Limb Development Flashcards
when do limb buds form
4th week
when do digits form
8th week
when does primary ossification occur
12th week
where does cartilage, bone, and connective tissue come from
somatic layer of lateral plate mesoderm
limb forming mesoderm releases what
FGF 10
FGF-10 stimulates what
thickening of surface ectoderm to apical ectoderm ridge
Apical ectoderm ridge releases what
FGF 8 and FGF 4
stylopod is most proximal region of limb bud makes what
humerus and femur
zeugopod makes what
radius/ulna or tibia/fibula
auto pod makes what
carpels, metacarpals, digits
hand and foot plates and chondrification center made when
5th week
digital rays of hands and limb skeleton is completely cartilaginous
6th week
digital rays of feet, osteogenesis of long bones, and rotation of limbs
7th week
separate digits are formed due to apoptosis; due to BMP family
8th week
limb musculature
derived from dorsolateral cells of somites; MYOTOMES
where does upper limb bud form
cervical region
leg limb buds form from where
lumbar and thoracic regions
when do motor neurons (from neural tube/neuroectoderm) enter the limb buds
5th week
sensory axons follow motor neurons and are are from what
neural crest cells
how does upper limbs rotate during week 7
laterally 90
how do lower limbs rotate during week 7
medially 90
derived from the primary axial artery
brachial artery and common interosseous (upper limb) or deep artery of thigh
proximo distal growth and patterning
AER releases FGF 8 and 4 after mesoderm stimulates with FGF 10; regulation by HOX genes
dorso ventral patterning
ventral surface maintained by BMPs and dorsal by Wnt7; these signal set up the AER
anterior-posterior patterning
established by the ZPA (zone of polarizing activity); Shh and retinoic acid signaling from ZPA stimulates posterior elements (little finger, ulna, digits 3 and 4)
loss of ZPA signaling
loss of posterior elements (no pinky)
up regulation of ZPA
additional posterior elements; polydactyly
