Brain Embryology

Question 1

Neuralation

Answer 1

Neural plate → Neural tube
Neural plate lengthens, lateral edges elevate to form the neural folds and the depressed mid region forms the neural groove.
Neural folds approach each other in the midline and fuse.
Fusion begins in cervical region (22 days) and proceeds craniocaudally.

Question 2

How does the cephalic end of the neural tube communicate with the amniotic cavity until fusion is complete?

Answer 2

Cephalic end communicates with the amniotic cavity via the anterior (cranial) neuropore.

Question 3

How does the caudal end of the neural tube communicate with the amniotic cavity until fusion is complete?

Answer 3

Caudal end communicates with the amniotic cavity via the posterior (caudal) neuropore.

Question 4

When does the cranial neuropore close?

Answer 4

~25 days

Question 5

When does the caudal neuropore close?

Answer 5

28 days

Question 6

When and how does the pontine flexure develop?

Answer 6

Weeks 5-8.
Dorsal flexion at the site of the developing pons.
Metencephalon folded back on myelencephalon.

Question 7

When and how does the cervical flexure develop?

Answer 7

Weeks 5-8.

Ventral flexion between the myelencephalon and the spinal cord.

Question 8

When and how does the mesencephalic flexure develop?

Answer 8

Week 4/5.

Prosencephalon is folded under the mesencephalon.

Question 9

What does the alar plate in the spinal cord become?

Answer 9

Sensory dorsal horn

Question 10

What does the basal plate in the spinal cord become?

Answer 10

Motor ventral horn

Question 11

When do the spinal nerves begin to develop?

Answer 11

Week 6

Question 12

What is the main derivative of the myelencephalon?

Answer 12

The medulla oblongata

Question 13

What does the basal plate of the myelencephalon contain?

Answer 13

3 groups of motor nuclei

Question 14

What are the three groups of motor nuclei in the basal plate of the myelencephalon?

Answer 14

1 - Medial somatic efferent
2 - Intermediate special visceral efferent
3 - Lateral general visceral efferent

Question 15

What is the somatic efferent motor column?

Answer 15

Continuation of somatic efferent group from basal plate of myelencephalon.

Question 16

What does the somatic efferent motor column contain in the myelencephalon?

Answer 16

Neurons of the hypoglossal nerve (supplies tongue musculature)

Question 17

What does the somatic efferent motor column contain in the metencephalon and the mesencephalon?

Answer 17

Neurons of abducens (VI), trochlear (IV) and oculomotor (III). These nerves supply eye musculature.

Question 18

What is the special visceral efferent motor column?

Answer 18

Extension of the special visceral efferent group into the metencephalon

Question 19

What does the special visceral efferent motor column contain in the myelencephalon?

Answer 19

Neurons of the accessory (XI), vagus (X) and glossopharyngeal (IX) nerves.

Question 20

What does the general visceral efferent group of neurons from the basal plate of the myelencephalon contain?

Answer 20

Motor neurons which supply the involuntary musculature of the respiratory tract, intestinal tract and heart.

Question 21

What does the alar plate of the myelencephalon contain?

Answer 21

Three groups of sensory relay nuclei

Question 22

What are the three groups of sensory nuclei in the alar plate of the myelencephalon?

Answer 22

1 - Somatic afferent
2 - Special afferent
3 - General visceral afferent

Question 23

What do the alar plates of the metencephalon contain?

Answer 23

Three groups of sensory nuclei

Question 24

What are the three groups of sensory nuclei in the alar plate of the metencephalon?

Answer 24

1 - Lateral somatic afferent
2 - Special afferent
3 - General visceral afferent

Question 25

Where do the pontine nuclei originate?

Answer 25

The alar plate of the metencephalon

Question 26

What do the basal plates of the metencephalon contain?

Answer 26

Three groups of motor neurons

Question 27

What are the three groups of motor neurons in the basal plates of the metencephalon?

Answer 27

1 - Medial somatic efferent 2 - Special visceral efferent 3 - General visceral efferent

Question 28

What are the initial layers of the cerebellar plate?

Answer 28

Neuroepithelial Mantel Marginal

Question 29

How is the external granular layer formed?

Answer 29

During week 12 - cells formed by neuroepithelium migrate to surface of cerebellum to form external granular layer.

Question 30

What does the external granular layer give rise to?

Answer 30

Granule cells

Question 31

When are granule cells produced by the external granular layer?

Answer 31

6th month of development

Question 32

What are produced from the proliferating cells in the cerebellar white matter?

Answer 32

Basket cells | Stellate cells

Question 33

What is formed from the alar plates in the mesencephalon?

Answer 33

Superior and inferior colliculi | Substantia nigra and red nucleus

Question 34

What is the function of the inferior colliculi?

Answer 34

Synaptic relay stations for auditory reflexes

Question 35

What is the function of the superior colliculi?

Answer 35

Correlation and reflex centres for visual impulses

Question 36

What is found in the basal plates of the mesencephalon?

Answer 36

Two groups of motor nuclei

Question 37

What are the two groups of motor nuclei in the basal plates of the mesencephalon?

Answer 37

1 - Medial somatic efferent - oculomotor (III) and trochlear (IV) 2 - General visceral afferent - nucleus of Edinger-Westphal - innervates sphincter pupillae.

Question 38

What is formed by the marginal layer of the basal plate?

Answer 38

Crus cerebri

Question 39

What is the crus cerebri?

Answer 39

Pathway for descending fibres from the cortex to the spinal cord

Question 40

What makes up the prosencephalon?

Answer 40

Telencephalon and diencephalon

Question 41

What does the telencephalon form?

Answer 41

Cerebral hemispheres

Question 42

What does the diencephalon form?

Answer 42

``` Optic cup Optic stalk Pitutary Thalamus Hypothalamus Epiphysis ```