Embryology

Question 1

Describe neurulation.

Answer 1

Mesoderm cells around notochord
differentiate into three specialised types of
cells
 Paraxial mesoderm, intermediate
mesoderm, lateral plate mesoderm;
make different tissues, organs
* Notochord starts process called neurulation
→ stimulates cells of ectoderm to form
neural plate
* Neural plate folds, forms neural groove with
edges called neural folds
* Neural plate continues to grow, neural folds
come together, pinch off from surface of
ectoderm to form neural tube between
ectoderm and mesoderm
The neural tube structure begins in the cervical region
and ends caudally

Question 2

Discuss the development of the neural crest cells.

Answer 2

Adjacent to the neural plate is the neural plate border.
when the neural fold is formed the NPB cells develop
into the stem cells – neural crest cells, specifically premigratory.
when the neural tube is created, the Delaminating neural crest cells are positioned above the neural tube and then migrate later (detaching themselves).

Question 3

Which structures do the neural tube form?

Answer 3

CNS
Retina
Pineal gland
Posterior pituitary gland

Question 4

Outline the different zones of the neural tube in the development of the spinal cord and medulla.

Answer 4

Ependymal zone/Ventricular zone: gives rise to all neurons and microglia
Mantle zone/Intermediate zone: primordial neurons differentiate= grey matter
Marginal Zone: White matter of spinal chord, axons

Question 5

Which structure divides the spinal cord into alar and basal plates?

Answer 5

Sulcus limitans.

Question 6

Outline the alar plate and basal plate.

Answer 6

A: Dorsal horns, sensory, afferent fibres
B: Ventral horns, Motor, efferent fibres

Question 7

Describe the development of the spinal meninges.

Answer 7

mesenchyme surrounding the neural tube condenses
primordial meninx- external layer; dura mater
internal layer; arachnoid and pia mater

Question 8

Discuss the evidence as to why the spinal cord develops faster than the vertebral column.

Answer 8

6 months: the conus medullaris lies at s1
l2/3 in neonates
l1 in adults

Question 9

What structures are formed from the neural crest cell migration?

Answer 9

cranial & sensory
ganglia & nerves
* adrenal medulla
* melanocytes
* branchial arch cartilages
* heart - bulbar &
conal ridges
* meninges
* cranial
mesenchyme &
c.t.

Question 10

Discuss the closure of the neural tube.

Answer 10

Rostral (anterior) neuropore closes on day 25 & caudal (posterior) neuropore closes on day 27

Question 11

Discuss secondary neuralation.

Answer 11

Dispersed mesenchyme
M. Condensation
Medullary cord
cavitation
neural tube complete

Question 12

Compare the reposition of the dorsal and ventral horns in the spinal cord and the medulla.

Answer 12

The developed medulla oblongata / brainstem region is on the right. The alar plates have separated laterally and this allows neurones
(grey matter) to migrate from the inside to the outside of the developing brain

Question 13

What is the 3 primary vesicles of the brain?

Answer 13

Prosencephalon (forebrain)
*Mesencephalon (midbrain)
*Rhombencephalon
(hindbrain)

Question 14

What does the prosencephalon give rise to?

Answer 14

Telencephalon, lateral ventricles
and Diencephalon, 3rd ventricle

Question 15

What does the mesencephalon give rise to?

Answer 15

midbrain- cerebral aqueduct

Question 16

What does the rhombencephalon give rise to?

Answer 16

Metencephalon: Pon and cerebellum, Upper fourth ventricle
myelencephalon: Medulla, lower fourth ventricle

Question 17

Outline the neural tube differentiation.

Answer 17

Differentiation occurs on three levels
macroscopic anatomical level
* bulges and constrictions
* parts of brain and spinal cord
tissue changes
* rearrangements of different cell populations
* forms functional regions
cellular changes
* neurones (transmit impulses)
* glial cells (supporting cells)

Question 18

Name the curvatures found in the brain.

Answer 18

Cephalic flexure, pontine flexure and cervical flexure.

Question 19

Discuss the development of the Pituitary gland.

Answer 19

Stomodeum gives rise to the hypophysial pouch, upgrowth
the diencephalon give rise to the neurohypophysial bud, down growth, also the infundibulum from the invagination
as the hypophyseal pouch ascends the stalk disappears
The Pars tuberalis (A) gives rise to the pars intermedia that connects to the Pars nervosa (P)

Question 20

Explain the development of the cerebellum.

Answer 20

The cerebellum develops from the alar plate.
Therefore the cerebellum is unable to initiate motor activity……….