Embryology 1

Question 1

What is the process by which brain and spinal cord develops?

Answer 1

Neurulation

Question 2

What structure induces formation of CNS?

Answer 2

Notochord - signals ectoderm to form neural plate

Question 3

What does the neural plate form?

Answer 3

folds to form neural tube which will later differentiate to form spinal cord and brain

Question 4

Where do neural crest cells come from and what is their function?

Answer 4

derived from neural tube and work to form PNS

Question 5

What are the three embryonic germ layers that make up the trilaminar disc of the embryo

Answer 5

• ectoderm
• mesoderm
• endoderm

Question 6

What is the neural plate made of?

Answer 6

Neuralectoderm

Question 7

Where does the notochord develop?

Answer 7

in the mesoderm layer

Question 8

What is the function of notochord?

Answer 8

• influences cells beside it (can’t reach the further out ectodermal cells)
• turning them into neural tissue by changing shape of ectoderm cells (become wider at the base)
• this causes formation of tube in ectoderm layer (neural tube)

Question 9

What is the border between cells influenced by notochord and not influenced called?

Answer 9

Neural crest

Question 10

How does the neural crest disconnect from rest of ectoderm?

Answer 10

• neural tube separates from surface of ectoderm (now lives within mesoderm)
• this leaves borders of either side of neural plates to join together forming neural crest
• neural crest sits between ectoderm layer and neural tube

Question 11

What nervous structures are formed from neural crest cells?

Answer 11

• spinal ganglia
• ganglia of ANS
• ganglia of CN
• sheaths of peripheral nerves
• meninges
• melanocytes
• suprarenal medulla
• skeletal and musclular components of head

Question 12

What structures make up intervertebral disc?

Answer 12

Annulus fibrosus (outer ring)
Nucleus pulposus (inner)

Question 13

What other cells does notochord influence?

Answer 13

• mesoderm cells beside it

- mesoderm form somites (paired cuboidal bodies, one on each side of neural tube)

Question 14

What are the three parts of the somites?

Answer 14

sclerotome (form bone)
myotome (muscle)
dermatome (connective tissue)

Question 15

What are the possible congenital abnormalities caused by folate deficiency?

Answer 15

Head
- Cranioarachischis 
- Anencephaly 
- Encephalocele 
- Iniencephaly 
Spine
- Spina Bifida (occulta or dysraphism) 
- meningocele
- myelomeningocele

Question 16

What are the different forms of spina bifida?

Answer 16

Occulta
meningocele
myelomeningocele

Question 17

What is spina bifida Occulta?

Answer 17

• failure of vertebrae to fuse
• no herniation of spinal cord doesn’t occur
• asymptomatic
• nerves can be involved if their is change to skin

Question 18

What is spina bifida meningocele?

Answer 18

• meninges protrude
• open neural plate
• vertebrae can still form normally

Question 19

What is spina bifida myelomeningocele?

Answer 19

• protrusion of meninges and neural tissue
• brainstem and rest of brain ends up being pulled down
• often develop hydrocephalus due to defect causing blockage

Question 20

What is encephaloceles?

Answer 20

• sac-like protrusion of brained meninges through opening in the cranial vault
• cranial meningocele (meninges only)
• Cranial encephalocele (meningeal sac and part of brain)

Question 21

What is anencephaly?

Answer 21

• absent cerebral hemispheres and cerebellum

- occurs in 1/1000 live births

Question 22

What is the best way to prevent congenital defects?

Answer 22

• take folate at least 400mg especially for first 4 weeks of pregnancy

Question 23

When are neural tube defects most likely tot develop?

Answer 23

wk 3-16

Question 24

What structure does the notochord become in adults?

Answer 24

Nucleus pulpous of intervertebral discs