of the emissaria.

Answer 30

Branches of the ciliary nerves that supply the cornea sometimes leave the sclera to form loops posterior to the nasal and temporal limbus. They are sometimes pigmented and, consequently, have been mistaken for uveal tissue or malignant melanoma. They are typically found a constant distance from the corneoscleral junction, usually within 3-4 (?) mm of the limbus. ``` DD: Nevi Malignant Melanoma Cysts Scleral Foreign Bodies ```

Answer 31

A dense vascular connective tissue that merges deeply with the superficial sclera and superficially with the Tenon capsule and the conjunctiva.

Answer 32

- bundles of collagen - fibroblasts - a moderate amount of ground substance

Answer 33

- outer scleral collagen fibers 1600 Å | - inner collagen fibers 1000 Å

Answer 34

- electron-dense bodies - fibroblasts - melanocytes

Answer 35

- greater variation in fibril separation and diameter - the greater degree of fibril interweaving in the sclera In addition, the lack of vascular elements, such as the scleral emissaria, contributes to corneal clarity.

Answer 36

- vary in size and shape and taper at their ends, indicating that they are not continuous fibers as in the cornea - The inner layer of the sclera (lamina fusca) blends imperceptibly with the suprachoroidal and supraciliary lamellae of the uveal tract. The collagen fibers in this portion of the sclera branch and intermingle with the outer ciliary body and choroid.

Answer 37

l. conjunctiva and limbal palisades 2. Tenon capsule 3. episclera 4. corneoscleral stroma 5. aqueous outflow apparatus

Answer 38

termination of the Descemet membrane

Answer 39

2 equal zones: (1) an anterior bluish-gray zone overlying the clear cornea and extending from the Bowman layer to the Schwalbe line and (2) a posterior white zone overlying the trabecular meshwork and extending from the Schwalbe line to the scleral spur, or iris root.

Answer 40

- The transition from opaque sclera to clear cornea occurs gradually over 1.0-1.5 mm and is difficult to define histologically. - The corneoscleral junction begins centrally in a plane connecting the end of the Bowman layer and the Schwalbe line - Internally, its posterior limit is the anterior tip of the scleral spur - Pathologists consider the posterior limit of the limbus to be formed by another plane perpendicular to the surface of the eye, approximately 1.5 mm posterior to the termination of the Bowman layer in the horizontal meridian and 2.0 mm posterior in the vertical meridian, where there is greater scleral overlap

Answer 41

- located at the medial third of the superior margin of the orbit. - transmits blood vessels (supraorbital artery /ICA -> opthalmic artery -> supraorbital artery/ and vein) and the supraorbital nerve (CN V -> ophthalmic nerve -> frontal nerve -> supraorbital nerve)

Answer 42

- located at the frontoethmoidal suture | - transmits the anterior ethmoidal vessels and nerve.

Answer 43

- lies at the junction of the roof and the medial wall of the orbit - transmits the posterior ethmoidal vessels and nerve through the frontal bone

Answer 44

- lies in the lateral aspect of the zygomatic bone | - contains the zygomaticofacial and zygomaticotemporal branches of the zygomatic nerve and the zygomatic artery.

Answer 45

travels inferiorly from the lacrimal fossa into the inferior meatus of the nose.

Answer 46

- continues anteriorly from the infraorbital groove and exits 4 mm below the inferior orbital margin. - From here it transmits the infraorbital nerve, which is a branch of V 2 (the maxillary division of CN V), (and artery: maxillary artery -> infraorbital artery, but often arises in conjunction with the posterior superior alveolar artery.)

Answer 47

located between the greater and lesser wings of the sphenoid bone and lies lateral to and partly above and below the optic foramen. It is approximately 22 mm long and is spanned by the common tendinous ring of the rectus muscles (annulus of Zinn).

Answer 48

consists of superior and inferior orbital tendons and is the origin of the 4 rectus muscles - The upper tendon gives rise to the entire superior rectus muscle, as well as portions of the lateral and medial rectus muscles - The inferior tendon gives rise to the entire inferior rectus muscle and portions of the medial and lateral rectus muscles

Answer 49

``` 1. Above the ring (annulus of Zinn): • lacrimal nerve of CN V 1 • frontal nerve of CN V 1 • CN IV (trochlear nerve) • superior ophthalmic vein ``` 2. Within the ring or between the 2 heads of the rectus muscle are the following: • superior and inferior divisions of CN III (the oculomotor nerve) • nasociliary branch of CN V 1 • sympathetic roots of the ciliary ganglion • CN VI (the abducens nerve) The course of the inferior ophthalmic vein is variable, and it can travel within or below the ring as it exits the orbit. :) The nerves passing through the fissure can be remembered with the mnemonic, "Live Frankly To See Absolutely No Insult" - for Lacrimal, Frontal, Trochlear, Superior Division of Oculomotor, Abducens, Nasociliary and Inferior Division of Oculomotor nerve

Answer 50

lies just below the superior fissure between the lateral wall and the floor of the orbit, providing access to the pterygopalatine and inferotemporal fos- sae. Therefore, it is close to the foramen rotundum and the pterygoid canal.

Answer 51

transmits the infraorbital and zygomatic branches of CN V 2, an orbital nerve from the pterygopalatine ganglion, and the inferior ophthalmic vein. The inferior ophthalmic vein connects with the pterygoid plexus before draining into the cavernous sinus.

Answer 52

-between the greater and lesser wings of the sphenoid bone and lies lateral to and partly above and below the optic foramen

Answer 53

- lacrimal nerve of CN V - frontal nerve of CN V - CN IV (trochlear nerve) - superior ophthalmic vein

Answer 54

It lies just below the superior fissure between the lateral wall and the floor of the orbit, providing access to the pterygopalatine and inferotemporal fossae.

Answer 55

approximately 45°

Answer 56

middle cranial, temporal, and pterygopalatine fossa

Answer 57

approximately 1 em in front of the annulus of Zinn, on the lateral side of the ophthalmic artery between the optic nerve and the lateral rectus muscle

Answer 58

- long sensory root - short motor root - sympathetic root

Answer 59

arises from the nasociliary branch of CN V1. It is 10-12 mm long and contains sensory fibers from the cornea, the iris, and the ciliary body.

Answer 60

arises from the inferior division of CN III, which also supplies the inferior oblique muscle. The fibers of the motor root synapse in the ganglion, and the postganglionic fibers carry parasympathetic axons to supply the iris sphincter

Answer 61

comes from the plexus around the internal carotid artery. It enters the orbit through the superior orbital fissure within the tendinous ring, passes through the ciliary ganglion without sy.napse, and innervates ocular blood vessels and the dilator muscles of the pupil.

Answer 62

Only the parasympathetic fibers

Answer 63

- the nonsynapsing sympathetic fibers - the sensory fibers - the myelinated, fast -conducting postganglionic parasympathetic fibers

Answer 64

postganglionic from the superior cervical ganglion and pass through it without synapse

Answer 65

Sensory fibers from cell bodies in the trigeminal ganglion carry sensation from the eye, orbit, and face.

Answer 66

Two groups of short ciliary nerves, totaling 6-10

Answer 67

both sides of the optic nerve and, together with the long ciliary nerves, pierce the sclera around the optic nerve. They pass anteriorly between the choroid and the sclera into the ciliary muscle, where they form a plexus that supplies the cornea, the ciliary body, and the iris.

Answer 68

anteriorly on the globe. Starting at the medial rectus muscle and then proceeding to the inferior rectus, lateral rectus, and superior rectus muscles, the muscle insertions lie progressively farther from the limbus

Answer 69

An imaginary curve drawn through the insertions of the rectus muscles

Answer 70

after passing through the trochlea in the superior nasal orbital rim, inserts onto the sclera superiorly, under the insertion of the superior rectus

Answer 71

inserts onto the sclera in the posterior inferior temporal quadrant

Answer 72

Annulus of Zinn

Answer 73

medially, in horizontal meridian, 5.5 mm from limbus

Answer 74

inferior muscular branch of ophthalmic artery

Answer 75

40. 8 mm long tendon: 3.7 mm long 10. 3 mm wide

Answer 76

Annulus of Zinn at orbital apex

Answer 77

Inferiorly, in vertical meridian, 6.5 mm from limbus

Answer 78

Inferior muscular branch of ophthalmic artery and infraorbial artery

Answer 79

40 mm long tendon: 5.5 mm long 9. 8 mm wide

Answer 80

Annulus of Zinn spanning the superior orbital fissure

Answer 81

Laterally, in horizontal meridian, 6.9 mm from limbus

Answer 82

a single vessel derived from the lacrimal artery

Answer 83

40. 6 mm long tendon: 8 mm long 9. 2 mm wide

Answer 84

Annulus of Zinn at orbital apex

Answer 85

superiorly, in vertical meridian, 7.7 mm from limbus

Answer 86

superior muscular branch of ophthalmic artery

Answer 87

41. 8 mm long tendon: 5.8 mm long 10. 6 mm wide

Answer 88

the periosteum of the body of the sphenoid bone, above and medial to optic foramen, between annulus of Zinn and periorbita

Answer 89

to trochlea through pulley, at orbital rim, then hooking back under superior rectus, inserting posterior to center of rotation

Answer 90

Superior muscular branch of ophthalmic artery

Answer 91

40 mm long tendon: 20 mm long 10,8 mm wide

Answer 92

anteriorly, from a shallow depression in the orbital plate of the maxillary bone, at the anteromedial corner of the orbital floor, near the lacrimal fossa / near orbital rim (maxilla)/

Answer 93

posterior inferior temporal quadrant at level of macula, posterior to center of rotation

Answer 94

Inferior branch of ophthalmic artery and infraorbital artery

Answer 95

37 mm long no tendon 9.6 mm wide at insertion

Answer 96

lesser wing of the sphenoid bone, at the apex of the orbit, just superior to the annulus af Zinn

Answer 97

From its origin, the inferior oblique muscle then extends posteriorly, laterally, and superiorly to insert into the globe

Answer 98

- the upper division innervates the levator palpebrae superioris and superior rectus muscles - the lower division innervates the medial rectus, inferior rectus, and inferior oblique muscles.

Answer 99

very high 1:3-1 :5 (skeletal: 1:50-1:125).

Answer 100

mixture of slow, tonic-type and fast, twitch-type fibers

Answer 101

This high ratio enables precise control of ocular movements

Answer 102

- unique to extraocular muscles. - Smaller than twitch-type fibers, they contract slowly and smoothly and tend to be located more superficially in the muscle, nearer the orbital wall. - they are innervated by multiple grapelike nerve endings (en grappe) and are useful for smooth pursuit movements

Answer 103

- more similar to skeletal muscle fibers. - Larger than tonic-type fibers - located deeper in the muscle, - they contract rapidly - have platelike nerve endings (en plaque). - they aid in rapid saccadic movements of the eye.

Answer 104

27-30 mm long and 8-11 mm wide

Answer 105

15 mm by the m. levator pp sup alone and an additonal 2 mm if the frontalis muscle of the brow is used

Answer 106

1. skin 2. eyelid margin 3. subcutaneous connective tissue 4. orbicularis oculi muscle 5. orbital septum 6. levator palpebrae superioris muscle 7. Muller muscle 8. tarsus 9. conjunctiva

Answer 107

on the anterior aspect of the tarsus, approximately 3 mm superior to the eyelid margin.

Answer 108

orbicularis oculi muscle, the muscle of Riolan, and to the avascular plane of the eyelid

Answer 109

orbital preseptal pretarsal

Answer 110

by myomyous junctions

Answer 111

``` CN VII (and end plates are arranged in clusters over the entire length of the muscle) ```

Answer 112

it inserts in a complex way into the medial canthal tendon and into other portions of the orbital rim and the corrugator supercilii muscle

Answer 113

it acts as a sphincter and functions solely as a voluntary muscle.

Answer 114

it functions both voluntarily and involuntarily in spontaneous and reflex blinking.

Answer 115

along the superior palpebral furrow

Answer 116

it adheres firmly to the tarsus; a portion of it attaches to the anterior lacrimal crest and the posterior lacrimal crest (sometimes called the Horner muscle)

Answer 117

it plays a role in tear drainage

Answer 118

Orbicularis fibers extend to the eyelid margin, where there is the small bundle of striated muscle fibers called the muscle of Riolan

Answer 119

laxity of the lower eyelid, followed by spastic entropion

Answer 120

orbital lobe, palpebral lobe

Answer 121

the lateral horn of the levator palpebrae superioris muscle

Answer 122

secretion: exocrine content: aqueous

Answer 123

- plica, caruncle - Krause: eyelid - Wolfring: eyelid

Answer 124

secretion: exocrine | content aqueous

Answer 125

secretion: modified holocrine sebaceous glands content: oily

Answer 126

- follicles of cilia | - eyelid, caruncle

Answer 127

secretion: holocrine content: oily

Answer 128

secretion: eccrine content: sweat

Answer 129

conjunctiva, plica, caruncle

Answer 130

secretion: holocrine content: mucus

Answer 131

connective tissue

Answer 132

- encircles the orbit as an extension of the periosteum of the roof and the floor of the orbit. - It also attaches to the anterior surface of the aponeurosis of the levator palpebrae superioris muscle

Answer 133

it provides a barrier to anterior or posterior extravasation of blood or the spread of inflammation

Answer 134

lesser wing of the sphenoid bone

Answer 135

- superior transverse ligament | - it is formed by a condensation of tissue surrounding the superior rectus and levator muscles

Answer 136

Together, the levator muscle and tendon are 50-55 mm long. The muscle, which elevates the upper eyelid, is 40 mm long

Answer 137

superior division of CN III

Answer 138

- Near the Whitnall ligament, the levator muscle changes direction from horizontal to more vertical, and it divides anteriorly into the aponeurosis and posteriorly into the superior tarsal (Müller) muscle. - The aponeurosis inserts into the anterior surface of the tarsus and passes by the medial and lateral horns into the canthal tendons - The fibrous elements of the aponeurosis pass through the orbicularis oculi muscle and insert subcutaneously to produce the superior eyelid fold - The aponeurosis also inserts into the trochlea of the superior oblique muscle and into the fibrous tissue bridging the supraorbital notch - Aponeurotic attachments also exist with the conjunctiva of the upper fornix and the orbital septum

Answer 139

a smooth (nonstriated), sympathetically innervated muscle that originates from the undersurface of the levator palpebrae superioris muscle in the upper eyelid.

Answer 140

A similar smooth muscle (but musch weaker than the Müller muscle) arises from the capsulopalpebral head of the inferior rectus in the lower eyelid

Answer 141

the upper border of the upper tarsus and to the conjunctiva of the upper fornix

Answer 142

the lower border of the lower tarsus

Answer 143

connective tissue

Answer 144

- by the medial and lateral palpebral ligaments

Answer 145

the upper and lower tarsal plates are similar in length (29 mm) and in thickness (1 mm), the upper tarsus is almost 3 times as wide vertically ( 11 mm) as the lower tarsus ( 4 mm)

Answer 146

Infrared transilluination of the eyelid

Answer 147

A single row of 30-40 meibomian orifices is present in the upper eyelid, but there are only 20-30 orifices in the lower lid

Answer 148

As a piece of modified skin, it contains sebaceous glands and fine, colorless hairs. The surface is covered by nonkeratinized, stratified squamous epithelium.

Answer 149

- highly vascular - fold of conjunctiva - histologically resembles the bulbar conjunctiva - rich in goblet celles - contains fat and some nonstraited muscle - vestigial structure analogous to the nictitating membrane, or third eyelid, of dogs and other animals.

Answer 150

- > palpebral gland The ducts con- tinue downward, and about 12 of them empty into the conjunctival fornix approximately 5 mm above the superior margin of the upper tarsus.

Answer 151

Because the lacrimal excretory ducts pass through the palpebral portion of the gland, it is usually performed on the main part to avoid sacrificing the ducts.

Answer 152

- acinar cells, which line the lumen of the gland - myoepithelial cells, which surround the parenchyma and are covered by a base- ment membrane

Answer 153

lacrimal artery, a branch of the ophthalmic artery

Answer 154

- secretomotor cholinergic acts through inositol 1,4,5-triphosphate-activated protein kinase C), -vasoactive intestinal polypeptide (VIP)-ergic, - sympathetic nerve fibers (Cyclic adenosine monophosphate is the second messenger for VIP-ergic and B-adrenergic stimulation of the gland)(the gland also has alpha1 adrenergic receptors) - sensory innervation via the lacrimal nerve (CN V1)

Answer 155

Proximal lid borders and the fornices

Answer 156

identical to the main lacrimal gland

Answer 157

identical to the main lacrimal gland

Answer 158

- upper and lower puncta, - lacrimal canaliculi, - lacrimal sac, - nasolacrimal duct

Answer 159

The inferior punctum | is approximately 6.5 mm from the medial canthus; the superior punctum is 6.0 mm from it.

Answer 160

- lined with stratified squamous nonkera- tinized epithelium that merges with the epithelium of the eyelid margins. - Near the lacrimal sac, the epithelium changes into 2 layers: 1. a superficial columnar layer 2. a deep, flattened cell layer - goblet cells and occasionally cilia are present - in the canaliculi, the substancia propria consists of collagenous connective tissue and elastic fibers - The wall of the lacrimal sac resembles adenoid tissue and has a rich venous plexus and many elastic fibers.

Answer 161

palpebral, forniceal, bulbar

Answer 162

anterior ciliary arteries

Answer 163

- branches of the marginal arcades of the lids - The proximal arcade, running along the upper border of the lid, sends branches proximally to supply the forniceal conjunctiva and then the bulbar conjunctiva as the posterior conjunctival arteries

Answer 164

derives from the ciliary arteries through the anterior conjunctival arteries.

Answer 165

- nonkeratinizing squamous epithelium with numerous goblet cells - thin, richly vascularized substantia propria containing lymphatic vessels, plasma cells, macrophages, and mast cells - a lymphoid layer extends from the bulbar conjunctiva to the subtarsal folds of the lids. In places, specialized aggregations of conjunctiva-associated lymphoid tissue (CALT) correspond to mucosaassociated lymphoid tissue (MALT) elsewhere and comprise collections ofT and B lymphocytes underlying a modified epithelium. These regions are concerned with antigen processing.

Answer 166

2 to 5 cells

Answer 167

The basal cells are cuboidal and evolve into flattened polyhedral cells as they reach the surface

Answer 168

3 mm posterior to the limbus

Answer 169

- fascia bulbi - an envelope of elastic connective tissue that fuses posteriorly with the optic nerve sheath and anteriorly with the intermuscular septum - the cavity within which the globe moves

Answer 170

compactly arranged collagen fibers and a few fibroblasts.

Answer 171

equator of the globe

Answer 172

10mm posterior to their insertions (The connective tissues form sleeves around the penetrating extraocular muscles, creating pulleys suspended from the periorbita. These pulleys stabilize the position of the muscles relative to the orbit during eye movements. The pulleys are connected to one another and to the Tenon fascia by connective tissue bands containing collagen, elastin, and smooth muscle)

Answer 173

acquired strabismus

Answer 174

- fusion of the sheath of the inferior rectus muscle, the inferior tarsal muscle, and the check ligaments of the medial and lateral rectus muscles - provides support for the globe and the anteroinferior orbit

Answer 175

palpebral fissure changes (Note: the fusion of the sheath of the inferior rectus muscles, the Lockwood ligament, and the inferior tarsal muscle is an important consideration in surgery)

Answer 176

- Approximately 20 short posterior ciliary arteries and 10 short posterior ciliary nerves - in a ring around the optic nerve

Answer 177

Usually, 2 long ciliary arteries and nerves enter the sclera on either side of the optic nerve close to the horizontal meridian

Answer 178

opththalmic artery

Answer 179

- the whole uveal tract - the cilioretinal arteries - the sclera - the margin of the cornea - the adjacent conjunctiva.

Answer 180

- pl. giant cell arteritis | - may cause aion

Answer 181

ophthalmic artery | A single anterior ciliary vessel enters the lateral rectus muscle from the lacrimal artery.

Answer 182

usually supply (in pairs) the superior, medial, and inferior rectus muscles. A single anterior ciliary vessel enters the lateral rectus muscle from the lacrimal artery.

Answer 183

via anastomoses that perforate the sclera anterior to the rectus muscle insertions.

Answer 184

posterior ciliary vessel

Answer 185

within the apex of the ciliary muscle,

Answer 186

- branches frm it supply the major arterial circle * ciliary muscle * iris

Answer 187

choroid, ciliary body, and iris

Answer 188

Each eye contains 4-7 (or more) veins. One or more veins are usually located in each quadrant

Answer 189

14-25 mm from the limbus between the rectus muscles.

Answer 190

8-9 mm from the ora serrata and are visible by indirect ophthalmoscopy. A circle connecting these ampullae corresponds roughly to the equator and divides the central or posterior fundus from the peripheral portion.

Answer 191

- oblate spheroid shape - The anteroposterior diameter of the adult eye is approximately 23-25 mm. - The average transverse diameter of the adult eye is 24 mm. - The radius of curvature of the cornea (8 mm) is smaller than that of the sclera ( 12 mm),

Answer 192

~ 3 mm(,15)

Answer 193

6,5-7,5 mL

Answer 194

about 12 mm in the horizontal meridian and about 11 mm in the vertical

Answer 195

1 mm thick at its periphery and 0.5 mm thick centrally.

Answer 196

In addition to lubricating the surface of the cornea and conjunctiva, tears produce a smooth optical surface; allow for the diffusion of oxygen and other nutrients; and contain immunoglobulins, lysozyme, and lactoferrin.

Answer 197

- nearly spherical | - ~ 4 mm

Answer 198

The cornea becomes flatter in the periphery, but the rate of flatten- ing is not symmetric. Flattening is more extensive nasally and superiorly than temporally and inferiorly. This topography is important in contact lens fitting.

Answer 199

surface ectoderm

Answer 200

nonkeratinized, stratified squamous epithelium whose basal columnar layer is attached to a basal lamina by hemidesmosomes (The occasional recurrence of corneal erosion following a traumatic corneal abrasion may be due to improper formation ofhemidesmo- somes after an epithelial abrasion)

Answer 201

by desmosomes

Answer 202

randomly dispersed collagen fibrils. | It is a modified region of the anterior stroma

Answer 203

NO. It is replaced by scar tissue

Answer 204

- Schwalbe line - Schlemm canal and trabecular meshwork - scleral spur - anterior border of the ciliary body (where its longitudinal fibers insert into the scleral spur) - iris

Answer 205

~ 3 mm at its center and reaches its narrowest point sightlycentral to the angle recess

Answer 206

Ciliary epitheium in the posterior chamber

Answer 207

Up to 50% in young people

Answer 208

- Schlemm canal externally | - trabecular meshwork internally

Answer 209

The Schwalbe line forms the anterior margin of the sulcus; the scleral spur is its posterior landmark

Answer 210

- receives the insertion of the longitudinal ciliary muscle, and contraction opens up the trabecular spaces - Contractile cells are found within the scleral spur - as are structures resembling mechanoreceptors, which receive a sensory innervation.

Answer 211

Myofibroblast-like scleral spur cells with contractile properties are disposed circumferentially within the scleral spur. They are connected by elastic tissue to the trabecular meshwork - in experiments, stimulation with vasoactive intestinal polypeptide (VIP) or calcitonin gene-related peptide (CGRP) causes an increase in outflow facility

Answer 212

unmyelinated axons, the terminals of which contact the cell membranes of the spur cells without an intervening basal lamina

Answer 213

- neuropeptide Y, substance P, CGRP, VIP, and nitrous oxide - mediated by sympathetic, sensory, and pterygopalatine nerve pathways - there are no cholinergic fibers in this region

Answer 214

Myelinated nerve fibers extending forward from the ciliary region to the inner aspect of the scleral spur yield branches to the meshwork and to dub-shaped endings in the scleral spur. These endings have the morphologic features of mechanoreceptors found elsewhere in the body, such as in the carotid artery. The endings are incompletely covered by a Schwann cell sheath and make contact with extracellular matrix materials such as elastin.

Answer 215

Various functions have been proposed for these endings, including ( 1) proprioception to the ciliary muscle, which inserts into the scleral spur, signaling contraction of the scleral spur cells, and (2) baroreception in response to changes in intraocular pressure.

Answer 216

circular spongework of connective tissue lined by trabeculocytes.

Answer 217

- contractile properties, which may influence outflow resistance. - phagocytic properties

Answer 218

The meshwork is roughly triangular in cross section; the apex is at the Schwalbe line, and the base is formed by the scleral spur and the ciliary body. Some trabecular tissue passes posterior to the spur

Answer 219

1. uveal portion 2. corneoscleral meshwork 3. juxtacanalicular tissue, which is directly adjacent to the Schlemm canal The uveal portion and the corneoscleral meshwork can be divided by an imaginary line drawn from the Schwalbe line to the scleral spur. The uveal meshwork lies internal and the corneoscleral meshwork external to this line.

Answer 220

- composed of cordlike trabeculae - has fewer elastic fibers than does the corneoscleral meshwork. - The trabeculocytes usually contain pigment granules, - the trabecular apertures are less circular and larger than those of the corneoscleral meshwork.

Answer 221

- consists of a series of thin, flat, perforated connective tissue sheets arranged in a laminar pattern. - Each trabecular beam is covered by a monolayer of thin trabecular cells exhibiting multiple pinocytotic vesicles. - The basal lamina of these cells forms the outer cortex of the trabecular beam; the inner core is composed of collagen and elastic fibers

Answer 222

- increased piigmentation - decreased number of trabecular cells - thickening of the basement membrane beneath trabecular cells These changes can cause resistance to aqueous outflow or possibly glaucoma

Answer 223

Pericanalicular connective tissue invests the entire extent of the Schlemm canal

Answer 224

- lies on the trabecular aspect af the pericanalicular connective tissue, between the outermost layers of the corneoscleral meshwork and the endothelial lining of the Schlemm canal - multilayered collection of cells forming a loose network - Between these cells are spaces up to 10 um wide through which aqueous humor can percolate to reach the endothelial lining of the Schlemm canal

Answer 225

Pericanalicular connective tissue / endothelial meshwork This region of the drainage system contributes the most to outflow resistance, partly because the pathway is narrow and tortuous and partly because of the resistance offered by extracellular proteoglycans and glycoproteins

Answer 226

- circular tube that closely resembles a lymphatic vessel - formed by a continuous monolayer of nonfenestrared endothelium and a thin connective tissue wall - the basement membrane of the endothelium is poorly defined

Answer 227

tight junctions

Answer 228

- micropinocytic vesicles are present at hte apical and basal surfaces of the cells - larger vesicles (giant vacuoles) have been observed along the internal canal wall. These vacuoles are lined by a single membrane, and their size and number are increased by a rise in the intraocular pressure. They are thought to contribute to the pressure-dependent outflow of aqueous humor

Answer 229

- highly irregular (cells show luminal bulges corresponding to cell nuclei and macrovascular configirations. The latter represent cellular invaginations from the basal aspect that eventually open on the apical aspect of the cell to form transcellular channels, through which aqueous humor flows down a pressure gradient. ) - the endothelial lining of a diverticulum is continuous with that if the canal. Such blind, tortuous diverticula course for a variable distance into the trabecular meshwork but remain separated from the open spaces of the meshwork by their continuous endothelial lining

Answer 230

interrupted, irregular basement membrane and a zone of pericanalicular connective tissue of variable thickness. The cellular element predominates in this zone, and the fibrous elements, especially elastic fibers, are irregularly arranged in a netlike fashion. Here, the open spaces are narrower than those of the trabecular meshwork.

Answer 231

- The corneoscleral trabecular sheets show frequent branching, and the endothelial covering may be shared between adjacent sheets - The corneascleral wall of the Schlemm canal is more compact than the trabecular wall; a lamellar arrangement of collagen and elastic tissue predominates

Answer 232

Approximately 25-30

Answer 233

into the deep and midscleral venous plexuses

Answer 234

up to 8 | visible in the conjunctiva by biomicroscopy

Answer 235

- twofold to threefold thickening of trabecular sheets (the cortex thickens and the core thins) - Endothelial cellularity is lost - connective tissue (eg, in the endothelial meshwork) increases - debris accumulates in the meshwork - glycosaminoglycans accumulate in the extracellular space. - Such changes are exaggerated in chronic open-angle glaucoma.

Answer 236

small, tortuous, blind diverticula that extend from the canal to tha trabecular meshwork

Answer 237

- iris - ciliary body - choroid

Answer 238

- scleral spur - exit points of the vortex veins - optic nerve These attachments account for the characteristic anterior balloons formed in choroidal detachment

Answer 239

- tthey are located on the iris on either side of the collaterette in the pupillary and ciliary portions and peripherally near the iris root

Answer 240

major arterial circle in the ciliary body -> Radial branches of the arteries and veins extend toward the pupillary region. The arteries form the incomplete minor arterial circle, from which branches extend toward the pupil, creating capillary arcades In humans, the anterior border layer is normally avascular

Answer 241

- pigmented cells (melanocytes) - nonpigmented cells - collagen fibrils - matrix containing hyaluronic acid - Myelinated and nonmyelinated nerve fibers serve sensory, vasomotor, and muscular functions throughout the stroma.

Answer 242

The aqueous humor flows freely through the loose stroma along the anterior border of the iris, which contains multiple crypts and crevices that vary in size, shape, and depth. This surface is covered by an interrupted layer of connective tissue cells that merges with the ciliary body

Answer 243

The overall structure of the iris stroma is similar in irides of all colors. Differences in color are related to the amount of pigmentation in the anterior border layer and the deep stroma. The stroma of blue irides is lightly pigmented, and brown irides have a densely pigmented stroma that absorbs light

Answer 244

studies how the chemical substances cycle through the biological system

Answer 245

examines the biological and chemical effects of the chemical on the biological system

Answer 246

the study of how to achieve desirable effects or avoid or minimize adverse effects or toxicity of the drug

Answer 247

pharmacokinetics and pharmacodynamics

Answer 248

pharmacikinetics and dose together

Answer 249

concentration of the active drug at the therapeutic site

Answer 250

using the receptor for that drug; for example, a drug may be categorized as an a-adrenergic agonist or b-adrenergic antagonist.

Answer 251

3-4 years of life

Answer 252

6-12 months of life

Answer 253

- type I IgE mediated hypersenstivity reaction | - delayed reaction to either the medication or preservatives

Answer 254

- quaternary cationic surfactants (pl. belzalkonium chloride or benzododecinium bromide) - mercurials (pl. thiomersal, chlorobutanol, parahydroxybenzoates) - aromatic alcohols

Answer 255

- can be toxic to the ocular surface following topical administration - can enhance corneal permeability of various drugs

Answer 256

1. preservative dissipates upon exposure to light or to the ions in the tear film (pl. stablized oxychloro complex - breaks down to sodium chloride and water, and sodium perborate - breaks down to hydrogen peroide before becoming hydrogen and oxygen) - These "disappearing preservatives" theoretically should have no toxicity to the corneal surface 2. ionic buffer containing borate, sorbitol, propylene glycol, and zinc that breaks down into innate elements upon encountering the cations in the tear film of the eye 3. polyquaternium -1 is a cationic polymer of quaternary ammonium structures that lacks a hydrophobic region. Although it is a detergent, human corneal epithelial cells tend to repel the compound

Answer 257

blood vessels

Answer 258

The collaterette - in this region, anastomoses occur between the arterial and venous arcades to form the minor vascular circle of the iris, which is often incomplete

Answer 259

- apex of the ciliary body, not the iris

Answer 260

Their endothelium is nonfenestrated and is surrounded by a basement membrane, associated pericytes, and a zone of collagenous filaments. The intima has no internal elastic lamina

Answer 261

the nonpigmented epithelium of the ciliary body and thence with the neurosensory portion of the retina

Answer 262

The basal surface of the pigmented layer borders the posterior chamber. The apical surface faces the stroma and adheres to the anterior pigmented layer, which gives rise to the dilator muscle

Answer 263

neural ectoderm (not neural crest)

Answer 264

pigmented layer extends farther onto the anterior surface of the iris, a condition called ectropion. The term ectropion uveae, which refers to an outfolding over the pupil of the iris pigment epithelium (IPE), is a misnomer because the IPE derived from neural ectoderm (not neural crest) and therefore is not considered part of the uvea.

Answer 265

outer layer of the optic cup, which is neuroectoderm

Answer 266

Parallel and anterior to the posterior pigmented epithelium

Answer 267

- the smooth muscle cells cntain fine myofilaments and melanosomes - the myofibrils are confined mainly to the basal portion of the cellsand extend anteriorly to the iris stroma - the melanosomes and the nucleus are in the apical region of each myoepithelial cell

Answer 268

- dual sympathetic and parasympathetic innervation - the dilator muscle contracts in response to sympathetic L1-adrenergig stimulation - cholinergic parasympathetic stimulation may have an inhibitory role

Answer 269

- The first-order neuron of the sympathetic chain begins in the ipsilateral posterolateral hypothalamus and passes through the brainstem to synapse in the intermediolateral gray matter of the spinal cord, chiefly at thoracic level 1. - The second- order preganglionic neuron exits the spinal cord, passes over the pulmonary apex and through the stellate ganglion without synapsing, and synapses in the superior cervical ganglion - The third-order postganglionic neuron originates here, joins the internal carotid plexus, enters the cavernous sinus, and travels with the ophthalmic division of cranial nerve (CN) V to the orbit and then to the dilator muscle.

Answer 270

Horner syndrome, with miosis, in addition to ptosis and anhydrosis.

Answer 271

neuroectoderm

Answer 272

a circular band of smooth uscle fibers

Answer 273

near the pupillary marginin the deep stroma, anterior to the pigment epithelium of hte iris

Answer 274

Although dual innervation has been demonstrated morphologically, the sphincter muscle receives its primary innervation from parasympathetic nerve fibers that originate in the CN III nucleus, and it responds pharmacologically to muscarinic stimulation. The reciprocal sympathetic innervation to the sphincter appears to serve an inhibitory role, helping relax the sphincter in darkness.

Answer 275

The fibers subserving the sphincter muscle leave the Edinger-Westphal subnucleus and follow the inferior division of CN III after it bifurcates in the cavernous sinus. The fibers continue in the branch supplying the inferior oblique muscle, exit, and synapse with postganglionic fibers in the ciliary ganglion. The postganglionic fibers travel with the short ciliary nerves to the iris sphincter. They are unusual in that they are myelinated, presumably reflecting a need for fast conduction.

Answer 276

triangular

Answer 277

towards the ora serrata

Answer 278

- only at its base, via its longitudinal muscle fibers, where they insert into the scleral spur

Answer 279

base of the ciliary body

Answer 280

- aqueous humor formation - lens accomodation It also plays a role in the trabecular and uveoscleral outflow of aqueous humor.

Answer 281

- pars plana | - pars plicata

Answer 282

When a 50-IlL drop is delivered from the usual commercial dispenser, the volume of the tear lake rises from 7 uL to only 10 uL in the blinking eye of an upright patient. Thus, at most, 20% of the administered drug is retained (10 uL/50 uL) - A rapid turnover of fluid also occurs in the tear lake-16% per minute in the undisturbed eye-with even faster turnover if the drop elicits reflex tearing. Consequently, for slowly absorbed drugs, at most only 50% of the drug that was initially retained in the tear reservoir (50% of the 20% of the delivered medication, or 10%) remains 4 minutes after instillation (0.844 = 0.50), and only 17% remains after 10 minutes, or 3.4% of the original dose.

Answer 283

The amount of time that a drug remains in the tear reservoir and tear film

Answer 284

- durg formation - timing of subsequent medication - tear production - and drainage

Answer 285

relatively avascular, smooth, pigmented zone; it is 4 mm wide and extends from the ora serrata to the ciliary processes

Answer 286

through the pars plana, located 3-4 mm from the corneal limbus

Answer 287

The pars plicata is richly vascularized and consists of approximately 70 radial folds, or ciliary processes. The zonular fibers of the lens attach primarily in the valleys of the ciliary processes but also along the pars plana

Answer 288

The capillary plexus of each ciliary process is supplied by arterioles as they pass anteriorly and posteriorly from the major arterial circle; each plexus is drained by 1 or 2 large venules located at the crest of each process

Answer 289

- capillary hydrostatic pressure gradient - whether blood flows into the capillary plexus or directly to the draining choroidal vein, bypassing the plexus completely

Answer 290

Neuronal innervation of the vascular smooth muscle and humoral vasoactive substances may be important in determining regional blood flow, capillary surface area available for exchange of fluid, and hydrostatic capillary pressure.

Answer 291

- The inner, nonpigmented epithelium is located between the aqueous humor of the posterior chamber and the outer, pigmented epithelium

Answer 292

by a complex system of junctions and cellular interdigitations

Answer 293

Along the lateral intercellular spaces, near the apical border of the nonpigmented epithelium, are tight junctions (zonulae occludentes) that maintain the blood-aqueous barrier.

Answer 294

- The basal surface of the nonpigmented epithelium, which borders the posterior chamber, is covered by the basal lamina, which is multilaminar in the valleys of the processes. - The basal lamina of the pigmented epithelium, which faces the iris stroma, is thick and more homogeneous than that of the nonpigmented epithelium.

Answer 295

cuboidal. They are characterized by multiple basal infoldings (The pigmented epithelium is relatively uniform throughout the ciliary body)

Answer 296

- large nucleus - mitochondria - extensive endoplasmatic reticulum - many melanosomes

Answer 297

- cuboidal in the pars plana but columnar in the pars plicata. - multiple basal infoldings - abundant mitochondria - large nuclei - The endoplasmic reticulum and Golgi complexes in these cells are important for aqueous humor formation. - Sometimes melanosomes are present, especially anteriorly, near the iris.

Answer 298

- comparatively large fenesrated capillaries - collagen fibrils - fibroblasts

Answer 299

comes from the anterior and long posterior ciliary arteries, which join together to form a multilayered arterial plexus consisting of a superficial episcleral plexus; a deeper intramuscular plexus; and an incomplete major arterial circle often mistakenly attributed to the iris but actually located posterior to the anterior chamber angle recess, in the ciliary body

Answer 300

- The major veins drain posteriorly through the vortex system - although some drainage also occurs through the intrascleral venous plexus and the episcleral veins into the limbal region

Answer 301

- the amount of connective tissue between the muscle bundles increases - there is a loss of elastic recoil after contraction.

Answer 302

- the amount of connective tissue between the muscle bundles increases, and there is a loss of elastic recoil after contraction. - The radial muscle fibers arise in the midportion of the ciliary body - the circular fibers are located in the innermost portion

Answer 303

- Clinically, the 3 groups of muscle fibers function as a unit. - The ciliary muscles behave like other smooth, nonstriated muscle fibers

Answer 304

Ultrastructural studies reveal that they contain multiple myofibrils with characteristic electrondense attachment bodies, mitochondria, glycogen particles, and a prominent nucleus. -

Answer 305

- The smooth muscle cells are surrounded by a basal lamina separated from the cell membrane by a 300-A space - Bundles of fibers are surrounded by a thin fibroblastic sheath rather than by collagen

Answer 306

VI | it forms a sheath around the anterior elastic tendons

Answer 307

into the scleral spur and around the tips of the oblique and circular muscle fibers as they insert into the trabecular meshwork

Answer 308

both myelinated and nonmyelinated

Answer 309

Approximately 97% of these ciliary fibers are directed to the ciliary muscle, and about 3% are directed to the iris sphincter

Answer 310

may play a role in relaxing the muscle

Answer 311

contraction Because some of the muscle fibers form tendinous attachments to the scleral spur, their contraction increases aqueous flow by opening up the spaces of the trabecular meshwork.

Answer 312

outer portion of the retina

Answer 313

It averages 0.25 mm

Answer 314

1. the choriocapillaris, the innermost layer 2. a middle layer of small vessels 3. an outer layer of large vessels

Answer 315

!!! both from the long and short posterior ciliary arteries and from the perforating anterior ciliary arteries

Answer 316

Blood flow through the choroid is high compared with that of other tissues. As a result, the oxygen content of choroidal venous blood is only 2%-3% lower than that of arterial blood.

Answer 317

It extends from the margin of the optic disc to the ora serrata

Answer 318

- defects develop spontaneously in myopia or pseudoxanthoma elasticum - trauma - inflammation

Answer 319

1) basal lamina of RPE, 2) inner collagenous zone, 3) porous band of elastic fibers, 4) outer collagenous zone, 5) basal lamina of the choriocapillaris

Answer 320

A PAS-positive layer resuting from the fusion of the basal laminae of the RPE and choriocapillaris

Answer 321

vortex veins

Answer 322

the anterior ciliary arteries and long posterior ciliary arteries

Answer 323

2 layers of epithelial cells (non-pigmented and pigmented epithelial layers)

Answer 324

the pars plicata is richly vascularized

Answer 325

- it is a continuous layer oflarge capillaries - The vessel walls are extremely thin and contain multiple fenestrations, especially on the surface facing the retina - Pericytes are located along the outer wall.

Answer 326

The large vessels, typical of small arteries elsewhere, possess an internal elastic lamina and smooth muscle cells in the media. As a result, small molecules such as fluorescein, which diffuse across the endothelium of the choriocapillaris, do not leak through medium and large choroidal vessels.

Answer 327

no, but the choriocapillaris is

Answer 328

- abundant melanocytes - occasional macrophages - lymphocytes - mast cells - plasma cells

Answer 329

- collagen fibers | - nerve fibers

Answer 330

it influences the absorption of laser energy

Answer 331

6.5 mm at birth; it increases in the first 2-3 decades of life and remains approximately 9-10 mm in diameter in late life

Answer 332

approximately 3 mm at birth and increases after the second decade of life to approximately 6 mm by age 80 years

Answer 333

growth is accompanied by a shortening of the anterior radius of curvature of the lens, which would increase its optical power if not for a compensatory change in the refractive gradient across the lens substance

Answer 334

entirely due to a change in nuclear shape

Answer 335

At age 8 years, the power is 14.00 D. By age 28 years, the accommodative power decreases to approximately 9.00 D, and it decreases further to 1.00 D by age 64 years

Answer 336

- increased size of the lens - altered mechanical relationships - increased stiffness of the lens nucleus secondary to changes in the crystalline proteins of the fiber cytoplasm - Other factors, such as alterations in the geometry of zonular attachments with age and changes in lens capsule elasticity, may also play a role

Answer 337

After regression of the hyaloid vasculature during embryogenesis, the lens depends solely on the aqueous and vitreous for its nourishment

Answer 338

A basal lamina put down by the lens epithelial cells, rich in type IV collagen and other matrix proteins.

Answer 339

Yes, its synthesis proceeds througout life so its thickness increases, while that of posterior capsule does not

Answer 340

Values of 15.5 f.!m for the thickness of the anterior capsule and 2.8 1-lm for the posterior capsule have been cited for the adult lens.

Answer 341

it consists of fine filaments arranged in lamellae, parallel to the surface. The anterior lens capsule contains a fibrogranular material, identified as laminin, which is absent from the posterior capsule at the ultrastructural level

Answer 342

beneath the anterior and equatorial capsule, but it is absent under the posterior capsule.

Answer 343

- The basal aspects of the cells abut the lens capsule without specialized attachment sites. - The apices of the cells face the interior of the lens, and the lateral borders interdigitate, with practically no intercellular space

Answer 344

Each cell contains a prominent nucleus but relatively few cytoplasmic organelles.

Answer 345

- The central zone represents a stable population of cells whose numbers slowly decline with age - An intermediate zone of smaller cells shows occasional mitoses - Peripherally, there are meridional rows of cuboidal preequatorial cells thal form the germinative zone of the lens

Answer 346

peripherally, meridional rows of cuboidal preequatorial cells - Here, cells undergo mitotic division, elongate anteriorly and posteriorly, and form the differentiated fiber cells of the lens - In the human lens, cell division continues throughout life and is responsible for the continued growth of the lens

Answer 347

they can give rise to posterior capsular opacification as a result of aberrant proliferation and cell migration

Answer 348

The nucleus is the part of the fiber mass that is formed at birth, and the cortex forms as new fibers are added postnatally

Answer 349

hexagonal in cross section, have a spindle shape, and possess numerous interlocking, fingerlike projections

Answer 350

It contains lens crystallins. | - Apart from the most superficial cortical fibers, the cytoplasm is homogeneous and contains few organelles

Answer 351

The high refractive index of the lens results from the high concentration of lens crystallins (α, β, and γ) in the fiber cytoplasm

Answer 352

The lens sutures are formed by the interdigitation of the anterior and posterior tips of the spindle-shaped fibers. In the fetal lens, this interdigitation forms the anterior Y-shaped suture and the posterior inverted Y-shaped suture. As the lens ages, further branches are added to the sutures; each new set of branch points corresponds to the appearance of a fresh optical zone of discontinuity.

Answer 353

basal lamina of the nonpigmented epithelium of the pars plana and the pars plicata o the ciliary body

Answer 354

chiefly to the lens capsule anterior and posterior to the equator

Answer 355

Each zonular fiber is made up of multiple filaments of fibrillin that merge with the equatorial lens capsule. In Marfan syndrome, mutations in the fibrillin gene lead to weakening of the zonule and subluxation of the lens.

Answer 356

due to the transmission of light reflected from the posterior sclera through the capillary bed of the choroid

Answer 357

Inner and outer layers of the optic cup

Answer 358

1. internal limiting membrane 2. nerve fiber layer 3. ganglion cell layer 4. inner plexiform layer 5. inner nuclear layer 6. middle limiting membrane 7. outer plexiform layer 8. outer nuclear layer 9. external limiting membrane 10. rod and cone inner and outer segments

Answer 359

The RPE consists of a monolayer of hexagonal cells that extends anteriorly from the optic disc to the ora serrata, where it merges with the pigmented epithelium of the ciliary body

Answer 360

- vit A metabolism - maintenance of the outer blood-retina barrier - phagocytosis of the photoreceptor puter segments - absorption of light (reduction of scatter) - heat exchange - formation of the basal lamina of the Bruch membrane - production of the mucopolysaccharide matrix surrounding the outer segments - active transport of materials into and out of the RPE

Answer 361

yes, like other epithelial and endothelial cells

Answer 362

The basal aspect is intricately folded and provides a large surface of attachment to the thin basal lamina that forms the inner layer of the Bruch membrane

Answer 363

The apices have multiple villous processes that engage with the photoreceptor outer segments

Answer 364

Separation of the RPE from the neurosensory retina

Answer 365

- firmly, by a series of lateral, intercellular junctional complexes. - zonulae occludentes: they consist of fused plasma membranes forming a circular band of belt between adjacent cells - a small intercellular space is present between zonulae adherentes - both of them provide structural stability and also plays an important role in maintaining the outer blood-retina barrier

Answer 366

- in the papillomacular bundle near the optic nerve: 0.23 mm - foveola: 0.10 mm - ora serrata: 0.11 mm

Answer 367

10-60 um RPE cells in the fovea are taller and thinner, contain more melanosomes, and have larger melanosomes. These characteristics account in part for the decreased transmission of choroidal fluorescence observed during fundus fluorescein angiography. Cells in the periphery are shorter, broader, and less pigmented.

Answer 368

4-6 billion

Answer 369

yes, but only a little

Answer 370

- multiple round and ovoid pigment granules in the cytoplasmn of the RPE cells

Answer 371

These organelles develop in situ during formation of the optic cup and first appear as nonmelanized premelanosomes. (Their development contrasts sharply with that of the pigment granules in uveal melanocytes, which are derived from the neural crest and later migrate into the uvea. )

Answer 372

they are derived from the neural crest and later migrate into the uvea

Answer 373

- probably arise from the discs of photoreceptor outer segments and represent residual bodies arising from phagosomal activity. - This so-called wear-andtear pigment is less electron dense than the melanosomes, and its concentration increases gradually with age. - Clinically, these lipofuscin granules are responsible for the signal observed with fundus autofluorescence

Answer 374

- membrane-enclosed packets of disc outer segments that have been engulfed by the RPE - Several stages of disintegration are evident at any given time - In some species, shedding and degradation of the membranes of rod and cone outer segments follow a diurnal rhythm synchronized with daily fluctuations of environmental light

Answer 375

- melanosomes - lipofuscin granules - phagosomes - numerous mitochondria (involved in the aerobic metabolism) - rough-surfaced endoplasmic reticulum - Golgi - large and round nucleus

Answer 376

Throughout life, incompletely digested residual bodies, lipofuscin pigment, phagesomes, and other material are excreted beneath the basal lamina of the RPE. These contribute to the formation of drusen, which are accumulations of this extracellular material.

Answer 377

between the basement membrane of the RPE cells and the inner collagenous zone of the Bruch membrane.

Answer 378

by fundoscopic appearance as either hard or soft

Answer 379

neuronal, glial, and vascular elements

Answer 380

The outer segments, surrounded by a mucopolysaccharide matrix, make contact with the apical processes of the RPE. Tight junctions or other intercellular connections do not exist between the photoreceptor cell outer segments and the RPE. The factors responsible for keeping these layers in apposition are poorly understood but probably involve active transport.

Answer 381

- contains multiple laminated discs resembling a stack of coins - and a central connecting cilium * The microt ubules of the cilium have a 9-plus-0 cross-sectional configuration rather than the 9-plus-2 configuration found in motile cilia

Answer 382

1. outer ellipsoid - contains numerous mitochondria 2. inner myoid - contains large amount of glycogen - continuous with the main cell body (where the nucleus is located) - The inner portion of the cell contains the synaptic body, or spherule, of the rod, which is formed by a single invagination that accommodates 2 horizontal cell processes and 1 or more central bipolar dendrites

Answer 383

different morphology depending on their location in the retina

Answer 384

- he extrafoveal cone photoreceptors of the retina have conical ellipsoids and myoids, and their nuclei tend to be closer to the external limiting membrane than are the nuclei of the rods - The cone synaptic body, or pedicle, is more complex than the rod spherule. Cone pedicles synapse with other rods and cones as well as with horizontal and bipolar cell processes - Foveal cones have cylindrical inner segments similar to rods but otherwise are cytologically identical to extrafoveal cones

Answer 385

- their structire is similar, but: Rod discs are not attached to the cell membrane; they are discrete structures. Cone discs are attached to the cell membrane and are thought to be renewed by membranous replacement

Answer 386

with many rod spherules and cone pedicles; they also extend cell processes horizontally throughout the outer plexiform layer

Answer 387

- vertical orientation - Their dendrites synapse with either rod or cone synaptic bodies, and their axons make synaptic contact with ganglion cells and amacrine cells in the inner plexiform layer

Answer 388

The axons of the ganglion cells bend to become parallel to the inner surface of the retina, where they form the nerve fiber layer and later the axons of the optic nerve.

Answer 389

more than 1 million

Answer 390

- The nerve fibers from the temporal retina follow an arcuate course around the macula to enter the superior and inferior poles of the optic disc - The papillomacular fibers travel straight to the optic nerve from the fovea - The nasal axons also pursue a radial course

Answer 391

green (red-free) illumination

Answer 392

120 million

Answer 393

- fibrous and protoplasmic astrocytes - microglia - Müller cells * they provide structural support and nutrition to the retina and are crucial to normal physiology.

Answer 394

- extend vertically from the external limiting membrane inward to the internal limiting membrane. - Their nuclei are located in the inner nuclear layer

Answer 395

branches of the central retinal artery | In addition, a cilioretinal artery can branch from the ciliary circulation to supply the macula

Answer 396

18-32% of eyes

Answer 397

the single layer of nonfenestrated endothelial cells, whose tight junctions are impervious to tracer substances such as fluorescein and horseradish peroxidase

Answer 398

- single layer of nonfenestrated endothel cells connected ny tight junctions - basal lamina covers the surfface of the endothelium - basement membrene contains an interrupted layer of peric)rtes, or mural cells, surrounded by their own basement membrane material - Retinal blood vessels lack an internal elastic lamina and the continuous layer of smooth muscle cells found in other vessels in the body - Smooth muscle cells are occasionally present in vessels near the optic nerve head. They become a more discontinuous layer as the retinal arterioles pass farther out to the peripheral retina

Answer 399

basal lamina

Answer 400

do not ordinarily extend deeper than the middle limiting membrane

Answer 401

at arteriovenous crossings | Where venules and arterioles cross, they share a common basement membrane

Answer 402

- located next to the RPE - not a true membrane - formed by the attachment sites of adjacent photoreceptors and Müller cells - highly fenestrated

Answer 403

- composed of the interconnections between the photoreceptor synaptic bodies and the horizontal and bipolar cells - In the macular region, the OPL is thicker and contains more fibers, because the axons of the rods and cones become longer and more oblique as they deviate from the fovea (Henle fiber layer) - At the edge of the foveola, it lies almost parallel to the internal limiting membrane

Answer 404

It contains nuclei of bipolar, Müller, horizontal, and amacrine cells

Answer 405

It contains nuclei of rods and cones

Answer 406

OPL in the macular region

Answer 407

formed by a zone of desmosome-like attachments in the region of the synaptic bodies of the photoreceptor cells. The retinal blood vessels ordinarily do not extend beyond this point.

Answer 408

- consists of axons of the bipolar and amacrine cells | - and the dendrites of the ganglion cells and their synapses

Answer 409

- it is made up of the cell bodies of the ganglion cells that lie near the inner surface of the retina

Answer 410

it is formed by axons of the ganglion cells Normally, these axons do not become myelinated until after they pass through the lamina cribrosa of the optic nerve.

Answer 411

- not a true membrane | - formed by the footplates of the Müller cells and attachments to the basal lamina

Answer 412

smooth on the vitreal side but appears undulating on the retinal side, where it follows the contour of the Müller cells. The thickness of the basal lamina varies

Answer 413

Overall, cells and their processes in the retina are oriented perpendicular to the plane of the RPE in the middle and outer layers but parallel to the retinal surface in the inner layers For this reason, deposits of blood or exudates tend to form round blots in the outer layers (where small capillaries are found) and linear or flame-shaped patterns in the nerve fiber layer At the fovea, the outer layers also tend to be parallel to the surface (Henle fiber layer). As a result, radial or star-shaped patterns may arise when these extracellular spaces are filled with serum and exudate.

Answer 414

the region with more than 1 layer of ganglion cell nuclei

Answer 415

250-600 um

Answer 416

due to the presence of carotenoid pigments, which are located chiefly in the Henle fiber layer

Answer 417

zeaxantin and lutein

Answer 418

In the central area (0.25 mm from the fovea), the lutein-to-zeaxanthin ratio is 1:2.4, and in the periphery (2.2-8.7 mm from the fovea), the ratio is greater than 2:1. This variation in pigment ratio corresponds to the rod-to-cone ratio. Lutein is more concentrated in rod-dense areas of the retina; zeaxanthin is more concentrated in cone-dense areas

Answer 419

Lipofuscin, the yellow age pigment, has been observed in the cytoplasm of the perifoveal ganglion cells by electron microscopy.

Answer 420

0.5 mm wide, where the GCL, the INL, and the OPL are thickest

Answer 421

- most peripheral region of the macula - sorrounds the parafovea - 1.5 mm wide

Answer 422

caused partly by xanthophyll pigment and partly by the higher melanin pigment content of the foveal RPE

Answer 423

approximately 4.0 mm temporal and 0.8 mm inferior to the center of the optic disc

Answer 424

It is approximately 0.35 mm across and 0.10 mm thick at its center

Answer 425

The borders of the foveola merge imperceptibly with the fovea

Answer 426

The nuclei of the photoreceptor cells in the region of the foveola bow forward toward the ILM to form the fovea externa

Answer 427

- Usually, only photoreceptors, Muller cells, and other glial cells are present in this area - Occasionally, light microscopy reveals ganglion cell nuclei just below the ILM

Answer 428

composed entirely of cones, whose close packing accounts for the high visual acuity for which this small area is responsible

Answer 429

- shaped like rods but possess all the cytologic characteristics of extramacular cones. - The outer segments are oriented parallel to the visual axis and perpendicular to the plane of the RPE ( In contrast, the peripheral photoreceptor cell outer segments are tilted toward the entrance pupil)

Answer 430

is an important clinical landmark in the treatment of subretinal neovascular membranes by laser photocoagulation. Its location is approximately the same as that of the foveola, and its appearance in fundus fluorescein angiograms varies greatly

Answer 431

- boundary between the retina and the pars plana - Topographically, the ora serrata is relatively smooth temporally and serrated nasally - The ora serrata is in a watershed zone between the anterior and posterior vascular systems, which may in part explain why peripheral retinal degeneration is relatively commoo. The peripheral retina in the region of the ora serrata is markedly attenuated. The photoreceptors are malformed, and the overlying retina frequently appears cystic in paraffin sections

Answer 432

between 5.75 mm nasally and 6.50 mm temporally | - In myopia, this distance is greater; in hyperopia, it is shorter

Answer 433

The Bruch membrane extends anteriorly, beyond the ora serrata, but is modified because there is no choriocapillaris in the ciliary body

Answer 434

At the ora serrata, the diameter of the eye is 20 mm and the circumference is 63 mm; at the equator, the diameter is 24 mm and the circumference is 75 mm

Answer 435

no, they end in loops before the ora serrata

Answer 436

Retina appears cystic in paraffin sections in the region of the ora serrata

Answer 437

the transparent vitreous humor is important to the metabolism of the intraocular tissues because it provides a route for metabolites used by the lens, ciliary body, and retina

Answer 438

close to 4.0 mL

Answer 439

Its viscosity is approximately twice that of water, mainly due to the presence of the mucopolysaccharide hyaluronic acid

Answer 440

chiefly type II

Answer 441

At the ultrastructural level, fine collagen fibrils (chiefly type II) and cells have been identified in the vitreous

Answer 442

The origin and function of these cells, termed hyalocytes, are unknown, but they probably represent modified histiocytes, glial cells, or fibroblasts

Answer 443

with the basal lamina of the nonpigmented epithelium of the pars plana and the ILM of the retina

Answer 444

peripherally at the vitreous base, which extends from 2.0 mm anterior to the ora serrata to approximately 4.0 mm posterior to it. Additional attachments exist at the disc margin, at the perimacular region, along the retinal vessels, and at the periphery of the posterior lens capsule

Answer 445

During embryonic development, regression of the hyaloid vasculature results in the formation of an S-shaped channel (the Cloquet canal), which passes sinuously from a point slightly nasal to the posterior pole of the lens (Mittendorf dot) to the margin of the optic nerve head

Answer 446

A point slightly nasal to the posterior pole of the lens from which the CLoquet canal passes

Answer 447

Vascular loops and Bergmeister papilla

Answer 448

small olfactory receptors in the mucous membrane of the nose

Answer 449

Unmyelinated CN I fibers pass from these receptors in the nasal cavity through the cribriform plate of the ethmoidal bone and enter the ventral surface of the olfactory bulb, where they form the nerve

Answer 450

- posteriorly from the bulb beneath the frontal lobe of the brain in a groove (or sulcus) and lateral to the gyrus rectus The gyrus rectus forms the anterolateral border of the suprasellar cistern. Meningiomas arising from the arachnoid cells in this area can cause important ophthalmic signs and symptoms associated with loss of olfaction.

Answer 451

more than 1 million

Answer 452

intraocular region of the optic nerve: optic disc, or nerve head; prelaminar area; and laminar area intraorbital region (located within the muscle cone) intracanalicular region (located within the optic canal) intracranial region (ending in the optic chiasm)

Answer 453

1.76 x 1.92 mm

Answer 454

- retinal arterioles | - branches of posterior ciliary arteries

Answer 455

25-30 mm | it is greater than greater than the distance between the back of the globe and the optic canal (18 mm)

Answer 456

Intraneural branches of central retinal artery CRA; pial branches from CRA and choroid

Answer 457

ophthalmic artery

Answer 458

Branches of internal carotid and ophthalmic arteries

Answer 459

- similar to that of the white matter of the brain | - Developmentally, the optic nerve is part of the brain

Answer 460

glial cell sheats (not Schwann!)

Answer 461

sinuous Axial proptosis secondary to thyroid-related eye disease or a retrobulbar tumor can lead to stretching of the optic nerve, which may cause chronic nerve injury and optic neuropathy.

Answer 462

The size of the optic disc varies widely, averaging 1.76 mm horizontally and 1.92 mm vertically

Answer 463

- cup-shaped depression of the optic nerve head - located slightly temporal to the disc's geometric center - represents an axon-free region the main branches of the central retinal artery (CRA) and the central retinal vein (CRV) pass through the center of the cup

Answer 464

- superficial nerve fiber layer - prelaminar area - laminar area - retrolaminar area

Answer 465

- nonmyelinated ganglion cell axons retain their retinotopic organization ( fibers from the upper retina above and those from the lower retina below; from the temporal lateral and from the nasal medial) - macular fibers are laterally placed - In the nerve head, foveal fibers are located peripherally, and peripapillary fibers are located centrally

Answer 466

- in the prelaminar area - The ganglion cell axons that enter the nerve head are supported by a "wicker basket" of astrocytic glial cells and are segregated into bundles, or fascicles, that pass through the lamina cribrosa

Answer 467

- astrocytes invest the optic nerve and form continuous circular tubes that enclose groups of nerve fibers throughout their intraocular and intraorbital course, separating them from connective tissue elements at all sites - At the nerve head, the Muller cells that make up the internal limiting membrane (ILM) are replaced by astrocytes. - astrocytes form an ILM that covers the surface of the nerve head and is continuous with the Muller cell-derived ILM of the retina

Answer 468

the pigment epithelium may be exposed at the temporal margin of the disc

Answer 469

pigment epithelium and choroid fail to reach the temporal margin

Answer 470

- The relationship between the choroid and the prelaminar portion of the optic nerve partly accounts for the staining - The disc vessels do not leak, but the choroidal capillaries are freely permeable to fluorescein, which can therefore diffuse into the lamina

Answer 471

When the optic nerve is damaged, axons and supporting glial elements can be lost, causing pathologic enlargement of the optic cup. This cupping may be the first objective sign of damage

Answer 472

- they are integrated with the sclera | - their pores transmit the axon bundles

Answer 473

The openings are wider above than below, which may imply less protection from the mechanical effects of pressure in glaucoma

Answer 474

type I and III collagens - abundant elastin - laminin - fibronectin - astrocytes surround the axon bundles - small blood vessels are present

Answer 475

(1) scaffold for the optic nerve axons (2) point of fixation for the CRA and CRV (3) reinforcement of the posterior segment of the globe.

Answer 476

- behind the lamina cribrosa in the retrolaminar area - it increases to 3 mm - cause: * myelination of the nerve fibers * presence of oligodendroglia * presence of the surrounding meningeal sheaths (pia, arachnoid, and dura)

Answer 477

- neurofilments - microtubules - mitochondria - smooth endoplasmatic reticulum

Answer 478

The retrolaminar nerve continues proximally (as the intraorbital part of the optic nerve) to the apex of the orbit

Answer 479

The superior and medial rectus muscles partially share a connective tissue sheath with the optic nerve This connection may partly explain why patients with retrobulbar neuritis report symptoms of pain on eye movement

Answer 480

At the optic canal, the dural sheath of the nerve fuses to the periosteum, completely immobilizing the nerve and rendering it susceptible to shearing forces from trauma transmitted to the orbital apex via the bony buttresses of the orbit.

Answer 481

It is a nscular connective tissue coat, covered with meningothelial cells, that sends numerous septa into the optic nerve, dividing its axons into bundles.

Answer 482

- the pia mater sends septa into the optic nerve, dividing axons into buldles - The septa continue throughout the intraorbital and intracanalicular regions of the nerve and end just before the chiasm

Answer 483

- collagen - elastic tissue - fibroblasts - nerves - small arterioles and venules

Answer 484

- They provide mechanical support for the nerve bundles | - and nutrition to the axons and glial cells

Answer 485

no. A mantle of astrocytic glial cells prevents the pia and septa from having direct contact with nerve axons.

Answer 486

- collagenous tissue - small amounts of elastic tissue - small amounts of meningothial cells

Answer 487

lines the dura mater and is connected to the pia across the subarachnoid space by vascular trabeculae

Answer 488

- it ends anteriorly at the level of the lamina cribrosa | - Posteriorly, it is usually continuous with the subarachnoid space of the brain

Answer 489

the dense connective tissue that joins the sclera with the Bruch membrane, enclosing the choroid and forming the scleral ring that defines the margin of the optic disc - At the posterior termination of the choroid on the temporal side, the border tissue of Elschnig lies between the astrocytes surrounding the optic nerve canal and the stroma of the choroid - On the nasal side, the choroidal stroma is directly adjacent to the astrocytes surrounding the nerve (This collection of astrocytes surrounding the canal is known as the border tissue, which is continuous with a similar glial lining at the termination of the retina)

Answer 490

approximately 1000

Answer 491

On reaching the lamina cribrosa, the nerve fascicles and their surrounding astrocytes are separated from each other by connective tissue

Answer 492

- an extension of scleral collagen and elastic fibers through the nerve - The external choroid also sends some connective tissue to the anterior part of the lamina

Answer 493

at the external part of the lamina cribrosa. | columns of oligodendrocytes and a few astrocytes are present within the nerve fascicles

Answer 494

- The central retinal vessels are surrounded by a perivascular connective tissue throughout its course in the nerve - this connective tissue blends with the connective tissue of the lamina cribrosa

Answer 495

Because the central retinal vessels cross subarachnoid space, a rise in intracranial pressure can compress the retinal vein and raise the venous pressure within the retina above the intraocular pressure. This situation causes intraocular venous dilatation and the loss of spontaneous venous pulsation at the nerve head. Such an absence of pulsation may clinically indicate raised intracranial pressure

Answer 496

0.3-0.5 mm

Answer 497

- dense bundles of collagen and elastic tissue that fuse anteriorly with the outer layers of the sclera

Answer 498

The meninges of the optic nerve are supplied by sensory nerve fibers, which account IN PART for the pain experienced by patients with retrobulbar neuritis and other inflammatory optic nerve diseases.

Answer 499

derived from pial vessels originating from the ophthalmic artery.

Answer 500

The optic nen e and surrounding arachnoid are tethered to the periosteum of the bony canal within the intracanalicular region. Blunt trauma, particularly over the eyebrow, can transmit the force of injury to the intracanalicular region, causing shearing and interruption of the blood supply to the nerve in this area.

Answer 501

compartment syndrome

Answer 502

- After passing through the optic canals, the 2 optic nerves lie above the ophthalmic arteries, above and medial to the internal carotid arteries - The anterior cerebral arteries cross over the optic nerves and are connected by the anterior communicating artery, which completes the anterior portion of the circle of Willis - The optic nerves then pass posteriorly over the cavernous sinus to join in the optic chiasm - The chiasm then divides into right and left optic tracts, which end in their respective lateral geniculate bodies - From these bodies arise the geniculocalcarine pathways (or optic radiations), which pass to each primary visual cortex

Answer 503

The CRA and, usually, 2 long posterior ciliary arteries branch off from the ophthalmic artery once it enters the muscle cone at the annulus of Zinn

Answer 504

- the retrolaminar nerve is supplied chiefly by pial vessels and short posterior ciliary vessels, with some help from the CRA and recurrent choroidal arteries

Answer 505

The lamina is supplied by short posterior ciliary arteries or by branches of the arterial circle of Haller and Zinn (circle of Zinn-Haller). This circle arises from the paraoptic branches of the short posterior ciliary arteries and is usually embedded in the sclera around the nerve head. It is often incomplete and may be divided into superior and inferior halves. The CRA does not supply this region

Answer 506

The prelaminar nerve is supplied by the short posterior ciliary arteries ( cilioretinal arteries, if present) and recurrent choroidal arteries, although their relative contribution is debated

Answer 507

The nerve fiber layer is supplied by the CRA

Answer 508

The posterior ciliary arteries are terminal arteries, and the area where the respective capillary beds from each artery meet is termed the watershed zone. When perfusion pressure drops, the tissue lying within this area is the most vulnerable to ischemia. Consequences can be significant when the entire optic nerve head or a part of it lies within the watershed zone.

Answer 509

- proximally by the pial vascular network and by neighboring branches of the ophthalmic artery - Distally, it is also supplied by intraneural branches ofthe CRA - Most anteriorly, it is supplied by short posterior ciliary arteries and occasional peripapillary choroidal arteries

Answer 510

almost exclusively by the ophthalmic artery.

Answer 511

primarily by branches of both the ICA and the ophthalmic artery

Answer 512

The lumen of the CRA is surrounded by nonfenestrated endothelial cells with typical zonulae occludentes that are similar to those in retinal vessels

Answer 513

- The CRA contains a fenestrated internal elastic lamina and an outer layer of smooth muscle cells surrounded by a thin basement membrane - the retinal arterioles have no internal elastic lamina, and they lose their smooth muscle cells shortly after entering the retina

Answer 514

- endothelial al cells - thin basal lamina - thick collagenous adventitia

Answer 515

The optic chiasm makes up part of the anterior inferior floor of the third ventricle. It is surrounded by pia and arachnoid and is richly vascularized

Answer 516

12 mm wide, 8 mm long in the anteroposterior direction, and 4 mm thick

Answer 517

- The extramacular fibers from the inferonasal retina cross anteriorly in the chiasm at the "Wilbrand knee" before passing into the optic tract - Extramacular superonasal fibers cross directly to the opposite tract - Extramacular temporal fibers remain uncrossed in the chiasm and optic tract

Answer 518

pursue a direct course through the chiasm as a bundle of uncrossed fibers

Answer 519

cross in the posterior part of the chiasm

Answer 520

Approximately 53% of the optic nerve fibers are crossed, and 47% are uncrossed.

Answer 521

- Each optic tract contains ipsilateral temporal and contralateral nasal fibers from the optic nerves - Fibers (both crossed and uncrossed) from the upper retinal projections travel medially in the optic tract - lower projections move laterally - The macular fibers adopt a dorsolateral orientation as they course toward the lateral geniculate body

Answer 522

- The lateral geniculate body, or nucleus, is the synaptic zone for the higher visual projections - It is an oval, caplike structure that receives approximately 70% of the optic tract fibers within its 6 alternating layers of gray and white matter - The 6 layers, numbered consecutively from below upward, give rise to the optic radiations.

Answer 523

6 alternating layers of gray and white matter

Answer 524

they connect the lateral geniculate body with the cortex of the occipital lobe

Answer 525

- The fibers of the optic radiations leave the lateral geniculate body and wind around the temporal horn of the lateral ventricle, approaching the anterior tip of the temporal lobe, or loop of Meyer. - They then sweep backward toward the visual area of the occipital lobe

Answer 526

wedge-shaped, upper homonymous "pie in the sky" visual field defect

Answer 527

occupies the superior and inferior lips of the calcarine fissure on the posterior and medial surfaces of the occipital lobes

Answer 528

The visual cortex, the thinnest area of the human cerebral cortex, has 6 cellular layers

Answer 529

Macular function is extremely well represented in the visual cortex and occupies the most posterior position at the tip of the occipital lobe

Answer 530

contralateral nasal retinal fibers only

Answer 531

The posterior cerebral artery, a branch of the basilar artery, supplies the visual cortex almost exclusively. However, the blood supply to the occipital lobe does show anatomical variation; in some individuals, the middle cerebral artery contributes

Answer 532

- it supplies all the extraocular muscles except the superior oblique and the lateral rectus - It also carries cholinergic innervation to the pupillary sphincter and the ciliary muscle

Answer 533

arises from a complex group of cells in the rostral midbrain, or mesencephalon, at the level of the superior colliculus. This nuclear complex lies ventral to the periaqueductal gray matter, is immediately rostral to the CN IV nuclear complex, and is bounded inferolaterally by the medial longitudinal fasciculus

Answer 534

- several distinct, large motor cell subnuclei, each of which subserves the extraocular muscle it innervates - Except for a single central caudal nucleus that serves both levator palpebrae superioris muscles, the cell groups are paired

Answer 535

Fibers from the dorsal nucleus cross, or decussate, in the caudal aspect of the nucleus and therefore supply the contralateral superior rectus muscles

Answer 536

One central caudal nucleus supplies both muscles | - Notably, the shared innervation of both levator muscles is responsible for Hering's law of equal innervation.

Answer 537

cephalad and dorsomedial in location

Answer 538

It provides the parasympathetic preganglionic efferent innervation to the ciliary muscle and pupillary sphincter

Answer 539

the most ventral

Answer 540

A subnucleus for ocular convergence has been described but is not consistently found in primates

Answer 541

- The fascicular portion of CN III travels ventrally from the nuclear complex, through the red nucleus, between the medial aspects of the cerebral peduncles, and through the corticospinal fibers - It exits in the interpeduncular space - In the subarachnoid space, CN III passes below the posterior cerebral artery and above the superior cerebellar artery, the 2 major branches of the basilar artery - The nerve travels forward in the interpeduncular cistern lateral to the posterior communicating artery and penetrates the arachnoid between the free and attached borders of the tentorium cereb elli - pierces the dura on the lateral side of the posterior clinoid process, initially traversing the roof of the cavernous sinus - It runs along the lateral wall of the cavernous sinus and above CN IV and enters the orbit through the superior orbital fissure.

Answer 542

the junction of the posterior communicating artery and the ICA.

Answer 543

usually separates into superior and inferior divisions after passing through the annulus of Zinn in the orbit. Alternatively, it may divide within the anterior cavernous sinus

Answer 544

The nerve maintains a topographic organization even in the midbrain, so lesions almost anywhere along its course may cause a divisional nerve palsy

Answer 545

the superior rectus and levator palpebrae muscles

Answer 546

The larger inferior division splits into 3 branches to supply the medial and inferior rectus muscles and the inferior oblique muscle

Answer 547

- wind around the periphery of the nerve, enter the inferior division, and course through the branch that supplies the inferior oblique muscle - They join the ciliary ganglion, where they synapse with the postganglionic fibers, which emerge as many short ciliary nerves

Answer 548

pierce the sclera and travel through the choroid to innervate the pupillary sphincter and the ciliary muscle The superficial location of these fibers makes them more vulnerable to compression, such as from an aneurysm, than to ischemia. However, a pupil-sparing oculomotor nerve palsy, even in the context of systemic vascular disease, is not a perfect indicator of the absence of an enlarging aneurysm, and a growing number of neuro-ophthalmologists recommend emergent imaging (by computed tomography/computed tomography angiography or magnetic resonance imaging/magnetic resonance angiography) for anyone with new-onset CN III palsy with incomplete ptosis

Answer 549

- The afferent pupillary pathway coincides with that of the visual pathway and includes a decussation of nasal fibers in the chiasm - At the posterior part of the optic tract, the pupillary fibers leave the visual fibers and pass to the lateral side of the midbrain to reach the pretectal nuclei at the level of the superior colliculus - Here, efferent fibers arise and pass to the Edinger-Westphal nuclei, decussating partially (both ventral to the aqueduct and dorsally, in the posterior commissure) - Preganglionic parasympathetic fibers leave each Edinger-Westphal nucleus and run in the oculomotor nerve as it leaves the brainstem. The fibers spiral downward to lie medially in the nerve at the level of the petroclinoid ligament and inferiorly in the inferior division of CN III as it enters the orbit - These fibers synapse in the ciliary ganglion and give rise to postganglionic myelinated short ciliary nerves

Answer 550

~ 3-5 % | The rest are designated for the ciliary muscle and are concerned with the near reflex

Answer 551

The near reflex is a synkinesis that occurs when attention is changed from distance to near. This reflex includes accommodation, pupil constriction, and convergence

Answer 552

- initiated in the occipital association cortex, from which impulses descend along corticofugal pathways to relay in pretectal and possibly tegmental areas - From these relays, fibers pass to the Edinger-Westphal nuclei, the motor nuclei of the medial rectus muscles, and the nuclei of CN VI - Fibers for the near reflex approach the pretectal nucleus from the ventral aspect; thus, compressive dorsal lesions of the optic tectum spare the near pupil reflex relative to the light reflex (light-near dissociation) - Efferent fibers for accommodation follow the same general pathway as do those for the light reflex, but their final distribution (via the short ciliary nerves) is to the ciliary muscle.

Answer 553

Fibers for the near reflex approach the pretectal nucleus from the ventral aspect; thus, compressive dorsal lesions of the optic tectum spare the near pupil reflex relative to the light reflex (light-near dissociation).

Answer 554

~ 3400 | the fewest nerve fibers of any cranial nerve

Answer 555

``` 75 mm (longest of the CNs) ```

Answer 556

- in the caudal mesencephalon at the level of the inferior colliculus near the periaqueductal gray matter, ventral to the aqueduct of Sylvius - It is continuous with the caudal end of the CN III nucleus and differs histologically from that nucleus only in the smaller size of its cells - Like the CN III nucleus, it is bounded ventrolaterally by the medial longitudinal fasciculus

Answer 557

- The fascicles of CN IV curve dorsocaudally around the periaqueductal gray matter and decussate completely in the superior medullary velum - The nerves exit the brainstem just beneath the inferior colliculus. Thus, CN IV is the only cranial nerve that is completely decussated and the only motor nerve to exit dorsally from the nervous system - As it curves around the brainstem in the ambient cistern, CN IV runs beneath the free edge of the tentorium, passes between the posterior cerebral and superior cerebellar arteries, and then pierces the dura mater to enter the cavernous sinus - Cranial nerve IV travels beneath CN III and above the ophthalmic division of CN V in the lateral wall of the cavernous sinus - It enters the orbit through the superior orbital fissure outside the annulus of Zinn and runs superiorly to innervate the superior oblique muscle - Because of its location outside the muscle cone, CN IV is usually not affected by injection of retrobulbar anesthetics

Answer 558

CN V(trigeminal)

Answer 559

sensory and motor

Answer 560

the greater part of the scalp, forehead, face, eyelids, eyes, lacrimal glands, extraocular muscles, ears, dura mater, and tongue

Answer 561

muscles of mastication through branches of the mandibular division

Answer 562

from the midbrain to the upper cervical segments, often as caudal as C4

Answer 563

1. mesencephalic nucleus 2. main sensory nucleus 3. spinal nucleus and tract 4. motor nucleus located in the pons Important interconnections exist between the different subdivisions of the CN V sensory nuclei and the reticular formation

Answer 564

The mesencephalic nucleus mediates proprioception and deep sensation from the masticatory, facial, and extraocular muscles

Answer 565

The nucleus extends inferiorly into the posterior pons as far as the main sensory nucleus

Answer 566

It receives its input from ascending branches of the sensory root, and it serves light touch from the skin and mucous membranes

Answer 567

in the pons, lateral to the motor nucleus. It is continuous with the mesencephalic nucleus (above) and with the spinal nucleus (below)

Answer 568

upon entering the pons, divides into an ascending tract and a descending tract. - The ascending tract terminates in the main sensory nucleus - the descending tract ends in the spinal nucleus

Answer 569

- The nucleus receives pain and temperature afferents from the descending spinal tract, which also carries cutaneous components of CN VII, CN IX, and CN X that serve sensations from the ear and external auditory meatus

Answer 570

extend through the medulla to C4 - The sensory fibers from the ophthalmic division of CN V (V 1) terminate in the most ventral portion of the spinal nucleus and tract - CN V (V 1) terminate in the most ventral portion of the spinal nucleus and tract - The fibers from the mandibular division (V3) end in the dorsal parts of the nucleus

Answer 571

in the spinal nudeus and tract in a rostral-caudal direction - Fibers from the perioral region are thought to terminate most rostrally in the nucleus; fibers from the peripheral face and scalp end in the caudal portion. The zone between them, the midfacial region, is projected onto the central portion of the nucleus

Answer 572

bilateral sensory loss in concentric areas of the face, with the sensory area surrounding the mouth in the center - If a patient verifies this distribution of sensory loss, the lesion is in the brainstem Conversely, sensory loss that follows the peripheral distribution of the trigeminal sensory divisions (ophthalmic, maxillary, and mandibular) indicates that the lesion lies in CN V after it exits the brainstem

Answer 573

- they relay sensory information to higher sensory areas of the brain - The axons cross the midline in the pons and ascend to the thalamus along the ventral and dorsal trigeminothalamic tracts - They terminate in the nerve cells of the ventral posteromedial nucleus of the thalamus - These cells, in turn, send axons through the internal capsule to the postcentral gyrus of the cerebral cortex.

Answer 574

The afferent limb of the oculocardiac reflex is mediated by the trigeminal nerve. Although the mechanism underlying the oculocardiac reflex is not known, the size and length of the trigeminal nucleus may suggest a physical etiology for the interaction between the trigeminal nerve and the vagus nerve ( CN X).

Answer 575

medial to the main sensory nucleus in the pons

Answer 576

- both cerebral hemispheres - reticular formation - red nucleus - tectum - medial logitudinal fasciculus - mesencephalic nucleus A monosynaptic reflex arc is formed by cells from the mesencephalic nucleus and the motor nucleus

Answer 577

The motor nucleus sends off axons that form the motor root, which eventually supplies: - the muscles of mastication (pterygoid, masseter, and temporalis) - tensor tympani muscle - tensor veli palatini muscle - mylohyoid muscle - anterior belly of the digastric muscle

Answer 578

- emerges from the upper lateral portion of the ventral pons - passes over the petrous apex - forms the trigeminal ganglion, and then divides into 3 branches

Answer 579

The trigeminal ganglion, also called the gasserian or semilunar ganglion, contains the cells of origin of all the CN V sensory axons

Answer 580

trigeminal ganglion

Answer 581

trigeminal ganglion

Answer 582

- The crescent -shaped ganglion occupies a recess in the dura mater posterolateral to the cavernous sinus - This recess, called the Meckel cave, is near the apex of the petrous part of the temporal bone in the middle cranial fossa - Medially, the trigeminal ganglion is close to the ICA and the posterior cavernous sinus.

Answer 583

The trigeminal ganglion occupies a recess in the dura mater posterolateral to the cavernous sinus. This recess, called the Meckel cave, is near the apex of the petrous part of the temporal bone in the middle cranial fossa

Answer 584

The 3 divisions ofCN V are the ophthalmic (V1), the maxillary (V2), and the mandibular (V3).

Answer 585

The ophthalmic division enters the cavernous sinus lateral to the ICA and courses beneath CN III and CN IV

Answer 586

- Within the sinus, it gives off a tentorial-dural branch * which supplies sensation to the cerebral vessels, dura mater of the anterior fossa, cavernous sinus, sphenoid wing, petrous apex, Meckel cave, tentorium cerebelli, falx cerebri, and dural venous sinuses

Answer 587

CN V1 passes into the orbit through the superior orbital fissure and divides into 3 branches: frontal, lacrimal, and nasociliary

Answer 588

- supraorbital and supratrochlear nerves - which provide sensation to the medial portion of the upper eyelid and the conjunctiva, forehead, scalp, frontal sinuses, and side of the nose

Answer 589

According to common teaching, the supratrochlear nerve exits the orbit 17 mm from midline, whereas the supraorbital nerve exits at 27 mm from midline, through either a notch or a true foramen

Answer 590

- lacrimal gland and the neighboring conjunctiva and skin

Answer 591

It was formerly suggested that postganglionic parasympathetic lacrimal secretory fibers, arising in the pterygopalatine ganglion, were carried to the lacrimal gland via a zygomaticotemporal connection with the lacrimal nerve. However, it is now thought more likely that the gland receives its parasympathetic supply directly from the retro-orbital plexus

Answer 592

Occasionally, the lacrimal nerve exits the orbit via a lacrimal foramen to supply the lateral forehead. Otherwise, that area is supplied by branches of the supraorbital nerve

Answer 593

- nasal branches - infratrochlear branch - long ciliary nerves. - short ciliary nerves - The CN V fibers pass through the ciliary ganglion to join the nasociliary nerve ( The ciliary nerves also contain postganglionic parasympathetic fibers from the ganglion to the pupillary sphincter and the ciliary muscle)

Answer 594

The trigeminal nerve, like other sensory nerves, interacts with its innervated tissues. In the cornea, sensory innervation is important for corneal homeostasis, and loss of sensation leads to neurotrophic keratopathy.

Answer 595

middle and inferior turbinates, septum, lateral nasal wall, and tip of the nose

Answer 596

lacrimal drainage system, the conjunctiva, and the skin of the medial canthal region

Answer 597

carry sensory fibers from the ciliary body, the iris, and the cornea and provide sympathetic innervation to the dilator muscle of the iris

Answer 598

short ciliary nerves

Answer 599

The maxillary division leaves the trigeminal ganglion to exit the skull through the foramen rotundum, which lies below the superior orbital fissure

Answer 600

- courses through the pterygopalatine fossa into the inferior orbital fissure - then passes through the infraorbital canal as the infraorbital nerve - After exiting the infraorbital foramen, CN V2 divides into an inferior palpebral branch supplying the lower eyelid, a nasal branch for the side of the nose, and a superior labial branch for the upper lip. - The teeth, maxillary sinus, roof of the mouth, and soft palate are also innervated by branches of the maxillary division

Answer 601

After exiting the infraorbital foramen, CN V2 divides into an inferior palpebral branch supplying the lower eyelid, a nasal branch for the side of the nose, and a superior labial branch for the upper lip - The teeth, maxillary sinus, roof of the mouth, and soft palate are also innervated by branches of the maxillary division

Answer 602

- The afferent pathway is provided by the first and second divisions of CN V. - The efferent path proceeds from the lacrimal nucleus (close to the superior salivary nucleus) via CN VII (nervus intermedius), through the geniculate ganglion, the greater superficial petrosal nerve, and the nerve of the pterygoid canal (where it is joined by sympathetic fibers from the deep petrosal nerve). - The nerve then passes to the pterygopalatine ganglion, where it synapses with postganglionic fibers. These fibers reach the lacrimal gland directly, via the retro-orbital plexus of nerves (particularly CN V1 ). The fibers carry cholinergic and vasoactive intestinal polypeptide (VIP)-ergic fibers to the gland.

Answer 603

sensory and motor

Answer 604

foramen ovale

Answer 605

- provides motor input for the masticatory muscles | - Sensation is supplied to the mucosa and skin of the mandible, lower lip, tongue, external ear, and tympanum

Answer 606

in the floor oft he fourth ventricle, beneath the facial colliculus, in the caudal pons. Fibers of CN VII pass over or loop around the CN VI nucleus and exit in the cerebellopontine angle. The medial longitudinal fasciculus lies medial to the CN VI nucleus

Answer 607

The fascicular portion of the nerve runs ventrally through the paramedian pontine reticular formation and the pyramidal tract and leaves the brainstem in the pontomedullary junction

Answer 608

Cranial nerve VI takes a vertical course along the ventral face of the pons and is crossed by the anterior inferior cerebellar artery. It continues through the subarachnoid space along the surface of the clivus, surrounded by the Batson venous plexus, to perforate the dura mater below the crest of the petrous portion of the temporal bone, approximately 2 em below the posterior clinoid process. It then passes intradurally through or around the inferior petrosal sinus and beneath the petroclinoid (Gruber) ligament through the Dorello canal, where it enters the cavernous sinus. This long route, especially along the surface of the clivus and beneath the petroclinoid ligament, is responsible for this nerve's susceptibility to stretch injury leading to paresis in the context of increased intracranial pressure. In the cavernous sinus, CN \Ir uns below and lateral to the carotid artery and may transiently carry sympathetic fibers from the carotid plexus. It passes through the superior orbital fissure within the annulus of Zinn and innervates the lateral rectus muscle on its ocular surface.

Answer 609

second branchial arch

Answer 610

It is a complex mixed sensory and motor nerve. The motor root contains special visceral efferent fibers that innervate the muscles of facial expression

Answer 611

nervus intermedius | - contains special visceral afferent, general somatic afferent, and general visceral efferent fibers

Answer 612

- convey the sense of taste from the anterior twothirds of the tongue - terminate centrally in the nucleus of the tractus solitarius

Answer 613

- convey sensation from the external auditory meatus and the retroauricular skin - centrally, they enter the spinal nucleus of CN V.

Answer 614

- provide preganglionic parasympathetic innervation by way of the sphenopalatine and submandibular ganglia to the lacrimal, submaxillary, and sublingual glands

Answer 615

The motor nucleus of CN VII is a cigar-shaped column, 4 mm long, located in the caudal third of the pons. It is ventrolateral to the CN VI nucleus, ventromedial to the spinal nucleus of CN V, and dorsal to the superior olive

Answer 616

- Four distinct subgroups within the nucleus innervate specific facial muscles; - the ventral portion of the intermediate group probably supplies axons to the orbicularis oculi - The part of the nucleus supplying the upper half of the face receives corticobulbar input from both cerebral hemispheres - The lower half of the face is influenced by corticobulbar fibers from the opposite cerebral hemisphere

Answer 617

Fibers from the motor nucleus course dorsomedially to approach the floor of the fourth ventricle and then ascend immediately dorsal to the CN VI nucleus. At . the rostral end of the CN VI nucleus, the main facial motor fibers arch over its dorsal surface (forming the internal genu of CN VII) and then pass ventrolaterally between the spinal nucleus of CN V and the CN VII nucleus to exit the brainstem at the pontomedullary junction.

Answer 618

The bulge formed by the CN VII genu in the floor of the fourth ventricle is the facial colliculus

Answer 619

The sensory nucleus ofC N VII is the rostral portion of the tractus solitarius, sometimes known as the gustatory nucleus. It lies lateral to the motor and parasympathetic nuclei in the caudal pons

Answer 620

Sensations of taste from the anterior two-thirds of the tongue are carried by special visceral afferent fibers to this nucleus. The impulses travel along the lingual nerve and chorda tympani; the cell bodies for these impulses are located in the geniculate ganglion. The impulses eventually reach the brain through the nervus intermedius

Answer 621

Cranial nerve VII, the nervus intermedius, and CN VIII (the acoustic nerve) pass together through the lateral pontine cistern in the cerebellopontine angle and enter the internal auditory meatus in a common meningeal sheath. Cranial nerve VII and the intermedius nerve then enter the fallopian canal, the longest bony canal traversed by any cranial nerve (30 mm).

Answer 622

fallopian canal (30 mm)

Answer 623

- After passing anterolaterally for a short distance known as the labyrinthine segment - the nerves bend sharply at the geniculate ganglion and are then directed dorsolaterally past the tympanic cavity. This 90° bend, known as the tympanic segment, is the external genu of CN VII - The third segment of the nerve, the mastoid segment, is directed straight down toward the base of the skull.

Answer 624

the nerves bend sharply at the geniculate ganglion on the fallopian canal and are then directed dorsolaterally past the tympanic cavity. This 90° bend, known as the tympanic segment, is the external genu of CN VII

Answer 625

Two parasympathetic branches from the superior salivatory and lacrimal nuclei leave the nerve at the tympanic segment: the greater superficial petrosal nerve and a small filament that joins the inferior petrosal nerve.

Answer 626

stapedius nerve

Answer 627

chorda tympani

Answer 628

at the stylomastoid foramen

Answer 629

after CN VII exits the skull at the stylomastoid foramen, it separates into a large temporofacial division and a small cervicofacial division between the superficial and deep lobes of the parotid gland This area of branching is known as the pes anserinus.

Answer 630

- temporal (frontal ?) - zygomatic - buccal

Answer 631

The cervicofacial division is the origin of the marginal mandibular and calli branches anastomoses and branching patterns are numerous

Answer 632

- upper half of the -orbicularis oculi | - frontalis, corrugator supercilii, and pyramidalis muscles

Answer 633

- lower half of the orbicularis oculi

Answer 634

- The temporal (or frontal) branch of the facial nerve crosses the zygomatic arch as one or multiple "twigs" inside the deep layers of the temporoparietal fascia. - The nerve is fairly superficial as it crosses the zygomatic arch at the junction of the anterior one-third and posterior two-thirds of the arch - It then enters the more superficial layer of the temporoparietal fascia while staying below the superficial musculoaponeurotic system (SMAS) - A good approximation of the course of the nerve across the zygomatic arch follows the point at which a line between the tragus and the lateral eyelid commissure is bisected by a line that begins at the earlobe

Answer 635

The nerve can be injured in the context of perizygomatic or temple surgical approaches, such as Tenzel or Mustarde semicircular flap reconstruction of the eyelid, temporal artery biopsy, and cosmetic forehead and midface surgery.

Answer 636

originates in the superior salivatory nucleus and the lacrimal nucleus, both of which lie posterolateral to the motor nucleus and probably receive afferent fibers from the hypothalamus These preganglionic parasympathetic fibers pass peripherally as part of the nervus intermedius and divide into 2 groups near the external genu of CN VII. The lacrimal group of fibers passes to the pterygopalatine ganglion in the greater superficial petrosal nerve. The salivatory group of fibers projects through the chorda tympani nerve to the submandibular ganglion to innervate the submandibular and sublingual salivary glands.

Answer 637

- probably from the hypothalamus | - olfactory system

Answer 638

The hypothalamic fibers reaching the lacrimal nucleus may mediate emotional tearing, and there is supranuclear input from the cortex and the limbic system

Answer 639

- Reflex lacrimation is controlled by afferents from the sensory nuclei of CN V.

Answer 640

- extends forward on the anterior surface of the petrous temporal bone to join the deep petrosal nerve (sympathetic fibers) and form the nerve of the pterygoid canal - This nerve enters the pterygopalatine fossa; joins the pterygopalatine ganglion; and gives rise to unmyelinated postganglionic fibers that innervate the globe, lacrimal gland, glands of the palate, and nose - Those parasympathetic fibers destined for the orbit enter it via the superior orbital fissure, along with branches of the ophthalmic nerve (CN V 1) - Here, they are joined by sympathetic fibers from the carotid plexus and form a retro-orbital plexus of nerves, whose rami oculares supply orbital vessels or enter the globe to supply the choroid and anterior segment structures. Some of these fibers enter the globe directly; others enter via connections with the short ciliary nerves. The rami oculares also supply the lacrimal gland

Answer 641

an interconnected series of venous channels located just posterior to the orbital apex and lateral to the sphenoidal air sinus and pituitary fossa

Answer 642

* the ICA surrounded by the sympathetic carotid plexus * CN III, CN IV, and CN VI * the ophthalmic and maxillary divisions of CN V

Answer 643

cavernous, superior sagittal, transverse, straight, sigmoid, petrosal

Answer 644

internal jugular veins

Answer 645

The major arteries supplying the brain are the right and left I CAs (which distribute blood primarily to the rostral portion of the brain) and the right and left vertebral arteries (which join to form the basilar artery). The basilar artery distributes blood primarily to the brainstem and the posterior portion of the brain. These arteries interconnect at the base of the brain at the circle of Willis

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