Flashcards in Embryology Deck (21)
When do the limb buds start to appear?
End of the 4th week
What does the remnant of the notochord become?
What structure contains the nucleus pulposus?
What structure is responsible for ensuring elongation of the limb bud?
AER = apical ectodermal ridge
Keeps the cells close to it undifferentiated
How many degrees of asymmetry are there in limbs?
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.
AER marks which boundary?
Dorsal - ventral
What does ZPA stand for?
Zone of polarising activity
What is the ZPA?
A signalling centre located on the posterior base of the limb bud. It controls patterning and maintains the AER.
Limb defects most commonly affect which limb?
Fusion of digits
Complete absence of a limb
Partial absence of one or more limb structures
Which way do the limbs rotate?
Upper limbs = laterally
Lower limbs = medially
A strip of skin supplied by a single spinal nerve
A muscle/group of muscles supplied by a single spinal nerve
Where do limb buds appear?
Ventro-lateral body wall
Where are the sclerotome and dermatomyotome in relation to one another?
Sclerotome = ventral
Dermatomyotome = dorsal
Approximately when do the hand and foot plates form?