13. Eye Development (KEIM)

Question 1

What gives rise to the dilator pupillae and sphincter pupillae Ms.?

Answer 1

The neuroectoderm of the optic cup, coming from the anterior epithelial cells of the iris.

(Smooth muscle.)

These are the ONLY two muscles to arise from neuroectoderm as well.

Question 2

What artery does the hyaloid artery come off of?

What is supplied by the hyaloid artery?

Answer 2

Hyaloid artery comes off of the opthalmic artery (branch of the internal carotid).

It supplies the inner layer of the optic cup, the lens vesicle, and the mesenchyme of the cavity of the optic cup.

Question 3

What do the hyaloid vessels give rise to in the adult?

Answer 3

The central A. and V. of the retina.

Question 4

What causes retinal detachment?

Answer 4

The inner and outer layers of the retinal cup fail to fuse, causing the neuroretina to become detached more easily from the pigmented layer - which is attached to the choroid.

(Occurs more in pts with Marfan’s or Downs. Occurs in trauma.)

Question 5

What is the choroid derived from?

Answer 5

Neural crest cell derived mesenchyme.

Question 6

Describe development of the lens.

Answer 6

The lens vesicle has an anterior and a posterior part.

The anterior part forms the lens epihelium .

The posterior wall cells elongate and form the primary lens fibers, eliminating the space between the anterior and posterior walls.

The primary lens fibers elongate, lose their nuclei, and move to the edges of the lens, becoming secondary lens fibers.

(Secondary lens fibers continue to form, but primary lens fibers must last a lifetime.)

Question 7

What three things is the cornea made of?

Answer 7

Surface ectoderm.

Mesenchyme from the mesoderm continuous with the sclera.

Neural crest cells from the optic cup and corneal epithelium.

Question 8

What major signaling factor is involved in eye development?

Answer 8

PAX6

Question 9

What structures of the eye are derived from surface ectoderm?

Answer 9

Lens of the eye and corneal epithelium.

Question 10

What do the hyaloid blood vessels differentiate from?

Answer 10

The mesenchyme that came in through the slit in the bottom of the optic stalk differentiates into the hyaloid blood vessles

Question 11

What is the substantia propria?

Answer 11

The transparent CT of the cornea and mesothelium of the anterior chamber.

Aka the stroma of the cornea.

Question 12

Describe the formation of the lens placode.

Answer 12

The optic vesicle, after pinching off from the forebrain, travels towards the surface ectoderm on the lateral side of the embryo’s developing head. When the optic vesicle arrives, it forms the optic cup. This optic cup induces differentiation of the obtic placode from the surface ectoder.

Question 13

What comes from the inner and outer layers of the optic cup respectively?

Answer 13

Inner layer (near to the lens vesicle) becomes the neuroretina.

Outer layer becomes the pigmented layer of the retina.

Question 14

What will the optic stalk differentiate into?

Answer 14

The axons of the optic nerve.

Question 15

What structures of the eye are derived from neural crest cells?

Answer 15

Choroid

Sclera

Corneal endothelium

Stroma of the iris

Question 16

Describe the formation of the lens vesicle.

Answer 16

Once the optic cup induces differentiation of the lens placode, it begins to form an invagination called the lens pit. That lens pit continues to invaginate until a lens vesicle is formed.

Question 17

What gives rise to the iris?

Answer 17

The rim of the optic cup.

(Neural crest cells give rise to the connective tissue of the iris. The rest is neuroectoderm.)

Question 18

What is the sclera derived from?

Answer 18

Neural crest cell derived mesenchyme external to the choroid.

Question 19

What structures of the eye are derived from neuroectoderm?

Answer 19

Retina

Posterior layers of the iris

Optic nerve

Ciliary body epithelium

Question 20

What is a coloboma?

Answer 20

Incomplete closure of the optic fissure. Creates a gap in either the retina (retinochoroidal coloboma) or the iris (coloboma of the iris).

Question 21

What does the optic cup differentiate into?

Answer 21

The retina

Epithelium of iris

Ciliary body.

Question 22

What is congenital glaucoma?

Answer 22

Elevation of intraocular pressure in neonates due to abnormal formation of the scleral venous sinus (canal of schlemm)

caused by CYP1B1 gene mutation, rubella infection

Question 23

What is the optic disc in the development of the eye?

Answer 23

Where the neuroectoderm of the retina (optic cup) is continuous with the optic stalk.

Question 24

What structures of the eye are derived from mesoderm?

Answer 24

Fibrous and vascular coats of the eye.

Question 25

What gives rise to the primary vitreous humor?

Answer 25

Nerual crest derived mesenchyme.

Question 26

What signal regulates retinal ganglion differentiation?

Answer 26

FGF

Question 27

Eye origination

Answer 27

wk 4

starts in prosencephalon, ends in diencephalin

starts as optic sulcus and then vesicle which becomes the optic cup, conected by stalk with a fissure forming along the length of the stalk

Question 28

What is Anridia?

Answer 28

lack of iris tissue or complete absence

arrested development at rim of optic cup at 8th wk

can have glaucoma, cataracts, etc.

Pax6 gene mutation

Question 29

Describe congenital cataracts

Answer 29

lens is opaque (whole eye opaque in glaucoma)

caused by genetics, rubella virus between 4-7wks

radiation, congenital galactosemia (2-3wks after birth as galatose from milk accumulates)

Question 30

What comes from prechordal mesenchyme?

Answer 30

Superior, inferior, medial and lateral rectuses

super and inferior oblique

Question 31

persistence of a hyaloid artery

Answer 31

doesn’t disintrigrate

no issues, but will see hyaloid artery and mittendorf spot, eye often microphthalmic

Question 32

What are the main teratogens

Answer 32

rubella-glaucoma, cataracts

toxoplasma gandii-micropthalmia

VEEV-micropthlamia

varicella-cataracts, microphtalmia, optic atrophy