Question

What is Development of the Appendicular Skeleton

Answer 1

The appendicular skeleton con­sists of the pectoral and pelvic girdles
and bones of the upper and lower limbs. The bones of the appendicular skeleton develop from mesenchyme derived from the somatic mesoderm and not from the somites. Mesen­chymal differentiation occurs in the upper limbs first and proceeds in a proximodistal direction in each limb. Mesenchymal models are replaced by cartilaginous models during the 6th week of development. Primary centers of ossification begin to appear in the 8th week of development and are seen in almost all bones of the extremities by the 12th week. All secondary centers of ossification (except that of the lower end of femur) appear after birth. Fusion of the primary and secondary centers occurs mostly in the late adole­scence. One exception to the general pattern of development of the appen­dicular bones is the clavicle. This bone initially develops by intramembranous method of osteogenesis but later de­velops growth cartilages at both ends and the adult bone is mostly endo-chondral in development.
Development of Joints
Development of the joints (ar­ticulations) starts in the 6th week of development and advances quickly, so that, structurally, the developing joints come to resemble the adult joints by the end of the 8th week. The joints develop from mesenchyme which becomes condensed between two developing bones and is called inter­zonal mesenchyme.