Limb Development Flashcards
In what week to limbs develop? Which set of limbs develop first?
Limb buds form in week 3.
Upper limbs first then lower limbs.
When do digits form?
Week 8
Initial ossification of limbs begins in what week?
Week 12
At week 4, limb-forming mesoderm releases?
FGF 10 (fetal growth factor)
What occurs after FGF10 is released?
FGF10 stimulates surface ectoderm to become APICAL ECTODERMAL RIDGE (thickening of surface ectoderm)
Once formed, the apical ectodermal ridge releases? What does this stimulate?
FGF 8 and FGF 4, which stimulates the mesoderm
What direction does stimulated mesoderm (FGF 8 and 4) grow?
Proximal to Distal
Skeletal muscle come from what embryonic layer?
The hypomere of the soMITE mesoderm of the paraxial myotome
Cartilage and connective tissue come from what embryonic layer?
the lateral plate of the Somatic mesoderm
The stylopod gives rise to what bones?
Humerus and femur
The Zeugopod gives rise to what bones?
Radius/Ulna and Tibia/Fibula
The Autopod gives rise to what bones?
Carpels, metacapals, digits and tarsals, metatarsals and digits
What are the regions of the limbud (proximal to distal)?
SZA
Stylopod
Zeugopod
Autopod
What occurs in week 5 of limb development?
Hand Plates form (then foot plates)
What occurs in week 6 of limb development?
Digital rays of HAND form from mesenchymal tissue (whole limb is cartilage)
What occurs during week 7 of limb development?
Digital rays of FEET
Osteogenesis of long bones
Rotation of Limbs (think of the number 7)
What occurs during week 8 of limb development?
Separate digits form through apoptosis of surrounding tissues
What causes digits to form in week 8?
BMP which causes apoptosis
The peripheral axons are mylinated by?
Schwann Cells (from Neural crest cells)
Limb musculature is derived from what?
dorsolateral cells of the somites of the lateral plate mesoderm
Sensory axons come from what?
Neural crest cells
Sensory axons (neural crest cells) follow ____ and use them for guidance
motor axons (from neural tube/neuroectoderm)
Limb rotation occurs during which week?
Week 7!
Upper limb rotates _____ 90 degrees while lower limb rotates _____ 90 degrees.
Upper limb rotates laterally
Lower limb rotates medially
The brachial artery is derived from what primary arterial structure?
Primary axial artery
The primary axial artery eventually becomes what artery?
The brachial artery of the upper limb
Talipes Equinovarus
Club Foot
2x more common in males
What is the most common musculoskeletal defect?
Club foot (Talipes Equinovarus)
Hip dysplasia is more common in (males/females)
More common in females
Oligohydramnios
deficiency in amniotic fluid levels
can cause Club foot (unable to fully rotate)
Patterning is regulated by:
HOX genes
AER
Apical ectodermal ridge (progress zone of proliferating mesenchyme)
what regulates the types and shapes of bones?
HOX genes (patterning)
Development of the ventral surface is maintained by
BMPS
Development of the dorsal surface is stimulated by
Wnt7
___ and ___ collectively set up the apical ectodermal ridge
BMPS and Wnt7
Enterior-posterior patterning is established by the _____
Zone of polarizing Activity (ZPA)
