Development of the Limbs Flashcards
When do digits start forming
8th week
When does 1 ossification occur
12th week
Cartilage, connective tissue and bone of limbs come from
Somatic mesoderm
Development of limbs proceeds in what direction
Proximodistally
Stylopod
Humerus and femur
Zeugopod
Radius/ulna and tibia/fibula
Autopod
Carpels, metacarpals, digits and tarsals, metatarsals
Week 5 developments
Hand and foot plates
Chondrification center appears
Week 6 developments
Digital ray of hands
Entire limb skeleton is cartilagenous
Week 7 developments
Digital rays of feet
Osteogenesis of long bones begins
Rotation of limbs
Week 8 developments
Separate digits are formed
Apoptosis
When do motor axons from spinal cord enter limbs
5th week
How do sensory axons find their way to limbs
They follow motor axons
Where do schwann cells come from
Neural crest cells
Primary axial artery becomes
Brachial artery in upper limb or deep artery of thigh
Talipes Equinovarus
Club foot
Most common musculoskeletal defect
Sole of foot turned medially and inverted
More frequent in males
Developmental hip dysplasia
More common in females
Underdevelopment of acetabulum of hip bone
Generalized joint laxity
Positioning of limbs is regulated by
Hox genes
Scapula, humerus, radius/ulna, carpals, metacarpals positioned by which hox genes
Scapula-9 Humerus-10 Radius/ulna-11 Carpals-12 Metacarpals-13
Apical ectodermal ridge proceeds in which way and relies on what signal
Proceeds from proximal to distal and depends on FGF signaling
Ventral surface is maintained by what signal and dorsal surface maintained by what signal? What do these signals set up
Dorsal/extensors by Wnt7
Ventral/flexors by BMPS
These signals set up the apical ectodermal ridge AER
Anterior posterior patterning is set up by what, and what signal is involved
Zone of polarizing activity on posterior side of limb
Shh signaling from ZPA specifically signals posterior elements
Loss of ZPA results in
Loss of posterior elements
Upregulation of ZPA results in
Additional posterior elements (polydactyly)
Duplication of ZPA results in
Duplication of posterior elements (ex. little fingers on both sides of the thumb)
Posterior element formation vs anterior element formation in time
Posterior (little finger/ulna) are formed prior to anterior (radius/thumb)
Arthrogryposis
Congenital joint contractures
Usually involves more than one joint
Thought to be due to neurological defects, muscular abnormalities, joint and contiguous tissue problems, fetal crowding
