The blood supply to muscles In order that muscles may be kept in a physiological condition, they must be supplied by an almost continuous stream of blood, for two reasons: first, to bring to them the necessary nutritive materials and oxygen, and second, to remove from them the waste products of their metabolism. This means of transportation is performed by the blood and lymph. Muscles obtain their needed supplies directly from the lymph which bathes the tissues and indirectly from the blood stream. In the capillaries an exchange of materials is constantly taking place during life. These exchanges are accomplished by the well known physical forces of filtration, diffusion, dialysis, and osmosis. Normally, in a state of rest, these forces are adequate in maintaining practically a state of equilibrium between the tissues and the circulating fluids. In times of stress or disease, however, the mechanism may become inadequate and the tissues cannot obtain the proper amount of nourishment or have their waste products removed to the proper excretory organs. Lymphatics are present in the muscles, but are confined to the connective-tissue septa. It is here that the muscle lymph-capillaries take origin. Like most organs of the body, the muscles have only a single source from which they may obtain their nutriment (the blood) while they have a dual exit through which they may rid themselves of their wastes, namely, the venous blood and the lymph, although the latter is of little importance. Movement is the most conspicuous phenomenon of all higher forms of animals. The movement may be within the organism or external and in relation to its environment. The latter movements are executed by means of contracting muscles acting through bony levers over joints. Examples of the three types of levers known to mechanics are found in the body. Unlike those used in mechanics, however, where power is the primary consideration, those found in the body are arranged for speed. The usual axis of the muscle to that of the bony lever places the muscle under a greater disadvantage. The muscles must then be very powerful and dynamic machines. Muscles are named according to their structure and function. The three types are: smooth, cardiac, and striated or skeletal muscle. Each has its specific structural and functional properties which adapt it to the work it must perform. The structural unit of skeletal muscle is the muscle fiber. Thousands of these are bound together by connective tissue into fasiculi and many of these in turn into the muscle. Attachments of the muscles to the bones are through the tendons and aponeuroses; one end to a relatively immovable part, the other to a movable part. Each muscle fiber is composed of muscle fibrils or sarcostyles and sarcoplasm, the whole being enveloped by the sarcolemma. Muscles receive their nutriment from the blood and return their wastes through the channels of the blood stream and lymphatics.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity