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Biology I Blood

Biology I Blood. BIO103 OrR. BLOOD. Lecture Plan Introduction Composition of Blood Blood Plasma Blood Cells Blood Typing Production and Elimination of Blood cells. Introduction. Referred to as “ the river of life ,”

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Biology I Blood

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  1. Biology IBlood BIO103 OrR

  2. BLOOD • Lecture Plan • Introduction • Composition of Blood • Blood Plasma • Blood Cells • Blood Typing • Production and Elimination of Blood cells

  3. Introduction • Referred to as “the river of life,” • An adult human has about 5 to 6 litres (1 to 2 gal) of blood, which is roughly 7 to 8 percent of total body weight. • Infants and children have comparably lower volumes of blood, roughly proportionate to their smaller size. • The volume of blood in an individual fluctuates. During dehydration, for example while running a marathon, blood volume decreases. Blood volume increases in circumstances such as pregnancy, when the mother’s blood needs to carry extra oxygen and nutrients to the baby.

  4. Composition of Blood Blood is a fluid in two phases: • Blood plasma: a liquid phase consisting of water and dissolved materials. • Blood cells: a solid phase consisting of living cells suspended in the liquid phase.

  5. Blood Plasma • Plasma consists predominantly of water and salts. • The kidneys carefully maintain the salt concentration in plasma because small changes in its concentration will cause cells in the body to function improperly. • The pH of plasma, the common measurement of the plasma’s acidity, is also carefully controlled by the kidneys within the neutral range of 6.8 to 7.7. • Plasma also contains other small molecules, including vitamins, minerals, nutrients, and waste products • Plasma is usually yellow in colour due to proteins dissolved in it. • However, after a person eats a fatty meal, that person’s plasma temporarily develops a milky colour as the blood carries the ingested fats from the intestines to other organs of the body.

  6. Red Blood Cells In an average healthy person, approximately 45 percent of the blood is made of three major types of cells: • Red blood cells, or RBC (also known as erythrocytes), • White blood cells, or WBC (leukocytes), and • Platelets (also known as thrombocytes).

  7. Red Blood Cells • Red blood cells, or erythrocytes, make up almost 45 percent of the blood volume. • The red blood cells have no nuclei. • Yet each red blood cell functions well for almost four months. • Red blood cells are biconcave shaped. • The erythrocytes are the most numerous blood cells, i.e., about 4-6 millions/mm3.

  8. Functions of RBC • Major function: carry oxygen. • Red blood cells are composed predominantly of a protein and iron compound, called haemoglobin • Haemoglobin, captures oxygen molecules as the blood moves through the lungs, giving blood its red colour. • As blood passes through body tissues, haemoglobin then releases the oxygen to cells throughout the body.

  9. White Blood Cells • White blood cells (or leucocytes) only make up about 1 percent of blood. • They have nuclei. • They are colourless. • They can change shape, and can move in any direction, like amoebas. • WBCs engulf particles, including bacteria, by phagocytosis. • The density of the leukocytes in the blood is 5000-7000 /mm3.

  10. Function of WBCs • Phagocytosis WBCs play a vital role in the body’s immune system—the primary defence mechanism against invading bacteria, viruses, fungi, and parasites. They often accomplish this goal through direct attack, which usually involves identifying the invading organism as foreign, attaching to it, and then destroying it. This process is referred to as phagocytosis.

  11. Function of WBCs • Antibody Production White blood cells also produce antibodies, which are released into the circulating blood to target and attach to foreign organisms. After attachment, the antibody may neutralize the organism, or it may elicit help from other immune system cells to destroy the foreign substance.

  12. Antigen and Antibody • Antigen: an antigen is a substance that evokes the production of one or more antibodies. The term originally came from antibody generator. The substance may be from the external environment or formed within the body. The immune system will try to destroy or neutralize any antigen that is recognized as a foreign and potentially harmful invader. • Antibody: An antibody large Y-shaped protein produced by WBC that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen.

  13. Platelets • Platelets (or thrombocytes) are not true cells. They are the smallest cellular component of blood. • They have no nucleus. • Even if platelets appear round in shape, they are not real cells. Their density in the blood is 200000-300000/mm3.

  14. Function of Platelets Blood Clotting • The smallest cells in the blood are the platelets • single purpose—to begin the process of coagulation, or forming a clot, whenever a blood vessel is broken. • clump together and stick to the edges of the cut. • They also release messengers into the blood that perform a variety of functions: • constricting the blood vessels to reduce bleeding, • attracting more platelets to the area to enlarge the platelet plug, and • initiating the work of plasma-based clotting factors, such as fibrinogen • Through a complex mechanism involving many steps and many clotting factors, the plasma protein fibrinogen is transformed into long, sticky threads of fibrin. • Together, the platelets and the fibrin create an intertwined meshwork that forms a stable clot. This self-sealing aspect of the blood is crucial to survival.

  15. Blood Typing • There are several types of red blood cells and each person has red blood cells of just one type. • Blood type is determined by the occurrence or absence of substances, known as recognition markers orantigens, on the surface of the red blood cell. • Type A blood has just marker A on its red blood cells while type B has only marker B. If neither A nor B markers are present, the blood is type O. If both the A and B markers are present, the blood is type AB. • Another marker, the Rh antigen (also known as the Rh factor), is present or absent regardless of the presence of A and B markers. If the Rh marker is present, the blood is said to be Rh positive, and if it is absent, the blood is Rh negative. The most common blood type is A positive—that is, blood that has an A marker and also an Rh marker. More than 20 additional red blood cell types have been discovered.

  16. Blood Typing

  17. Blood Typing

  18. A: can receive blood from A B: can receive blood from B AB: receive blood from both universal acceptor O: can not receive blood from A/B/AB universal donor

  19. Production of Blood Cells • Blood is produced in the bone marrow, a tissue in the central cavity inside almost all of the bones in the body. • In infants, the marrow in most of the bones is actively involved in blood cell formation. By adult life, active blood cell formation gradually ceases in the bones of the arms and legs and concentrates in the skull, spine, ribs, and pelvis. • Red blood cells, white blood cells, and platelets grow from a single precursor cell, known as a haematopoietic stem cell. • Remarkably, experiments have suggested that as few as 10 stem cells can, in four weeks, multiply into 30 trillion red blood cells, 30 billion white blood cells, and 1.2 trillion platelets—enough to replace every blood cell in the body.

  20. Elimination of Blood Cells

  21. Elimination of Blood Cells Red Blood Cell • Red blood cells have the longest average life span of any of the cellular elements of blood. • A red blood cell lives 100 to 120 days after being released from the marrow into the blood. • Over that period of time, red blood cells gradually age. Spent cells are removed by the spleen and, to a lesser extent, by the liver. The spleen and the liver also remove any red blood cells that become damaged, regardless of their age. • The body efficientlyrecycles many components of the damaged cells, including parts of the haemoglobin molecule, especially the iron contained within it.

  22. Elimination of Blood Cells White Blood Cell • The majority of white blood cells have a relatively short life span. • They may survive only 18 to 36 hours after being released from the marrow. • However, some of the white blood cells are responsible for maintaining what is called immunologic memory. These memory cells retain knowledge of what infectious organisms the body has previously been exposed to. If one of those organisms returns, the memory cells initiate an extremely rapid response designed to kill the foreign invader. Memory cells may live for years or even decades before dying.

  23. Elimination of Blood Cells Platelets • Platelets have a life span of seven to ten days in the blood. • They either participate in clot formation during that time or, when they have reached the end of their lifetime, are eliminated by the spleen and, to a lesser extent, by the liver.

  24. Thank you. Handout + Slide

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