Cellular elements of the blood- RBC
Cellular components occupies 40- 45% of the blood and are of three types:
- Red blood cell (erythrocyte)
- White blood cell (leukocytes)
- Blood platelet (thrombocytes)
| Production | Bone marrow |
| Structure | Small, biconcave, disc like structure, nucleus absent |
| Size | 7 micron diameter |
| Lifespan | 120 days |
| Death | Approx. 2,00,00,000 RBC per minute |
| RBC count | Male: 5 million RBCs Female: 4- 5 million RBCs |
| Major component | Haemoglobin |
| Major function | Oxygen carrier |
| Abnormality | Excessive RBC count- Polycythaemia Abnormally low RBC count- Erythropenia |
Structure of RBC
- The shape of a red blood cell is a biconcave disk, it has a sunken centre on both sides, this allows the cell to have a larger cell membrane surface which can be exposed to diffusing oxygen while it is travelling to the lungs.
- The structure also enables the cells to be more flexible when it comes to them passing through tight passages like the capillaries. This is because they are flexible, bendy and bounce about, the cells are around 7.8 micrometers in diameter.
- The immature red blood cell contains a nucleus but the mature ones don't, they also don't have mitochondria or other organelles. However, the red blood cells do contain hemoglobin, these are molecules of protein and iron.
Life and death Erythrocytes.
Erythropoiesis is the process by which new red blood cells are produced. The production of RBCs is stimulated by hormone erythropoietin secreted by the kidney. Through this process, the red blood cells are continuously produced in the red bone marrow of large bones.
The average life of RBCs is 100 to 120 days. During this period it is continuously circulating in the system. The plasma membrane of old or aging RBCs undergoes changes. These changes help macrophages to identify them. The RBCs undergo phagocytosis in spleen liver and lymph nodes which removes the old RBCs from the blood. This process is known as eryptosis or apoptosis.
The average life of RBCs is 100 to 120 days. During this period it is continuously circulating in the system. The plasma membrane of old or aging RBCs undergoes changes. These changes help macrophages to identify them. The RBCs undergo phagocytosis in spleen liver and lymph nodes which removes the old RBCs from the blood. This process is known as eryptosis or apoptosis.
Cellular elements of the blood- WBC
| Production | Bone marrow, lymph node and spleen |
| Structure | Amoeboid shape, nucleus present, lack haemoglobin |
| Lifespan | 2 weeks |
| Death | Approx. 2,00,00,000 WBC per minute |
| WBC count | 4,000- 8,000 per cubic mm |
| Abnormality | Excessive WBC count- Leukemia Abnormally low WBC count- Leukopenia |
| Function | Phagocytosis Inflammation Formation of Antibodies |
Cellular elements of the blood- Platelet
| Production | Megakaryocyte in the bone marrow |
| Structure | Oval or round, non nucleated |
| Lifespan | 3- 5 days |
| Platelet count | 2,00,000 to 4,00,000 per cubic mm. |
| Major component | Thrombokinase |
| Major function | Blood clotting |
| Abnormality | Abnormally low platelet count- Viral dengue feve |
Rh sensitization
Rh sensitization occurs during pregnancy when the mother is and the baby is . During pregnancy or labour, some amount of blood from the circulation of the baby enters the circulation of the mother through the placenta. The immune system of the mother will react to the Rh factor by making antibodies against it. This immune response is known as Rh sensitization. Rh sensitization causes serious complications in the second child as the antibodies of Rh sensitised mother starts destroying the red blood cells of the fetus (hemolytic anaemia).This condition is known as Erythroblastosis fetalis.
Coagulation process
The excessive blood flow during the injury or cut is prevented by clot formation that takes place due to platelet.
The process of coagulation is as follows:
The process of coagulation is as follows:
- The injured tissue cells and platelet release enzyme thrombokinase that converts prothrombin into thrombin (active) in presence of calcium ion.
- Thrombin reacts with fibrinogen in presence of calcium ion to form a thread-like structure called fibrin
- Fibrin forms a mesh-like network on the wound that squeezes out the serum forming a clot thereby preventing blood loss.
Open and closed circulatory system
Open circulatory system
- In open circulatory system, blood is pumped by the heart through large vessels into open spaces or body cavities called sinuses.
- Example: Circulation in Arthropods and Molluscs
- In closed circulatory system, the blood pumped by the heart is always circulated through a closed network of capillaries.
- This type of circulation is present in Annelids and chordates
Circulatory system (open and close)
- In closed circulatory system, blood is transported to different parts with the help of the vessels.
- For example, vertebrates.
- In open circulatory system, blood is pumped into the body cavity called haemocoel and diffuses back the blood to the heart.
- For example, invertebrates like arthropods.
Single circuit circulation
Fishes have a single circulatory system. In a single circulatory system, the blood flows through the heart only once completing a full circuit in the fish's body. The blood travels from the heart to the gills, where the exchange of gases takes place (carbon dioxide is released and oxygen is absorbed). The oxygenated blood from the gills then flows to various parts of the body and from these parts back to the heart.
Systemic circulation
- Systemic circulation - The flow of oxygenated blood from the left ventricle of the heart to various parts of the body and deoxygenated blood from various parts of the body to the right atrium is called systemic circulation. The systemic arteries arising from aorta carry oxygenated blood from the left of the ventricle to various parts of the body. The systemic veins carry deoxygenated blood from various parts of the body to the right atrium of the heart.
Pulmonary circulation.
- Pulmonary circulation - The flow of deoxygenated blood from the right ventricle to the lungs and the return of oxygenated blood from the lungs to the left atrium is called pulmonary circulation. The pulmonary trunk( right and left pulmonary artery) carries blood from the right ventricle to the lungs where the exchange of gases takes place. The oxygenated blood from the lungs returns to the left atrium of the heart through two pulmonary veins, one from each lung.
Hypophysial portal system
The hypophysial portal system is a minor portal system consisting two hypophysial portal veins. It carries blood from the hypothalamus to the anterior lobe of the pituitary gland (hypophysis). This portal system enables the hormones of the hypothalamus to reach the anterior pituitary.
Renal and hypophysial portal system
Renal portal system
- Veins which collect blood from posterior parts of the body and legs combine to form a renal portal vein. The vein goes into kidney and divides into capillaries, kidney separate nitrogenous wastes from this blood.
- The partly purified blood is now transported to the heart.
- It is a portal system formed by a vein from hypothalamus which breaks up into capillaries in hypophysis in pituitary gland.
- The vein is called hypophysial portal vein.
Pulse rate test
Pulse rate at rest
- Sit in a comfortable position and place the palm forward.
- Three fingers of the other hand is placed on the wrist where the pulse can be felt.
- Count the pulsation for 15 seconds and multiply it by 4 which is approximately 72.
- This is average pulse rate in a minute.
- After a physical exercise relax for 10 minutes and check the pulse rate in the same manner.
- The pulse rate increases to more than 120.
Origin of heart beat
- The heart beat is of two types: neurogenic and myogenic.
- The neurogenic heart beat is initiated by a nerve impulse coming from a nerve ganglion situated near heart.
- The mammalian heart beat is myogenic i.e., it originates from the muscle, however it is regulated by nerves.
Phases of heart beat
The two main phases of heartbeat are as follows:
Atrial systole
Atrial systole
- Atrial systole is the contraction of heart of the left and right atria.
- Thus, blood is flown into the ventricles.
- When the blood is ejected due to contraction of ventricle, it flows down through the aorta and pulmonary artery from the left and right ventricles respectively.
Waves of normal ECG
- P wave: The sequential activation (depolarization) of the right and left atria. P-R interval is < 0.12 to 0.2 sec.
- QRS complex: Right and left ventricular depolarization (normally the ventricles are activated simultaneously). QRS complex duration is < 0.10 sec.
- T wave: Ventricular repolarization (ventricular relaxation). Q-T interval is < 0.42 sec.
Hypertension
- Hypertension is the condition in which the systolic and diastolic pressure exceeds normal blood pressure value.
- In this condition, the blood pressure value exceeds upto 140/90 mm Hg.
- Arteriosclerosis
- Atherosclerosis
- Obesity
- Stress
- Alcoholism
- Smoking
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