Development of the Limbs - Larsen's Human Embryology

Question 1

The …..limb budsappear on day … as small bulges on the lateral body wall
limb morphogenesis takes place from … to …. weeks, with development of the lower limbs ……. that of the upper limbs

Answer 1

upper, 24
4th, 8th
lagging slightly

Question 2

Each limb bud consists of a……………. covered by an……….. Along the ………….of the limb bud, the ectoderm thickens to form anapical ectodermal ridge.

Answer 2

mesenchymal coreof mesoderm
epithelial capof ectoderm
distal margin
apical ectodermal ridge

Question 3

AER - maintains outgrowth of limb bud along which axis

Answer 3

proximal-distal axis

Question 4

The bones, tendons, and other connective tissues of the limbs arise from the ……………, but the limb muscles and endothelial cells arise in the ………… and migrate into the limb buds.

Answer 4

lateral plate mesoderm,
somitic mesoderm

Question 5

what does tetra-amelia( mean

Answer 5

absence of all four limbs

Question 6

Time frame of limb development

Answer 6

Limb development takes place from 4th to 8th week
- Upper limb bud develop slightly in advance of lower limb buds
- Although by the end of the period of limb development - upper and lower limb buds are nearly synchronized

Question 7

Limb development - facts

Answer 7

• Each limb bud consists of an outer ectodermal cap and an inner mesodermal core
• As each limb bud forms, the ectoderm along the distal tip of the bud is induced by the underlying somatic mesoderm to form a ridge-like thickening called the apical ectodermal ridge (AER)

Question 8

Patterning of limb bud - facts
Name the 3 axes of limb bud………….

Answer 8

• Once limb bud has formed, it differentiates with respect to 3 axes:
• Proximal-distal axis
  -Cranial-caudal axis
• Dorsal-ventral axis