- See:
limb development
- Discussion:
- skeleton and skeletal muscle develop from the mesoderm;
- thin layer of cells in early embryo located between ectoderm &
endoderm & interrupted in midline by notochord;
- mesoderm on either side of notochord forms longitudinal mass, paraxial mesoderm;
- at 21st day of development, paraxial mesoderm forms paired,
cuboidal masses, somites;
- somites first form first occipital somites, at cranial end of the notochord;
- subsequent pairs of somites appear caudally next to previous pair;
- total of some 42 to 44 pairs of somites are formed between the 21st
and the 30th days of development;
- lateral plate mesoderm:
- remains largely unsegmented
- remains attached to ventrolateral angle of each somite by intermediate
mesoderm, which later forms the nephrogenic cord;
- in neck & trunk, each somite develops into three recognizable portions
- laterally a dermatome, destined to differentiate into dermis;
- medially & ventrally sclerotome, from which develop vertebrae,
intervertebral discs, & ligaments of vertebral column;
The Ectodermal Thickening and Ridge in the Limbs of Staged Human Embryos.
R. O'Rahilly et al.
J. Embrylolgy Experimental Morphology. Vol 4, Part 3, p 254-264.
