Embryology

Question 1

During neural development, what induces the ectoderm to differentiate into neuroectoderm and form the neural plate?

Answer 1

The Notochord

Question 2

Alar plate vs basal plate

Answer 2

Alar plate: sensory (dorsal)

Basal plate: ventral (motor)

Question 3

Three primary vesicles of the developing brain
Five secondary vesicles of the developing brain - What do the walls and cavities of these parts make up in the adult brain. Walls listed first.

Answer 3

Primary:
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)

Secondary:
Telencephalon - Cerebral hemisphere, Lateral ventricals
diencephalon - Thalamus, hypothalamus, epithalamus, optic nerve & retina, posterior lobe of pituitary (neurohypophysis), Third ventricle
mesencephalon - Midbrain, Aqueduct
metencephalon - Pons and Cerebellum, upper part of fouth centricle
myelencephalon - Medulla, Lower part of fourth ventricle

Question 4

Where and when does neural fusion of the neural tube begin?

Answer 4

Fusion begins in the region of the 5th somite (cervical region) very early in Week 4.

Question 5

names of the front and back neuro pores and when they close

Answer 5

Rostral and caudal neuropores, rostral closes about day 24, caudal around 26

Question 6

What portion of the neural tube, with respect to the somites, will form the brain?

Answer 6

rostral to the 4th pair -> brain

caudal to the 4th pair -> cord

Question 7

In general, what do neural crest cell form?

Answer 7

peripheral nervous system (i.e. dorsal root ganglia) , along with many other non-neural cells such as odontoblasts and melanocytes.

Question 8

Three zones of the spinal cord and what they develop into

extra: which layer contains all spinal cord nerve cell bodies?

Answer 8

ventricular zone - inner layer - neuroepithelial cells that develop into neurons and glial cells, which form ependymal cells during maturity

intermediate zone - middle layer - neuroblasts that turn into the gray matter of the spinal cord (dorsal, ventral, lateral horns). Containts all spinal cord nerve cell bodies.

Marginal zone - Includes the axons of neuroblasts whose cell bodies are in the intermediate layer and in the spinal ganglia. Becomes the white matter of the spinal cord.

Question 9

Longitudinal groove in the lumen, marking the division between alar and basal plates. Continues along the length of the neural tube; seen early in development as well as in medulla and pons.

Answer 9

Sulcus limitans

Question 10

Alar vs basal plate-

which developes into which horns, and what does each horn do? Where do the axons of these horns terminate?

Answer 10

alar - dorsal (posterior) horn - sensory (alar = afferent) neurons

basal

ventral (anterior) horn - large motor neurons which innervate skeletal muscle. (terminate on muscle)

lateral horn - preganglionic neurons of the sympathetic nervous system. (terminate on peripheral autonomic ganglia)

Question 11

Are there synapses in the dorsal root ganglion?

Answer 11

No.

Dorsal root ganglion house the cell bodies of afferent neurons, which synapse in the grey matter of the dorsal horn as well as on receptors in the skin and elsewhere.

Question 12

Glial cells and two types

Answer 12

myelinating cells

schwann - pns (one node of myelination)

oligodendrocytes - cns (multiple cites)

Question 13

When does myelination start and stop

Answer 13

Begins in 4th month of prenatal development but continues into the second year of postnatal life

Question 14

3 example diseases resulting in loss of myelination

Answer 14

multiple sclerosis, Charcot-Marie-Tooth, Guillan-Barre (loss of sense in distal legs moving up) syndrome.

Question 15

Name of the test where you stroke the bottom of a foot and look for toe extension

Answer 15

babinski’s sign:

positive if myelination in incomplete (normal up to two years)

Question 16

Where is the conus medullaris with respect to vertebra at birth? in an adult?

Answer 16

birth - L2-3

adult L1-2

Question 17

what makes up the brain stem

Answer 17

midbrain + pons + medulla

Question 18

name for anterior pituitary

Answer 18

adenohypophysis

Question 19

What forms the neurohypophysis and what is it

Answer 19

it is the posterior pituitary (the neural tissue portion), formed from the infundibulum (a downward extension from the floor of the diencephalon.

Question 20

What forms the adenohypophysis and what is it?

Answer 20

anterior lobe of pituitary (the glandular portion). made from an outgrowth of oral ectoderm from the stomodeum (primitive oral cavity) called rathke’s pouch.

Question 21

Rathke’s pouch

Answer 21

outgrowth of ectoderm from the stomodeum (primitive oral cavity) that gives rise to the adenohypophysis.

Question 22

Where does the primitive optic cup grow from?

Answer 22

the diencephalon

Question 23

What does the interventricular foramina connect?

Answer 23

the lateral ventricles with the third ventricle.

Question 24

olifactory tract is an outgrowth of what portion of the brain?

Answer 24

telencephalon

Question 25

Function of the choroid plexus

What ventricles can it be found in?

Answer 25

produces cerebrospinal fluid.

all ventricles

Question 26

Elements composing the choroid plexus

Answer 26

• single layer of modified ependymal cells known as the choroidal epithelium
• pia mater (vascular mesenchyme)
• pial blood vessels

Question 27

Which secondary brain vesicles give rise to which cranial nerves?

Answer 27

a. Cranial Nerve I: Telencephalon
b. Cranial Nerve II: Diencephalon

(the rest are in the brain stem:)

c. Cranial Nerves III, IV: Mesencephalon
d. Cranial Nerves V to XII: Metencephalon and Myelencephalon

Question 28

Hirschsprung’s disease

Answer 28

Neural crest cells fail to migrate into the colon; the parasympathetic ganglia do not form resulting in congenital megacolon.

no peristalsis

Question 29

Waardenburg syndrome

Answer 29

occurs with diffuse disruption of migration of neural crest cells

1. Abnormal appearance of face, deafness, due to head neural crest cell involvement
2. Lack of pigmentation (melanocytes)
3. Digestive problems (enteric ganglia)

Question 30

Craniorachischisis

Answer 30

complete failure of the neural tube to close resulting in exposure of the malformed tissue to the outside of the head and body.

Question 31

Anencephaly and meroanencepaly

Answer 31

Failure of the rostral neuropore to close and subsequent failure of the cranial vault to form
• Anencephaly = total absence of brain tissue
• Meroanencephaly = remnants of brainstem tissue may be present

Question 32

Encephalocele

Answer 32

protrusion of brain through a defect in the skull, often in the occipital area

Question 33

Spina bifida occulta

Answer 33

• Mildest form of spina bifida in which there is malformation of the vertebral arch; no obvious involvement of the spinal cord, meninges or skin. Only evidence may be a tuft of hair on the skin surface overlying the defect. In some cases, the spinal cord might be tethered to the subcutaneous tissue

Question 34

Holoprosencephaly (HPE):

Answer 34

failure of the normal development of the forebrain such that it is not divided into two hemispheres

Question 35

Hydrocephalus

associated diseases?

Answer 35

a. Dilation of the cerebral ventricles by CSF due to CSF overproduction, obstruction of flow or failure of CSF reabsorption.
b. Often seen as part of other malformations such as Dandy-Walker or Chiari malformations

Question 36

Arnold-Chiari type II

type I

Answer 36

type II - herniation of cerebellum and brain stem into cervical spinal canal, hydrocephalus.

type I - Milder variant of Type II. Many of these patients have syringomyelia and some have hydrocephalus. May be asymptomatic

Question 37

syringomyelia

symptoms

Answer 37

tubular cavitation (cyst) in the spinal cord.

loss of pain and temperature sensation over the shoulders and down the arms due to damage of the fibers crossing the ventral white commissure.

Question 38

Dandy-Walker malformations

physiology

symptoms

Answer 38

agenesis of the cerebellar vermis

Symptoms: in infants–slow motor development, irritability, vomiting; in older children –lack of muscle coordination, jerky eye movements