Embryology (Lecture 2) Flashcards
(117 cards)
Limb bud appear in the __ week
4th
limb bud appear as
as small elevations on the ventrolateral body wall
limb buds are derived from
the somatic body wall (lateral plate mesoderm)
Mesenchyme (embryonic tissue) covered in
ectoderm
upper limb buds are visible in the
cervical region ~day 24
lower buds are visible in the
lumbar region ~day 28
limb bud contains MESENCHYME that will form ____ of the lower extremity
cartilage/bone and dermis
muscles are derived from
somites, myoblasts migrate into developing limb
where are motor units derived from?
spinal cord
schwann cells,
melanocytes,
sensory neurons
and sympathetics are derived from
neural crest cells
proximal/distal directional axes of limb
thigh,leg,foot
dorsal/ventral directional axes of limb
anterior vs posterior thigh/leg
dorsum vs plantar foot
cranial/caudal directional axes of limb
big toe (cranial,preaxial) to little toe (caudal, postaxial)
limb elongation progresses from `
proximal to distal
stylopod
thigh
zeugopod
leg
autopod
foot
in early stages of limb elongation the limbs appear as
flippers on the ventrolateral wall
ectoderm over distal tip of limb condenses to form
the apical ectoderm ridge (AER)
what represents to dorsal/ventral boundary
apical ectoderm ridge (AER)
underlying mesenchyme induces
the formation of AER
AER induces the proliferation of
the underlying mesenchyme and elongation of the limb (progress zone)
mesenchyme obtains positional information about
future proximal/distal location
studies that removed the AER showed
the formation of truncated limb