Delivering oxygen from the lungs and nutrients from the digestive tract to all body cells.

Transporting metabolic waste products from cells to elimination sites.

Transporting hormones from the endocrine organs to their target organs.

Maintaining appropriate body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss.

Maintaining normal pH in body tissues. Blood also acts as the reservoir for the body’s “alkaline reserve” of bicarbonate ions.

Maintaining adequate fluid volume in the circulatory system.

Preventing blood loss. Platelets and plasma proteins initiate clot formation. Preventing infection by drifting along in blood are antibodies, complement proteins, and leukocytes (white blood cells), that help defend the body against bacteria and viruses.

Intrinsic organs are able to regulate their own blood flows by varying the resistance of their arterioles. They are metabolic (chemical) or myogenic (physical). Metabolic and myogenic factors determine the final autoregulatory response of a tissue. An example is the reactive hyperemia refers to the increased blood flow into a tissue that occurs after the blood supply to the area has been temporarily blocked. This gives a myogenic response and from the metabolic wastes that accumulated during occlusion.

Arteries carry blood away from the heart, so they are said to “branch,” “diverge,” or “fork” as they form smaller and smaller divisions. They carry oxygenated blood in systemic circulation

Veins carry blood toward the heart and so are said to “join,” “merge,” and “converge” into the successively larger vessels approaching the heart. They carry deoxygenated blood in systemic circulation

Capillary beds cause the flow of blood from an arteriole to a venule in a process called microcirculation. These then drain into a postcapillary venule. Blood flow through the capillary bed is controlled by the diameter of the terminal arteriole as well as by all of the arterioles upstream from it. As blood flows through the capillaries, it takes part in exchanges of gases, nutrients, and wastes with the surrounding tissue cells.

The epicardium is the thin, transparent outer layer of the wall and is composed of delicate connective tissue.

The myocardium, comprised of cardiac muscle tissue, makes up the majority of the cardiac wall and is responsible for its pumping action. The thickness of the myocardium mirrors the load to which each specific region of the heart is subjected

The endocardium is a thin layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves.