MSK embryology - unlikely to ask in OSPE Flashcards
MSK system develops from which germ layer
Lateral plate somatic mesoderm
What genes regulate the patterning of mesenchymal cells in the lateral plate somatic mesoderm
Homeobox (HOX) genes
Upper limb buds develop opposite
Lower limb buds develop opposite
caudal cervical segments
lumbar + sacral segments
At the apex of each limb bud, the ectoderm thickens to form an …
apical ectodermal ridge
At the apex of each limb bud, the ectoderm thickens to form an apical ectodermal ridge, what is the function of this
Induces growth of surrounding limb mesenchyme
What process is responsible in forming defined webbed digits
Apoptosis - breaks down tissue in the interdigital regions
Cartilaginous precursors of limb bones develop by what process within the mesoderm
chondrification
What type of ossification occurs in limb bones
Endochondral
except clavicle - membranous
Upper limbs need to … so that extensors are on the lateral and posterior surfaces
rotate 90 degrees laterally
Lower limbs need to … so that the extensors are on the anterior surface
rotate 90 degrees medially
MSK system develops near the end of which week
4th
What is
- amelia
- meromelia
- phocomelia
- micromelia
Amelia - total limb absence
Meromelia - partial limb absence
Phocomelia - some long bone absence
Micromelia - small limbs
Critical period of limb development is how many days after fertilisation
24-36
What is polydactyly
More than 5 digits on hands or feet - extra digit lacks muscle development
What is syndactyly + developmental basis of syndactlyl
Joined digits - either webbing of skin (cutaneous syndactyly) or fused underlying bones (osseous syndactyly)
More common in FOOT
