Changes

==Introduction==

==Introduction==

Muscle cells can come from two lineages in the somite. Limb and body muscle develop from hypaxial muscle in the lateral regions of the somite. Back muscle develops from epaxial muscle in the dorsal regions of the somite. Muscle fibres have hundreds of nuclei and function as a syncytium.

[[Muscles - Anatomy & Physiology|Muscle]] cells can come from two lineages in the [[Developmental Biology - Somite Development - Anatomy & Physiology|somite]]. Limb and body muscle develop from hypaxial muscle in the lateral regions of the somite. Back muscle develops from epaxial muscle in the dorsal regions of the somite. Muscle fibres have hundreds of nuclei and function as a syncytium.

#Cells differentiate to form '''myoblasts'''.

#Cells differentiate to form '''myoblasts'''.

#*Cells still mesenchymal but can no longer migrate as differentiated.

#*Cells still mesenchymal but can no longer migrate as differentiated.

#*Muscle gene expression.

#*[[Muscles - Anatomy & Physiology|Muscle]] gene expression.

#The '''myotube''' is formed; cells become multi - nucleated to form a syncytium.

#The '''myotube''' is formed; cells become multi - nucleated to form a syncytium.

#*Muscle enzymes are produced.

#*Muscle enzymes are produced.

==Limb Muscle Development==

==Limb Muscle Development==

*Skeletal muscle of the limbs originates from those somites closest to the limbs.

*[[Muscles - Anatomy & Physiology#Skeletal Muscle|Skeletal muscle]] of the limbs originates from those [[Developmental Biology - Somite Development - Anatomy & Physiology|somites]] closest to the limbs.

#Signalling factors from the limbs cause cells to migrate from the somite.

#Signalling factors from the limbs cause cells to migrate from the somite.

#*Singalling factors cause the hypaxial lamina to break down.

#*Singalling factors cause the hypaxial lamina to break down.

#*This allows cells to migrate.

#*This allows cells to migrate.

#*''Few cells migrate; but they rapidly prolifate during migration to increase cell numbers.''

#*''Few cells migrate; but they rapidly prolifate during migration to increase cell numbers.''

#Muscle precursors migrate into the limb bud (proliferating).

#Muscle precursors migrate into the [[Developmental Biology - Limb Development - Anatomy & Physiology|limb bud]] (proliferating).

#*At the proximal region of the limb, two populations of cells exists.

#*At the proximal region of the limb, two populations of cells exists.

#*These are the dorsal and ventral masses.

#*These are the dorsal and ventral masses.