Basic Anatomy and Physiology 1 - Cardiovascular System - Topic 5 PDF

Basic Anatomy and Physiology1 Topic 5 : Cardiovascular System Prepared by: Madam Leong Yee Leng 5.1 Blood  INTRODUCTION Blood is a fluid connective tissue. It circulates constantly around the body, propelled by the pumping action of the heart. Trans...

Basic Anatomy and Physiology1 Topic 5 : Cardiovascular System Prepared by: Madam Leong Yee Leng 5.1 Blood  INTRODUCTION Blood is a fluid connective tissue. It circulates constantly around the body, propelled by the pumping action of the heart. Transport: oxygen, nutrients, hormones, heat antibodies and cells of the immune system , clotting factors, wastes. Blood is composed of a clear, straw-coloured, watery fluid called plasma. Several different types of blood cell are suspended. Blood consist of : ✓Plasma -55% ✓cell fraction -45% LEARNING OUTCOME At the end of this session, students will be able to: list the constituents of plasma; describe their functions PLASMA Main constituent of plasma is water (90-92%) Dissolved and suspended substances, including: 1. Plasma proteins 2. Inorganic salts (electrolyte) 3. Nutrient 4. Waste products 5. Hormones 6. gases PLASMA PROTEINS Make up about 7% of plasma Retained within blood because they are too big to escape through capillary pores into the tissue mainly albumin and fibrinogen formed in the liver Function: Creating osmotic pressure of blood Maintain plasma viscosity (thickness) If plasma protein fall: Osmotic pressure is also reduced Fluid shifts into the tissues (oedema) and body cavities. Albumin Most abundant plasma proteins Function: maintain normal plasma osmotic pressure Act as a carrier molecules for free fatty acid, some drugs and steroid hormones. Globulins Most are found in the liver and the remainder in lymphoid tissue. Function: As antibodies (immunoglobulins)-complex protein produced by lymphocytes. They binds to , and neutralise, foreign materials such as micro-organism Transportation of some hormones and mineral salts; eg.thyroglobulin carries the hormone thyroxine. Inhibition of some proteolytic enzymes, e.g.α2 macroglobulin inhibits trypsin activity. Clotting factors Substances essential for coagulation of blood. Serum is plasma from which clotting factors have been removed. Fibrinogen – is synthesised in the liver and is essential for blood coagulation. INORGANIC (mineral) SALTS Involve in a wide variety of activities, including: ▪ muscle contractions ▪ transmission of nerve impulse ▪ Formation of secretions ▪ maintenance of acid-base balance ▪ Blood is slightly alkaline. ▪ Alkalinity and acidity are expressed in terms of pH, which is a measure of hydrogen ion concentration, or H+. pH 7.35-7.45 NUTRIENTS In alimentary tract Food is broken down into small molecules, eg. Monosaccharides, amino acids, fatty acids and glycerol, and are absorbed. Together with mineral salts, they are required by all body cells to: ▪ provide energy, ▪ heat, ▪ materials for repair and replacement, ▪ synthesis of other blood components and body secretions. WASTE PRODUCTS Urea, creatinine and uric acid are waste products of protein metabolism. They are formed in the liver and carried in blood to the kidneys for excretion. Carbon dioxide from the tissue metabolism is transported to the lungs for excretion. 5.0 HORMONES Hormones are chemical messengers synthesised by endocrine glands; They are secreted into the blood and transported to their target tissues and organs around the body. 6.0 GASES Oxygen is not very soluble in water, only small amount can be transported dissolved in plasma. Additional oxygen transport mechanism is needed. Oxygen bound to haemoglobin in red cell. (98% oxygen in blood) Haemoglobin also binds some carbon dioxide. Most carbon dioxide is converted to bicarbonate ion in red blood cells, then transported in the plasma. Cellular content of blood LEARNING OUTCOME At the end of this session, students will be able to : 1. Discuss the structure , function and formation of red blood cells, including the system used in medicine to classify the different types; 2. Discuss the functions and formation of the different types of white blood cell; 3. Outline the role of platelets in blood clotting CELLULAR CONTENT OF BLOOD Stem cells The stem cells are the primitive cells in bone marrow which give rise to blood cells. A stem cells can give rise to different types of blood cells, these are called pluripotent hemopoietic stem cells (PHSC) Early stage- uncommitted pluripotent hemopoietic stem cells CELLULAR CONTENT OF BLOOD Stem cells Committed pluripotent hemopoietic stem cells 1. Lymphoid stem cells (LCS)-give rise to lymphocytes 2. Colony forming blastocytes-blood cells (cont.) Erythrocytes Granulocytes /monocytes Megakyaryocytes CELLULAR CONTENT OF BLOOD THREE (3) types of blood cell 1. Erythrocytes (red cells) 2. Leukocytes (White cells) 3. Platelets (thrombocytes) Most blood cells are synthesised in red bone marrow. Some lymphocytes, are produced in lymphoid tissue. In bone marrow, all blood cells originate from pluripotent stem cells and go through several development stages before entering the blood. CELLULAR CONTENT OF BLOOD (cont.) Different types of blood cell follow separate lines of development. The process of blood cell formation is called haemopoiesis. Red marrow completely fills the space within bone for the first few years of life. Fatty yellow marrow (no haemopoietic function) will then replace red marrow over the next 20 years. Haemopoiesis in the skeleton is confined to flat bones, irregular bones, and the ends of long bones. The main sites being the sternum, ribs, pelvis and skull. ERYTHROPOIESIS Erythropoiesis is the process by which the origin, development and maturation of erythrocytes occur. Changes during erythropoiesis Stem cell of colony forming unit pass through different stages and finally become the matures red blood cells. During this process four important changes are noticed. 1. Reduction in size of the cell 2. Disapperance of nucleoli and nucleus 3. Appearance of hemoglobin 4. Change in the staining properties of the cytoplasm ERYTHROPOIESIS Stages of erythropoiesis The various stages between stem cell and matured red cell are as follows 1. Proerythroblast 2. Early normoblast 3. Intermediate normoblast Erythroblast 4. Late normoblast 5. Reticulocyte (immature RBC) 6. Mature erythrocyte Reticulocyte Reticulocyte is known as immature red blood cell. The cytoplasm contains the reticular network. Slightly larger than matured red blood cell In newborn babies the reticulocyte count is 2 to 6% i.e. 2-6 reticulocytes are present for every 100 red blood cells. The number reticulocytes is reduced during the first week after birth. Later , the reticulocytes count remains constant at or below 1 % of red blood cells. The number may increase whenever there is increased production and release of red blood cell into the circulation. this helps doctors see how many new red blood cells the bone marrow is making in anemia patient. ERYTHROCYTE Red blood cells are by far the most abundant type of blood cell. 99% of all blood cell are erythrocytes Developed from stem cells takes about 7 days (erythropoiesis) Immature cells are released into the bloodstream as reticulocytes, and mature into erythrocytes over a few days Both vitamin B12 and folic acid are required for red blood cell synthesis. ERYTHROCYTE Function: Transport gas, mainly oxygen Some carbon dioxide Characteristic: Biconcave discs (increase surface area for gas exchange) No nucleus Diameter about 7 μm ERYTHROCYTE Characteristics (cont.) The thin central portion allows fast entry and exit of gases. Cell are flexible, so they can squeeze through narrow capillaries, and contain no intracellular organelles. Large pigmented protein responsible for gas transport Flattened shape allows them to stack like dinner plates in the bloodstream (reducing turbulence) Life spend 120 days  Haemoglobin Large, complex molecule containing a globular protein and a pigmented iron-containing complex called haem. Each haemoglobin molecule contains four globin chains and four haem units, each with one atom of iron. Iron is carried in the blood stream bound to its transport protein, transferrin, and stored in the liver. Oxygen transport Saturated- When all four oxygen-binding sites on haemoglobin molecule are full. Haemoglobin binds reversibly to oxygen to form oxyhaemoglobin, according to the equation: Haemoglobin + oxygen →oxyheamoglobin (HB) (O2) (HbO2) Oxygen transport Blood rich in oxygen is bright red (Usually arterial blood) because of high level of oxyheamoglobin it contain. Blood with lower oxygen levels (usually venous blood), which is dark bluish in color because it is not saturated. The association of oxygen with haemoglobin is a loose one, so that oxyheamoglobin releases its oxygen readily. Low pH. Metabolically active tissues, e.g. exercising muscle, release acid waste products , and so the local pH falls. Under these conditions, oxyhaemoglobin readily breaks down, giving up additional oxygen for tissue use. Oxygen transport Low oxygen levels (hypoxia) when oxygen level are low, oxyheamoglobin breaks down, releasing oxygen. E.g. In the body tissues, which constantly consume oxygen keeping levels low. Temperature Actively metabolizing tissues, which have higher than normal oxygen needs, are warmer than less active ones, which drives the equation above to the left, increasing oxygen dissociation, and ensures that very active tissues receive a higher oxygen supply than less active ones. Haemoglobin + oxygen →oxyheamoglobin (HB) (O2) (HbO2) Oxygen transport Temperature (cont.) In the lungs, where the alveoli are exposed to inspired air, the temperature is lower, favouring oxyhaemoglobin formation. Haemoglobin + oxygen →oxyheamoglobin (HB) (O2) (HbO2) Control of erythropoiesis Erythropoiesis is the process by which the origin, development and maturation of erythrocytes occurs. Hemopoiesis is the process which includes origin, development and maturation of all the blood cells. Bone marrow produces erythrocytes at the rate at which they are destroyed. (negative feedback mechanism) The primary stimulus to increase erythropoiesis is hypoxia i.e. deficient oxygen supply to body cells. This occurs when: ❑The oxygen –carrying power of blood is reduced by E.g. haemorrhage or excessive erythrocyte breakdown due to disease. ❑The oxygen tension in the air is reduced, as at high altitudes. Control of erythropoiesis (Cont.) Hypoxia increases erythrocyte formation by stimulating the production of the hormone erythropoietin, mainly by the kidneys. Erythropoietin stimulates an increase in the production of proerythroblasts and the release of increased numbers of reticulocytes into the blood. Control of erythropoiesis (Cont.) These changes increase the oxygen-carrying capacity of the blood and reverse tissue hypoxia, the original stimulus. When the tissue hypoxia is overcome, erythropoietin production declines. When erythropoietin levels are low, red cell formation does not take place even in the presence of hypoxia. (anemia develop) Erythropoietin regulates normal red cell replacement, in the absence of hypoxia.  Destruction of erythrocytes The life span of erythrocytes is about 120 days and their breakdown, or haemolysis is carried out by phagocytic reticuloendothelial cells. Main site of hemolysis are the spleen, bone marrow and liver. Ion released by hemolysis is retained in the body and reused in the bone marrow to form new haemoglobin molecules.  Destruction of erythrocytes Biliverdin is formed from haem part of the heamoglobin. It is almost completely reduced to the yellow pigment bilirubin, before being bound to plasma globulin and transported to the liver. in the liver, it is changed from a fat soluble to a water soluble form to be excreted as a constituent of bile. White Blood Cell (Leukocytes) White blood cell (WBC) or leukocyte is the colorless and nucleated formed element of blood. Leukocytes play very important role in defense mechanism of the body. Depending upon present or absence of granules in the cytoplasm, the leukocytes are classified into 2 types: Granulocytes or agranulocytes. ▪ Granulocytes-with granules ▪ Agranulocytes-without granules ▪ Granulocytes are neutrophils, eosinophils and basophils. ▪ Agranulocytes are monocytes, and lymphocytes. Functions of white blood cells 2.1.1 Neutrophils Neutrophils play an important role in the defense of the body. Along with monocytes, neutrophils provide the first line of defense against the invading microorganisms. Neutrophils are the free cells in the body and wander freely through the tissue and practically no part of the body is spared by these leukocytes. The granules of neutrophils contain enzymes like proteases, myeloperoxidases, elastases and metalloproteinases. The granules also contain antibody like substances call defensins. Functions of white blood cells 2.1.1 Neutrophils (cont.) Defensins are antimicrobial peptides, which are active against bacteria and fungi. The membrane of neutrophils contains an enzymes called membrane NADPH oxidase. This is activated by toxic metabolites released from infected tissues. Neutrophils also secrete platelet activating factor (PAF) which accelerate the aggregation of platelets during injury to the blood vessel. Functions of white blood cells 2.1.2 Eosinophils The major function of eosinophils are detoxification, disintegration and removal of foreign protein. Eosinophils are specifically meant for acting against the parasites. Eosinophils count increases during parasitic infestations and allergic conditions. Eosinophils’ granules contain many substances, which become cytotoxic when release over the invading organisms. Functions of white blood cells 2.1.3 Basophils Basophils play an important role in healing processes after inflammation and in acute hypersensitivity reactions (allergy). The number of basophils is increased during healing process. The functions of basophils are executed by the release of some important substances from their granules. 1. Histamine-produces the acute hypersensitivity reactions 2. Heparin- prevent the intravascular blood clotting. 3. Hyaluronic acid- deposition of ground substances in the basement membrane Functions of white blood cells 2.1.3 Basophils The functions of basophils are executed by the release of some important substances from their granules. (cont.) 4. Proteases and myeloperoxidase: these enzymes may exaggerate the inflammation responses. The basophils also have IgE receptors, which help them to produce hypersensitivity responses. Functions of white blood cells 2.1.3 Basophils (cont.) Mast cell is a large tissue cell resembling the basophils. Present in bone marrow and around the cutaneous blood vessels but does not enter the circulation. Play an important role in allergy and anaphylaxis. It secretes heparin, histamine, serotonin, and hydrolytic enzyme. Functions of white blood cells 2.1.4 Monocytes Monocytes play an important role in defense of the body. Along with neutrophils, these leukocytes constitute the first line of defense. Monocytes are motile and phagocytic. Monocytes secrete interleukin-1, colony stimulating factors (CSF) and platelet activation factor (PAF). Monocytes are precursors of the tissue macrophages. Matured monocytes stay in the blood only for few hours then enter tissue become tissue macrophages. Figure 4.13 The body’s main fixed macrophage collection. lymphocytes 2.1.4 Lymphocytes are classified into two categories 1. T lymphocytes (cellular immunity) 2. B lymphocytes (humoral immunity) Platelets Platelets or thrombocytes are small collourless , nonnucleated and moderately refractive bodies. These formed elements of blood are considered to be fragments of cytoplasm. Platelets have a cell membrane, microtubles below the cell membrane and the cytoplasm. Platelets are spherical or rod shaped and become oval or disc shaped when inactivated. Life span- 8-11 days, those not used in hemostasis are destroyed by macrophages, mainly in the spleen. A third of platelet are stored within the spleen rather than in the circulation. This is an emergency store, released as required to control bleeding. Properties Of Platelets PLATELETS have THREE IMPORTANT PROPERTIES (3As) 1. Adhesiveness when platelet come in contact with any wet surface or rough surface, these are activated and stick to the surface. The factors, which cause adhesiveness, are collagen, thrombin, ADP, thromboxane A2, calcium ions and von Willebrand factor. 2. Aggregation (grouping of platelets) The activated platelets group together and become sticky. The stickiness is due to ADP and thromboxame A2 Properties Of Platelets PLATELETS have THREE IMPORTANT PROPERTIES (3As) 3. Agglutination Agglutination is the clumping together of platelet. The agglutination of platelets occurs due to the actions of some platelet agglutinins. Function of platelets Normally the platelets are inactive, and execute their actions only when activated. 1. Role in blood clotting The platelet are responsible for the formation of intrinsic prothrombin activator. This substance is responsible for the onset of blood clotting 2. Role in clot retraction In the blood clot, the blood cells including platelets are entrapped in between the fibrin threads. The cytoplasm of platelets contains the contractile proteins namely actin, myosin, and thrombosthenin. The contractile proteins are responsible for clot retraction. Function of platelets 3. Role in prevention of blood loss (haemostasis) Platelets accelerate the processes of haemostasis by three ways: a) Platelets secrete 5 HT, which causes the constriction of blood vessels. b) Due to the adhesive property, the platelets can seal the damage in blood vessels like capillaries. c) By formation of temporary plug also platelets seal the damage in blood vessels. Function of platelets 4. Role in repair of ruptured blood vessel The platelet derived growth factor (PDGF) formed in cytoplasm of platelets is useful for the repair of the endothelium and other stuctures of the ruptured blood vessels. 5. Role in defense mechanism By the property of agglutination, platelets encircle the foreign bodies and kill them by the process of phagocytosis. Haemostasis Haemostasis is defined as arrest of bleeding or stoppage of bleeding. Stages of hemostasis When a blood vessel is injured, the injury intiates a series of reactions resulting in hemostasis. This occurs in three stages. 1. Vasoconstriction 2. Platelet plug formation 3. Coagulation of blood Video of Haemostasis https://coursewareobjects.elsevier.com/objects/elr/Waugh/anatomy 13e/animations/ Haemostasis 1. Vasoconstriction Immediately after injury, there is constriction of blood vessel and this decreases the loss of blood from the damaged vessel. Arterioles and small arteries constrict (local phenomenon). When the blood vessels are cut, the endothelium is damages and the collagen is exposed. Platelets adhere to this collagen, and get activated. Activated platelets secrete serotonin and other vasoconstrictor substances causes constriction of the blood vessels. Haemostasis 1. Vasoconstriction (cont.) The adherence of platelets to the collagen is accelerated by von Willebrand factor. This factor acts as a bridge between a specific glycoprotein present on the surface of platelet and collagen fibrils. The platelet aggregation is also accelerated by another factor called platelet activating actor (PAF) secreted by neutrophils, monocytes and platelets. Haemostasis 2. Formation of platelet plug When platelets adhere to the collagens of ruptured blood vessel, these platelets secrete ADP and thromboxane A2. These two substances attract more and more platelet and activate them. More platelets aggregate and form a temporary loose plug, which closes the vessel and prevents the blood loss.  Haemostasis 3. Coagulation of blood During this process, the fibrinogen is converted into fibrin. The fibrin threads get attached to the loose platelet plug, which blocks the ruptured part of blood vessels and prevent blood loss completely.  Haemostasis 4. Thrombolysis After clot has formed, the process if removing it and healing the damaged blood vessel begins. The breakdown of fibrin, or fibrinogen, is the first stage. Plasminogen, trapped within the clot as it forms, is converted to the enzyme plasmin by activators released from the damaged endothelial cells. Plasmin break down fibrin, progressively removing the clot to allow tissue repair to proceed. Blood group Red blood cell membrane carries a range of different protein (called antigens) that can stimulate an immune response if transferred from one individual into the blood stream of an incompatible individual. Antigens, which are inherited, determined the individuals’ blood group. Landsteiner discovered two blood group systems called ABO system and Rh system. Both are the most important ones that are considered in blood transfusion. Blood group Based on the presence or absence of antigen A and antigen B, blood is divided into four groups A,B,AB and O groups. The blood having antigen A is called A group. This group has ß antibody in the serum. The blood with antigen B and α antibody is called B group. If both the antigens are present, the blood group is called AB group and serum of this group does not contain any antibody. If both antigens are absent, the blood group is called O group and both α and ß antibodies are present in the serum. Blood group Figure 2.0: The ABO system of blood grouping. Blood group Figure 2.0: The ABO system of blood grouping. Blood group Rh factor is an antigen present in the red blood cell. The persons having D antigen are called Rh positive. Those without D antigen are called Rh negative. If Rh negative person is exposed to Rh positive blood for the first time, then anti D is formed in that person. Rh positive person can receive Rh negative blood without the risk of developing complications. Blood group Importance of ABO groups in blood transfusion During blood transfusion, only compatible blood can be used. The one who gives blood is called donor The recipient is the one who receives the blood While transfusing blood, antigen of the donor and the antibody of the recipient are considered. Antibody of donor and antigen of the recipient are ignored mostly. Thus the red blood cell of “o” group blood has no antigen and so agglutination does not occur with any other group of blood. Blood group Importance of ABO groups in blood transfusion (cont.) ‘O’ group can be given to people with any blood group. People with ‘O’ group blood are called universal donors. The plasma of AB group has no antibody. This does not cause agglutination of red blood cell from any other group of blood. The people of AB group can receive blood from persons with any blood group. People with AB group are called universal recipient. Blood group Cross matching For blood typing, red blood cell of the individual (recipient) and test sera is used. Cross matching is done by mixing the serum of recipient and the red blood cell of donor. In clinics, cross matching is always done before blood transfusion. If agglutination of red blood cells from donor occurs during cross matching, the blood from that person is not used for transfusion. CONCLUSION 1. Constituents of plasma; 2. Functions of constituents of plasma 3. Structure , function and formation of red blood cells, including the system used in medicine to classify the different types; 4. Functions and formation of the different types of white blood cell; 5. Role of platelets in blood clotting