Introduction
Blood contains a fluid part called plasma. Red blood cells [erythrocytes] have red pigment hemoglobin which binds oxygen and transports it to all cells. They are formed in the red bone marrow and have a lifetime of 120 days. They are destroyed in the spleen. White blood cells [leucocytes] fight against germs that enter the body. White blood cells is neutrophils [destroy foreign bodies]; basophils [inflammatory response], eosinophils [allergic response], lymphocytes [immune response] and monocytes [destroy foreign bodies]. Platelets [thrombocytes] in the blood are responsible for clotting
Types of Blood Group
Blood cells can have two antigens A, B, AB [both], or O [none]. O blood group is the universal donor and AB is the universal recipient.
Blood’s Flow
Blood vessels are arteries that carry oxygen-rich blood to different body parts. The walls are thick, and elastic as blood flow is rapid and high pressure. Veins carry carbon dioxide-rich blood to the heart. They have thin walls and valves that allow blood to flow in one direction only.
Our muscles release lactic acid during anaerobic respiration. This lactic acid causes cramps. When we are drowsy, we slow down breathing and our body doesn’t get sufficient oxygen so we yawn to take excess air.
Blood Oxidation and Purification
During respiration, ribs move up, and the diaphragm moves down, this increases the size of the chest cavity and air comes in. During exhaling, ribs move down and in, and the diaphragm moves back to position and this reduces the chest cavity so air is released. Respiration is an exothermic reaction i.e. heat is evolved. Reactions of decomposition of wastes into compost are also exothermic. Blood capillaries in the kidneys filter waste material as urine. This is passed into the urinary bladder through the ureters. The urethra is connected to the urinary opening through which urine is passed. In dialysis, blood is filtered by an artificial kidney, when the natural kidneys fail.
The pulmonary artery carries CO2-rich blood from the heart to the lungs, Pulmonary vein carries oxygen-rich blood to the heart from the lungs. Arteries divide to form capillaries to reach tissues, capillaries rejoin to form veins to take blood from tissues to the heart.
Carbon monoxide reduces the oxygen-carrying capacity of the blood. It combines with hemoglobin to form carboxyhemoglobin and this reduces the oxygen-carrying capacity of the blood.
Human Heart
The heart has four chambers, two atria, and two ventricles. The right atria and ventricle have deoxygenated blood. The left atria and ventricle have oxygenated blood. Ventricles have thick walls as they have to pump blood to different organs.
Miscellaneous
Organisms that need the energy to regulate body temperature need separate oxygenated and de-oxygenated blood. Others who regulate the temperature of the body based on the temperature of their surroundings can tolerate the mixing of blood.
Hydra and sponges don’t have a circulatory system or blood. Water that flows through their body carries food and oxygen to different parts and waste material from parts is thrown out by it too.
Birds, and insects excrete uric acid [least toxic so doesn’t need water for excretion]. Fishes excrete ammonia [highly toxic so needs lots of water]. The mode of excretion depends on the availability of water.
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