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It has been learned the fact that living cells need to be supplied with O2, nutrients, and other vital substances. Additionally, the waste or harmful substances created must be eliminated continuously to ensure the health of tissues. It is , therefore, crucial to have efficient methods to move these substances to cells and out of the cells. Different animal species have come up with different ways for transport. Simple animals such as sponges and coelenterates move the water around them through their bodies in order to enable cells to exchange the substances. More advanced organisms make use of specific fluids inside the body to carry these substances. It is blood that is most widely used fluid in the body by the majority of higher-level organisms, including humans, for this reason. A different fluid in the body, lymph aids in the transportation of specific substances. The chapter in this section, you’ll discover the structure and properties of blood as well as the lymph (tissue liquid) and the way in which they assist in the circulation of blood will be explained in the chapter. 18.1 BLOOD is unique connective tissue made up of a fluid matrix plasma, and a variety of formed elements. 

18.1.1 Plasma Plasma is a viscous, straw-colored fluid, which makes up almost 55 percent of blood. 90-92 percent in plasma are water. proteins make up 6-8 percent of it. Albumins, globulins, and fibrinogen are the main proteins. BODY FLUIDS and CHAPTER 18 OF CIRCULATION 18.1 The blood 18.2 Lymph (Tissue Fluid) 18.3 Circulatory Pathways 18.4 Double Circulation 18.5 Regulation of Cardiac Activity 18.6 Conditions of the Circulatory System 2022-23 BODY FLUIDS and Circulation 279 Fibrinogens are essential for coagulation or clotting of blood. Globulins are principally involved in the defense mechanism of the body. The albumins aid in maintaining the maintaining the balance of osmotic pressure. Plasma also has small amounts of minerals such as Na+, Ca++ Mg++, HCO3 – Cl-. amino acids, glucose as well as lipids. are also present in the plasma because they travel constantly throughout the body. Factors involved in coagulation, or clotting blood are also found in the plasma, but in their inactive state. Plasma that does not contain factors that coagulate is known as serum. 18.1.2 The Formed 

Elements: Erythrocytes leucocytes, and platelets are known as made elements (Figure 18.1) and make up nearly 45 percent of blood. Red blood cells or erythrocytes (RBC) represent the most abundant of blood cells. A healthy adult is able to count, on average, between 5 and 5.5 million of RBCs per millimeter of blood. RBCs are made by the red bone marrow in adults. They lack nucleus in the majority of mammals, and are biconcave in shape. They’re red in colour iron-containing complex haemoglobin protein. This is the color and name the cells. A healthy person has between 12 and 16 grams of haemoglobin for every 100 millilitres of blood. These molecules play a crucial function in transporting respiratory gasses. RBCs are able to live an average duration of 120 days following when they are destroyed by the spleen (graveyard of RBCs). Leucocytes can also be referred to by the name of”white blood cells” (WBC) since they are colorless because they lack haemoglobin. They are nucleated and less numerous, and the number ranges from 6000-8000 mm-3 blood. 

Leucocytes generally last for a short time. There are two major types of WBCs: Agranulocytes and Granulocytes. Basophils, eosinophils and neutrophils are a variety of granulocytes. On the other hand, lymphocytes and monocytes are agranulocytes. Neutrophils are the largest cells (60-65 percent) of all WBCs. Basophils are the smallest (0.5-1 percent) of them. Monocytes and neutrophils (6-8 percent) are phagocytic cell types that eliminate foreign invaders that enter the body. Basophils produce serotonin, histamine, heparin as well as serotonin, heparin, and so on. and play a role in inflammation reactions. Eosinophils (2-3 percent) fight off infections and also have R B C Platelets. Eosinophil Monoclonal Basophil lymphocyte B lymphocytes Diagram 18.1 Schematic depiction of the formed elements found in blood 2022-23 280 BIOLOGY that is associated with allergic reactions. Lymphocytes (20-25 percent) are divided into two major kinds – the “B” and “T” types. 

Both types of lymphocytes play a role in the immune responses in the body. Platelets, also referred to as thrombocytes are cell fragments that are produced by megakaryocytes (special cells found in bone marrow). Blood typically has 1,500,00-3.500,00 platelets per millimeter. Platelets release a wide range of chemicals, most of which play a role in the coagulation process or blood clotting. The loss of their numbers could cause clotting problems which can cause excess bleeding out of the body. 18.1.3 blood groups As we all know human blood does differs in some aspects, even however, it appears alike. Different types of grouping of blood have been conducted. Two groups – ABO and Rh are extensively used across the globe. 18.1.3.1 ABO grouping ABO grouping relies in the existence or absence of two antigens (chemicals that trigger an immune responses) on RBCs, namely A as well as B. 

The plasma of various individuals contains two antibodies that are natural (proteins created in reaction in response to specific antigens). Distribution of the antigens as well as antibodies within the four categories of blood A B, AB and O are listed in Table 18.1. It is common knowledge that, when you receive a blood transfusion, any blood can’t be used. the blood of donors has to be closely matched to the blood of the recipient prior to any blood transfusion, to prevent serious problems with the clumping (destruction of the RBC). The compatibility of the donor is indicated in Table 18.1. Blood Group Antigens on Antibodies Donor’s group RBCs Plasma A Anti-B A, B, B B anti-A B O AB B, Nil AB, A B O O nil against-A B O Table 18.1 Blood Groups, and Donor Compatibility Based on the previously Table, it is apparent that blood of the group “O” is available to those with other blood groups and thus ‘O’ people are referred to as ‘universal donors’. The ‘AB’ blood group are able to accept blood from those who have AB as well as other blood groups. 

Thus, they are referred to as universal recipients. 2022-23 BODY FLUIDS AND CIRCULATION 281. 18.1.3.2 Rh grouping Another antigen that is the Rh antigen, which is similar to that found within Rhesus monkeys (hence Rh), is also present on the RBCs’ surface of the majority (nearly 80 percent) of human. The people who have this antigen are known as Rh positive (Rh+ve) and those for which this antigen is not present are referred to as Rh negative (Rh-ve). A person who is Rh-ve, exposed to blood containing Rh+ve is likely to develop specific antibodies against Rh antigens. So, the Rh group should be identified prior to transfusions. A specific instance in Rh incompatibility (mismatching) is discovered between and the blood from a pregnant woman with the Rh+ve blood of a foetus. The foetus’ Rh antigens are not exposed to the bloodstream of the mother during the first pregnancy since the two bloods are divided by placenta. But, in the birth of the first baby there is the possibility of exposure of the mother’s blood to small amounts Rh+ve blood that is derived from the foetus. 

In these cases the mother begins to prepare antibodies to Rh antigens within her blood. In the event of subsequent births and subsequent births, the Rh antibodies of her mother (Rh-ve) may be released into the blood that the embryo is receiving (Rh+ve) and cause the destruction of foetal RBCs. This can be fatal for the foetus, or cause severe jaundice and anaemia for the infant. The condition is known as erythroblastosis foetalis. It is preventable by administering anti-Rh antibodies the mother as soon as possible following the birth of the first child. 18.1.4 The coagulation process of blood are aware that when you scratch your finger or injure yourself, the wound will not bleed for a long period of time. typically, the blood ceases to flow after a certain time. Are you aware of the reason? The blood clots or forms coagulation when it is injured or trauma. This is a way to stop the bleeding from your body. It is possible to see the dark brown scum that forms at the site of an injury or cut for a time. 

It’s a clot or coagulam made up from a thread of fibrins, threads, where damaged and dead blood-related elements are kept. Fibrins are created by the conversion of fibrinogens inactive into plasma through the enzyme known as thrombin. The thrombins are produced from an inactive substance found in plasma known as prothrombin. A complex of enzymes called the thrombokinase enzyme, is essential to carry out the above process. The formation of this complex occurs through an assortment of interlinked enzyme processes (cascade process) which involve several factors that are present in plasma when it is inactive. Trauma or injury causes the platelets present in blood to release certain substances that trigger the mechanism of blood coagulation. Certain substances released by tissues near the site of injury may trigger the process of coagulation. Calcium ions play an significant role in the process of clotting. 2022-23, 282 Biology 18.2 LIMPH (TISSUE FLUID) When blood flows through capillaries within tissues, a small amount of water and other water-soluble compounds move out in the gaps between cells of tissues , leaving behind the bigger proteins and the majority of the formed components in the blood vessels. The fluid that is released is referred to as the interstitial fluid also known as tissue fluid. 

It shares the same mineral distribution that of plasma. Exchange of gases, nutrients and other gases. between cells and blood always happen via this liquid. A vast network of blood lymphatic vessels collects the fluid and then drains it back to the main veins. The fluid found inside the lymphatic systems is known as the lymph. Lymph is a clear, colorless liquid composed of lymphocytes that are responsible for the immune system in the human body. Lymph also serves as a vital transporter of hormones, nutrients as well as other hormones. The lymphatic system is a major conduit for the absorption of fats through the lacteal lining of the villi of the intestinal tract. 18.3 Circulatory pathways The circulatory patterns come in two kinds – open and closed. The open circulatory system can be found in arthropods and molluscs , in where blood pumping by the heart flows through large vessels and into large spaces, or body cavities known as sinuses. The chordates and the anelids have closed circulatory systems in which blood pumped from the heart flowed through a closed network of blood vessels. This arrangement is believed to be more beneficial since the flow of blood can be more precisely controlled. 

Every vertebrate has the heart chamber that is muscular. Fishes have a heart with a two-chambered chamber that has an atrium as well as ventricle. Reptiles and amphibians (except the crocodiles) have a heart with three chambers that has two atria and only one ventricle. In contrast, mammals, birds, and crocodiles have a four-chambered heart, which has two ventricles and two atria. In fishes, the hearts pump out deoxygenated blood, which is oxygenated by the gills , and transported to body parts from which deoxygenated blood is then returned back into the heart (single circulation). In reptiles and amphibians, the left atrium gets oxygenated blood from gills, lungs or skin as well as the right atrium receives the blood deoxygenated from the different body parts. However, they mix within the ventricle, which pumps mixed blood (incomplete double circulation). In mammals and birds the deoxygenated and oxygenated blood that is pumped out from the right and left atria, respectively, is transferred to the ventricles on the identical sides. 

The ventricles then pump it out without mixing it up, i.e., two separate circulation pathways exist in these animals, and as a result they have double circulation. Let’s look at the circulatory system of humans. 2022-23 BODY FLUIDS and Circulation 283 18.3.1 Human Circulatory Systems The human circulatory systemis also known as the system of blood circulation, consists of a heart with a muscle chamber as well as a system of closed blood vessels with branches and blood, which is the fluid that circulates. Heart, which is a mesodermally derivated organ.