Blood - 3 PDF

The Blood CHAPTER 19 The Cardiovascu lar System  Blood Internal environment: Blood inside blood vessels Interstitial fluid around body cells Lymph inside lymph vessels To obtain nutrients and remove wastes, cells must be serviced by blood and interstitial fluid. Blood - liquid...

The Blood CHAPTER 19 The Cardiovascu lar System  Blood Internal environment: Blood inside blood vessels Interstitial fluid around body cells Lymph inside lymph vessels To obtain nutrients and remove wastes, cells must be serviced by blood and interstitial fluid. Blood - liquid connective tissue consisting of: formed elements - cellular The branch of science components concerned with the study of liquid extracellular matrix - blood, blood-forming plasma tissues, and disorders is called hematology. Interstitial fluid bathes body cells and Properties of Blood Blood consists of 55% plasma and 45% formed elements. Blood plasma consists of 91.5% water and 8.5% solutes. Principal solutes include: proteins (albumins, globulins, fibrinogen) nutrients enzymes hormones respiratory gases electrolytes waste products Formed Elements / Cellular Components The formed elements in blood include: erythrocytes (red blood cells or RBCs) leukocytes (white blood cells or WBCs) thrombocytes (platelets) The % of total blood volume occupied by RBC’s is called the hematocrit. Properties of Blood Physical characteristics of blood include: a viscosity greater than water Temperature 38 C pH of 7.35 – 7.45 Blood constitutes about 8% of body weight; volume ranges from 4 to 6 liters. Properties of Blood *Plasma Components* Functions and Properties of Blood TRANSPORTS REGULATES PROTECTS oxygen homeostasis of preventing blood carbon dioxide all body fluids loss through nutrients pH clotting hormones body combats toxins heat temperature and microbes waste products water content of through certain cells phagocytic WBC’S or specialized plasma proteins  Formation of Blood Cells Pluripotent stem cells (found in red bone marrow) have the capacity to develop into many types of cells. Lymphocytes can live for years while most other blood cells live for hours, days, or weeks. The number of RBC’s and platelets remains rather steady. WBCs vary depending on invading pathogens and other foreign antigens. The process of producing blood cells is hemopoiesis (hematopoiesis). Red Blood Cells Erythropoiesis (production of RBC’s) Erythrocyte formation begins in the red bone marrow. Erythropoietin - a hormone released by the kidneys in response to hypoxia (lowered oxygen concentration) stimulates differentiation of hematopoietic stem cells into erythrocytes. Reticulocytes (immature red blood cells) enter the circulation and mature in 1 to 2 days. Red Blood Cells RBCS have NO NUCLEUS or other organelles. BICONCAVE DISCS The lack of a nucleus and the shape allow the cells to efficiently carry oxygen. RBCS live for about 120 DAYS. Dead cells are removed from the circulation by the spleen and liver. Breakdown products from the cells are recycled and reused.  Red Blood Cells RBCs (erythrocytes) contain the protein HEMOGLOBIN. that carries oxygen to all cells carries 23% of total CO2 to the lungs Each hemoglobin molecule contains an IRON ION which allows each molecule to bind four oxygen molecules. Each erythrocyte has 280 million hemoglobin molecules. 5 million RBCs per microliter of blood is the normal count 5 million RBC’s x 280 million hemoglobin = 1,400,000,000,000,000 hemoglobin Multiply by 4 and that will give you the number of oxygen molecules in a 1 microlitre drop of blood Copyright © 2014 John Wiley & Sons, Inc. All right s reserved.  WBCs (leukocytes) contain a nucleus and White organelles, but no hemoglobin. Leukocytes are classified as either granular (containing vesicles that appear Blood when the cells are stained) or agranular (containing no granules) Cells Granular leukocytes: neutrophils, eosinophils, basophils Agranular leukocytes: lymphocytes, monocytes  White Blood Cells WBC’s may live for several months or years, but most only live a few days. Their main function is to combat invading microbes. Several chemicals released by inflamed tissues attract phagocytes - CHEMOTAXIS During an invasion, many WBC’s can leave the bloodstream and collect at sites of invasion. The process is called EMIGRATION, DIAPEDESIS White Blood Cells An elevation in the white blood count usually indicates an infection or inflammation. A low WBC count may develop due to several causes. A differential WBC count will help to determine if a problem exists. Easy way to remember this list of WBC’s from most to least abundant: Platelets Platelets are used to clot the blood. Platelets help stop blood loss from damaged vessels by forming a platelet plug. Their granules also contain chemicals that promote blood clotting. Megakaryocytes in red bone marrow splinter into 2000–3000 fragments to create the platelets that contain many vesicles but no nucleus. Normal blood contains 250,000 to 400,000 platelets/mm3. Platelets have a life span of only 5 to 9 days Aged and dead platelets are removed by macrophages in the Formed Elements of the Blood Copyright © 2017 John Wiley & Sons, Inc. All right s reserved. Platelets  Hemostasis Hemostasis is a sequence of responses that stop bleeding. When blood vessels are damaged or ruptured hemostatic response must be QUICK LOCALIZED to the region of damage carefully CONTROLLED The process involves: Vascular spasm - smooth muscle of a blood vessel wall contracts to reduce blood loss. Platelet plug formation involves the clumping of platelets around the damage to stop the bleeding. Blood clotting or coagulation - a gel that contains formed elements of the blood entangled in fibrin threads. Blood Clotting Blood remains in its liquid form as longs as it stays within its vessels. If drawn from the body, it thickens and forms a gel. The gel separates from the liquid. Straw coloured liquid is called SERUM - plasma minus clotting factors. The gel is called a blood clot - a network of insoluble protein fibers called FIBRIN in which the formed elements of the blood are trapped. The process of gel formation is called clotting or coagulation The chemicals involved in clotting are known as coagulation (clotting) factors. (13 clotting factors including calcium, prothrombin, fibrinogen) Blood clotting involves a cascade of reactions that may be divided into three stages: Extrinsic or intrinsic pathway lead to formation of prothrombinase (prothrombin activator) conversion of prothrombin into thrombin conversion of soluble fibrinogen into insoluble fibrin Blood Clotting continued Stage 1 - extrinsic or intrinsic pathway Extrinsic pathway starts with the trauma to the vascular wall or surrounding tissue, (fewer steps) occurs rapidly, within a matter of seconds if injury is severe. Tissue Factor leaks into the blood from cells outside the blood vessels and initiates the formation of prothrombinase. Intrinsic pathway starts when blood meets exposed collagen from damaged endothelial walls. (more complex) occurs more slowly, requiring several minutes. Activators are in direct contact with blood or contained within the blood outside tissue damage is not needed. Damaged endothelial cells and platelets causes release of phospholipids by the platelets activating clotting factor X and initiates prothrombinase. Stage 2 – Common Pathway Prothrombinase and Ca2+ catalyse the conversion of prothrombin to thrombin. Stage 3 Thrombin converts fibrinogen to loose, insoluble fibrin threads. Hemostasis Clot retraction - Once the clot forms, it consolidates (tightens) to pull the edges of the damaged vessel together. Vitamin K is needed for normal clot formation although it is not directly involved. It is used in the synthesis of 4 clotting factors. Small, unwanted clots are usually dissolved by plasmin (fibrinolysin). Hemostasis Blood usually clots within 3 to 6 minutes The clot remains as endothelium regenerates. The clot is broken down after tissue repair. Thrombus A clot in an unbroken blood vessel Can be deadly in areas such as the heart and brain Embolus A thrombus that breaks away and floats freely in the bloodstream Can later clog vessels in critical areas such as the brain Haemorrhage – blood takes too long to clot Blood Groups and Blood Types Blood is classified into different blood groups based on the presence or absence of antigens (agglutinogens) on the surface of RBC’s. Classification is based on antigens labeled A, B or AB with O being the absence of the antigens. An additional antigen, Rh, is present in 85% of humans. Positive or negative. Blood plasma usually contains antibodies (agglutinins) that react with A or B antigens. An individual will not have agglutinins against his or her own blood type. Disorders: Anemia A condition in which the oxygen carrying capacity of blood is reduced. Reduced number of RBC’s or a decreased amount of hemoglobin in the blood. Hemophilia A rare disorder in which blood doesn't clot normally because it lacks sufficient blood-clotting proteins (clotting factors). Bleed for a longer time after an injury.