Transcript Blood
Chapter 19 & 20 The Cardiovascular System Online notes INTRODUCTION • Blood inside blood vessels, interstitial fluid around body cells, and lymph inside lymph vessels constitute one’s internal environment. • To obtain nutrients and remove wastes, cells must be serviced by blood and interstitial fluid. • Blood, a connective tissue, is composed of plasma and formed elements. • Interstitial fluid bathes body cells (Figure Fluids of the Body • Cells of the body are serviced by 2 fluids – blood • composed of plasma and a variety of cells • transports nutrients and wastes – interstitial fluid • bathes the cells of the body • Nutrients and oxygen diffuse from the blood into the interstitial fluid & then into the cells • Wastes move in the reverse direction • Hematology is study of blood and blood disorders Functions of Blood • Transportation – O2, CO2, metabolic wastes, nutrients, heat & hormones • Regulation – helps regulate pH through buffers – helps regulate body temperature • coolant properties of water • vasodilatation of surface vessels dump heat – helps regulate water content of cells by interactions with dissolved ions and proteins • Protection from disease & loss of blood COMPONENTS OF BLOOD • Blood consists of 55% plasma and 45% formed elements (Figure 19.1). • Blood plasma consists of 91.5% water and 8.5% solutes. • Principal solutes include proteins (albumins, globulins, fibrinogen), nutrients, enzymes, hormones, respiratory gases, electrolytes, and waste products. • Table 19.1 summarizes the chemical composition of plasma. Blood Plasma • 0ver 90% water • 7% plasma proteins • created in liver • confined to bloodstream – albumin • maintain blood osmotic pressure – globulins (immunoglobulins) • antibodies bind to foreign substances called antigens • form antigen-antibody complexes – fibrinogen • for clotting • 2% other substances – electrolytes, nutrients, hormones, gases, waste products Formed Elements of Blood • Red blood cells ( erythrocytes ) • White blood cells ( leukocytes ) – granular leukocytes • neutrophils, eosinophils, basophils – agranular leukocytes • lymphocytes = T cells, B cells, and natural killer cells • monocytes • Platelets (special cell fragments) FORMATION OF BLOOD CELLS • Blood cells are formed from pluripotent hematopoietic stem cells (Figure 19.3). • Bone marrow may be obtained through aspiration or biopsy. The sample is then sent to pathology for examination. • Originating from the pluripotent stem cells are the myeloid stem cells and lymphoid stem cells. Formation of Blood Cells • Most blood cells types need to be continually replaced – die within hours, days or weeks – process of blood cells formation is hematopoiesis or hemopoiesis • In the embryo – occurs in yolk sac, liver, spleen, thymus, lymph nodes & red bone marrow • In adult – occurs only in red marrow of flat bones like sternum, ribs, skull & pelvis and ends of long bones Stages of Blood Cell Formation • Pluripotent stem cells – .1% of red marrow cells – replenish themselves as they differentiate into either myeloid or lymphoid stem cells • Myeloid stem cell line of development continues: – progenitor cells(colony-forming units) no longer can divide and are specialized to form specific cell types • example: CFU-E develops eventually into only red blood cells – next generation is blast cells • have recognizable histological characteristics • develop within several divisions into mature cell types • Lymphoid stem cell line of development – pre-B cells & prothymocytes finish their develop into B & T lymphocytes in the lymphatic tissue after leaving the red marrow Blood Cells • Myeloid stem cells give rise to RBCs, platelets, and all WBCs except for lymphocytes. • Lymphoid stem cells give rise to lymphocytes. • Myeloid stem cells differentiate into progenitor cells or precursor cells (blast cells) which will develop into the actual formed elements of blood. • Lymphoid stem cells differentiate into pre- Red Blood Cells or Erythrocytes (Figure 19.4a) • Contain oxygen-carrying protein hemoglobin that gives blood its red color – 1/3 of cell’s weight is hemoglobin • Biconcave disk 8 microns in diameter – increased surface area/volume ratio – flexible shape for narrow passages – no nucleus or other organelles • no cell division or mitochondrial ATP formation • Normal RBC count – male 5.4 million/drop ---- female 4.8 million/drop – new RBCs enter circulation at 2 million/second Fate of Components of Heme • Iron(Fe+3) – transported in blood attached to transferrin protein – stored in liver, muscle or spleen • attached to ferritin or hemosiderin protein – in bone marrow being used for hemoglobin synthesis • Biliverdin (green) converted to bilirubin (yellow) – bilirubin secreted by liver into bile • converted to urobilinogen then stercobilin (brown pigment in feces) by bacteria of large intestine WHITE BLOOD CELLS • Leukocytes (white blood cells or WBCs) are nucleated cells and do not contain hemoglobin. Two principal types are granular (neutrophils, eosinophils, basophils) and agranular (lymphocytes and monocytes) (Figure 19.7). – Granular leukocytes include eosinophils, basophils, and neutrophils based on the straining of the granules. – Agranular leukocytes do not have cytoplasmic granules and include the lymphocytes and WBC Physiology • Less numerous than RBCs – 5000 to 10,000 cells per drop of blood – 1 WBC for every 700 RBC • Leukocytosis is a high white blood cell count – microbes, strenuous exercise, anesthesia or surgery • Leukopenia is low white blood cell count – radiation, shock or chemotherapy • Only 2% of total WBC population is in circulating blood at any given time – rest is in lymphatic fluid, skin, lungs, lymph nodes Function of WBCs • Different WBCs combat inflammation and infection in different ways. – Neutrophils and wandering or fixed macrophages (which develop from monocytes) do so through phagocytosis. – Eosinophils combat the effects of histamine in allergic reactions, phagocytize antigen-antibody complexes, and combat parasitic worms. – Basophils develop into mast cells that liberate heparin, histamine, and serotonin in allergic reactions that intensify the inflammatory response. Function of WBCs • WBCs leave the blood stream by emigration (Figure 19.8). • Some WBCs, particularly neutrophils and macrophages, are active in phagocytosis. • The chemical attraction of WBCs to a disease or injury site is termed chemotaxis. WBC Anatomy and Types • All WBCs (leukocytes) have a nucleus and no hemoglobin • Granular or agranular classification based on presence of cytoplasmic granules made visible by staining – granulocytes are neutrophils, eosinophils or basophils – agranulocytes are monocyes or lymphocytes Neutrophils (Granulocyte) • Polymorphonuclear Leukocytes or Polys • Nuclei = 2 to 5 lobes connected by thin strands – older cells have more lobes – young cells called band cells because of horseshoe shaped nucleus (band) • Fine, pale lilac practically invisible granules • Diameter is 10-12 microns Eosinophils (Granulocyte) • Nucleus with 2 or 3 lobes connected by a thin strand • Large, uniform-sized granules stain orange-red with acidic dyes – do not obscure the nucleus • Diameter is 10 to 12 microns • 2 to 4% of circulating WBCs Basophils (Granulocyte) • Large, dark purple, variable-sized granules stain with basic dyes – obscure the nucleus • Irregular, s-shaped, bilobed nuclei • Diameter is 8 to 10 microns • Less than 1% of circulating WBCs Lymphocyte (Agranulocyte) • Dark, oval to round nucleus • Cytoplasm sky blue in color – amount varies from rim of blue to normal amount • Small cells 6 - 9 microns in diameter • Large cells 10 - 14 microns in diameter – increase in number during viral infections • 20 to 25% of circulating WBCs Monocyte (Agranulocyte) • Nucleus is kidney or horse-shoe shaped • Largest WBC in circulating blood – does not remain in blood long before migrating to the tissues – differentiate into macrophages • fixed group found in specific tissues – alveolar macrophages in lungs – kupffer cells in liver • wandering group gathers at sites of infection • Diameter is 12 - 20 microns • Cytoplasm is a foamy blue-gray • 3 to 8% o circulating WBCs Neutrophil Function • Fastest response of all WBC to bacteria • Direct actions against bacteria – release lysozymes which destroy/digest bacteria – release defensin proteins that act like antibiotics & poke holes in bacterial cell walls destroying them – release strong oxidants (bleach-like, strong chemicals ) that destroy bacteria Monocyte Function • Take longer to get to site of infection, but arrive in larger numbers • Become wandering macrophages, once they leave the capillaries • Destroy microbes and clean up dead tissue following an infection Basophil Function • Involved in inflammatory and allergy reactions • Leave capillaries & enter connective tissue as mast cells • Release heparin, histamine & serotonin – heighten the inflammatory response and account for hypersensitivity (allergic) reaction Eosinophil Function • Leave capillaries to enter tissue fluid • Release histaminase – slows down inflammation caused by basophils • Attack parasitic worms • Phagocytize antibody-antigen complexes Lymphocyte Functions • B cells – destroy bacteria and their toxins – turn into plasma cells that produces antibodies • T cells – attack viruses, fungi, transplanted organs, cancer cells & some bacteria • Natural killer cells – attack many different microbes & some tumor cells – destroy foreign invaders by direct attack Differential WBC Count • Detection of changes in numbers of circulating WBCs (percentages of each type) – indicates infection, poisoning, leukemia, chemotherapy, parasites or allergy reaction • Normal WBC counts – neutrophils 60-70% (up if bacterial infection) – lymphocyte 20-25% (up if viral infection) – monocytes 3 -- 8 % (up if fungal/viral infection) – eosinophil 2 -- 4 % (up if parasite or allergy reaction) – basophil <1% (up if allergy reaction or PLATELETS • Thrombopoietin stimulates myeloid stem cells to produce platelets. • Myeloid stem cells develop into megakaryocytecolony-forming cells that develop into megakaryoblasts (Figure 19.2). • Megakaryoblasts transform into megakaryocytes which fragment. • Each fragment, enclosed by a piece of cell membrane, is a platelet (thrombocyte). • Normal blood contains 250,000 to 400,000 platelets/mm3. Platelets have a life span of only Blood Clotting • Blood drawn from the body thickens into a gel – gel separates into liquid (serum) and a clot of insoluble fibers (fibrin) in which the cells are trapped • If clotting occurs in an unbroken vessel is called a thrombosis • Substances required for clotting are Ca+2, enzymes synthesized by liver cells and substances released by platelets or damaged tissues • Clotting is a cascade of reactions in which each clotting factor activates the next in a fixed sequence resulting in the formation of fibrin threads – prothrombinase & Ca+2 convert prothrombin into thrombin ABO Blood Groups • Based on 2 glycolipid isoantigens called A and B found on the surface of RBCs – display only antigen A -- blood type A – display only antigen B -- blood type B – display both antigens A & B -- blood type AB – display neither antigen -- blood type O • Plasma contains isoantibodies or agglutinins to the A or B antigens not found in your blood – anti-A antibody reacts with antigen A – anti-B antibody reacts with antigen B RH blood groups • Antigen was discovered in blood of Rhesus monkey • People with Rh agglutinogens on RBC surface are Rh+. Normal plasma contains no anti-Rh antibodies • Antibodies develop only in Rh- blood type & only with exposure to the antigen – transfusion of positive blood – during a pregnancy with a positive blood type fetus • Transfusion reaction upon 2nd exposure to the Location of the heart • The heart is situated between the lungs in the mediastinum with about two-thirds of its mass to the left of the midline (Figure 20.1). • Because the heart lies between two rigid structures, the vertebral column and the sternum, external compression on the chest can be used to force blood out of the heart and into the circulation. (Clinical Application) Heart Orientation • Apex - directed anteriorly, inferiorly and to the left • Base - directed posteriorly, superiorly and to the right • Anterior surface - deep to the sternum and ribs • Inferior surface - rests on the diaphragm • Right border - faces right lung • Left border (pulmonary border) - faces left lung Pericardium • The heart is enclosed and held in place by the pericardium. – The pericardium consists of an outer fibrous pericardium and an inner serous pericardium (epicardium. (Figure 20.2a). • The serous pericardium is composed of a parietal layer and a visceral layer. – Between the parietal and visceral layers of the serous pericardium is the pericardial cavity, a potential space filled with pericardial fluid that reduces friction between the two membranes. – An inflammation of the pericardium is known as • Chambers and Sulci of the Heart (Figure 20.3). Four chambers – 2 upper atria – 2 lower ventricles • Sulci - grooves on surface of heart containing coronary blood vessels and fat – coronary sulcus • encircles heart and marks the boundary between the atria and the ventricles – anterior interventricular sulcus • marks the boundary between the ventricles anteriorly – posterior interventricular sulcus • marks the boundary between the ventricles posteriorly Atrioventricular Valves Open • A-V valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure – occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed Atrioventricular Valves Close • A-V valves close preventing backflow of blood into atria – occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting Blood Circulation • Two closed circuits, the systemic and pulmonic • Systemic circulation – left side of heart pumps blood through body – left ventricle pumps oxygenated blood into aorta – aorta branches into many arteries that travel to organs – arteries branch into many arterioles in tissue – arterioles branch into thin-walled capillaries for exchange of gases and nutrients – deoxygenated blood begins its return in venules Blood Circulation (cont.) • Pulmonary circulation – right side of heart pumps deoxygenated blood to lungs – right ventricle pumps blood to pulmonary trunk – pulmonary trunk branches into pulmonary arteries – pulmonary arteries carry blood to lungs for exchange of gases – oxygenated blood returns to heart in pulmonary veins Coronary Circulation • The flow of blood through the many vessels that flow through the myocardium of the heart is called the coronary (cardiac) circulation; it delivers oxygenated blood and nutrients to and removes carbon dioxide and wastes from the myocardium (Figure 20.8b). • When blockage of a coronary artery deprives the heart muscle of oxygen, reperfusion may damage the tissue further. This damage is due to free radicals. Drugs that lessen reperfusion damage after a heart attack are being developed . Coronary Circulation • Coronary circulation is blood supply to the heart • Heart as a very active muscle needs lots of O2 • When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels • Many anastomoses – connections between arteries supplying blood to the same region, provide alternate routes if one artery becomes occluded Coronary Arteries • Branches off aorta above aortic semilunar valve • Left coronary artery – circumflex branch • in coronary sulcus, supplies left atrium and left ventricle – anterior interventricular art. • supplies both ventricles • Right coronary artery – marginal branch • in coronary sulcus, CARDIAC MUSCLE AND THE CARDIAC CONDUCTION SYSTEM • The vagus nerve stimulates the SA node located in the right Atrium. • This causes the atriums to contract. • This stimulates the AV bundle. • This stimulus travels down the intraventricular septum to the Perkinje fibers that spread the stimulus to the remaining portions of the ventricles. Autorhythmic Cells: The Conduction System • Cardiac muscle cells are autorhythmic cells because they are self-excitable. They repeatedly generate spontaneous action potentials that then trigger heart contractions. • These cells act as a pacemaker to set the rhythm for the entire heart. • They form the conduction system, the route for propagating action potential through the heart muscle. Conduction System of Heart • Autorhythmic Cells – Cells fire spontaneously, act as pacemaker and form conduction system for the heart • SA node – cluster of cells in wall of Rt. Atria – begins heart activity that spreads to both atria – excitation spreads to AV node • AV node – in atrial septum, transmits signal to bundle of His • AV bundle of His – the connection between atria and ventricles – divides into bundle branches & purkinje fibers, large diameter fibers that conduct signals quickly Rhythm of Conduction System • SA node fires spontaneously 90-100 times per minute • AV node fires at 40-50 times per minute • If both nodes are suppressed fibers in ventricles by themselves fire only 20-40 times per minute • Artificial pacemaker needed if pace is too slow • Extra beats forming at other sites are called ectopic pacemakers Electrocardiogram---ECG or EKG • EKG – Action potentials of all active cells can be detected and recorded • P wave – atrial depolarization • P to Q interval – conduction time from atrial to ventricular excitation • QRS complex – ventricular depolarization • T wave – ventricular repolarization Regulation of Heart Rate • Nervous control from the cardiovascular center in the medulla – Sympathetic impulses increase heart rate and force of contraction – parasympathetic impulses decrease heart rate. – Baroreceptors (pressure receptors) detect change in BP and send info to the cardiovascular center • located in the arch of the aorta and carotid arteries • Heart rate is also affected by hormones – epinephrine, norepinephrine, thyroid hormones – ions (Na+, K+, Ca2+) – age, gender, physical fitness, and temperature Desirable Levels of Blood Cholesterol for Adults • • • • TC (total cholesterol) under 200 mg/dl LDL under 130 mg/dl HDL over 40 mg/dl Normally, triglycerides are in the range of 10190 mg/dl. • Among the therapies used to reduce blood cholesterol level are exercise, diet, and drugs.