Blood is a biological fluid that provides organs and tissues with nutrients and oxygen. Together with lymph, it forms a system of circulating fluids in the body. It performs a number of vital functions: nutritional, excretory, protective, respiratory, mechanical, regulatory, thermoregulatory.
The composition of human blood varies significantly with age. It should be said that children have a very intensive metabolism, so in their body it is much more per 1 kg of body weight compared to adults. On average, an adult has about five to six liters of a given biological fluid.
The blood contains plasma (the liquid part) and formed elements (red blood cells, white blood cells, platelets). Its color depends on the concentration of red blood cells. A plasma lacking protein (fibrinogen) is called blood serum. This biological fluid has a slightly alkaline reaction.
Biochemical composition of blood - buffer systems. The main blood buffers are hydrocarbonate (7% of the total mass), phosphate (1%), protein (10%), hemoglobin and oxyhemoglobin (up to 81%), as well as acid (about 1%) systems. In plasma, bicarbonate, phosphate, protein and acid predominate, in erythrocytes - bicarbonate, phosphate, in hemoglobin - oxyhemoglobin and acid. The composition of the acidic buffer system is represented by organic acids (acetate, lactic, pyruvic, etc.) and their salts with strong bases. The most important are hydrocarbonate and hemoglobin buffer systems.
The chemical composition of the blood. Blood is characterized by a constant chemical composition. Plasma makes up 55-60% of the total blood volume and 90% consists of water. The dry residue is organic (9%) and mineral (1%) substances. The main organic substances are proteins, most of which are synthesized in the liver.
The protein composition of the blood. The total protein content in the blood of mammals ranges from 6 to 8%. About a hundred protein components of plasma are known. Conventionally, they can be divided into three fractions: albumin, globulin and fibrinogen. The plasma proteins that remain after the removal of fibrinogen are called serum blood proteins.
Albumins are involved in the transport of many nutrient and biologically active substances (carbohydrates, fatty acids, vitamins, inorganic ions, bilirubin). Participate in the regulation of water-mineral metabolism. Serum globulins are divided into three fractions of alpha, beta and gamma globulins. Globulins transport fatty acids, steroid hormones, fat-soluble vitamins, are immune bodies.
Carbohydrate composition of blood. Plasma contains monoses (glucose, fructose), glycogen, glucosamine, monose phosphates and other products of the intermediate exchange of carbohydrates. Most carbohydrates are glucose. Glucose and other monoses in blood plasma are in free and protein-bound states. The content of bound glucose reaches 40-50% of the total carbohydrate content. Among the products of the intermediate exchange of carbohydrates, lactic acid is isolated, the content of which increases sharply after heavy physical exertion.
Glucose concentration can vary in many pathological conditions. The phenomenon of hyperglycemia is characteristic of diabetes mellitus, hyperthyroidism, shock, anesthesia, and fever.
Lipid composition of the blood. Plasma contains up to 0.7% or more lipids. Lipids are in free and protein bound states. The concentration of lipids in the plasma changes with pathology. So, with tuberculosis, it can reach 3-10%.
The gas composition of the blood. This biofluid contains oxygen (oxygen), carbon dioxide and nitrogen in free and bound states. For example, about 99.5–99.7% of oxygen is associated with hemoglobin, and 03–0.5% is in a free state.