Neurulation & Somitogenesis

Question 1

What is neurulation?

Answer 1

Neurulation is the formation of the vertebrate nervous system in embryos.

Question 2

When does the neural plate form?

Answer 2

Day 19

Question 3

How is the notochord developed?

Answer 3

Some mesodermal cells migrate cranially in the midline of the mesodermal layer which forms the rod like notochord.

Question 4

What happens as a result of the notochord forming?

Answer 4

The notochord induces the formation of the thick and flat neural plate in the ectoderm. This is the Neuroectoderm.

Question 5

How is the neural tube formed?

Answer 5

The neural plate folds in on itself to form the neural tube.

Question 6

What does the neural tube differentiate into?

Answer 6

The spinal cord and brain

Question 7

What do neural crest cells derive into?

Answer 7

Migrate out to form PNS

Question 8

Describe the process of neural tube formation. (4)

Answer 8

1. Neuroectodermal tissues differentiate to form neural plate.
2. The neural plate bends dorsally and converges at the neural crest.
3. The closure of the neural tube disconnects the neural tube from the ectoderm. Neural crest cells differentiate to form PNS
4. Other mesoderm cells differentiate into somites.

Question 9

What are somites

Answer 9

Paraxial mesoderm differentiates and divides into the precursors of the axial skeleton and skeletal muscle

Question 10

What happens to the notochord?

Answer 10

It degenerates and only persists as the nucleus pulposus of the intervertebral discs.

Question 11

How many pairs of somites are there at the end of week 5?

Answer 11

42-44 pairs

Question 12

What can somites differentiate into?

Answer 12

Cartilage then bone of the axial skeleton. Muscles o the rib cage, limbs and back. Connective tissue of the dermis.

Question 13

What are the 3 types of somites?

Answer 13

Sclerotome (Bone), Myotome (Muscle), and Dermatome (Connective tissue)

Question 14

Draw sclerotome, myotome and dermatome

Answer 14

in notes

Question 15

What can neural crest cells differentiate into?

Answer 15

1. Spinal Ganglia
2. Ganglia of the autonomic nervous system
3. Ganglia of some cranial nerves
4. Sheaths of peripheral nerves
5. Meninges of brain and spinal cord
6. Melanocytes
7. Suprarenal medulla
8. Skeletal and muscular components of the head

Question 16

At what days do the anterior and posterior neuropores close?

Answer 16

Anterior - Day 24

Posterior - Day 26

Question 17

What does the forebrain develop into?

Answer 17

The Prosencephalon develops into the cerebrum and diencephalon

Question 18

What does the midbrain develop into?

Answer 18

The mesencephalon develops into the brain stem

Question 19

What does the hindbrain develop into?

Answer 19

The Rhombencephalon develops into the Brainstem, Cerebellum and spinal cord

Question 20

What are some causes of teratogenesis and at what stage of pregnancy does this occur?

Answer 20

Can happen throughout but most prevalent at week 5, Alcohol, amphetamines, hyperthermia, x rays etc etc

Question 21

What is the cause of Spina Bifida

Answer 21

Failure of fusion of vertebral arches

Question 22

What are the common tell tale signs of the different types of spina bifida?

Answer 22

Spina Bifida Occulta - Hair growth on lower spine
Spina Bifida Meningocele - A small bulge on lower spine
Spina Bifida. The protrusion of meninges.
Myelomeningocele - A large bulge from lower spine

Question 23

What is encephaloceles?

Answer 23

Like spina bifida but in the back of the head

Question 24

What is anencephaly?

Answer 24

A failure of the neural tube to close, only have frontal lobe of brain.

Question 25

What is hydrocephalus?

Answer 25

Build up of fluid on the brain, as a result of neurulation not occurring properly