Plasma refers to the liquid that suspends the red blood cells within the body. Plasma is the liquid part of blood and is approximately 91% water. The solvent ability of water enables the plasma to transport many types of substances. Nutrients absorbed in the digestive tract, such as glucose, amino acids, and minerals, are circulated to all body tissues. Waste products of the tissues, such as urea and creatinine, circulate through the kidneys and are excreted in urine.
Hormones produced by endocrine glands are carried in the plasma to their target organs, and antibodies are also transported in plasma. Most of the carbon dioxide produced by cells is carried in the plasma in the form of bicarbonate ions (HCO3 – ). When the blood reaches the lungs, the CO2 is re-formed, diffuses into the alveoli, and is exhaled.The important thing to know is over half of the total volume of blood is plasma. The plasma itself is 90% water. Many different substances dissolved or suspended in the water, make up the other 10%.
The plasma content varies somewhat, since the substances carried by the blood to and from the organs get used and added to. However, the body tends to maintain a fairly constant level of these substances. For example, the level of glucose, a simple sugar, is maintained at a remarkably constant level of about on tenth of a 1% solution. After water, the next largest percentage of material in the plasma is protein. Proteins are the principal constituents of cytoplasm and are essential to the growth and the rebuilding of body tissues.
The plasma proteins include the following:
1.Albumin, Albumin is the most abundant plasma protein. It too is synthesized by the liver. Albumin contributes to the colloid osmotic pressure of blood, which pulls tissue fluid into capillaries. This is important for maintaining the osmotic pressure of the blood. This protein is manufactured in the liver.
2.Globulins. This is the second most common plasma proteins which is the A heterogeneous group, there are three main subgroups known as alpha, beta, and gamma globulins.
The alpha and beta globulins transport iron, lipids, and the fat-soluble vitamins A, D, E, and K to the cells; like albumin, they also contribute to osmotic pressure. The gamma globulins are proteins involved in immunity and are better known as an antibodies or immunoglobulins. Although other plasma proteins are produced by the liver, immunoglobulins are produced by specialized leukocytes known as plasma cells. (Seek additional content for more information about immunoglobulins.) Globulins make up approximately 38 percent of the total plasma protein volume, in clinical levels of 1.0–1.5 g/dL blood.
3.Fibrinogen.This is the least abundant plasma protein.Like albumin,the alpha and beta globulins, fibrinogen is produced by the liver. It is essential for blood clotting. In addition Fibrinogen accounts for about 7% of the total plasma protein volume, in clinical levels of 0.2–0.45 g/dL blood.
Nutrients are also found in the plasma. One group of nutrients is the carbohydrates.
The principal form of carbohydrate found in the plasma is glucose, which is absorbed by the capillaries of the intestine following digestion. Glucose is stored mainly in the liver as glycogen and released as needed to supply energy. Amino acids, the products of protein digestion, are also found in the plasma.
These are also absorbed into the blood through the intestinal capillaries. Lipids constitute a small percentage of blood plasma. Lipids include fats. They may be stored as fat for reserve energy or carried to the cells as a source of energy. Mineral salts in the plasma appear primarily as chloride, carbonate, or phosphate salts of sodium, potassium, and magnesium.
These salts have a variety of functions, including the formation of bone,the production of hormones by certain glands ,the transportation of the gases oxygen and carbon dioxide (iron), and the maintenance of the acid base balance (sodium and potassium carbonates and phosphates). Small amounts of other elements also help maintain homeostasis. Many other materials, such as waste products and hormones, are also transported in the plasma.