Lecture: Butaric - Embryology Flashcards
_______ are responsible for initial division of mesenchymal cells and segmentation (leg vs. thigh elements)
HOX genes
all lower limb nerves are part of …
lumbosacral plexus
describe a clubbed foot
congenital talipes equinovarus
foot is inverted, with sole pointed mediall
tendons (including Achilles’ tendon) are shortened
summary of key points
- end week 4 limb bud consists of mesenchyme surrounded by ectoderm
- AER and HOX genes promote limb growth
- week 7 digital rays appear, week 8 digits separate by apoptosis
- bones: from mesenchymal precursors (week 5) follow endochondral ossification (beginning week 7)
- muscles: from myogenic cells, organized as myotomes and by extensor/flexor compartments
- dermatomes: follow myotome organization and relate to medial 90 rotation of lower limb
failure of toes to separate
syndactyly
At what level do the lower limb buds form?
L2-S2
what are muscle, bone and connective tissue derived from?
mesoderm
6-7 weeks you see …
digital rays and bone precursors
8 weeks you see …
differentiated toes and bone
when is the formation of trilaminar disc?
week 3
the skin, CNS, and neural crest cells are derived from what?
ectoderm
when do mesenchymal precursors to cartilage begin?
week 5
great toe medial dermatome
L4-5 ***
Describe the outer and inner layers of the lower limb bud?
Outer ectoderm layer w/ apical ectodermal ridge AER
Inne rcore of mesenchyme
Adult dermatomes inguinal ligament anterior knee (patella) medial side of foot, great toe posterior thigh, leg lateral side of foot
L1 L3,4 L4,5 S1,2 S1