Muscles

The muscular system is the body's network of tissues that controls movement both of the body and within it (such as the heart's pumping action and the movement of food through the gut). Movement is generated through the contraction and relaxation of specific muscles.
The muscles of the body are divided into two main classes: skeletal (voluntary) and smooth (involuntary). Skeletal muscles are attached to the skeleton and move various parts of the body. They are called voluntary because a person controls their use, such as in the flexing of an arm or the raising of a foot. There are about 650 skeletal muscles in the whole human body. Smooth muscles are found in the stomach and intestinal walls, vein and artery walls, and in various internal organs. They are called involuntary muscles because a person generally cannot consciously control them. They are regulated by the autonomic nervous system (part of the nervous system that affects internal organs).

venous insufficiency

Venous insufficiency is a condition in which the veins have problems sending blood from the legs back to the heart. Normally, valves in your deeper leg veins keep your blood flowing back toward the heart so it does not collect in one place. But the valves in varicose veins are either damaged or missing. This causes the veins to stay filled with blood, especially when you are standing. Chronic venous insufficiency is a long-term condition. It occurs because a vein is partly blocked, or blood is leaking around the valves of the veins.