A material source can be found at the end of the section. The 700 or more muscles of the body are grouped in various ways. Even the metabolic character of the muscle fibers is different in these muscles, although in humans there are no exclusively fast or slow muscles, as there are in many other organisms.
Most muscles have Latin names that refer to their primary function, location, shape, or size.
Some muscles even gain extra origin or insertion to such fibous tissue, which is made of the same tough, inert material as tendons. Deep fascia often becomes specialized in certain areas in order to hold down tendons and prevent them from bowstringing. For example, the flexor running to the last joints in the fingers are held down by fibrous-tissue loops and tunnels at the front of the wrist, palm, and fingers. Because many tendons run through retinacula, they experience friction all around them. Hence, tubular synovial sheaths surround and protect the tendons.