Transcript Document

• Somites are transient segmented
structures derived from paraxial
mesoderm.
• contain the progenitors of the axial
skeleton, trunk musculature and
associated tendons, trunk dermis,
endothelial cells, and meninges of the
spinal cord
• ventromedial part of the somite forms the
sclerotome
• the remainder of the somite consists of a
dorsal epithelial layer called the
dermomyotome
• dermomyotome quickly separates into two
structures: a dermatome and a myotome
The dermatomes contribute to the dermis
(including fat and connective tissue) of the
neck and the back.
• The myotomes differentiate into myogenic
(muscle-producing) cells
• Each myotome splits into two structures: a
dorsal epimere and a ventral hypomere
• The epimeres give rise to the deep
epaxial muscles of the back, including
the erector spinae and transversospinalis
groups.
• The hypomeres form the hypaxial
muscles of the lateral and ventral body
wall in the thorax and abdomen
[intercostal muscles,external oblique,
internal oblique, and transversus
abdominis, and the rectus abdominis]
• Cervical region:hypaxial myoblasts form
the strap muscles of the neck, including
the scalene and infrahyoid muscles.
• Lumbar region, the hypomeres form the
quadratus lumborum muscles.
• At limb-forming levels, hypaxial myoblasts
invade the developing limb buds and give
rise to the limb musculature.