Blood has many functions:
- Blood helps maintain homeostasis. Blood and tissue fluid are the body's internal environment, and as such, their characteristics must remain within certain limits if the body is to remain healthy.
- Blood helps regulate body temperature. If the body is hot, excess heat generated by muscles is taken to the skin by the blood, where the heat can be dissipated. If the body is cold, heat remains within the body where the vital organs are located.
- Blood contains buffers that help maintain the pH of the blood.
- The fluid and electrolyte balance of blood is largely maintained by the kidneys, which excrete or retain electrolytes and water as necessary. However, the blood transports the hormones responsible for this regulation.
- Blood plays a significant role in infection fighting.
- Some white blood cells phagocytize pathogens, and others produce antibodies, proteins that combine with and inactivate antigens, which are foreign substances in the blood.
- Blood keeps the composition of tissue fluid constant by transporting nutrients and oxygen to capillaries, where they diffuse into tissue fluid. It also picks up carbon dioxide at capillaries and takes it to the lungs for excretion.
- When blood vessels are damaged, blood clots and clotting prevent hemorrhage (hem'o-rij)-that is, the escape of blood from blood vessels.
- Blood transports oxygen from the lungs to the capillaries and nutrients from the intestine to the capillaries, where they enter tissue fluid.
- When a blood vessel is cut, it immediately constricts to reduce blood flow to the area. Then, the platelets stick to collagenous fibers in the connective tissue layer beneath the endothelium. As more and more platelets congregate, they form a platelet plug that can fill a small break.
Blood has many functions, including helping to maintain homeostasis. regulating body temperature, and fighting infection. Two additional functions are transport and clotting.
