2a and b. Embryology of the CNS and PNS

Question 1

Telecephalon

- Forms 1 Structure

Answer 1

Cerebral cortex

Question 2

Diencephalon

- Forms 3 Structures

Answer 2

Hypothalamus
Thalamus
Optic cups (retina and optic nerve)

Question 3

Mesencephalon

- Forms 2 Structures

Answer 3

Rostral colliculus

caudal colliculus

Question 4

Metencephalon

- Forms 2 Structures

Answer 4

Pons

Medulla

Question 5

Myelencephalon

- Forms 1 Structure

Answer 5

Medulla oblongata

Question 6

Flexures

- 3

Answer 6

1. Cephalic flexure
   - Disappears in domestic species
2. Cervical flexure
   - Not visible in the domestic species
3. Pontine flexure
   - Forms between the metencephalon and myelencephalon
   - Bends the rhombencephalon ventrally

Question 7

Ventricles

- 4

Answer 7

• 2 lateral ventricles in the telencephalon
• 3rd ventricle in the diencephalon
• 4th ventricle in the rhombencephalon

Question 8

Ventricle Connections

- 2

Answer 8

Lateral ventricles to the 3rd ventricle:

• Foramen of Monroe
• Interventricular foramen

3rd to 4th ventricle

• Aqueduct of sylvius
• Interventricular aqeuduct
• Mesencephalic aqueduct

Question 9

Brainstem

- 3 Structures

Answer 9

Rhombencephalon
Mesencephalon
Diencephalon

Question 10

Neurone Origins

- 2

Answer 10

If the cell body is in the CNS the neurone if formed from the ectoderm neural tube

If the cell body is outside the CNS the neurone if formd from either:

• Neural Crest
• Ectoderm palcode

Question 11

CNS Neurones

- 3

Answer 11

• Motor neurones in the ventral horn of the spinal cord or any of the motor nuclei in the brainstem
• Pre-ganglionic autonomic neurones in the brain or spinal cord
• Retinal ganglion cells

Question 12

PNS Neurones

- 3

Answer 12

1. Neural crest derived
   - Most sensory neurones in the dorsal root ganglion, paravertebral ganglion or middle cervical ganglion
   - post-ganglionic autonomic neurones
2. Ectoderm placode
   - Sensory neurones involved in the special senses form from the ectodermal places

Question 13

Holoprosencephaly

Answer 13

Occurs when the bifurcation of the prosencephalon into 2 telecephali fails, causing failure of duplication of structures in the head

Question 14

PNS

- Derivation Tissue

Answer 14

• Neural Crest

- Ectoderm placodes

Question 15

PNS

- Neural Crest Origin

Answer 15

Neural crest cells emigrate from the dorsal neural tube into the embro

Question 16

PNS

- Neural Crest Structures

Answer 16

1. Most peripheral neurones
   - All autonomic ganglia
   - Almost all peripheral somatosensory neurones
   
   • All neurones in the dorsal root ganglia
   • Most neurones in the trigeminal ganglia
   • All neurones in the superior ganglia of cranial nerves VII, IX and X
2. All peripheral glia
   - Schwann cells
   - Satellite glia

Question 17

PNS

- Ectoderm Placodes

Answer 17

Olfactory placed = olfactory epithelium

Optic placed = lens

Otic placode = inner ear hair cells and afferent neurones which form cranial nerve VIII

Lateral line organs and afferent neurones in fish and amphibia

Some somatosensory neurones in the trigmeinal ganglia, which form cranial nerve V

All taste and viscerosensory afferent neurones in the inferior ganglia of cranial nerve VII, IX and X