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Musculoskeletal System > Embryology > Flashcards

Flashcards in Embryology Deck (21):
1

When do the limb buds start to appear?

End of the 4th week

2

What does the remnant of the notochord become?

Nucleus pulposus

3

What structure contains the nucleus pulposus?

Annulus fibrosus

4

What structure is responsible for ensuring elongation of the limb bud?

AER = apical ectodermal ridge
Keeps the cells close to it undifferentiated

5

How many degrees of asymmetry are there in limbs?

3

6

How do the digits develop?

AER regresses so it is only left over what will be the tips of the digits. Therefore the digits continue to grow leaving gaps/thin tissue between. Webbing left behind is then removed by apoptosis.

7

AER marks which boundary?

Dorsal - ventral

8

What does ZPA stand for?

Zone of polarising activity

9

What is the ZPA?

A signalling centre located on the posterior base of the limb bud. It controls patterning and maintains the AER.

10

Limb defects most commonly affect which limb?

Upper limb

11

Define syndactyly

Fusion of digits

12

Define polydactyly

Extra digits

13

Define amelia

Complete absence of a limb

14

Define meromelia

Partial absence of one or more limb structures

15

Which way do the limbs rotate?

Upper limbs = laterally
Lower limbs = medially

16

Define dermatome

A strip of skin supplied by a single spinal nerve

17

Define myotome

A muscle/group of muscles supplied by a single spinal nerve

18

Where do limb buds appear?

Ventro-lateral body wall

19

Where are the sclerotome and dermatomyotome in relation to one another?

Sclerotome = ventral
Dermatomyotome = dorsal

20

Approximately when do the hand and foot plates form?

6 weeks

21

Approximately when does limb rotation occur?

7 weeks