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Human Circulation Every organism must exchange materials and energy with its environment, and this exchange ultimately occurs at the cellular level. Cells live in aqueous environments. The resources that they need, such as nutrients and oxygen, move across the plasma membrane to the cytoplasm. Metabolic wastes, such as carbon dioxide, move out of the cell. Most animals have organ systems specialized for exchanging materials with the environment, and many have an internal transport system that conveys fluid (blood or interstitial fluid) throughout the body. For aquatic organisms, structures like gills present an expansive surface area to the outside environment. Oxygen dissolved in the surrounding water diffuses across the thin epithelium covering the gills and into a network of tiny blood vessels (capillaries). At the same time, carbon dioxide diffuses out into the water. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Diffusion alone is not adequate for transporting substances over long distances in animals - for example, for moving glucose from the digestive tract and oxygen from the lungs to the brain of mammal. Diffusion is insufficient over distances of more than a few millimeters. The circulatory system solves this problem by ensuring that no substance must diffuse very far to enter or leave a cell. FUNCTIONS OF VERTEBRATE CIRCULATORY SYSTEMS A. Nutrient and Waste Transport 1. 2. 3. 4. 5. 6. Nutrients enter blood through wall of small intestine Carried to liver for storage or metabolism-gyycogen Dissolved glucose and metabolites carried to all body cells Metabolizing cells release wastes into blood Wastes carried to kidney for removal Constitutes metabolic circuit or systemic circulation B. Oxygen and Carbon Dioxide Transport 1. 2. 3. 4. 5. 6. Oxygen diffuses into blood through gills or lungs Oxygen accumulates in hemoglobin of red blood cells Oxygen released at metabolizing cells Carbon dioxide, a metabolic product, is released by cells into blood Waste carbon dioxide carried back to gills or lungs and released Constitutes respiratory circuit or pulmonary circulation C. Temperature Regulation 1. Most vertebrates are poikilotherms, body temperature varies with environmental temperature 2.Mammals and birds are homeotherms, maintain constant body temperature 3.Heat distributed by circulating blood 4.Temperature adjusted by directing flow to interior or extremities a. Decrease body temperature by dissipating heat to environment b. Retain heat by directing blood from extremities to interior D. Hormone Circulation 1. Hormones transported to target tissues throughout body 2. Hormones persist only a short time, are destroyed by body enzymes " A dream is not what you see in sleep, it is the thing that does not let you sleep." A. Closed system: blood enclosed within vessels – – – – – – 1. 2. 3. 4. 5. 6. Circulating fluid does not mix with other body fluids Materials pass across by diffusion through walls of vessels Annelids have a closed system Movement of fluid in vessels assisted by muscle contraction All vertebrates have closed circulatory system Advantage of closed systems • a. Can change diameter of individual muscle-encased vessels • b. Regulate fluid flow in specific parts of body independently • B. Open system: no distinction between circulating fluid and body fluid – 1. Arthropods have an open system – 2. Muscular tube in body cavity pumps fluid through network of channels – 3. Fluid drains back into central cavity Three main circuits Pulmonary Systemic Blood goes from heart to lungs to pick up oxygen and release carbon dioxide Blood pumped out of heart to the rest of the body Coronary Heart muscle itself supplied with oxygen, nutrients, etc. Blood flow through the body Blood vessels Arteries--take oxygenated blood away from the heart Thick/muscular walls Do not contain valves All carry oxygen but one. Which one? PULMONARY ARTERY Go from large diameter to small diameter Become arterioles before capillaries Blood flow through the body • Blood vessels • Gases diffuse across very thin wall of small vessels called capillaries • Most are 1 cell thick • Exchange CO2 for O2 • Nutrients for wastes • Return to heart •Blood flow through the body Blood vessels Veins--take deoxygenated blood back to the heart Thin walls Have valves Prevents backflow QuickTime™ and a Where are they in greatest numbers? Photo - JPEG decompressor are needed to see this picture. Lower body. Why? Gravity • Metabolic rate is an important factor in the evolution of cardiovascular systems. Shift from filter feeding to active capture of prey – In general, animals with high metabolic rates have more complex circulatory systems and more powerful hearts than animals with low metabolic rates. – Similarly, the complexity and number of blood vessels in a particular organ are correlated with that organ’s metabolic requirements. ALL BLOOD CIRCUITS HEART EVOLUTION Frogs and other amphibians have a threechambered heart with two atria and one ventricle. 1. Evolution of large veins from lungs called pulmonary veins a. Altered blood flow: blood from lungs returns to heart for Repumping 2. Advantage: blood pumped to tissues The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmonary and systemic circulations. at higher pressure 3. Disadvantage: oxygenated blood mixed with unoxygenated blood Frogs and other amphibians have a threechambered heart with two atria and one ventricle. 1. Evolution of large veins from lungs called pulmonary veins a. Altered blood flow: blood from lungs returns to heart for Repumping 2. Advantage: blood pumped to tissues The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmonary and systemic circulations. at higher pressure 3. Disadvantage: oxygenated blood mixed with unoxygenated blood The evolution of a powerful four-chambered heart was an essential adaptation in support of the endothermic way of life characteristic of birds and mammals. Endotherms use about ten times as much energy as ectotherms of the same size. Therefore, the endotherm circulatory system needs to deliver about ten times as much fuel and O2 to their tissues and remove ten times as much wastes and CO2. Birds and mammals evolved from different reptilian ancestors, and their powerful four-chambered hearts evolved independently - an example of convergent evolution. The closed circulatory system of humans and other vertebrates is often called the cardiovascular system. The heart consists of one atrium or two atria, the chambers that receive blood returning to the heart, and one or two ventricles, the chambers that pump blood out of the heart. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Heart Covered with a sac called the pericardium Hollow, cone-shaped structure made of muscle called myocardium 4 Chamber or Cavities 2 Atrium 2 Ventricles 4 Valves Allows blood to flow in one direction Separates chambers-prevents backflow of blood HEART STRUCTURE Blood flow through the heart (heart pumping animation!) Into vena cava-superior or inferior Into right atrium Thru AV valve Down to right ventricle Thru pulmonary valve Out pulmonary artery to lungs--gets 02 and dumps CO2 Back to heart through pulmonary vein Into left atrium Thru AV valve Down to left ventricle Thru aortic valve Out aorta to body St. Joseph’s asp. animation Trace Blood Flow in the Heart Using Pencil trace the flow of blood through the heart (starting in the superior and inferior vena cava) Shade the areas of the heart that contain deoxygenated blood http://www.sumanasinc.c om/webcontent/animation s/content/human_heart.ht ml Click the Link Below to Review One More Time Four valves in the heart, each consisting of flaps of connective tissue, prevent backflow and keep blood moving in the correct direction. Between each atrium and ventricle is an atrioventricular (AV) valve which keeps blood from flowing back into the atria when the ventricles contract. Two sets of semilunar valves, one between the left ventricle and the aorta and the other between the right ventricle and the pulmonary artery, prevent backflow from these vessels into the ventricles while they are relaxing. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings HEART SOUND AND REGULATION Sound of heart (lub/dub) made by valves closing Lub is the AV valves closing-first sound Dub is the Aortic and Pulmonary valves closing-second sound Delivery of oxygen to the body’s organs is critical for survival. Certain cells of vertebrate cardiac muscle are self-excitable, meaning they contract without any signal from the nervous system. Each cell has its own built in contraction rhythm. However, these cells are synchronized by the sinoatrial (SA) node, or pacemaker, which sets the rate and timing at which all cardiac muscle cells contract. The SA node is located in the wall of the right atrium. The cardiac cycle is regulated by electrical impulses that radiate throughout the heart. Cardiac muscle cells are electrically coupled by intercalated disks between adjacent cells. Fig. 42.7 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings HEART BEAT REGULATION (1) The SA node generates electrical impulses, much like those produced by nerves that spread rapidly (2) through the wall of the atria, making them contract in unison. The impulse from the SA node is delayed by about 0.1 sec at the atrioventricular (AV) node, the relay point to the ventricle, allowing the atria to empty completely before the ventricles contract. (3) Specialized muscle fibers called bundle branches and Purkinje fibers conduct the signals to the apex of the heart and (4) throughout the ventricular walls. This stimulates the ventricles to contract from the apex toward the atria, driving blood into the large arteries. Contraction stimulated by membrane depolarization, reversal of electrical polarity Contraction triggered by SA node-pacemaker Membrane of cells depolarize spontaneously with regular rhythm Depolarization passes from one cardiac muscle cell to another Spreads because cardiac cells(myocardial) are electrically coupled by gap junctions Ventricular wave of depolarization delayed by nearly 0.1 second Atria and ventricles separated by connective tissue Connective tissue cannot generate depolarization-SO Wave passes via atrioventricular node (AV node) Delay permits atria to completely empty before ventricles contract Depolarization conducted over both ventricles via bundle of His Transmitted by Purkinje fibers that stimulate ventricle myocardial cells Right and left ventricles contract almost simultaneously ELECTRICAL CONDUCTION http://www.youtube.com/watch?v=zS9dEeI HE98&feature=related VALVE SOUNDS http://www.bostonscientific.com/templatedata /imports/HTML/CRM/heart/heart_valves.h tml Blood pressure and pulse Blood pressure compares diastolic and systolic pressures Diastole--heart relaxes and blood flows into heart chambers Systole--ventricles contract, sending blood out of heart • http://www.bostonscientific.com/templatedata/imports/HT ML/CRM/heart/index.html • Heart sounds http://www.youtube.com/watch?v=WXwYYsi6z7Q&feature =related • Hearts electrical system • http://www.bostonscientific.com/templatedata/imports/HT ML/lifebeatonline/summer2004/learning.shtml • Blood in the closed circulatory systems of vertebrates is a specialized connective tissue consisting of several kinds of cells suspended in a liquid matrix called plasma. • The plasma is about 45% of the blood volume, transparent and straw-colored. • 90% water • Variety of ions, sometimes referred to as blood electrolytes – Plasma is a dilute salt solution. Primarily sodium, chloride and bicarbonate – Maintain osmotic balance of the blood and help buffer the blood. – Proper functioning of muscles and nerves depends on the concentrations of key ions in the interstitial fluid. • Plasma carries a wide variety of substances in transit from one part of the body to another, including nutrients, metabolic wastes, respiratory gases, and hormones. Fig. 42.14 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • The plasma proteins have many functions. – Collectively, they acts as buffers against pH changes, help maintain osmotic balance, and contribute to the blood’s viscosity. – Some specific proteins transport otherwise-insoluble lipids in the blood. – Other proteins, the immunoglobins or antibodies, help combat viruses and other foreign agents that invade the body. Liver produces most plasma proteins, including albumin – Alpha and beta globin proteins are carriers of lipids and steroid hormones – Fibrinogen proteins help plug leaks when blood vessels are injured. • Blood plasma with clotting factors removed is called serum. Red blood cells, or erythrocytes, are by far the most numerous blood cells. Each cubic millimeter of blood contains 5 to 6 million red cells, 5,000 to 10,000 white blood cells, and 250,000 to 400,000 platelets. There are about 25 trillion red cells in the body’s 5 L of blood. Carry oxygen transport, depends on rapid diffusion of oxygen across the red cell’s plasma membranes. Human erythrocytes are small biconcave disks, presenting a great surface area. Mammalian erythrocytes lack nuclei, an unusual characteristic that leaves more space in the tiny cells for hemoglobin, the iron-containing protein that transports oxygen. Red blood cells also lack mitochondria and generate their ATP exclusively by anaerobic metabolism. Contains about 250 million molecules of hemoglobin. Each hemoglobin molecule binds up to four molecules of O2. Recent research has also found that hemoglobin also binds the gaseous molecule nitric oxide (NO). Also CO As red blood cells pass through the capillary beds of lungs, gills, or other respiratory organs, oxygen diffuses into the erythrocytes and hemoglobin binds O2 and NO. The NO relaxes the capillary walls, allowing them to expand, helping delivery of O2 to the cells. RED BLOOD CELLS There are five major types of white blood cells, or leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes. Less than 1% of total blood cells Their collective function is to fight infection. White blood cells spend most of their time outside the circulatory. Diapedesis system, patrolling through interstitial fluid and the lymphatic system, fighting pathogens. Injured cells release histamine Dilation of arterioles increases blood flow, makes area red For example, monocytes and neutrophils are phagocytes, which engulf and digest bacteria and debris from our own cells. Lymphocytes develop into specialized B cells and T cells, which produce the immune response against foreign substances. Produces in the lymphatic system, bone marrow and the thymus WHITE BLOOD CELLS The third cellular element of blood, platelets, are fragments of cells about 2 to 3 microns in diameter. They have no nuclei and originate as pinched-off cytoplasmic fragments of large cells in the bone marrow. Platelets function in blood clotting. Erythrocytes, leukocytes, and platelets all develop from a single population of cells, pluripotent stem cells, in the red marrow of bones, particularly the ribs, vertebrae, breastbone, and pelvis. “Pluripotent” means that these cells have the potential to differentiate into any type of blood cells or cells that produce platelets. This population renews itself while replenishing the blood with cellular elements. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.13 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings A negative-feedback mechanism, sensitive to the amount of oxygen reaching the tissues via the blood, controls erythrocyte production. If the tissues do not produce enough oxygen, the kidney converts a plasma protein to a hormone called erythropoietin, which stimulates production of erythrocytes. If blood is delivering more oxygen than the tissues can use, the level of erythropoietin is reduced, and erythrocyte production slows. Recent breakthroughs in isolating and culturing pluripotent stem cells, may soon lead to treatments of problems such as leukemia. Individuals with leukemia have a cancerous line of stem cells that produce leukocytes. These cancerous cells crowd out cells that make red blood cells and produce an unusually high number of leukocytes, many of which are abnormal. One strategy now being used experimentally for treating leukemia is to remove pluripotent stem cells from a patient, destroy the bone marrow, and restock it with noncancerous pluripotent cells. BLOOD CLOTTING Blood contains a self-sealing material that plugs leaks from cuts and scrapes. A clot forms when the inactive form of the plasma protein fibrinogen is converted to fibrin, which collects into threads that form the framework of the clot. The clotting mechanism begins with the release of clotting factors from platelets. The clotting process begins when the endothelium of a vessel is damaged and connective tissue in the wall is exposed to blood. Platelets adhere to collagen fibers and release a substance that makes nearby platelets sticky. The platelets form a plug. The seal is reinforced by a clot of fibrin when vessel damage is severe. Fig. 42.16 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Anticlotting factors in the blood normally prevent spontaneous clotting in the absence of injury. Sometimes, however, platelets clump and fibrin coagulates within a blood vessel, forming a clot called a thrombus, and blocking the flow of blood. These potentially dangerous clots are more likely to form in individuals with cardiovascular disease, diseases of the heart and blood vessels. Blood types A,B,O dictated by the antigen that is on the surface of the RBC’s Antigens are substances that trigger an immune response A has A antigen B has B AB has both O has no antigens BLOOD TYPES Removal of wastes Blood takes CO2 back to lungs Delivers salts, water, and nitrogenous wastes (urea) to the kidneys for excretion Urea Main nitrogenous waste of body Produced in liver (from ammonia--NH3) Removed by kidneys