Anatomy of the Eye Flashcards

Question

Describe the palpebral conjunctiva?

Answer 1

It is richly vascular, extremely thin and strongly bounded to the tarsal plate

Answer 2

1. Marginal 2. Tarsal 3. Orbital

Answer 3

- Extends from the lid margin to about 2mm back of the lid upto the sulcus subtarsalis - Actually a transitional zone between skin and the conjunctiva proper - Lacrimal puncta open in the marginal zone

Answer 4

- It is transparent and lies loose over the underlying structures and thus can be moved easily - It is separated from the anterior sclera by episcleral tissue and tenon's capsule

Answer 5

•Arteries supplying the conjunctiva are derived from 3 sources. They are: 1. Marginal arcade of the eyelid 2. Peripheral arterial arcade of the eyelid 3. Anterior ciliary artery • The palpebral conjunctiva and the fornices are supplied by branches from the marginal and peripheral arcades of the artery

Answer 6

- The veins from conjunctiva drain into the venous plexus of eyelids which in turn drain into the superior and inferior ophthalmic veins. - A cicumcorneal zone of limbus drain into the anterior cilliary veins

Answer 7

1. lateral side drain into the periauricular lymph nodes 2. medial side drain the submandibular lymph nodes

Answer 8

•BULBAR CONJUNCTIVA: - long ciliary nerve - Naso ciliary nerve - Ophthalmic division of trigeminal nerve •SUP.PALPEBRAL AND FORNICEAL CONJUNCTIVA: -Frontal and lacrimal branches of ophthalmic division of trigeminal nerve

Answer 9

1. Conjunctivitis 2. Malignant lymphoma 3. Conjunctival papilloma

Answer 10

•Choroid •Ciliary body •Iris

Answer 11

The choroid, ciliary body and iris together form the uveal tract - this layer contains blood vessels Note: Pupil is the small opening in front of it

Answer 12

- is the vascular layer of the eye containing connective tissues - lying between the retina and the sclera - It is composed of an outer pigmented layer and an inner highly vascular layer

Answer 13

Provides oxygen and nourishment to the outer layers of the retina

Answer 14

The uveal tract - along with the ciliary body and iris

Answer 15

are branches of the ophthalmic artery and enter the eyeball without passing with the optic nerve.

Answer 16

- ciliary body is continuous posteriorly with the choroid, and anteriorly it lies behind the peripheral margin of the iris - is composed of the ciliary ring, the ciliary processes, and the ciliary muscle

Answer 17

The ciliary ring is the posterior part of the body - its surface has shallow grooves = the ciliary striae

Answer 18

The ciliary processes are radially arranged folds, or ridges, to the posterior surfaces of which are connected the suspensory ligaments of the lens

Answer 19

composed of meridianal and circular fibers of smooth muscle. - The meridianal fibers run backward from the region of the corneoscleral junction to the ciliary processes - The circular fibers are fewer in number and lie internal to the meridianal fibers.

Answer 20

is supplied by the parasympathetic fibers from the oculomotor nerve - After synapsing in the ciliary ganglion, the postganglionic fibers pass forward to the eyeball in the short ciliary nerves.

Answer 21

Contraction of the ciliary muscle, especially the meridianal fibers, pulls the ciliary body forward - This relieves the tension in the suspensory ligament, and the elastic lens becomes more convex - This increases the refractive power of the lens

Answer 22

• The suspensory ligaments are either taut or relaxed based on the action of the ciliary muscles. • The tension on the ligaments changes the shape of the lens, depending on the distance of the object being viewed. • This process is called "accommodation"

Answer 23

Colored part of the Eye • it is the most anterior portion of the vascular tunic • Made up of radial muscle & circular muscle • Controls the amount of light entering the eye • the opening in the middle of the iris is called the "pupil," which appears as the dark center of the eye.

Answer 24

Regulates the amount of light entering the eye so that there is enough light to stimulate the cones, but not enough to damage them

Answer 25

Circular > sphincter pupillae Radial > dilator pupillae Note: have opposite affects (antagonistic)

Answer 26

By contracting and relaxing these muscles the pupil can be constricted and dilated

Answer 27

Parasympathetic nerve impulse Circular muscles contract Radial muscles relax Pupil constricts Less light enters eye

Answer 28

Sympathetic nerve impulse Circular muscles relax Radial muscles contract Pupil dilates More light enters eve

Answer 29

1. The sphincter pupillae - supplied by parasympathetic fibers from the oculomotor nerve > After synapsing in the ciliary ganglion, the postganglionic fibers pass forward to the eyeball in the short ciliary nerves. 2. The dilator pupillae - is supplied by sympathetic fibers > which pass forward to the eyeball in the long ciliary nerves.

Answer 30

1. The sphincter pupillae - constricts the pupil in the presence of bright light and during accommodation. 2. The dilator pupillae - dilates the pupil in the presence of light of low intensity or in the presence of excessive sympathetic activity such as occurs in fright.

Answer 31

under control of the autonomic nervous system - Sympathetic Nerve > pupil dilation - Parasympathtic Nerve > pupil constriction Note: The drug atropine inhibits the parasympathetic nerve, causing pupil to dilate

Answer 32

Stimulus = more light > receptor = rods and cones > sensory neuron > coordinator = brain > motor neuron > effector = iris muscles > response = pupil constricts

Answer 33

1. The anterior chamber - in front of the iris 2. The posterior chamber - immediately behind the iris > These two chambers which communicate through the pupil are filled with clear aqueous humour. 3. The vitreous cavity - filled by gel-like structure

Answer 34

Filled with aqueous humor • produced by ciliary body • continually drained by scleral venous sinus • replaced every 90 minutes • drainage of aqueous humor from eye to bloodstream

Answer 35

-increased intraocular pressure - that could produces blindness - problem with drainage of aqueous humor

Answer 36

• Clear liquid produced by the ciliary body and secreted onto the posterior chamber • flows into the anterior chamber through the pupil. • It is absorbed in the sclera venous sinus, the Schlemm's canal - a circular venous channel at the junction between the cornea and the iris

Answer 37

The pressure within the eye is maintained at a steady level by continuous formation & drainage of aqueous. - The intraocular pressure is normally 10 - 21 mmHg - High IOP almost always due to an obstruction of aqueous outflow > increased IOP is ocular hypertension

Answer 38

> Aqueous is secreted by the ciliary epithelium into the posterior chamber > flows through anterior chamber (through the pupil) > drained through the anterior chamber angle

Answer 39

1. Supplies nutrients to avascular cornea and lens 2. maintains intraocular pressure

Answer 40

If the normal cycle of production and absorption is disturbed so that the amount of fluid increases then intraocular pressure will increase - This condition is called Glucoma and can lead to a variety of visual problems E.g. such as blindness due to compression of the retina and its blood supply

Answer 41

biconvex optically transparent intraocular structure - The crystalline lens is the only structure continuously growing throughout the life - Separates the anterior 1/5th of the eyeball and posterior 4/5th - Changeable refractive media. - contains Capsule, epithelium and lens fibers. Note: Congenital anomalies and effect of systemic diseases are seen within the lens

Answer 42

Opacity of lens

Answer 43

1. focuses image on retina > suspensory ligament and ciliary muscles control curvature to focus images on retina 2. divides interior of eyeball into anterior cavity and posterior cavity

Answer 44

Refers to the ability of the eye to alter its focus so that clear images of both close and distant objects can be formed on the retina - The lens shape can be altered by suspensory ligaments and the ciliary muscles : This adjusts the focus

Answer 45

- Light rays are almost parallel so do not need much refraction to focus onto the retina. - The lens therefore needs to be thin and "weak" (i.e. have a long focal length). > Flattened (less convex) for distant images

Answer 46

- Light rays are likely to be diverging, so need more refraction to focus them onto the retina. - The lens therefore needs to be thick and "strong" (i.e. have a short focal length). > Rounded (more convex) for close images

Answer 47

• posterior to lens cavity filled with vitreous humor (jellylike) • Holds retina in place • formed once during embryonic life Clinical correlates: floaters are debris in vitreous of older individuals

Answer 48

Posterior ¾ of eye ball only anterior margin - ora serrata retina (rods only)

Answer 49

attachment of optic nerve / blind spot - no photoreceptors

Answer 50

near the middle of the retina - highest concentration of cones - region of highest visual acuity

Answer 51

derived from the central retinal artery and vein, and from the choroid. - The retinal vessels enter and leave the eye through the optic nerve and run in the nerve fibre layer. Note: A major arterial and venous branch, forming an 'arcade', supplies each of the retinal quadrants

Answer 52

Contains photoreceptor cells (rods and cones) and associated interneurones and sensory neurones.

Answer 53

- superficial layer of pigment epithelium (melanin) - non-visual portion - absorbs stray light & helps keep image clear deeper layer of neurons

Answer 54

- rods/cones are photoreceptor layer - bipolar neuron layer - ganglion cell layer

Answer 55

rod shaped cells • shades of gray in dim light • nocturnal vision - black and white vision, great sensitivity in dim light • 120 million rod cells • discriminates shapes & movements, distributed along periphery of retina

Answer 56

cone shaped cells • sharp, color vision at all higher light intensities • 6 million • Fovea centralis - widest distribution at center of retina

Answer 57

• This is the process by which light initiates a nerve impulse. • Detection of light is carried out on the membrane disks of a rod cell - These disks contain thousands of molecules of rhodopsin (photoreceptor molecule)

Answer 58

1. Definition Rhodopsin is a pigment of the photoreceptor cells in the retina. 2. Function It is responsible for the first events in the perception of light. 3. Composition It is comprised of Opsin (a protein with 7 transmembrane helices) and Retinal (photoreactive chromophore)

Answer 59

1. Opsin (membrane bound protein) 2. Retinal (covalently-bound prosthetic group) • Retinal is made from vitamin A • Retinal is the light sensitive part - exists in 2 forms: cis and trans forms

Answer 60

• In the dark retinal is in the cis form. • When it absorbs a photon of light it quickly switches to the trans form. • This changes the shape of the opsin protein - a process called bleaching

Answer 61

The reverse reaction (trans to cis) - requires an enzyme reaction and is very slow (taking a few minutes) - This process requires ATP, as rhodopsin has to be resynthesised

Answer 62

> Bleaching of the rhodopsin in a rod cell > Alters the permeability of the membrane to Na+ > nerve impulse > sensory neurone in the optic nerve > to the brain

Answer 63

• Rhodopsin controls sodium channels • Rhodopsin with cis retinal opens sodium channels (absence of light) • Rhodopsin with trans retinal closes sodium channels (light)

Answer 64

• In the dark the channel is open - Na+ flow in can cause rod cells to depolarise. - Therefore in total darkness, the membrane of a rod cell is polarised • Therefore rod cells release neurotransmitter in the dark • However the synapse with bipolar cells is an inhibitory synapse i.e. the neurotransmitter stops impulse

Answer 65

As cis retinal is converted to trans retinal, the Na+ channels begin to close less neurotransmitter is produced. If the threshold is reached, the bipolar cell will be depolarised forms an impulse which is then passed to the ganglion cells and then to the brain

Answer 66

1. Shape : Outer segment is rod shaped 2. Number : 109 cells per eye 3. distributed : throughout the retina, so used for peripheral vision. 4. Sensitivity: Good sensitivity 5. Type : Only 1 type > monochromatic vision 6. Vision : Many rods connected to one bipolar cell > poor acuity = poor resolution

Answer 67

1. Shape : Outer segment is cone shaped 2. Number : 106 cells per eye 3. Distribution : found mainly in the fovea, so can only detect images in centre of retina. 4. Sensitivity : Poor sensitivity 5. Types : 3 types (R, G & B) - colour vision 6. Vision : Each cone is connected to one bipolar cell > good acuity = good resolution

Answer 68

Each have a different form of opsin (they have the same retinal) • 3 forms of rhodopsin are sensitive to different parts of the spectrum - 10% red cones - 45% blue cones - 45% green cones

Answer 69

Coloured light will stimulate these 3 cone cells differently - by comparing the nerve impulses from the 3 kinds of cones the brain can detect any colour - Red light > stimulates R cones - Yellow light > stimulates R and G cones equally - Cyan light > stimulates B and G cones equally - White light > stimulates all 3 cones equally

Answer 70

• When we look at something the image falls on the fovea and we see it in colour and sharp detail. Objects in the periphery of our field of view are not seen in colour, or detail. • The fovea has high density of cones. • Each cone has a synapse with one bipolar cell and one ganglion -> each cone sends impulses to the brain about its own small area of the retina > high visual acuity

Answer 71

> Ganglion cells > bipolar cells > photoreceptor cells

Answer 72

> Photoreceptor cells > bipolar cells > ganglion cells > optic nerve

Answer 73

• The ganglion cell axons in the retinal nerve fibre layer make a right- angled turn into the optic nerve at the optic • disc, which has no photoreceptors and corresponds to the physiological blind spot. • Behind the eyeball these axons become myelinated. • Here the optic nerve is surrounded by cerebrospinal fluid in an anterior extension of the subarachnoid space and is protected by the same membranous layers as the brain.

Answer 74

› contains around 1.2 million nerve fibers, which are axons of the retinal ganglion cells. •1 mm in the globe. • 25 mm in the orbit. •9 mm in the optic canal. • 16 mm in the cranial space • Partial decussation occurs and about 53% of the fibers cross to form the optic tracts.

Answer 75

1. Bipolar cell, lies within the retina. 2. Ganglion cell, synapse in lateral geniculate body 3. Third neuron terminates in visual cortex

Answer 76

1. Left occipital lobe receives visual images from nasal 1/2 of the right eye and temporal 1/2 of the left eye 2. Right occipital lobe receives visual images from nasal 1/2 of the left eye and temporal 1/2 of the right eye

Answer 77

- Light must have a clearly pathway to be clearly focused on the sensory receptors of the retina i.e. Clear cornea, anterior chamber, lens and vitreous cavity - The Refractive power of the eye is about 58 - 62 diopters.

Anatomy of the Eye Flashcards

(101 cards)