Lecture 23+24 +DLA 25

Question 1

contents of the superior orbital fissure

Answer 1

CN III, IV, V(1), and the superior ophthalmic v.

Question 2

contents of the inferior orbital fissure

Answer 2

V(2), zygomatic nerve, inferior ophthalmic v, infraorbital a. and v.

Question 3

contents of the optic canal

Answer 3

CN II and ophthalmic a.

Question 4

development of the eye

Answer 4

originally develop as a diverticulum of the forebrain neural tube

the diverticulum becomes an optic stalk and near surface ectoderm forms the optic cup

invagination of the optic cup will form the retinal fissure

Question 5

development of the optic N. (II)

Answer 5

the optic nerve develops from the optic stalk

Question 6

sclera and choroid development

Answer 6

both develop from mesenchyme tissue surrounding the optic cup

Question 7

corneal development

Answer 7

corneal epithelium comes from skin ectoderm

fibrous stroma from the mesodermal capsule covering the optic cup

corneal endothelium from NCS

Question 8

Iris and ciliary body development

Answer 8

Iris = rim of the optic cup

ciliary body = from the optic disk

hyaloid A becomes the central A of the retina

Question 9

keyhole pupil

Answer 9

results due to the incomplete closure of the retinal fissure

defect can extend to the ciliary and retina

Question 10

development of the retina

Answer 10

develops from two layers of the optic cup

pigment layer (outer) 
neural layer (inner)

Question 11

development of the lens

Answer 11

develops from the lens vesicle (surface ectoderm)

Question 12

cataracts

Answer 12

may be congenital due to teratogenic agents / infections

or occur later in life due to aging, trauma, radiation, etc

can be removed surgically

Question 13

innervation of the eye muscles

Answer 13

superior oblique = trochlear n. (CN IV)
lateral rectus = abducens n. (CN VI)

all other extraocular muscles and LPS by oculomotor n. (CN III)

Question 14

muscles that elevate eye

Answer 14

superior rectus

inferior oblique

Question 15

muscles that depress or lower the eye

Answer 15

inferior rectus

superior oblique

Question 16

Muscle testing - H test

LR, SR, IR, MR, IO, and SO

Answer 16

lateral rectus = abduction (out) 
superior rectus = out and up 
inferior rectus = out and down 
medial rectus = in 
inferior oblique = in and then up 
superior oblique = in then down

Question 17

layer of the eye

Answer 17

1. corneoscleral coat
   outer fibrous layer (cornea and sclera)

2. vascular coat (uvea) 
middle layer (iris, ciliary body, and choroid) 

3. retina
   inner layer

Question 18

about the corneoscleral coat

Answer 18

anterior surface of the eye
avascular

function: refraction of light

Question 19

layers of the cornea

Answer 19

1. corneal epithelium
   strat squamous
   can regenerate
   lots of free nerve endings

2. bowman's membrane 
homogenous layer of epithelium 
collagen fibers are random
provides strength and acts as barrier to infection 
does NOT regenerate  

3. corneal stroma
corneal fibroblasts (keratocytes)  

4. Descemet’s membrane
   meshwork of collagen fibers and pores
   can regenerate
   thickens as we age

5. corneal endothelium 
metabolic exchange 
regulates water (lots of Na/K pumps) 
simple squamous 
limited regeneration

Question 20

histology of the sclera

Answer 20

thick fibrous layer (DCT)

flat collagen bundles with networks of elastic fibers

lamina cribosa: allow for entering and exiting of nerves/vessels.
the optic disk overlies this (blind spot)

Question 21

3 layers of the sclera?

Answer 21

1. external episcleral layer
   loose CT
2. middle layer substantia propria (tenon’s capsule)
   investing fascia of eye
   dense network of collagen fibers
   tendons attach here
3. inner suprachoroidal lamina
   thinner collagen fibers and elastic fibers

Question 22

about the vascular coat (uvea)

Answer 22

features: CT, blood vessels, and pigmented cells

1. iris
   anterior part
   forms a contractile diaphragm in front of lens
   pupil
2. ciliary body
   between the iris and choroid
   ciliary processes and ciliary muscle
3. choroid
   posterior portion
   lies between sclera and retina

Question 23

histology of choroid

Answer 23

pigmented, dark brown vascular layer

functions: blood supply and absorption of scattered light.

2 layers:

1. choriocapillary layer
   inner vascular layer
   fenestrated capillaries
2. Bruch’s membrane (lamina vitrea)
   forms the basal lamina of RPE cells
   has 5 layers
   hyaline membrane

Question 24

about the iris

Answer 24

arises from the anterior border of ciliary body
contractile diaphragm

discontinuous layer of fibroblasts and melanocytes
highly vascular Ct stroma

Question 25

histology of the ciliary muscle

Answer 25

ciliary muscle = smooth muscle (parasympathetic) | fibers spread in all directions

Question 26

histology of the ciliary processes

Answer 26

vascular covered by double layer of columnar epithelium zonular fibers = fibrillin function: produce and anchor zonular fibers that form the suspensory ligament of the lens secretion of aqueous humor part of the blood-aqueous barrier

Question 27

Corneoscleral limbus (junction)

Answer 27

transition zone between the cornea and sclera Bowman's capsule ends generate and maintain corneal epithelium

Question 28

Glaucoma

Answer 28

increased intraocular pressure ``` symptoms: headache eye pain loss of vision vomiting Halo around light ``` signs: vision decreases peripherally redness raised pressure

Question 29

vitreous body

Answer 29

transparent jelly like substance mainly collagen fibrils and GAGs (hyaluronan) has spindle shaped cells = hyalocytes maintains eye shape and keeps retina in place change in vitreous humor and lead to retinal detachment

Question 30

histology of retina

Answer 30

2 layers 1. neural retinal (inner layer of optic cup) non-photosensitive anterior to ora serrata photosensitive is posterior to ora serrata 2. retinal pigment epithelium (RPE) outer layer of optic cup

Question 31

where does retinal detachment most likely occur?

Answer 31

the junction of pigment epithelial layer and the rods & cones layer

Question 32

rods

Answer 32

cylindrical outer segment visual pigment is rhodopsin (lack of this leads to night blindness; via no Vit A) black and white vision highest density outside of fovea centralis

Question 33

cones

Answer 33

thicker and shorter than the rods conical outer segment visual pigment is iodopsin color vision largest density in fovea centralis

Question 34

Retinal Pigment Epithelium

Answer 34

single layer of cuboidal cells seen to have tight junctions (blood-retina barrier) basal lamina attached to Bruch's membrane ``` functions: absorption of light major component of blood-retina barrier active in visual pigment pathway vitamin A metabolism phagocytosis ```

Question 35

histology of the lens

Answer 35

biconvex avascular held in place by the zonular fibers 3 parts: 1. lens capsule thick basal lamina produced by anterior lens cells 2. subcapsular epithelium: single layer of cuboidal cells proliferate in the germinal layer 3. lens fibers thin and flattened loose organelles and accumulate proteins formed by epithelial cells in the germinal layer

Question 36

conjunctiva

Answer 36

stratified epithelium with goblet cells lines outside of eyelid secretes fluid into the eye

Question 37

glands of the eyelid

Answer 37

1. Meibomian glands sebaceous within tarsal plate delays the drying of tears 2. glands of Zeiss sebaceous glands associated with the eyelashes 3. glands of moll sweat glands at the lid margins