EMBRYOLOGY

Question 1

Morula

Answer 1

first clump of cells after fertilisation - 16 cells

Question 2

blastocyst

Answer 2

more than 16 cells

Question 3

blastocele

Answer 3

hole in the middle of blastocyst

Question 4

gastrulation

Answer 4

single layer blastula developing into a tri-laminar disc (gastrula)

Question 5

embryo develops into trilaminar disc made up of :

Answer 5

• ectoderm
• mesoderm
• endoderm

Question 6

Neuraltion

Answer 6

process of formation of embryonic nervous system

Question 7

(1) 3rd week of embryonic development and neuraltion

Answer 7

ectoderm thickens in the midline to form neural plate

Question 8

(2) After formation of neural plate what happens in embryonic development

Answer 8

ectoderm undergoes differentia mitosis to cause formation fo a midline groove = NEURAL GROOVE

Question 9

(3) After neural groove what happens in embryonic development

Answer 9

neural groove deepens and eventually detached from the overlying ectoderm to form the NEURAL TUBE

Question 10

(4) what lie lateral to the neural plate and what do these do in embryonic development

Answer 10

Lateral to neural plate lie presumptive NEURAL CREST CELLS which run dorsolaterally along the neural groove

these develop to form many cells types e.g
- Sensory (dorsal root) ganglia of the spinal cord and cranial nerves V, VII, IX, X
- shwanna cells
-pigment cells
- adnrenal medulla
- bony skull
- meninges
- dermis
(quite a lot of head and neck made from neural crest cells)

Question 11

(5) What part of neural tube develops faster than the other and what does this develop into

Answer 11

rostral (e.g. superior) portion of neural tube - which develops into brain (CNS),
grows faster than caudal (i.e. inferior) - which develops into spinal cord

(the central cavity within the neural tube becomes the central canal of the spinal cord and the ventricles of the brain)

Question 12

(6) by the 5th week of embryonic development what can be identified?

Answer 12

three primary brain vesicles:

1 PROCEPHALON (forebrain)
2 MESENCEPHALON (midbrain) 
3 RHOMBENCEPHALON (hindbrain)

Question 13

(7) by the 7th week, further differentiation occurs resulting in the formation of secondary brain vesicles:

Answer 13

1 Procephalon => Telecephalon & Diencephalon

2 Mesencephalon = Mesencephalon

3 Rhombencephalon => Metencephalon & Myelencephalon

look at pic lol

Question 14

(8) Secondry brain vesicles give rise to derivatives in mature brain:

Telecephalon=

Diencephalon =

Mesencephalon=

Metencephalon =

Myelencephalon=

Answer 14

Telecephalon– Cerebral hemisphere & Lateral ventricles

Diencephalon – Thalamus, Hypothalamus & third ventricle

Mesencephalon– Midbrain (colliculli) & aqueduct

Metencephalon– Cerebellum, Pons, upper part of 4th ventricle

Myelencephalon – Medulla oblongata & lower part of 4th ventricle

Question 15

Neural tube usually closes when? and what does failure of this in the spinal cord cause?

Answer 15

end of 4th week

Spina bifida

Question 16

Failure of neural tube closing in Cephalic region causes ?

Answer 16

anencephalus

Question 17

reasons for failure of neural tube closing?

Answer 17

-faulty induction
-environmental teratogens (egents disturbing development)
acting on neuroepithelial cells

Question 18

developmental milestones:

3 weeks 
10 weeks 
3 months 
5 months 
7 months 
9 months

Answer 18

3 weeks - eye formation

10 weeks - cerebral expansion & commissures

3 months - basic structures established

5 months - Myelination has begun

7 months - lobes cerebrum has formed

9 months - gyri & sulci formed

Question 19

Abnormalities to CNS are dependant on time of infection;

6th week =
9th week =
5th- 10th week =

CNS Disorders generally occur in 2nd trimester
risk of disorder falls after … weeks due to fact most CNS structures developed by this time

Answer 19

6th week = eye malformations e.g. cataracts

9th week = Deafness can occur e.g. organ of corti

5th- 10th week = cardiac malformation

16 weeks

Question 20

Innervation fo dermal skin from

Answer 20

28 weeks

Question 21

Non noxious

Answer 21

means no pain detected e.g

dorsal root ganglion connects to spinal cord from 8 weeks but this is non noxious

Question 22

C-Fibre connection

Answer 22

(noxious (painful) Stimuli ) from 19+ weeks

Question 23

Organised thalamus what weeks

Answer 23

from 8+

Question 24

retinal inputs work at what weeks ?

Answer 24

14-16 weeks

Question 25

Myelination occurs when

Answer 25

from 25 weeks

speed of conduction increases with myelination

Question 26

connections from thalamus to cortex occur from

Answer 26

24 weeks