Chapter 20: EYe

Question 1

____ may occur if the choroid fissure fails to close. Normally, this fissure closes during the seventh week of development. When it does not, a cleft persists

Answer 1

Coloboma

Question 2

Although such a cleft is usually in the iris only ____ it may extend into the ciliary body, the retina, the choroid, and the optic nerve

Answer 2

coloboma iridis

Question 3

Mutations in the ____ gene have been linked with optic nerve colobomas and may play a role in the other types as well

Answer 3

PAX2

Question 4

The ____ may persist instead of being resorbed during formation of the anterior chamber

Answer 4

iridopupillary membrane

Question 4

Renal defects also occur with mutations in PAX2 as part of the ____

Answer 4

renal coloboma syndrome

Question 5

____cause the lens to become opaque during intrauterine life

Answer 5

Congenital cataracts

Question 6

many children born to mothers who had rubella [____] between the fourth and seventh weeks of pregnancy had cataracts

Answer 6

German measles

Question 7

If the mother is infected after the seventh week of pregnancy, the lens escapes damage, but the child may have hearing loss as a result of cochlear abnormalities. Because of the __ [measles, mumps, and rubella] vaccine, congenital rubella syndrome has been nearly eradicated in the United States

Answer 7

MMR

Question 8

____ [absence of the lens] and aniridia [absence of the iris are rare anomalies that result from disturbances in induction and development of tissues responsible for formation of these structures

Answer 8

Congenital aphakia

Question 8

The ____ may persist to form a cord or cyst. Normally, the distal portion of this vessel degenerates, leaving the proximal part to form the central artery of the retina

Answer 8

hyaloid artery

Question 9

ln ____, the eye is too small; the eyeball may be only two-thirds of its normal volume. Usually associated with other ocular abnormalities, can result from intrauterine infections, such as cytomegalovirus and toxoplasmosis

Answer 9

microphthalmia

Question 9

___ is absence of the eye. In some cases, histological analysis reveals some ocular tissue. The defect is usually accompanied by severe cranial abnormalities

Answer 9

Anophthalmia

Question 10

___ [single eye] and ___ [fusion of the eyes] comprise a spectrum of defects in which the eyes are partially or completely fused

Answer 10

Cyclopia - synophthalmia

Question 11

Mutations in ___ result in aniridia and may also contribute to anophthalmia and microphthalmia

Answer 11

PAX6

Question 11

These defects are invariably associated with a brain defect called ____, in which the cerebral hemispheres are partially or completely merged into a single telencephalic vesicle

Answer 11

holoprosencephaly

Question 12

Factors associated with holoprosencephaly include alcohol, maternal diabetes, mutations in ____, and abnormalities in cholesterol metabolism that may disrupt ___ signaling

Answer 12

SHH - SHH