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Somite Development - Anatomy & Physiology (view source)
Revision as of 14:37, 29 August 2008
, 14:37, 29 August 2008→Somite Maturation
::'''Dermotome''' - develops into the dermis.
::'''Dermotome''' - develops into the dermis.
*Somites develop in an identical manner, although those at the posterior develop after those at the anterior.
*Somites develop in an identical manner, although those at the posterior develop after those at the anterior.
*Somitic derivatives form according to the somite's position along the anterior - posterior axis.
**Formation of sclerotome, myotome and dermotome is not intrinsic, but governed by '''environmental signals'''.
**However, positional information is '''predetermined and intrinsic''' to the somite. Positional information is important to form the appropriate type of vertebrae, muscle and skin along the anterior - posterior axis.
**Positional information is governed by HOX gene expression. Each somite expresses a unique number of HOX genes.
*The chick has 12 somites.
*The chick has 12 somites.
''Stages of somite maturation as observed along the anterior - posterior axis:''
''Stages of somite maturation as observed along the anterior - posterior axis of the chick embryo:''
===Somites I - III===
===Somites I - III===
===Somites IV - X===
===Somites IV - X===
*Epithelial cells on the ''dorsal'' aspect of the somite develop into the dermomyotome.
*Epithelial cells on the ''dorsal'' aspect of the somite develop into the '''dermomyotome'''.
*Epithelial cells of the ''ventral - medial'' portion of the somites develop into the sclerotome.
*Epithelial cells of the ''ventral - medial'' portion of the somites develop into the '''sclerotome'''.
**Cells undergo an epithelial to mesenchymal transition.
**Cells undergo an epithelial to mesenchymal transition.
**Somitocoel cells join these new mesenchymal cells to also become part of the sclerotome.
**Somitocoel cells join these new mesenchymal cells to also become part of the sclerotome.