Test 43   (embryology)

1. The following are true:

a. the retinal blood vessels reach the ora serrata after birth

b. the nasal retina is vascularised before the temporal retina

c. the hyaloid vascular system disappears in the third trimester

d. the retinal artery is a branch of the hyaloid artery

e. Bergmeister papillae is hyaloid artery remnant found on the 
    optic disc

Answera.F   b.T   c.T   d.F   e.T
The retinal blood vessels reach the ora serrata at about 39 weeks gestation.
The temporal retina is further from the optic disc and therefore takes a longer time for the vascularization to complete.

2. The following are true about the embryology of the eye:

a. closure of the optic cup begins posteriorly

b. the choroid is the first in the body to produce melanin

c. macular development begins in the fifth months of gestation

d. macular development is not complete until after birth

e. the primary vitreous forms the bulk of the vitreous in 
    developed eye

Answera.F   b.F   c.T   d.T   e.F
Closure of the cup begins centrally.
The RPE is the first in the body to produce melanin.
The secondary vitreous forms the bulk of the vitreous.
 

3. With regard to posterior embryology:

a. the tertiary vitreous forms the zonules

b. myelinated optic disc contains schwann cells

c. pigmentation of the choroid begins anteriorly

d. the hyaloid artery is derived from the mesoderm

e. the outer layer of the invaginated optic cup forms the 
    photoreceptors

Answera.T   b.F   c.F   d.T   e.F
Mylinated optic disc contain oligodendrocytes.
Pigmentation of the choroid begins posteriorly.
The outer layer of the invaginated optic cup forms the RPE
 

4. The hyaloid artery:

a. comes off the dorsal ophthalmic artery

b. forms part of the vascula propria lentis

c. Cloquet's canal is a a remnant

d. regresses after birth

e. communicates freely with the choridal circulation through 
    development.

Answera.T   b.T   c.F   d.F   e.F
Blood in the hyaloid artery ceases in the 7th month and the artery disappears in the eight months.
The remnants of the hyaloid artery are Bergmeister papillae and Mittendorf's dot.

5. The following are true:

a. the conjunctival epithelium is derived from the mesoderm

b. the maxillary process forms the lower eyelid

c. the Schlemm canal is present in the first trimester

d. the drainage of aqueous through the trabecular meshwork 
    begins at 6 months gestation age

e. the cilliary epithelium is derived from the mesoderm

Answera.F   b.T   c.T   d.T   e.F
The conjunctival epithelium is derved from the ectoderm.
The ciliary epithelium is derived from the neuroectoderm.