Learning aims

The following knowledge is provided in this module:

• The origin of the three muscle types
• The development of the hypaxial and epaxial parts of the muscles based on the development of the somites and their differing innervation
• The histological development of muscle fiber to maturity
• The approximate segment level of the innervation of large muscle groups as well as the partial displacement
• Congenital muscle ailments and their causes which can be understood by knowing muscle development

What you already should know

• Formation of the 3-layered embryo

Introduction

In human bodies muscle tissue is met with almost everywhere. One distinguishes thereby three types of muscle tissue:

• Skeletal musculature
• Cardiac musculature
• Smooth musculature

With very few exceptions muscle tissue stems from mesoderm that represents the middle germinal layer in early embryonic development. With the development of the skeletal muscle four successive cell types appear: premyoblasts, myoblasts, myotubes and finally the muscle fibers themselves. With 9-10 weeks the anlagen of almost all the muscle groups have formed and can be compared with how they appear in adults.

In this development there are also disorders that affect the spreading, the form or - far more fundamentally - the metabolism of the musculature.

Delving deeper

• How and when does the differentiation of the somites occur?
• Why is the autochthonous back musculature not innervated by the same nerves as the skeletal musculature?
• Which are the precursor cells of the skeletal musculature (histogenesis of the muscle cells)?
• How do you explain that the cardiac anlage moves from a location in front of the embryo (cardiogenic plate) into a ventral position at the level of the thorax?
• From where does the head musculature come?
• Why does the nerve that innervates the diaphragm derive from spinal nerves C3-C5?