Myotome

The term myotome (from Greek Mys " muscle " tomos " cutting " ) is used in embryology and neuroanatomy and characterized a muscle segment.

Embryology

In the embryo, the myotome is the muscular mesoblastic somite. During embryonic development occur in the trunk area from the mesoderm, the somites ( So ). From the dorsolateral part of the skin ( dermatome ) and forms from the deeper cells, the precursors of muscle cells ( myoblasts ). These cells are referred to as myotome. In the head and neck muscles arise from unsegmented myotomes.

In the short range, a myotome is divided into:

• Epimer: upper range, which indicates the dorsal spinal musculature. It is supplied by the posterior primary rami of the spinal nerves.
• Hypomere: lower range, which is developed to the three layers of the lateral abdominal wall and supplied by the ventral rami of the spinal nerves. The same applies to the limb muscles, which also arise from the Hypomeren. At the lower part of a longitudinal muscle strand, which is the rectus abdominis arises ( there is still tendinae to the Inter cesarean sections recognizable originally segmental origin) and the ventral neck muscles developed.

Anatomy

As a result of segmental conditioning of the muscles in the embryo, showing the muscles in the adult a assignment to specific spinal segments, more precisely to their Spinalerven. Also anatomically is a myotome muscles, which is innervated by a spinal nerve.

Due to the plexuses of the spinal nerves every anatomical muscle of the limbs but from several spinal nerves innervate ( plurisegmental innervation ). Therefore, a failure of a spinal nerve does not lead to total failure of the myotome, but it occurs only a partial paralysis ( paresis ). If several segments affected, or is a Plexusnerv damaged, so there is a flaccid (complete) paralysis ( paralysis ).

The afferent pathways of the spinal nerves from the muscles is called Mackenzie zone. They play a role in the phenomenon of the transferred pain.