1.2 - Blood Plasma

Blood plasma composition

Composed primarily of water (about 92 percent), with proteins, electrolytes (salts) such as sodium, potassium, and magnesium, and hundreds of other dissolved or suspended substances

Plasma proteins

Make up about 7 percent of the volume of plasma, nearly all that is not water; includes plasma proteins unique to plasma plus a smaller number of regulatory proteins such as enzymes and some hormones

Three major groups of plasma proteins

Albumin, globulins, and fibrinogen

Albumin

The most abundant plasma protein, manufactured by the liver; serves as a binding protein/transport vehicle for fatty acids and steroid hormones and is the most significant contributor to colloid osmotic (oncotic) pressure

Colloid osmotic pressure (oncotic pressure)

A type of osmotic pressure that drives the movement of fluid from the interstitial fluid back into the capillaries; albumin is its most significant contributor

Ascites

A condition where fluid collects in the abdomen, contributed to by protein deficiency and lack of albumin in the blood

Globulins

The second most common plasma proteins, making up approximately 38 percent of total plasma protein volume; three subgroups are alpha, beta, and gamma globulins; contribute to osmotic pressure

Alpha and beta globulins

Synthesized in the liver; transport iron, lipids, and fat-soluble vitamins to the cells

Gamma globulins

Proteins involved in immunity, better known as antibodies or immunoglobulins; produced by specialized leukocytes known as plasma cells (unlike other plasma proteins, which are produced by the liver)

Fibrinogen

The third major plasma protein group, produced by the liver; essential for blood clotting

Other plasma solutes

Electrolytes (sodium, potassium, calcium ions), dissolved gases (oxygen, carbon dioxide, nitrogen), organic nutrients (vitamins, lipids, glucose, amino acids), and metabolic wastes; combined, these contribute approximately 1 percent to the total volume of plasma

Plasma (% of blood, Table 1.1)

46-63 percent of blood; composed of water (92 percent, transport medium) and plasma proteins (7 percent)

Formed elements (% of blood, Table 1.1)

37-54 percent of blood; includes erythrocytes (99 percent), leukocytes (less than 1 percent), and platelets (less than 1 percent)

Erythrocytes (Table 1.1)

99 percent of formed elements; produced in red bone marrow; function is to transport gases, primarily oxygen and some carbon dioxide

Granular leukocytes

Neutrophils, eosinophils, and basophils; produced in red bone marrow; provide nonspecific immunity

Agranular leukocytes

Lymphocytes and monocytes; lymphocytes are produced in bone marrow and lymphatic tissue and provide specific immunity; monocytes are produced in red bone marrow and provide nonspecific immunity

Platelets (Table 1.1)

Less than 1 percent of formed elements; produced by megakaryocytes in red bone marrow; function in hemostasis