CHAPTER 4

Question 1

1. The neural retina is derived from the
   (A) alar plate
   (B) choroid
   (C) neural crest
   (D) neural tube
   (E) telencephalic vesicle wall

Answer 1

l-D. The retina is derived from the neural tube, which gives rise to the entire central nervous
system (CNS).

Question 2

2. At birth, the conus medullaris is found at
   which vertebral level?
   (A) VT12
   (B) VL1
   (C) VL3
   (D) VS1
   (E) VS4

Answer 2

2-C. At birth, the conus medullaris extends to VL3, and in the adult it extends to the VL1-VL2
interspace. At 8 weeks, the spinal cord extends the entire length of the vertebral canal.

Question 3

3. Caudal herniation of the cerebellar tonsils
   and medulla through the foramen magnum is
   called
   (A) Dandy-Walker syndrome
   (B) Down syndrome
   (C) Arnold-Chiari syndrome
   (D) cranium bifidum
   (E) myeloschisis

Answer 3

3-C. Arnold-Chiari syndrome is a cerebellomedullary malformation in which the inferior vermis
and medulla herniate through the foramen magnum, resulting in communicating hydro-
cephalus. Arnold-Chiari syndrome is frequently associated with spina bifida.

Question 4

4. A newborn has multiple congenital defects
   due to dysgenesis of the neural crest. Which of
   the following cells would most likely be spared?
   (A) Dorsal root ganglion cells
   (B) Geniculate ganglion cells
   (C) Melanocytes
   (D) Motoneurons
   (E) Parafollicular cells

Answer 4

4-D. Motoneurons develop from the neural tube, more specifically, from the basal plate. The
other options are derivatives of the neural crest.

Question 5

5. The diencephalon gives rise to all of the fol-
   lowing structures EXCEPT the
   (A) mamillary bodies
   (B) pineal body
   (C) subthalamic nucleus
   (D) adenohypophysis
   (E) neurohypophysis

Answer 5

5-D. The adenohypophysis (pars distalis, pars tuberalis, and pars intermedia) develops from
Rathke pouch, an ectodermal diverticulum of the stomodeum. The neurohypophysis develops
from the infundibulum of the hypothalamus.

Question 6

6. All of the following statements concerning
   myelination are correct EXCEPT
   (A) it is accomplished by neural crest cells
   (B) it is accomplished by Schwann cells in the
   peripheral nervous system (PNS)
   (C) it is accomplished by oligodendrocytes in
   the central nervous system (CNS)
   (D) it commences in the fourth fetal month
   (E) it is completed by birth

Answer 6

6-E. Myelination is not complete at birth. The corticospinal tracts are not completely myelinated
until the end of the second postnatal year.

Question 7

7. All of the following statements concerning
   spina bifida are correct EXCEPT
   (A) spina bifida results from failure of verte-
   bral arches to fuse
   (B) spina bifida is frequently associated with
   Arnold-Chiari malformation
   (C) spina bifida usually occurs in the cervi-
   cothoracic region
   (D) spina bifida occulta is the least severe
   variation
   (E) spina bifida with myeloschisis is the most
   severe variation

Answer 7

7-C. Spina bifida usually occurs in the lumbosacral region.

Question 8

8. The neural crest gives rise to all of the fol-
   lowing cells EXCEPT
   (A) odontoblasts
   (B) oligodendrocytes
   (C) cells of enteric ganglia
   (D) Schwann cells
   (E) chromaffin cells

Answer 8

8-B. The neural crest gives rise to dorsal root ganglion cells, the cells of autonomic and enteric
ganglia, Schwann cells, satellite cells, and chromaffin cells of the suprarenal medulla. The neural
crest also gives rise to pigment cells (melanocytes), odontoblasts, meninges, and mesenchyme of
the branchial arches. Oligodendrocytes arise from the glioblasts of the neural tube.

Question 9

Match the statements in items 9-13 with the appropriate lettered structure shown in the appropriate figure.

9. Is derived from the telencephalon
10. Gives rise to the choroid plexus
11. Is derived from the alar plate
12. Gives rise to motor neurons that innervate the tongue
13. Gives rise to the solitary nucleus

Answer 9

9-C. The corticospinal tract (pyramid) has its origin in the neocortex of the telencephalon.

10-A. The tela choroidea gives rise to the choroid plexus.

11-B. The inferior olivary nucleus is derived from the alar plate of the developing medulla.

12-D. The basal plate gives rise to the hypoglossal nucleus.

13-E. The alar plate gives rise to the solitary nucleus.

Question 10

Match the statements in items 14-18 with the appropriate lettered structure shown in the figure.

14. Innervates the lateral rectus muscle
15. Gives rise to a parasympathetic nucleus
16. Gives rise to the cerebellum
17. Is derived from the alar plate
18. Gives rise to motor neurons that migrate into the lateral pontine tegmentum

Answer 10

14-B. The general somatic efferent (GSE) column innervates the lateral rectus muscle.

15-E. The general visceral efferent column (GVE) gives rise to the superior salivatory nucleus of CN VII. This parasympathetic nucleus innervates the lacrimal, the sublingual, and the submandibular glands and also the palatine and nasal glands.

16-A. The cerebellum is derived from the alar plate. The alar plate gives rise to the rhombic lip, which becomes the cerebellum.

17-C. The pontine nuclei are derived from the alar plate.

18-D. The special visceral efferent (SVE) column gives rise to motor neurons that migrate into the lateral pontine tegmentum and become the facial nucleus, CN VII.