embryo Flashcards
what determines the course of limb development and controls future development of limb?
AER due to presence of fibroblast growth factor
what promotes the patterning of distal ends into flat paddle hands/feet
HOX gene
when do hand vs feet paddles have 5 digital rays
6th week-hand, 7th week foot
when does apoptosis occur of the mesenchymal tissue between digital rays
8th week
when do limb buds start to appear/aka activation of mesenchymal cells? specfically upper limb vs lower limb-include which vertebral region?
4th week
upper limb (C5-T1): 26-27 days lower limb (L2-S2): 2 days after
when does the cartilage model begin? what is it derived from?
5th week; mesenchymal cells
when is the entire cartilaginous skeleton complete?
6th week
when does endochondrial ossification begins? process? (ie whats the primary ossification center)
7th week; chondrocytes replaced by bone bone producing cells
begins in diaphysis of long bones(primary ossification center)
where do myogenic cells originate from? process?
dermomyotome region of somites. then it migrates into mesenchymal cells of limb buds where they differentiate into myoblasts and develop muscle cells of limb
what do somites differentiate into?
- dermatome–stay deep to ectoderm to give rise to skin
- . myotome
- sclerotome: axon process of spinal cord
upper and lower limb rotation direction, what does the lower limb rotate around
lower limb: 90 deg medial
upper limb: lateral
opposite direction
LL rotate around the profunda femoris
extra digits resulting from what? name?
polydactyly: extra digital rays
what is syndactyly
attached digits; malformation of apoptosis
amelia
absence of limbs
meromelia
absence of part of a limb
lobster claw deformity is also known as what? cause?
cleft foot/hand result from failure of development of one or more digital rays
appears to be split down in middle
brachy dactyly
short digits
what is the defect on club foot? how does this affect their gait, what is this also know as
abnormality involving talus
individual walk on ankle rather than foot
sole of foot is turned medially and inverted
Talipes equinovarus
what is the role of AER
promote outgrowth and lengthening of limb buds
what does mesenchyme form? in the influence of what?
bone, cartilage, blood vessels , joints, fascial layers, lymphatic vessels
in the influence of HOX genes
critical period for embryo
24-36 days
what does bone form from
mesenchyme
where does the core of mesenchymal cesll derive from
somatic component of lateral mesoderm layer of embryo
what is the role of HOX gene
control direct cell division and differentiation
