Lesson 1, Topic 1
The anatomy of muscles includes both gross anatomies, comprising all the muscles of an organism, and, on the other hand, microanatomy, which comprises the structures of a single muscle.
Microanatomy of Muscles
Muscles are a soft tissue made up mostly of water and proteins. They have a high concentration of blood vessels and nerves. Muscle is mainly composed of muscle cells.
Look at the illustration of the structure of a skeletal muscle shown below. Locate these anatomical features of a muscle. Skeletal muscle is arranged in discrete muscles or muscle bellies, an example of which is the biceps brachii. It is connected by tendons to processes of the skeleton.
- The muscle itself is called the muscle belly and is surrounded by a fascial membrane called the epimysium. Epimysium is a layer of connective tissue which ensheaths the entire muscle.
- Perimysium is a sheath of connective tissue which groups individual muscle fibers (anywhere between 10 to 100 or more) into bundles or fascicles.
- The fascicles are made up of muscle spindle fibers or muscle cells, also sometimes called myofibers, which are wrapped in a fascial membrane called endomysium. The endomysium, literally meaning within the muscle, is a layer of connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers. Muscle spindles are distributed throughout the muscles and provide sensory feedback information to the central nervous system.
- Within the cells are myofibrils; myofibrils contain sarcomeres, which are composed of actin and myosin.