Human Anatomy and Physiology - N. I. Fedyukovich 2003

The Muscular System
Muscle Structure

As an organ, a Muscle (musculus) consists of Muscle tissue, loose and Cytology/practical/45.html">Dense Connective Tissue, vessels, and nerves; it has a specific shape and performs a corresponding function.

The structural framework of a muscle is formed by thin bundles of striated muscle fibers, which are covered by a connective tissue sheath called the endomysium. Larger bundles are separated from one another by the perimysium, and the entire muscle is surrounded by the epimysium, which then continues into a tendon and is referred to as the peritendineum.

Loose connective tissue forms the soft framework of the muscle, from which the muscle fibers originate, while dense tissue forms the tendinous ends of the muscle. About 1/3 of the fibers attach to bones, while 2/3 are supported by the connective tissue structures of the Muscles. The muscle bundles form a fleshy belly that can actively contract and then, continuing into a tendon, attaches to bones. The initial part of muscles, especially long ones, is also called the HEAD, and the terminal part is called the tail.

Tendons vary in size across different muscles. They are longest in the limb muscles. Muscles that form the abdominal wall have a broad, flat tendon called an aponeurosis.

The digastric muscle has an intermediate tendon between its two bellies, or several short tendons that interrupt the course of the muscle bundles (for example, in the rectus abdominis muscle). A tendon is significantly thinner than a muscle, but its strength is immense. Thus, the calcaneal (Achilles) tendon can withstand a load of about 500 kg, and the tendon of the quadriceps femoris muscle can withstand 600 kg.

The Blood supply and innervation of a muscle occur from its inner side, where capillaries and nerve fibers carrying motor impulses run to each muscle fiber.

Sensory nerve endings are located in both tendons and muscles.