Blood is a sticky, opaque fluid with a characteristic metallic taste. Depending on the amount of oxygen it is carrying, the color of blood varies from scarlet (oxygen rich) to dark red (oxygen poor). Blood is more dense than water and about five times more viscous, largely because of its formed elements. Blood is slightly alkaline, with a pH between 7.35 and 7.45, and its temperature (38C or 100.4F) is always slightly higher than body temperature. Blood accounts for approximately 8% of body weight.
Blood is the only fluid tissue in the body. The microscope reveals that blood has both cellular and liquid components. Blood is a specialized type of connective tissue in which living blood cells, called the formed elements, are suspended in a nonliving fluid matrix called plasma (plaz mah). The collagen and elastic fibers typical of other connective tissues are absent from blood, but dissolved fibrous proteins

Distribution
1.Delivering oxygen from the lungs and nutrients from the digestive tract to all body cells.
2.Transporting metabolic waste products from cells to elimination sites
3.Transporting hormones from the endocrine organs to their target organs.

Regulation
4.Maintaining appropriate body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss.
5.Maintaining normal pH in body tissues. Many blood proteins and other blood-borne solutes act as buffers to prevent excessive or abrupt changes in blood pH
6.Maintaining adequate fluid volume in the circulatory system. Salts (sodium chloride and others) and blood proteins act to prevent excessive fluid loss from the bloodstream into the tissue spaces.

Protection
7.Preventing blood loss. When a blood vessel is damaged, platelets and plasma proteins initiate clot formation, halting blood loss.
8.Preventing infection. Drifting along in blood are antibodies, complement proteins, and white blood cells, all of which help defend the body against foreign invaders such as bacteria and viruses.

straw-colored, sticky fluid Although it is mostly water (about 90%), plasma contains over 100 different dissolved solutes, including nutrients, gases, hormones, wastes and products of cell activity, ions, and proteins.

Function of Plasma
1.Carries nutrients including glucose which is the primary source of energy for cell metabolism.
2.Hormones are transported around the body in plasma attached to plasma proteins.
3.Contains inorganic ions which are important in regulating cell function and maintaining homeostasis.
4.Contains clotting agents and on exposure to air it will form a clot. Aids healing and stops bleeding.
5.Contains antibodies (gammaglobulins) to help resist/fight off infections.