In order for the human being to carry out the many intricate movements that must be performed, approximately 650 skeletal muscles of various lengths, shapes, and strength play a part. Each muscle consists of many muscle cells or fibers held together and surrounded by connective tissue that gives functional integrity to the system. Three definite units are commonly referred to:
- endomysium—connective tissue layer enveloping a single fiber;
- perimysium—connective tissue layer enveloping a bundle of fibers;
- epimysium—connective tissue layer enveloping the entire muscle
Muscle Attachment and Function
For coordinated movement to take place, the muscle must attach to either bone or cartilage or, as in the case of the muscles of facial expression, to skin. The portion of a muscle attaching to bone is the tendon. A muscle has two extremities, its origin and its insertion.