The Cardiovascular System PDF

The Cardiovascular System Ryan R. Williams, M.D., Ph.D. Biology 122 California State University Dominguez Hills Overview of the Cardiovascular System The cardiovascular system works with the majority of the body systems to maintain homeostasis Made up of the heart and...

The Cardiovascular System Ryan R. Williams, M.D., Ph.D. Biology 122 California State University Dominguez Hills Overview of the Cardiovascular System The cardiovascular system works with the majority of the body systems to maintain homeostasis Made up of the heart and blood vessels The heart pumps blood through blood vessels Blood vessels transport oxygen and nutrients to the cells and helps get rid of wastes The exchanges of these substances occurs through interstitial fluid that surrounds the tissues Lymphatic system Assists the cardiovascular system by collecting excess tissue fluid and returning it to the blood When fluid enters the lymphatic vessels it is called lymph Does not carry blood Blood Function Transportation: oxygen, nutrients, wastes, carbon dioxide, and hormones Defense against invasion by pathogens White blood cells Antibodies—proteins that disable pathogens Protects against fluid loss by clotting Regulates body temperature by transferring heat Maintains osmotic pressure Proteins dissolved in the plasma (albumin) maintain osmotic Buffers present in blood regulate pH, keeping it at a constant 7.4 Blood Composition Blood is a liquid connective tissue made of formed elements (cells and cell fragments) suspended in plasma Formed elements are produced in the red bone marrow Red blood cells/erythrocytes (RBCs) White blood cells/leukocytes (WBCs) Platelets/thrombocytes Blood Blood Blood stem cells stem cells for the white blood cells erythroblasts lymphoblasts monoblasts myeloblasts megakaryoblasts Red Blood Cell Lymphocyte Monocyte Neutrophil Eosinophil Basophil Platelets (erythrocyte) active in specific becomes (contains (contains granules) (contains (thrombocytes) transports O2 and immunity large granules) active in allergies granules) aid blood helps transport CO2 phagocyte phagocytizes and worm releases clotting pathogens infections histamine Blood Plasma 91% water and 9% salts and organic molecules Solutes help maintain the osmotic pressure of blood Salts act as buffers Other solutes: nutrients, wastes, hormones. Plasma proteins are the most abundant organic molecules Most are produced by the liver Three major types of plasma proteins: Albumins Most abundant of the plasma proteins Contribute to osmotic pressure more than others. Transport molecules in blood Globulins Some transport substances in the blood Others, immunoglobulins (Ig), fight pathogens Fibrinogen Usually inactive; when activated, forms blood clots Blood Red blood cells (erythrocytes) Biconcave shape increases surface area Lack a nucleus and mitochondria Contain the protein hemoglobin (Hb) Has four subunits (quaternary structure) Each subunit contains a heme group Each heme has an iron (Fe) atom that binds to an oxygen Therefore, Hb can bind a total of four oxygens When bound to oxygen Hb turns red When not bound to oxygen Hb turns blue Blood The transport of carbon dioxide in blood 7% of CO2 is transported dissolved in plasma 23% binds to the globin portion of hemoglobin Does not compete with oxygen binding sites on Fe When CO2 is bound, hemoglobin has a decreased affinity for oxygen (allosteric inhibition) 70% is in plasma as bicarbonate ions (H2CO3−) Factors that influence the affinity of hemoglobin for oxygen Blood The production of red blood cells Occurs in the red bone marrow As RBCs are produced, they lose their nucleus and most organelles Without a nucleus, can’t make proteins for cell repair Therefore, only live about 120 days Old, worn out cells are removed from circulation by macrophages in the liver and spleen The disc shape of RBCs Allows them to squeeze through small capillaries Increases surface area (for gas diffusion) Blood Erythropoietin (EPO) A hormone produced by the kidneys when oxygen levels of the blood are low Stimulates the bone marrow to produce more red blood cells Blood doping Increasing the number of RBCs, sometimes by injecting EPO To increase stamina and athletic performance Very dangerous; blood becomes too thick and can cause heart failure Blood White blood cells (leukocytes) Several different types Large cells; have a nucleus Much less numerous than RBCs Produced in red bone marrow; production is regulated by colony-stimulating factor (CSF) Fight infection and are an important part of the immune system Some live for only days while others live months or years Blood Categorization of white blood cells Granular leukocytes—contain noticeable granules, lobed nuclei Neutrophil Eosinophil Basophil Agranular leukocytes—no granules, non-lobular nuclei Lymphocyte Monocyte Blood Neutrophils The most abundant WBC—about 50–70% of all WBCs Have a multilobed nucleus “First responders” to bacterial infections Engulf pathogens by phagocytosis Can leave the bloodstream so are found in interstitial fluid Contain enzymes that have a yellow/green color Blood Eosinophils Have a bilobed nucleus Have many large granules Involved with parasitic infections and allergies Basophils The rarest of WBCs Have a U-shaped or lobed nucleus In connective tissues, basophils and mast cells release histamine during allergic reactions Histamine dilates blood vessels but constricts breathing passageways (Example: during an asthma attack) Blood Lymphocytes About 25–35% of all WBCs (second most common) Two types: B cells and T cells B cells When mature, produce antibodies, which mark a pathogen for destruction T cells Various different types Some directly destroy pathogens (cell-mediate immunity) Monocytes Largest of the WBCs A type of macrophage, which engulf pathogens, old cells and debris White Blood Cells Function Grɑnular leukocytes Neutrophils Phagocytize pathogens and cellular debris. Eosinophils Use granule contents to digest large pathogens, such as worms. Basophils Promote blood flow to injured tissues and the inflammatory response. Agrɑnulɑr leukocytes Lymphocytes Responsible for specific immunity; B cells produce antibodies; T cells destroy cancer and virus-infected cells. Monocytes Become macrophages that phagocytize pathogens and cellular debris. Blood Platelets (thrombocytes) Fragments of large cells called megakaryocytes not true cells About 200 billion platelets are made per day Function in blood clotting (coagulation) Hemostasis (still blood) forms clots 13 different clotting factors (I-XIII), calcium ions, and enzymes participate in clot formation Vitamin K is necessary for the formation of several clotting factors and proteins Blood Blood clotting Prevents plasma and cells from leaking out of broken vessels When a vessel breaks, platelets clump to partially seal it Platelets and injured tissues release a clotting factor called prothrombin activator Converts prothrombin to thrombin Thrombin converts fibrinogen to fibrin Both steps require calcium ions Fibrin threads provide a framework for the clot Red blood cells get trapped in this framework The fibrin clot is temporary; an enzyme called plasmin destroys the fibrin network, so that tissue cells can grow to repair the vessel Serum The liquid that remains after the blood has clotted Basically plasma without fibrinogen and prothrombin Blood Blood type Determined by glycoproteins (antigens) on the surface of RBCs Blood transfusion transfer of blood from one person to another Need to make sure blood types are compatible to prevent agglutination (clumping), of red blood cells Blood ABO blood groups Type A blood RBCs have the A antigen Antigen—a foreign (glycoprotein) substance, often a glycoprotein, that Has anti-B antibodies stimulates an immune Type B blood response RBCs have the B antigen Antibodies are specific Has anti-A antibodies and only bind to the foreign Type AB blood antigen they are made for RBCs have both the A and the B Blood types are determined antigens by the presence and/or No antibodies to either A or B absence of two antigens Type O blood type A and type B RBCs have neither antigen Both anti-A and anti-B antibodies type A antigen anti-B antibodies Type A blood. Red blood cells have type A surface antigens. Plasma has anti-B antibodies. type B antigen anti-A antibodies Type B blood. Red blood cells have type B surface antigens. Plasma has anti-A antibodies. type A antigen type B antigen Type AB blood. Red blood cells have type A and type B surface antigens. Plasma has neither anti-A nor anti-B antibodies. anti-A antibody anti-B antibody Type O blood. Red blood cells have neither type A nor type B surface antigens. Plasma has both anti-A and anti-B antibodies. Blood Blood compatibility During a blood transfusion, if antibodies in the recipient’s plasma bind to antigens on the surface of donated red blood cells, agglutination can occur Type A cannot receive type B or AB blood Type B cannot receive type A or AB Type O can only receive type O blood Universal donor—type O Universal recipient—type AB To be sure, perform a crossmatch (mix small amounts of the blood to test for agglutination) Blood Rh blood groups The Rh factor is another blood type antigen if it is present, the blood is Rh positive (+) if it is not present, the blood is Rh negative (−) Unlike anti-A and anti-B antibodies, anti-Rh antibodies only develop in a person after they are exposed to the Rh factor Blood Hemolytic disease of the newborn When an Rh− woman gives birth to an Rh+ fetus, some Rh+ blood can leak from the fetus to the mother, causing the mother to make anti-Rh antibodies When the mother later has a second fetus that is Rh+, these antibodies can cross the placenta and attack the fetus’ red blood cells Can lead to anemia, disabilities and even death To prevent this, the mother should receive a RhoGAM shot, that prevents the formation of antibodies Typically given within 72 hours after birth of an Rh+ child  Rh-negative red blood cell of mother Rh- positive red blood cell of fetus blood of mother Fetal Rh-positive red blood cells leak across placenta into mother's bloodstream. anti-Rh antibody blood of mother Mother forms anti-Rh antibodies that cross the placenta and attack fetal Rh-positive red blood cells. Blood Vessels There are three types of blood vessels: arteries, veins, and capillaries Artery Carries blood away from the heart Walls have 3 layers: Inner layer (Endothelium) Thin, simple squamous epithelium Middle layer Smooth muscle and elastic tissue Allows arteries to expand and recoil Outer layer Connective tissue Blood Vessels Arterioles Small arteries Have little to no outer layer Mostly middle layer of smooth muscle Contracts to constrict the vessel, reducing blood flow and raising blood pressure When relaxed, the vessel dilates, increasing blood flow and reducing blood pressure Blood Vessels Capillaries Microscopic vessels between arterioles and venules Walls of capillaries are made only of endothelium Form capillary beds where gas, nutrient, and waste exchange occurs Have precapillary sphincters Circular smooth muscles Control blood flow through the capillary bed When closed, blood instead flows through an arteriovenous shunt Blood Vessels Veins and venules carry blood back the heart Both have the same 3 layers as arteries but less smooth muscle in the middle layer Venules small veins that receive blood from the capillaries Veins Those that carry blood against gravity have valves to keep blood flowing toward the heart Walls of veins are thinner than arteries so they can expand to hold more blood At any one time, they store 70% of the blood If blood is lost (that is, hemorrhage), the nervous system causes the veins to constrict to increase blood return to the heart  artery connective tissue arteriole a. precapillary blood sphincter capillary bed flow elastic tissue arteriovenous endothelium shunt smooth v. muscle valve venule blood vein flow v. = vein; a. = artery The Heart The heart pumps 75 ml of blood with each contraction On average, the heart beats 70 times/minute Therefore the heart pumps roughly 5,250 ml per minute The entire blood supply is circulated each minute The Heart Located between the lungs Twisted slightly to the left Points toward the left hip Consists mostly of the myocardium, which is made of cardiac muscle tissue Muscle fibers are branched and connected by intercalated disks, which contain gap junctions These allow cells to contract in unison  The Heart intercalated disc mitochondrion cardiac gap junction muscle cell 3,000× The Heart Surrounded by a sac called the pericardium, which secretes pericardial fluid for lubrication The heart is a double pump (left and right) Internally, a septum divides the heart into right and left sides Both sides pump at same time (closed loop) Consists of 4 chambers: 2 upper atria and 2 lower ventricles 2 types of valves AV valves Allow blood to flow from atria to ventricles reinforced by chordae tendineae that attach to papillary muscles Left AV valve—bicuspid (mitral valve) Right AV valve—tricuspid valve Semilunar valves pulmonary valve allows blood to flow into pulmonary circuit aortic valve allows blood to flow into systemic circuit  left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary veins right pulmonary artery right pulmonary veins left atrium left cardiac vein right atrium right coronary artery left ventricle right ventricle left anterior descending coronary artery inferior vena cava apex  left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary veins right pulmonary artery right pulmonary veins pulmonary valve left atrium right atrium left AV (mitral) valve right AV (tricuspid) valve chordae tendineae right ventricle septum left ventricle inferior vena cava The Heart Coronary circulation The myocardium needs its own blood supply Coronary arteries They are the first branches off the aorta The heart feeds itself first Coronary veins Empty into the right atrium Coronary artery disease Blockage in the coronary arteries Causes a myocardial infarction (heart attack) Left anterior descending (LAD) is effect most often The Heart Blood flow through the right side of the heart The superior vena cava (SVC) and inferior vena cava (IVC) empty into the right atrium Carry O2-poor, CO2-rich blood from the body Blood flows from the right atrium through the right AV (tricuspid) valve into the right ventricle The right ventricle pumps blood through the pulmonary valve into the pulmonary trunk The pulmonary trunk branches into right and left pulmonary arteries and enter the lungs (pulmonary circuit) The Heart Blood flow through the left side of the heart Pulmonary veins empty into the left atrium carry O2-rich, CO2-poor blood from the lungs Blood flows from the left atrium through left AV (bicuspid) valve into the left ventricle The left ventricle pumps blood through the aortic valve into the aorta The aorta (systemic circuit) branches into smaller arteries, which lead to arterioles, then capillaries, venules, veins and back to the vena cavae The Heart The walls of the left ventricle are thicker than the right ventricle because it must pump blood to the entire body (systemic circuit), not just to the lungs (pulmonary circuit) The walls of atria are much thinner than ventricles The Heart The cardiac cycle First the atria contract together, second the ventricles contract together, then the heart relaxes Systole (contraction) and Diastole (relaxation) Used in reference to the atria or ventricles (i.e. ventricular systole) Occurs 70 times per minute on average There are two audible sounds: “lub-dub” Lub: from the closure of the AV valves Dub: from the closure of the semilunar valves Murmurs A swishing sound from abnormal flow of blood Ex: regurgitation of blood (leaky valves) Ventricular Diastole & Systole Ventricular diastole: ventricles are filling Ventricular systole: ventricles are emptying  semilunar valves aortic semilunar valve mitral valve close pulmonary (“dub”) superior trunk semilunar vena aorta valves cava left right right atrium atrium atrium left inferior ventricle vena cava right pulmonary ventricle trunk aorta atrioventricular (AV) valves close (“lub”) represents contraction The Heart Internal (intrinsic) conduction system The SA node The cardiac pacemaker In the right atrium Initiates the heartbeat by sending out an electrical signal Causes both atria to contract The electrical impulse reaches the AV node A secondary pacemaker (can function independently) Also in the right atrium (in the atrioventricular septum) AV node sends a signal down the AV bundle and Purkinje fibers This causes ventricular contraction Impulses travel through gap junctions in the intercalated disks SA node AV node branches of atrioventricular bundle Purkinje fibers The Heart External (extrinsic) control of heartbeat The cardiac control center in the brainstem increases or decreases the heart rate depending on the body’s needs Sympathetic nervous system increases heart rate Parasympathetic nervous system decreases heart rate Some hormones also increase heart rate The Heart The Electrocardiogram (ECG or EKG) A recording of the electrical changes in the heart muscle during a cardiac cycle When the atria contract (atrial systole), they produce an electrical current, called the P wave When the ventricles contract (ventricular systole), they produce an electrical current, called the QRS complex The recovery of the ventricles (ventricular diastole) is represented as the T wave There are up to 12 different leads to record changes in electrical activity across different regions of the heart Electrocardiogram (ECG) Measuring Electrical Activity of the Heart The Heart Arrythmias Abnormal heart beats Many different types and causes Ventricular fibrillation Severe Uncoordinated, irregular electrical signals in the ventricles The heart can’t pump blood Tissues become starved of oxygen Causes hemostasis and blood clots Defibrillation—applying a strong electrical signal to reset the heart; hopefully, the SA node will start firing again Normal ECG Ventricular fibrillation Recording of an ECG Blood Flow Blood Pressure The pressure that blood exerts against a blood vessel wall Highest in the aorta, right next to the heart Gradually decreases as it flows through the vessels in the body Contraction of ventricles (systole) creates blood pressure, which propels blood through the arteries Measured with a sphygmomanometer (blood pressure cuff), in the brachial artery of the arm Pulse Surge of blood into an artery during ventricular systole that causes the walls to stretch, and then recoil Usually measured in the radial artery at the wrist or carotid artery in the neck A measurement of the heart rate; averages 60–80 beats per minute Blood Flow Systolic pressure—the highest pressure; when blood is ejected from the heart Diastolic pressure—the lowest pressure; when the ventricles relax Average is 120/80 mmHg (systolic/diastolic) Hypertension—high blood pressure Hypotension—low blood pressure  Table 5.1 Normal Values for Adult Blood pressure* Top Number Bottom Number (Systolic) (Diastolic) Hypotension Less than 95 Less than 50 Normal Below 120 Below 80 Prehypertension 120 to 139 80 to 89 Stage 1 hypertension 140 to 159 90 to 99 Stage 2 hypertension 160 or more 100 or more Hypertensive crisis Higher than 180 Higher than 110 (emergency care needed) *Blood pressure values established by the American Heart Association (www.heart.org). Blood Flow Blood pressure Decreases as it flows away from the heart Slowest in the capillaries to increase the exchange of gases, nutrients, and wastes Note that blood moves too fast for gas exchange to occur across medium to large blood vessels Blood pressure is very low in the veins, so doesn’t contribute much to the movement of blood Venous return is dependent on three additional factors: Skeletal muscle contraction pumps blood Breathing (respiratory muscles) creates negative pressure in the thoracic cavity which draws blood Valves present in veins Blood Flow Blood flows in two circuits: the pulmonary circuit and systemic circuit Pulmonary circuit circulates blood through the lungs Systemic circuit circulates blood through the body tissues Which each heart beat, blood flows through both circuits at the same time, a closed loop  Brain Upper limbs Pulmonary Pulmonary circuit circuit (arteries) (veins) Lungs LA RA Systemic Right Left circuit ventricle ventricle (arteries) Systemic circuit (veins) Kidneys Spleen Liver Digestive organs Gonads Lower limbs © 2015 Pearson Education, Inc. Blood Flow The pulmonary circuit Right atrium pumps deoxygenated blood into the right ventricle, which pumps it into the pulmonary trunk The pulmonary trunk splits into right and left pulmonary arteries, which go to the lungs In the lungs, the pulmonary arteries branch into arterioles, which lead to capillaries This is where gas exchange occurs with air in the alveoli of the lungs The pulmonary capillaries lead to venules, which merge into the pulmonary veins Four pulmonary veins (two left and two right) empty into the left atrium The pulmonary arteries carry oxygen-poor blood The pulmonary veins carry oxygen-rich blood Figure 22.7a The Pulmonary Circuit Trachea Aortic arch Ascending aorta Pulmonary trunk Superior vena cava Left lung Right lung Left pulmonary arteries Right pulmonary Left pulmonary veins arteries Right pulmonary veins Alveolus Capillary Inferior vena cava O2 Descending aorta CO2 a Anatomy of the pulmonary circuit. Blue arrows indicate the flow of oxygen-poor blood; red arrows indicate the flow of oxygen-rich blood. The breakout shows the alveoli of the lung and the routes of gas diffusion into and out of the bloodstream across the walls of the alveolar capillaries. © 2015 Pearson Education, Inc. Blood Flow The systemic circuit The left ventricle pumps blood into the aorta, which gives off branches to all the tissues of the body Arteries branch into arterioles, which lead to capillaries Capillaries lead to venules, which drain into veins, which lead to the superior and inferior vena cavae The vena cavae empty into the right atrium common carotid artery jugular vein subclavian artery superior vena cava subclavian vein brachial artery renal artery inferior vena cava renal vein abdominal aorta inferior mesenteric artery mesenteric vein common iliac artery common iliac vein radial artery femoral artery femoral vein great saphenous vein Blood Flow Two forces drive fluid in and out of capillaries: Hydrostatic pressure (blood pressure) Drives fluid out of the capillary, mainly at the arterial end of the capillary bed Similar to pressure down a pipe or hose This fluid contains everything that blood contains Except cells and plasma proteins Osmotic pressure Draws water into the capillary by osmosis, mostly at the venule end Dependent on albumin Some tissue fluid enters lymphatic capillaries and becomes lymph, which is eventually returned to the cardiovascular system arteriole from heart smooth muscle fiber Arterial End Blood pressure is water higher than osmotic salt pressure. Net pressure out. plasma protein oxygen amino acids Interstitial Fluid glucose carbon dioxide wastes Venous End Osmotic pressure water is higher than blood pressure. Net pressure in. venule to heart osmotic hydrostatic