Block 1 Development

Question 0

Where does neural tube fusion begin?

Answer 0

In the region of the 5th somite

Question 1

When does Neurulation begin?

Answer 1

Between 18 and 19 weeks

Question 2

When do the two neuropores close?

Answer 2

Rostal closes about day 24

Caudal close about day 26

Question 3

What somites form the spinal cord and the brain?

Answer 3

Rostal to the 4th is the brain.

4th to caudal is the spinal cord.

Question 4

What do neuralcrest cells develop into?

Answer 4

They form the PNS, primary neurons, Schwann cells, satellite cells, melanocytes, and chromaffin cells of the adrenal medulla.

Question 5

What are the three layers of the neural tube?

Answer 5

Ventricular layer - initially the entire tube wall, rapidly divides and thickens, differentiates into neuroblasts and after becomes the ependyma, a single layer of cells lining the spinal cord.

Intermediate layer - becomes populated by the neuroblasts from the ventricular layer, becomes the gray matter where all the cell bodies are located (dorsal, ventral, and lateral horns)

Marginal layer - becomes white matter where all the axons of the intermediate layer travel

Question 6

What cells maintain their mitotic ability?

Answer 6

Glial cells only

Question 7

Where are the alar and basal layers located?

Answer 7

The intermediate layer

Question 8

What divides the alar and basal layers?

Answer 8

Sulcus limitans

Question 9

What do the alar and basal layers become and what are their orientations?

Answer 9

Alar - forms the dorsal horn, secondary sensory neurons

Basal - forms ventral and lateral horns, motor neurons

They eventually become neurites and form axons and dendrites.

Question 10

What forms the dorsal root ganglion?

Answer 10

Neural crest cells. They start bipolar and become psuedounipolar

Question 11

When does Myelination start and end?

Answer 11

It starts the 4th month Prenatally and continues into the 2nd year.

Question 12

At 12 weeks the dura grows faster than the spinal cord. At what vertebrae does the spinal sit for an infant and adult?

Answer 12

Infant - L2/3

Adult L1

Question 13

Where are lumbar punctures done?

Answer 13

Between L3/4 or L4/5

Question 14

What are the three areas of the brain?

Answer 14

Forebrain or Prosencephalon

• telencephalon becomes the cerebral hemispheres
• diencephalon becomes the thalamus

Midbrain or mesencephalon
- stays the midbrain

Hindbrain or rhombencephalon

• metencephalon becomes the pons and cerebellum
• Myelencephalon becomes the medulla

Question 15

Where are the ventricles located?

Answer 15

2 lateral ventricles - in the cerebral hemispheres
Third ventricle - diencephalon with the thalamus
Cerebral aqueduct - within the mesencephalon or midbrain
Fourth ventricle - within the rhombencephalon

Question 16

What are the three flexures of the brain?

Answer 16

Cervical (hindbrain and spinal cord)

Cephalic (midbrain)

Pontine (mid of diencephalon)

Question 17

How is the cerebellum formed and what are the lobes and composition?

Answer 17

• It is formed by the thickening of the alar plate (rhombic lip)
• the anterior and posterior lobes are divided by the primary fissure
• the floccunodular is separated by the posterolateral fissure
• the cortex is gray matter, the middle is white, the center is gray

Question 18

What does the diencephalon form?

Answer 18

The thalamus, hypothalamus, epithalamus, optic nerve and retina, and posterior lobe of the pituitary gland neurohypophysis.
Has the third ventricle.

Question 19

What is the makeup of the pituitary gland?

Answer 19

Both neuroectoderm and ectoderm origins
The infundibulum is a downward extension from the floor of the diencephalon giving rise to the posterior half (neuroectoderm)

Rathk’s pouch is outgrowth of ectoderm lined from the stomoduem, gives rise to the anterior portion called the adenohypophysis, glandular part.

Located in the sella turcica of the sphenoid bone
Anatomically and physiologically associated with the hypothalamus

Question 20

What does the telencephalon form?

Answer 20

It is the rostal part of the prosencephalon
Forms the frontal, parietal, temporal, and occipital lobes
Forms the insula, an area buried in the cortex (grey matter)
Basal ganglion, fiber bundles, internal capsule, and corpus callosum, lateral ventricles, olfactory tract

Question 21

What does the choroid plexus do and how is it formed?

Answer 21

Makes CSF

Formed by pia with ependyma called the Choroidea

Question 22

Where do the different cranial nerves come from?

Answer 22

I telencephalon
II diencephalon
III, IV mesencephalon
V - XII brainstem

Question 23

What is the composition of the basal and alar plates?

Answer 23

Basal plate - three columns of cells on each side of the brain stem
Alar plate - four columns of cells on each side of the brainstem

Question 24

How are NTDs determined?

Answer 24

By measuring AFP and acetylcholine esterases

Question 25

When does defective closure of the neural tube result is malformations like NTDs?

Answer 25

Weeks 3 and 4

Question 26

What is Craniorachischisis?

Answer 26

Complete failure of the neural tube resulting in neural tissue outside the skull.

Question 27

What is Anencephaly?

Answer 27

Failure of the rostal neuropore to close and subsequent failure of the cranial vault to form.

Total absence of brain tissue

Question 28

What is meroanencephaly?

Answer 28

Failure of the rostal neuropore to close and subsequent failure of the cranial vault to form.

Remnants of brain tissue may be present

Question 29

What is Encephalocele?

Answer 29

Protrusion of the brain through a defect in the skull.

Question 30

What is spina bifida?

Answer 30

Failure of the caudal neuropore to close

Question 31

What is spina bifida occulta?

Answer 31

Spinal malformation of vertebral arch
May be a tuft of hair on back
Spinal cord may be tethered to SQ tissue

Question 32

What are the types of spina bifida cystica?

Answer 32

Meningocele - spinal cord in tact but meninges herniate through defect in the vertebral arch and skin usually lumber

Myelomeninocele - spinal cor and meninges herniate through the opening. May have Arnold-Chiari malformation resulting in hydrocephalus.

Occult spinal dysraphism - (tethered spinal cord) failure of tube to detach from surface ectoderm. Usually in sacral/coccygeal. May connect to central canal

Question 33

What are some factors of NTDs?

Answer 33

Diabetes mellitus

Abnormal folic acid metabolism

Question 34

What is Holoprosencephaly (HPE)?

Answer 34

Cyclops eye

Failure of normal of development so that the forebrain has no divisions.

Question 35

What is hydrocephalus?

Answer 35

A. Dilation of CSF ventricles due to overproduction, obstruction to flow, or failure of reabsorption.

B. Often seen in others, dandy walker of Arnold Chiari

Question 36

What are Arnold-Chiari malformations?

Answer 36

Type II - includes NTDs. Displacement of cerebellum and brainstem into the cervical spinal canal

Type I - milder. Many have syringomyelia and some have hydrocephalus. May be asymtomatic.

Question 37

What are Dandy-Walker malformations?

Answer 37

Posterior fossa abnormalities that include cerebellar vermis, formation of a large cyst, and blockage of Luschka and Magendie foramen

Symptoms in infants - slow motor development, irritability, vomiting
In older children lack of muscle coordination, jerky eye movements

Question 38

What is syringomyelia?

Answer 38

1. Tubular cavitation of spinal cord, usually in cervical/upper thoracic
2. Affects central canal fibers
3. Initially loss of sensation in pain/temp over shoulders and arms due to damage of fibers crossing in the ventral white commissures
4. Often with Arnold-charia type I
   Unknown cause

Question 39

What are some characteristics of alcohol and the prenatal vein?

Answer 39

It is teratogenic at all times during development.
Lesions may not be visible
Most common cause of mental retardation.
One drink in the 1st trimester can lower IQ by three points