Human Anatomy and Physiology : V. Circulatory System Part-II

The functional lifetime of an erythrocyte is about 100–120 days, during which time the erythrocytes are continually moved by the blood flow push (in arteries), pull (in veins) and a combination of the two as they squeeze through micro-vessels such as capillaries. The spleen is an organ found in virtually all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays an important role in regard to red blood cells (also referred to as erythrocytes) and the immune system. It removes old red blood cells and holds a reserve of blood, which can be valuable in case of haemorrhagic shock and also recycles iron. In the human adult, the bone marrow alone produces all of the RBCs, 60–70 percent of the WBCs (i.e. the granulocytes), and all of the platelets. The bone marrow and the lymphatic tissues, particularly the spleen, the thymus, and the lymph nodes, produce the lymphocytes (comprising 20–25 percent of WBCs).

The functional lifetime of an erythrocyte is about 100–120 days, during which time the erythrocytes are continually moved by the blood flow push (in arteries), pull (in veins) and a combination of the two as they squeeze through micro-vessels such as capillaries. The spleen is an organ found in virtually all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays an important role in regard to red blood cells (also referred to as erythrocytes) and the immune system. It removes old red blood cells and holds a reserve of blood, which can be valuable in case of haemorrhagic shock and also recycles iron. In the human adult, the bone marrow alone produces all of the RBCs, 60–70 percent of the WBCs (i.e. the granulocytes), and all of the platelets. The bone marrow and the lymphatic tissues, particularly the spleen, the thymus, and the lymph nodes, produce the lymphocytes (comprising 20–25 percent of WBCs).

The functional lifetime of an erythrocyte is about 100–120 days, during which time the erythrocytes are continually moved by the blood flow push (in arteries), pull (in veins) and a combination of the two as they squeeze through micro-vessels such as capillaries. The spleen is an organ found in virtually all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays an important role in regard to red blood cells (also referred to as erythrocytes) and the immune system. It removes old red blood cells and holds a reserve of blood, which can be valuable in case of haemorrhagic shock and also recycles iron. In the human adult, the bone marrow alone produces all of the RBCs, 60–70 percent of the WBCs (i.e. the granulocytes), and all of the platelets. The bone marrow and the lymphatic tissues, particularly the spleen, the thymus, and the lymph nodes, produce the lymphocytes (comprising 20–25 percent of WBCs).

Pulmonary arteries are the only arteries in the body that carry deoxygenated blood, transporting it from the heart to the lungs.

Carotid arteries are major arteries that supply blood to the head and neck, specifically the brain.

Hepatic arteries supply the liver and other nearby organs with oxygenated blood.

Thrombin is an enzyme that presides over the conversion of a substance called fibrinogen to fibrin, which promotes blood clotting. Thrombin is a serine protease in humans which is encoded by the F₂ gene. Prothrombin (coagulation factor II) is proteolytically cleaved to form thrombin in the coagulation cascade, which ultimately results in the reduction of blood loss. Thrombin, in turn, acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin as well as catalyzing many other coagulation-related reactions.

Thrombin is an enzyme that presides over the conversion of a substance called fibrinogen to fibrin, which promotes blood clotting. Thrombin is a serine protease in humans which is encoded by the F₂ gene. Prothrombin (coagulation factor II) is proteolytically cleaved to form thrombin in the coagulation cascade, which ultimately results in the reduction of blood loss. Thrombin, in turn, acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin as well as catalyzing many other coagulation-related reactions.

Plasma is the liquid portion of blood-protein-salt solution which is about 90 to 92% of water, and constitutes about 55% of blood volume. Plasma contains albumin (protein), fibrinogen and globulins (including antibodies).

Platelets help in the blood clotting process (or coagulation) by gathering at the site of an injury, sticking to the lining of the injured blood vessel and forming a platform on which blood coagulation can occur. Platelets are only about 20% of the diameter of red blood cells. The normal platelet count is about 150,000–350,000 per microlitre of blood, but since platelets are so small, they make up just a tiny fraction of the blood volume. The ratio of platelets to red blood cells in a healthy adult is about 1:10 to 1:20. Red blood cells are the most numerous blood cell, about 5,000,000 per microlitre. Red blood cells make up about 40% of our total blood volume, a measure called the hematocrit. White blood cells are the largest of the blood cells but also the fewest. There are normally only about 4,000 to 11,000 white blood cells per micro litre. Other three statements are incorrect with reference to the blood in a normal person.

Alum is a specific crystalline substance and the aluminium ion present in it has high coagulating property. So, the alum is considered very good for the coagulation of blood when someone gets wounded and blood starts coming out from the wound.