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Which of the following molecules plays an important role in the determination of the dorsoventral axis of the developing limb?

a. Msx-1
b. Wnt-7a
c. Hoxd-13
d. Pax-1
e. FGF-8

b. Wnt-7a


What molecule is associated with myogenic cells migrating into the limb bud from the somites?

a. shh
b. BMP-7
c. FGF-4
d. Pax-3
e. En-1

d. Pax-3


What is the principal function of the AER?

a. stimulating outgrowth of the limb bud
b. setting up the anteroposterior axis of the limb bud
c. determining the specific characteristics of the ectodermal appendages of the limb
d. determining the pattern of neural ingrowth into the limb
e. attracting the subcutaneous plexus of capillaries in the limb bud

a. stimulating outgrowth of the limb bud


In the developing limb the sonic hedgehog (shh) gene product is produced in the :

a. progress zone
b. region of interdigital cell death
c. ZPA
d. AER
e. common muscle mass

c. ZPA


The connective tissue of the limb arises from the:

a. paraxial mesoderm
b. neural crest
c. intermediate mesoderm
d. somitic mesoderm
e. lateral mesoderm

e. lateral mesoderm


The formation of clubfoot (talipes equinovarus) is associated with:

a. a misplaced ZPA
b. defective cellular migration from somites
c. thalidomide
d. oligohydramnios
e. a neural crest defect

d. oligohydramnios


An infant whose mother underwent chorionic villus sampling during pregnancy was born with the tips of two digits missing. What is a possible cause?

A tear of the amnion during the chorionic villus sampling procedure could have resulted in an amniotic band wrapping around the digits and strangulating their blood supply, thereby causing the tips to degenerate and fall off.


A woman who underwent amniocentesis during pregnancy gave birth to a child with a duplicated thumb. What is a possible cause?

This defect is unlikely to be related to the amniocentesis procedure because the morphology of the digits is well established by the time this procedure is done ( usually around 15 to 16 weeks). The most likely cause is a genetic mutation.


If the somites close to a limb-forming region are experimentally removed, the limbs form without muscles. Why?

Muscle-forming cells arise from the somites


A child is born with webbed fingers (syndactyly). What is the reason for this anomaly?

The immediate cause is likely the absence of programmed cell death in the interdigital mesoderm. The cause of the disturbance in cell death is currently not understood.


Rathke's pouch arises from the:

a. diencephalon
b. stomodeal ectoderm
c. mesencephalon
d. pharyngeal endoderm
e. infundibulum

b. stomodeal ectoderm


Which of these cell and tissue types arises from cranial, but not trunk, neural crest cells?

a. sensory ganglia
b. adrenal medulla
c. melanocytes
d. schwann cells
e. none of the above

e. none of the above


Which molecule is a poor substrate for migrating neural crest cells?

a. laminin
b. chondroitin sulfate
c. fibronectin
d. type IV collagen
e. hyaluronic acid

b. chondroitin sulfate


Neural crest cells arise from the:

a. somite
b. dorsal non-neural ectoderm
c. neural tube
d. splanchnic mesoderm
e. yolk sac endoderm

c. neural tube


A 6-month old infant exhibits multiple congenital defects, including a cleft palate, deafness, ocular hypertelorism, and a white forelock but otherwise dark hair on his head. The probable diagnosis is:

a. CHARGE association
b. von Recklingausen's disease
c. Hirschsprung's disease
d. Waardenburg's syndrome
e. none of the above

d. Waardenburg's syndrome


What molecule is involved in the migration of neural crest cells from the neural tube?

a. slug
b. BMP-2
c. mash 1
d. norepinephrine
e. glial growth factor

a. slug


Which is not a derivative of the neural crest?

a. sensory neurons
b. motoneurons
c. schwann cells
d. adrenal medulla
e. dental papilla

b. motoneurons


What maintains the competence of neural crest cells to differentiate into autonomic neurons?

a. sonic hedgehog
b. acetylcholine
c. mash 1
d. glial growth factor
e. transforming growth factor-beta

c. mash 1


If trunk neural crest cells are transplanted into the cranial region, they can form all of the following types of cells except:

a. pigment cells
b. schwann cells
c. sensory neurons
d. cartilage
e. autonomic neurons

d. cartilage


How does the segmental distribution of the spinal ganglia occur?

Along the length of the spinal cord, migrating neural crest cells are funneled into the anterior sclerotomal region of the somites and are excluded from the posterior half. This results in the formation of a pair of ganglia for each vertebral segment and space between ganglia in the craniocaudal direction.


What are the three major differences between cranial and trunk neural crests?

1. cranial crest cells can form skeletal elements, while trunk crest cells cannot.

2. migrating cranial neural crest cells have more morphogenetic information encoded in them than trunk cells do. (for ex. craniocaudal levels are specified in cranial crest cells)

3. cranial crest cells from large amounts of dermis and other connective tissues, whereas trunk crest cells do not.


Neural crest-derived cells constitute a significant component of which tissue of the eye?

a. neural retina
b. lens
c. optic nerve
d. cornea
e. none of the above

d. cornea


The otic placode arises through an inductive message given off by the:

a. telencephalon
b. rhombencephalon
c. infundibulum
d. diencephalon
e. mesencephalon

b. rhombencephalon


What molecule plays a role in guidance of advancing retinal axons through the optic nerve?

a. Pax-2
b. FGF-3
c. BMP-4
d. Pax-6
e. BMP-7

a. Pax-2


Surface ectoderm is induced to become corneal epithelium by an inductive event originating in the:

a. optic cup
b. chordamesoderm
c. optic vesicle
d. lens vesicle
e. neural retina

d. lens vesicle


The second pharyngeal arch contributes to the:

a. cochlea and earlobe
b. auditory tube and incus
c. stapes and earlobe
d. auditory tube and stapes
e. otic vesicle and stapes

c. stapes and earlobe


During a routine physical examination, an infant was found to have a small segment missing from the lower part of one iris. What is the diagnosis, what is the basis for the condition, and why may the infant be sensitive to bright light?

Coloboma of the iris is caused by failure of the choroid fissure to close during the sixth week of pregnancy. Because the area of the defect remains open when the rest of the iris constricts in bright light, excessive unwanted light can enter the eye through the defect.


why does a person sometimes get a runny nose while crying?

Some of the secretions of the lacrimal glands enter the nasolacrimal ducts, which carry the lacrimal fluid into the nasal cavity.


What extracellular matrix molecule is often associated with migration of mesenchymal cells, and where does such an event occur in the developing eye?

Hyaluronic acid. Migration of neural crest cells into the developing cornea occurs during a period when large amounts of hyaluronic acid have been secreted into the primary corneal stroma.


Why is the hearing of a newborn often not as acute as it is a few months later?

During the fetal period, the middle ear cavity is filled with a loose connective tissue that dampens the action of the middle ear ossicles. After birth, the connective tissue is resorbed.