Tiêu đề Ch8 Circulatory System _240328_201424.pdf ✅

The Circulatory System Components of Blood and Lymph (Detail Study) Need for Transport inside Our Body • In Digestive System: The nutrients absorbed from the digested food need to be transported to each cell to perform their functions. • In Excretory System: All the wastes generated need to be collected from whole body and flushed out. • In Endocrine System: The hormones produced need to be sent to each and every part of our body. • In Respiratory System: The oxygen and CO2 need to be transported through out the body. Blood: Connective tissue consisting of fluid matrix, plasma, and formed elements Functions of Blood (i) Transportation • Transport of digested food from alimentary canal to tissues • Transport of oxygen from lungs to the tissues • Transport of carbon dioxide from tissues to lungs • Transport of excretory material • Distribution of hormones from endocrine glands • Distribution of heat throughout the body (ii) Protection • Formation of clot in case of cut, thus preventing blood loss • Protecting body from bacteria • Production of antitoxins and antibodies Components of Blood: It consists of fluid part, called plasma, and cellular elements that consist of red blood cells, white blood cells, and platelets. Plasma • 55% of blood • Plasma = 90-92 % water + 6-8% proteins • Proteins present Fibrinogen − blood clotting
Globulins − defence mechanisms Albumins − osmotic balance • Also contain mineral, glucose, amino acids, and lipids in traces Blood clotting factors are present in inactive form in plasma. • Serum = Plasma − Clotting factors Formed Elements Formed elements (45% of blood) Erythrocytes Leucocytes Platelets (Thrombocytes) Most abundant: 5−5.5 million/mm3 of blood Relatively lesser in number: 6000−8000/ mm3 of blood 1.5−3.5 × 105/mm3 of blood Formed in red bone marrow; average life span is of 120 days; destroyed in spleen, hence spleen is called the graveyard of RBCs Have different sites for formation Formed in megakaryocytes Biconcave and devoid of nucleus Nucleated Anucleated Contain haemoglobin and hence involved in transport of respiratory gases Average value of haemoglobin − 12-16 gm/100 ml of blood Play major role in defence system of body Involved in blood clotting Red Blood Cells (RBCs) - These are responsible to carry oxygen through the body. • Haemoglobin : A chief chemical constituent of RBCs. It is present inside stroma - a spongy body of RBCs. • It is made up of iron and protein. • It easily combines with oxygen forming oxyhaemoglobin, an unstable compound that easily donates oxygen to the needy tissues.
• It also carries a small amount of CO2 in the form of carbaminohaemoglobin. • Carbon monoxide Poisoning • Haemoglobin has high affinity towards carbon monoxide as it forms a more stable compound carboxyhaemoglobin (HbCO). • It results in decreased efficiency of oxygen transport by blood, leading to less supply of oxygen in the body. • It may result even in death. Increased Efficiency of RBCs The mammalian red blood cells are more efficient as compared to others as they lack certain cell organelles. The factors that makes them more efficient are: • Loss of nucleus: This makes them biconcave in shape hence, increasing their surface area to volume ratio to maximise oxygen absorption. • Loss of mitochondria: Lack of mitochondria means that no cellular respiration can occur in the RBCs. Thus all the oxygen absorbed from the lungs are transported to the tissues as they don't need it for themselves any more. • No endoplasmic reticulum: It results in increased flexibility for their movement through the constricted capillaries. Functions of Leucocytes (WBCs) The basic function of white blood cells is body defence.
• Phagocytosis: This is a defence mechanism in which the WBCs engulf the solid substances like bacteria. • Inflammation: Inflammation is a result of reaction of tissues to injuries and to localised invasion of germs. The leucocytes (especially monocytes and neutrophils) reach the inflamed area by migrating through blood vessel walls (diapedesis). They can then fight against the disease causing germs and also destroy the damaged cells by phagocytosis. • Formation of Antibodies: These are produced by WBCs (lymphocytes) to kill or neutralise the germs and poison from them. These are stimulated by introducing weakened germs through vaccination. Lymph • Lymph is the fluid released out of blood capillaries leaving behind larger proteins and formed elements. • It consists of water and some water soluble substances. • It has some mineral distribution as present in plasma. • The network of lymph vessels composes lymphatic system. Uses • Lymph contains lymphocytes that are involved in immune response. • Lymph carries nutrients, hormones, etc. • Lymph absorbs fats in lacteals found in intestinal villi. Blood Coagulation: • Clotting is required to prevent excessive loss of blood from the body. • Blood clot - formed by threads of fibrin in which formed elements are trapped. • Prothrombin (inactive form) thrombin (active form) • Fibrinogen (inactive form) fibrin (active form) • Mechanism of coagulation is a cascade of reactions involving several clotting factors. • Calcium plays an important role in blood clotting mechanism. • Serum : The Clear liquid squeezed out of the network of fabrin in which the blood cells are trapped is called Serum. Blood Groups and Rh Factor Blood groups • Widely used blood grouping − ABO and Rh ABO Grouping