The blood of humanbeings constitute of two components: Blood plasma and cellular component. The blood plasma is a liquid component composed primarily of water ( 90%) and it includes also other components such as proteins and ions or electrolytes.
The blood plasma proteins are synthesized in the liver. They include the proteins albumin, globulin and fibrinogen. Albumin is responsible for maintaining the osmotic pressure inside blood vessels. In addition albumin participates in transporting several hormones to their target cells.
Globulins are products of the immune system. They are defined as antibodies that attack viruses and bacteria. Other types of globulins participate in the transport of iron and lipids. Fibrinigon is produced by hepatocytes in the liver. It participates and is important in the process of blood clotting. Its deficiency can lead to bleeding disorders.
Electrolytes such as sodium and potassium which are also components of the blood play a role in maintaining the blood pressure inside blood vessels. They do so by a process called osmosis and by activating hormones the adjust the pressure in blood vessels. In addition, electrolytes play roles in cells function.
The celluar component of blood includes three types of cells. These are red blood cells and white blood cells and platelets. Red blood cells are responsible for transporting oxygen from the lungs to body tissues where it is used for generating energy in the form of ATP. In addition red blood cells transport waste product of respiration (CO2) from the tissues to the lungs where it is removed by exhalation.
Red blood cells do not have nucleus and they do not prolifirate but their precursor is reticulocytes which have nucleus that they eject during the maturation process into a red blood cell. The ratio between the total size of red blood cells to total blood volume is called hematocrit and is used in clinical chemistry as a measure of normalness of red blood cells function. Erythropoietin is a hormone secreted by the kidneys and is responsible for stimulating red blood cells formation. This hormone synthesis is in turn stimulated by another hormone that is called testosterone.
Testosterone is predominant in males and is responsible for the hairy appearance of the body. The hematocrit of males is therefor higher than females. Namely, the number of red blood cells in males is a little higher than in females. This is so because of what was mentioned about the effect of testosterone stimulating the synthesis of erythropoietin which in turn stimulates the synthesis of red blood cells.
Polycythemia is a medical condition in which the hematocrit of the patient or red blood cells count is higher than normal. This condition can be triggered by abnormal growth of red blood cells or by dehydration. It can also be triggered by the excessive use of erythropoietin. Polycythemia can cause high blood pressure and stroke due to the excessive viscosity of blood which happens as a result of high red blood cells count in the blood.
White blood cells are divided into two main categories based on their appearance under microscope. These are granular and agranular cells. Macrophages are type of mature white blood cells. They are produced from their precursor monocytes. macrophages are active in the immune system and participate and destroying foreign microbes and cells by a process that is called phagocytosis. Neutrophils are another type of white blood cells and they are similar to macrophages.
high blood count of neutrophils is an indication of bacterial infection or burns. While low count of blood neutrophils is indicative of either exposure to radiation or deficiency of vitamin B12 which its beficience causes also anemia and nervous system symptoms. Another type of white blood cells are lymphocytes. They are divided as T lymphocytes or B lymphocytes. They protect the body from viruses and infection.
High blood count of lymphocytes indicate viral infection or leukemia. While, low blood count of lymphocytes is indicative of immunosuppression. Eosinophils are another granular type of white blood cells. They participate in allergic reactions. High count of blood eosinophils is indicative of allergy situation or autoimmune condition. While low count of them is indicative of drug toxicity or stress. Basophils are another type of granular white blood cells.
High blood count of basophils indicate the presence of cancer or leukemia and hypothyroidism. On the other hand, low count of blood basophils is indicative of hyperthyroidism and pregnancy.
The third type of cells in blood are platelets. They are not really cells but actually cells fragments surrounded by a membrane. Their precursors are called megakaryocytes and these are hudge cells which give rise to thousands of platelets when they differentiate. Platelets are important in the clotting process of blood. Their synthesis is triggered by a hormone in the liver that is called thrombopoietin. The deficiency of platelets can cause bleeding disorders. The same can happen also if the thrombopoietin hormone is deficient as well.