Anatomy of the Eye and Orbit

Question 1

What are the 3 coats of the eyeball?

Answer 1

Fibrous coat
Vascular coat
Sensory coat

Question 2

What is included in the fibrous coat of the eyeball?

Answer 2

Cornea
Sclera

Question 3

What is included in the vascular coat of the eyeball?

Answer 3

Ciliary body
Iris
Choroid

Question 4

What is included in the sensory coat of the eyeball?

Answer 4

Optic nerve
Retina

Question 5

Describe the cornea

Answer 5

Anterior 1/6th which is transparent
Is a window to allow light rays to enter the eyeball

Question 6

Describe the sclera

Answer 6

Is the opaque posterior 5/6th
Gives attachments to muscles moving the eyeball

Question 7

Describe the ciliary body

Answer 7

Suspends the lens and produces the aqueous humor

Question 8

Describe the iris

Answer 8

Controls the diameter of the pupil and thereby controls the amount of light rays entering the eyeball

Question 9

Describe the choroid

Answer 9

Supplies blood to outer layers of the retina

Question 10

Describe the retina

Answer 10

Has light sensitive rods and cons which enables us to see

Question 11

What does the sensory coat contain?

Answer 11

Vitreous humor (VH) in posterior segment

Question 12

Describe the crystalline lens

Answer 12

Is transparent
Bio-convex structure which is suspended by zonules (suspensory ligaments) from ciliary body
It can change shape

Question 13

What are the 2 segments of the eye?

Answer 13

Anterior is in front of lens and Posterior segment is behind lens
Anterior - AH
Posterior - VH

Question 14

What is the function of the aqueous humor?

Answer 14

Helps maintain intraocular pressure
Watery fluid

Question 15

What is the function of the vitreous humor?

Answer 15

Transparent gel posterior to the lens and helps cushion retina
Prevents detachment

Question 16

Where is the anterior and posterior chambers?

Answer 16

Anterior - in front of iris
Posterior - behind iris but in front of lens (narrow)

Question 17

Describe the angle of anterior chamber

Answer 17

If blocked, the AH can’t be drained into trabecular meshwork on sclera
AH drains out of the Schlemm’s canal

Question 18

What 7 bones make up the bony orbit?

Answer 18

Frontal, sphenoid, lacrimal, ethmoid, maxillary, zygomatic, and palatine

Question 19

What are the 3 foramina of the orbit?

Answer 19

Optic foramen
Superior orbital fissure
Interior orbital fissure

Question 20

Describe orbital depth and support

Answer 20

AP length of eyeball - 24mm
AP length of orbit - 40mm
Orbital fats cushions the globe

Question 21

Describe the eyelids

Answer 21

Skin on outside and mucus membrane called conjunctivae on inside
Eyelashes with sebaceous glands
Muscles, hard palate to keep shape and oil secretory glands for tear film

Question 22

What are the oily secretory glands of the eyelids called?

Answer 22

Meibomian glands

Question 23

What are the muscles of the eyelids?

Answer 23

Orbicularis oculi
LPS - levator palpebrae superioris

Question 24

Where is the conjunctiva?

Answer 24

Is transparent - Covers surface of inner eyelids and loops back over the sclera
Not cover the cornea

Question 25

Describe the lacrimal apparatus

Answer 25

Lacrimal gland is situated on orbit laterally and ducts open into conjunctival sac During each blink eyelids spread tears evenly on surface of cornea Tears drain into punctae sitting over lacrimal bone where its reabsorbed Drain through nasolacrimal duct into inferior meatus of nasal cavity

Question 26

What is the nerve control of the lacrimal gland?

Answer 26

Parasympathetic - facial nerve

Question 27

What are the 2 types of ocular muscles?

Answer 27

Intrinsic (start and end in the eyeball) - control pupil diameter and helps alter lens curvature to enable to see Extrinsic - move the eye

Question 28

What are the intrinsic muscles of the eye?

Answer 28

Ciliaris muscle and constrictor pupillae - parasympathetic Dilator pupillae - sympathetic

Question 29

What are the 6 extrinsic muscles of the eye?

Answer 29

4 straight - medial, lateral, inferior, superior rectus 2 oblique - superior and inferior oblique

Question 30

Where do the extrinsic muscles arise from?

Answer 30

Recti muscles - from apex of orbit from an annular fibrous ring Superior oblique - roof of orbit posteriorly Inferior oblique - floor of oblique anteriorly

Question 31

What nerves supply the muscles of the eye?

Answer 31

Trochlear nerve supplies the SO Abducent nerve supplies the LR (lateral retcus) Everything else is the oculomotor nerve

Question 32

What is the origin and insertion of the LPS?

Answer 32

Origin - roof of orbit Insertion - upper eyelid

Question 33

What is the origin and insertion of the recti muscles?

Answer 33

Origin - tendinous ring Insertion - sclera anteriorly

Question 34

What is the origin an insertion of the inferior and superior obliques?

Answer 34

SO - origin is lesser wing of sphenoid and inserts in sclera posteriorly IO - origin is medial part of orbit floor and inserts in sclera posteriorly

Question 35

Describe the function of the optic nerve in the eyeball

Answer 35

Carries visual impulses from the eyeball and leaves through the optic foramen

Question 36

Describe the oculomotor nerve

Answer 36

Supplies all muscles going to eye except 2 and also supplies levator muscle of the eyelid Carrie parasympathetic fibres which synapse at ciliary ganglion in orbit

Question 37

What are some branches of the ophthalmic division of the trigeminal nerve?

Answer 37

Nasociliary nerve Frontal branch - largest branch Lacrimal branch - smallest branch

Question 38

Describe the ophthalmic artery

Answer 38

Large branch of ICA Supplies all structures in the orbit and also branches to nasal cavities and forehead Enters through the optic foramen with optic nerve

Question 39

Where does the central retinal artery supply?

Answer 39

Supplies inner layers of retina Travels within substance of optic nerve

Question 40

Where does the short posterior ciliary arteries supply?

Answer 40

Posterior part of the choroid and outer retina

Question 41

Where does the long posterior ciliary arteries supply?

Answer 41

The anterior choroid ciliary body and iris

Question 42

Describe an ophthalmoscope

Answer 42

Fundus picture Can see optic disc - start of optic nerve and physiological blind spot 4 quadrants - superonasal, inferonasal, supero-temporal, infero-temporal

Question 43

Describe venous drainage of the eye

Answer 43

Superior and inferior ophthalmic veins which drain into cavernous sinus - posterior to apex of orbit

Question 44

What are the cavernous sinus contents?

Answer 44

Loop of internal carotid artery and nerves Beside pituitary gland Layers of dura mater covered by endothelium

Question 45

What does the eye develop from?

Answer 45

Neurectodermal

Question 46

Where do optic vesicles grow out from?

Answer 46

From diencephalic part of neural tube towards surface ectoderm

Question 47

Describe the formation of the optic vesicles

Answer 47

Reach surface ectoderm - cells of surface ectoderm thicken - lens placode Lens placode pushes inwards causing optic vesicle to form an optic cup - 2 layers

Question 48

Describe the lens vesicle and optic cup

Answer 48

Lens vesicle looses connection with surface ectoderm Choroid fissure forms as blood vessels pass through fissure in inferior wall of optic cup

Question 49

What does surface ectoderm form?

Answer 49

Eyelids, conjuctiva, corneal epithelium

Question 50

What does mesenchyme form?

Answer 50

Forms choroid, stroma of cornea, sclera and extraocular muscles

Question 51

What does lens fibres form?

Answer 51

Epithelium of lens vesicle and later loose their nuclei