The Arteries 8/30/2013. Chapter 12. Lecture and Animation Outline The Blood Vessels. The cardiovascular system has three types of blood vessels.

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1 Chapter 12 Lecture and Animation Outline To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click on the slide s background before you can advance to the next slide. See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and animations The Blood Vessels The cardiovascular system has three types of blood vessels. Arteries: carry blood away from the heart Capillaries: permit exchange of materials with tissues Veins: carry blood toward the heart All three vessel types have an inner endothelium. 2 The Arteries The Arteries Three layers in an arterial wall Endothelium Inner layer - simple squamous epithelium Middle layer Thickest layer, contains smooth muscle Outer layer Fibrous and loose connective tissue 3 1

2 arteriole venule b. Capillary valve inner layer middle layer outer layer a. Artery c. Vein Figure 12.1a, b, c 4 outer layer middle layer inner layer outer layer middle layer inner layer artery d. Ed Reschke 20 µm Figure 12.1d 5 Blood Vessels Figure 12.1 arteriole venule b. Capillary outer layer middle layer inner layer outer layer middle layer inner layer artery valve inner layer middle layer outer layer a. Artery c. Vein d. 20 µm d: Ed Reschke 6 2

3 The Arteries The largest artery in the human body is the aorta. Approximately 25mm wide Carries O 2 -rich blood from heart to other parts of body Arteries branch off eventually into arterioles Average about 0.5mm in diameter Can be dilated or constricted to regulate blood pressure 7 The Capillaries Join arterioles to venules Extremely narrow with thin walls of a single layer of endothelium Form vast networks in all regions of the body with a total surface area of 6000m 2 Organized into networks called capillary beds present in nearly all regions of the body 8 The Capillaries Play important role in homeostasis exchange of substances across thin walls Oxygen and nutrients diffuse out Wastes and carbon dioxide diffuse into Water may also leave capillaries Excess fluid picked up by lymphatic system 9 3

4 The Capillaries Blood flow to capillary beds varies so that only certain ones are completely open at any given time. Ex: After eating, capillary beds that serve the digestive system are mostly open. Those that serve the muscles are mostly closed. Capillary beds have arteriovenous shunts called anastomoses that bypass the bed. Blood flows directly from arterioles to venules. 10 Anatomy of a Capillary Bed artery arteriole O 2-rich blood flow precapillary sphincter arteriovenous shunt venule Figure 12.2 O 2-poor blood flow 11 The Veins Veins and venules take blood from capillary beds to the heart. Venules drain blood from capillaries and then join to form a. Vein walls are structured similarly to the walls of arteries (three layers). Less smooth muscle and connective tissue in s Overall, the wall of a is thinner than that of an artery. 12 4

5 The Veins Unlike arteries and arterioles, blood flow in s is not kept moving by the pumping of the heart. Some s have valves to prevent backflow of blood and direct blood towards the heart. Especially the s of the lower limbs Blood flow in s is primarily dependent on skeletal muscle contraction. 13 The Veins Damage to valves, due to aging or disease, may lead to blood pooling in the s. Varicose s, hemorrhoids are caused by s enlarging as blood pools and becomes visible at skin surface Due to thinner walls, s have a greater capacity to expand Serve as blood reservoir (70% of blood at any one time) Blood Blood is a connective tissue with a liquid matrix. Blood has many functions. Transport: nutrients, wastes, hormones Regulation: body temperature, blood and osmotic pressures, ph Protection: disease-causing pathogens, excess loss of blood by clotting mechanisms 15 5

6 12.2 Blood Blood placed in a test tube may be separated into three layers. Upper layer is the liquid plasma. Formed elements are the two lower layers. Middle layer contains white blood cells and platelets. Bottom layer contains red blood cells. 16 Plasma Plasma Plasma contains inorganic and organic substances dissolved or suspended in water. Plasma proteins (7-8% of plasma) serve various purposes. Transport: albumin transports bilirubin, lipoproteins transport cholesterol Blood clotting: fibrinogen Fight disease: immunoglobulins Help maintain blood volume due to large size 17 Plasma Type Function Source Water (90 92% of plasma) Maintains blood volume; transports molecules Absorbed from intestine Plasma proteins (7 8% of plasma) Maintain blood osmotic pressure and ph Albumin Maintains blood volume and pressure, transport Liver Antibodies Fight infection B lymphocytes Fibrinogen Clotting Liver Salts (less than 1% of plasma) Maintain blood osmotic pressure and ph; aid metabolism Absorbed from intestine Gases Oxygen Carbon dioxide Cellular respiration End product of metabolism Lungs Tissues Nutrients Lipids Glucose Amino acids Food for cells Absorbed from intestine Nitrogenous wastes Urea Uric acid Excretion by kidneys Liver Figure 12.3b Other Hormones, vitamins, etc. b. Aid metabolism Varied 18 6

7 Red Blood Cells Red Blood Cells (erythrocytes) Manufactured in red bone marrow of certain bones 4-6 million per mm 3 of whole blood When mature lack a nucleus and are biconcave discs Contain hemoglobin Red iron-containing heme pigment binds oxygen Carbon monoxide can also bind to heme Combines more readily than oxygen Can be lethal 19 capillary heme group iron helical shape of the polypeptide molecule a. Blood capillary 400 b. Red blood cells SEM 4,175 a: Ed Reschke/Peter Arnold; b: Andrew Syred/Photo Researchers, Inc. c. Hemoglobin molecule Figure Red Blood Cells Red Blood Cells 120-day lifespan, possibly due to lack of nucleus Destroyed in the liver and spleen Iron is mostly recycled Heme portion degraded and added to bile pigments Anemia Too few red blood cells or not enough hemoglobin Three causes Decreased production of red blood cells Loss of red blood cells Destruction of red blood cells 21 7

8 Red Blood Cells When arterial blood carries a reduced amount of O 2 (because of anemia or high-altitude location), kidneys increase production of the hormone erythropoietin. Speeds up maturation of red blood cells in bone marrow 22 Red Blood Cells Anemia Too few red blood cells Not enough hemoglobin in red blood cells Three causes Decreased production of red blood cells Iron-deficiency anemia Loss of red blood cells Destruction of red blood cells 23 The White Blood Cells White Blood Cells (Leukocytes) differ from red blood cells. Usually larger than red blood cells Nucleated Lack hemoglobin 5,000-11,000 cells per mm 3 of whole blood Fight infection and provide immunity 24 8

9 The White Blood Cells Divided based on structure into 2 groups Granular leukocytes - have visible granules in cytoplasm Neutrophils: most abundant, phagocytic to bacteria Basophils: granules stain deep blue, release histamine Eosinophils: stain deep red, fight parasitic worms 25 The White Blood Cells Agranular leukocytes Lack visible granules Typically have kidney-shaped or spherical nucleus Monocytes: largest white blood cells Dendritic cells: capture microbes with dendrites, then stimulate other white blood cells for defense Macrophages: phagocytes Lymphocytes: two types T lymphocytes (T cells): produce antibodies B lymphocytes (B cells): kill other cells or regulate responses of other cells 26 Plasma Liquid portion of the blood Formed Elements Red blood cells White blood cells Platelets 12.2 Blood Formed elements Plasma (about 55% of whole blood) Leukocytes and platelets (<1% of whole blood) Erythrocytes (about 45% of whole blood) Figure 12.3a 27 9

10 Function and Description Transport O2 and help 7 8 µm in diameter Bright-red to dark-purple biconcave disks without nuclei Fight infection µm in diameter Spherical cells with multilobed nuclei; fine, Pink granules in cytoplasm; phagocytize pathogens µm in diameter Spherical cells with Bilobed nuclei; coarse, deep-red, uniformly sized Granules in cytoplasm; Phagocytize antigenantibody complexes and allergens µm in diameter Spherical cells with lobed nuclei; large, irregularly shaped, deep-blue granules in cytoplasm; release histamine, which promotes blood flow to injured tissues 5 17 µm in diameter (average 9 10 µm) Spherical cells with large, round nuclei; responsible for specific immunity µm in diameter Large spherical cells with kidney-shaped, round, or lobed nuclei; become macrophages that phagocytize pathogens and cellular debris Aid clotting 2 4 m m in diameter Disk-shaped cell fragments with no nuclei; purple granules in cytoplasm 8/30/ Blood eosinophil platelets neutrophils monocyte basophil red blood cell lymphocyte Figure 12.3c 250 EdReschke Blood has Transport functions Regulatory functions Protective functions 28 Formed Elements Type Source Red blood cells (erythr ocytes) transport CO2 Red bone marrow 4 million 6 million per mm 3 blood White blood cells (leukocytes) 5,000 11,000 per mm 3 blood Neutrophils* 40 70% Red bone marrow Granular leukocytes Eosinophils* 1 4% Basophils* 0 1% Lymphocytes* 20 45% Monocytes* 4 8% Platelets (thrombocytes) Agranular leukocytes Red bone marrow Figure 12.3d 150, ,000 per mm 3 blood d. * Appearance with Wright s stain. 29 Plasma (about 55% of whole blood) Leukocytes and Formed platelets elements (<1% of whole blood) Erythrocytes (about 45% of whole blood) a. Plasma Type Function Source Water Maintains blood volume; (90 92% of plasma) transports molecules Absorbed from intestine Plasma proteins (7 8% of plasma) Albumin Antibodies Fibrinogen Salts (less than 1% of plasma) Gases Maintain blood osmotic pressure and ph Maintains blood volume and pressure, transport Fight infection Clotting Maintain blood osmotic pressure and ph; aid metabolism Liver Blymphocytes Liver Absorbed from intestine Oxygen Cellular respiration Lungs Carbon dioxide End product of metabolism Tissues Nutrients Lipids Glucose Amino acids Food for cells Absorbed from intestine Nitrogenous wastes Urea Uric acid Excretion by kidneys Liver Other Hormones, vitamins, etc. Aid metabolism Varied b. eosinophil platelets neutrophils monocyte basophil Figure 12.3a, b, c red blood cell c. c: EdReschke 250 lymphocyte 30 10

11 cytoplasmic extension from macrophage bacteria Figure 12.5 Dennis Kunkel/Phototake SEM 1, The White Blood Cells If the number of any type of white blood cell increases or decreases beyond normal, it may indicate presence of disease. Bacterial infections: neutrophils elevated Infectious mononucleosis: B cells elevated AIDS: T cell levels decreased Leukemia: abnormal white blood cells 32 The Platelets and Blood Clotting Platelets (thrombocytes) form as a result of fragmentation of megakaryocytes in the red bone marrow. Produced at a rate of 200 billion per day 150, ,000 per mm 3 of whole blood Involved in the process of clotting or coagulation At least twelve clotting factors participate with platelets in forming a blood clot 33 11

12 Blood Clotting When a blood vessel is damaged, the clotting process begins. Platelets clump and form a plug to partially seal a leak. Platelets and damaged tissues release prothrombin activator. Converts plasma protein prothrombin to thrombin Requires calcium 34 fibrin threads red blood cell b. Blood clot 4,400 Blood Clotting Thrombin activates fibrinogen to fibrin Clot is composed of network of fibrin threads and trapped cells As damage heals, plasmin breaks down the clot Figure 12.6b Blood vessel is punctured. 2. Platelets congregate and form a plug. Prothrombin activator 3. Platelets and damaged tissue cells release prothrombin activator, which initiates a cascade of enzymatic reactions. Prothrombin Fibrinogen Ca2 + Thrombin Ca2 + Fibrin threads 4. Fibrin threads form and trap red blood cells. Figure 12.6a a. Blood-clotting process 36 12

13 1. Blood vessel is punctured. Figure 12.6a Blood vessel is punctured. 2. Platelets congregate and form a plug. Figure 12.6a Blood vessel is punctured. 2. Platelets congregate and form a plug. Prothrombin activator 3. Platelets and damaged tissue cells release prothrombin activator, which initiates a cascade of enzymatic reactions. Prothrombin Fibrinogen Ca2 + Thrombin Ca2 + Fibrin threads Figure 12.6a 39 13

14 1. Blood vessel is punctured. 2. Platelets congregate and form a plug. Prothrombin activator 3. Platelets and damaged tissue cells release prothrombin activator, which initiates a cascade of enzymatic reactions. Prothrombin Fibrinogen Ca2 + Thrombin Ca2 + Fibrin threads 4. Fibrin threads form and trap red blood cells. a. Blood-clotting process fibrin threads red blood cell Figure 12.6 b. Blood clot b: Eye of Science/Photo Researchers, Inc. 4, Blood Clotting Hemophilia refers to a group of inherited disorders caused by deficiency in a clotting factor. The most common type is hemophilia A, found especially in males. Faulty gene on X chromosome Internal bleeding can cause serious damage to cells and tissues. Especially joints, muscles, cartilage Death can result from bleeding into the brain. Hemophilia is treated by blood transfusions and injections of clotting factors. 41 Bone Marrow Stem Cells A stem cell is capable of dividing and producing new cells that can differentiate into particular cell types. Bone marrow has multipotent stem cells. Gives rise to other stem cells for formed elements Research has shown that some bone marrow stem cells may be able to give rise to liver, bone, fat, cartilage, heart, and nerve cells

15 Bone Marrow Stem Cells A patient s own bone marrow stem cells could be used for curing certain conditions that may develop later in life. Stem cells may provide solutions for diseases such as diabetes, liver disease, heart disease, Alzheimer s and Parkinson s. Use of one s own stem cells eliminates possible rejection. 43 Stem cells Multipotent stem cells in red bone marrow divide to produce specific stem cells. Early differentiation separates myeloid stem cells from lymphatic stem cells. Myeloid stem cells Multipotent stem cells Lymphatic stem cell erythroblasts megakaryoblasts myeloblasts monoblasts Myeloblasts, monoblasts, and lymphoblasts produce the white blood cells. lymphoblasts megakaryocytes erythrocytes thrombocytes basophils eosinophils neutrophils monocytes B lymphocytes Tlymphocytes processed in processed in bone marrow thymus Red blood cells Figure 12.7 Platelets Granular leukocytes White blood cells Agranular leukocytes 44 Capillary Exchange Two forces control movement of fluid through a capillary wall. Osmotic pressure tends to cause water to move from tissues to blood. Created by plasma proteins and salts Blood pressure tends to cause water to move from blood to tissues

16 Capillary Exchange At arterial end of capillary, hydrostatic pressure is higher so water moves out, contributes to tissue fluids. Midway through the capillary, these forces are equalized result is no net movement of water. Solutes now move down their gradients Nutrients and oxygen diffuse out of capillary Wastes and carbon dioxide diffuse into capillary Movements of gases reversed in pulmonary circuit 46 Capillary Exchange in the Systemic Circuit from heart Arterial end Blood pressure is higher than osmotic pressure. Net pressure out. Tissue fluid amino Venous end Osmotic pressure is higher than blood pressure. Net pressure in. to heart water oxygen acids glucose carbon dioxide water wastes smooth muscle fiber arteriole osmotic pressure blood pressure salt plasma protein venule Figure Capillary Exchange Capillary Exchange At the venous end, osmotic pressure is greater than blood pressure so water moves into capillary. Almost the same amount of water gets reabsorbed as left the capillary at the arterial end. The small amount of fluid remaining behind can be absorbed by lymphatic capillaries. Tissue fluid now called lymph Returned back to systemic venous blood 48 16

17 12.3 The Human Heart Cone-shaped muscular organ about the size of a fist Located between the lungs directly behind the sternum Tilted so apex points to body s left 49 Myocardium 12.3 The Heart Major portion of the heart Consists mainly of cardiac muscle Pericardium Serous membrane that surrounds the heart Endocardium Lines the inner surface of the heart Membrane consisting of connective tissue and endothelium 50 left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary s right pulmonary artery right pulmonary s left atrium left cardiac right atrium right coronary artery left ventricle right ventricle inferior vena cava apex Figure 12.10a 51 17

18 superior vena cava aorta right coronary artery inferior vena cava pulmonary trunk left coronary artery Figure 12.10b right cardiac left cardiac 52 External Heart Anatomy left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary s right pulmonary artery right pulmonary s superior vena cava right coronary artery inferior vena cava aorta pulmonary trunk left coronary artery left atrium left cardiac right atrium right coronary artery left ventricle right cardiac left cardiac right ventricle b. inferior vena cava apex a. Figure Internal anatomy Four chambers 12.3 The Human Heart Two atria thin-walled; pump blood to ventricles Two ventricles thick-walled; pump blood to lungs and body Septum separates the right and left sides 54 18

19 12.2 The Heart Internal Anatomy Four valves prevent backflow Two atrioventricular valves AV valve on right = tricuspid valve AV valve on left = bicuspid or mitral valve Supported by chordae tendineae Two semilunar valves Pulmonary semilunar Aortic semilunar 55 Internal View of the Heart left subclavian artery left common carotid artery brachiocephalic artery superior vena cava aorta left pulmonary artery pulmonary trunk left pulmonary s right pulmonary artery right pulmonary s semilunar valve left atrium right atrium atrio ventricular (bicuspid) valve atrio ventricular (tricuspid) vave chordae tendineae papillary muscles right ventricle septum left ventricle Figure 12.11a inferior venacava 56 Path of Blood Through the Heart Path of Blood Through the Heart Vena cava right atrium tricuspid valve right ventricle pulmonary semilunar valve pulmonary trunk pulmonary arteries lungs pulmonary s left atrium bicuspid valve left ventricle aortic semilunar valve aorta body 57 19

20 O 2 -rich blood to body O 2 -poor blood to lungs O 2 -poor blood from body O 2 -rich blood from lungs Figure 12.11b 58 Path of Blood Through the Heart O 2 -rich blood does not mix with O 2 -poor Blood must travel through the lungs to go from the right side of the heart to the left side. The heart is a double pump. Right ventricle sends oxygen-poor blood into the pulmonary circuit. Left ventricle sends O 2 -rich blood into the rest of body. Thicker, more muscular walls to generate stronger force 59 Path of Blood Through the Heart Cardiac output is the volume of blood pumped by the left ventricle per minute. For a person with an average of 70 beats/min, the cardiac output is 5.25 liter of blood/min. The pulse is a wave effect that passes down the walls of arteries when the aorta expands and then recoils with each ventricular contraction. The pulse can be used to determine heart rate

21 The Heartbeat Heartbeat (Cardiac Cycle) Each heartbeat has the following sequence. First, the two atria contract simultaneously. Second, the two ventricles contract simultaneously. Lastly, all the chambers then relax. Systole: contraction of the heart muscle Diastole: relaxation of the heart muscle The heart contracts, or beats, about 70 times per minute. 61 Cardiac Cycle Time 0.15 sec 0.30 sec 0.40 sec Atria Systole Diastole Diastole Ventricles Diastole Systole Diastole 62 Heart Sounds The Heartbeat Described as a lub-dub sound Lub sound - atrioventricular valves closing Dub sound - semilunar valves closing Heart murmur (swishing sound) may be result of a leaky valve 63 21

22 pulmonary aorta semilunar valves superior vena cava semilunar valvesclose ( dub ) right atrium left atrium right atrium a. left ventricle c. inferior vena cava right ventricle aorta pulmonary atrioventricular valves close ( lub ) Figure b. 64 Intrinsic Control of Heartbeat The rhythmic contraction of the aorta and ventricles is due to the intrinsic conduction system. Made possible by nodal tissue, which has both muscular and nervous characteristics The SA (sinoatrial node) Located in the upper dorsal wall of the right atrium The AV (atrioventricular node) Located in the base of the right atrium wall 65 Intrinsic Control of Heartbeat SA node called the pacemaker Initiates the heartbeat Sends out an excitatory impulse every 0.85 seconds Excitatory impulse causes the atria to contract Excitatory impulse travels to the AV node through atrioventricular bundle (AV bundle) Then reaches smaller numerous Purkinje fibers 66 22

23 Intrinsic Control of Heartbeat If SA node fails, AV node generates a slower heartbeat 40 to 60 beats per minute Corrected by artificial pacemaker 67 SA node AV node branches of atrioventricular bundle Purkinje fibers Figure 12.13a 68 Extrinsic Control of Heartbeat The body also has extrinsic ways to regulate the heartbeat. A cardiac control center is located in the medulla oblongata. Influences heartbeat via autonomic nervous system Sympathetic division increases heart rate Parasympathetic system decreases heart rate 69 23

24 Extrinsic Control of Heartbeat Hormones epinephrine and norepinephrine Released by adrenal medulla Stimulate heart to pump faster 70 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 71 The Electrocardiogram Electrocardiogram (ECG) A recording of the electrical changes occurring in the myocardium R P T Q S Figure 12.13b Ed Reschke 72 24

25 The Electrocardiogram Electrocardiogram is a recording of electrical changes in the myocardium detected at the skin s surface. Electrodes placed on or near the chest are connected to an instrument that detects and records the myocardium s electrical changes. 73 R P T Q Figure 12.13b S Ed Reschke P Wave occurs when SA node triggers an impulse Indicates that atria are about to contract QRS complex indicates that ventricles are about to contract T wave occurs after ventricular contraction 74 The Electrocardiogram ECG can detect abnormalities (arrhythmias) Atrial fibrillation (AF) is most common type Multiple, chaotic impulses generated from SA node Irregular, fast heartbeat Palpitation (fluttering sensation) is a symptom of this condition 75 25

26 The Electrocardiogram Ventricular fibrillation Causes uncoordinated contraction of the ventricles Requires heart to be defibrillated by applying strong electrical current AED automatic external defibrillator Ed Reschke 76 SA node AV node branches of atrioventricular bundle Purkinje fibers a. R P T Q b. S Figure c. Ed Reschke The Vascular Pathways The cardiovascular system includes two circuits. The pulmonary circuit Circulates blood through the lungs The systemic circuit Circulates blood through the rest of the body 78 26

27 The Pulmonary Circuit Oxygen-poor blood from all regions of the body is collected in the right atrium. It is sent to the lungs from the right side of the heart. It returns from the lungs to the left side of the heart. 79 The Pulmonary Circuit Blood from body collects in right atrium Right Atrium Right Ventricle Pulmonary trunk Pulmonary Arteries Arterioles Capillaries Venules Pulmonary Veins Left atrium jugular (also subclavian from arms) pulmonary artery superior vena cava inferior vena cava hepatic hepatic portal renal iliac CO 2 O head and arms 2 CO 2 O 2 O 2 CO 2 liver kidneys lungs digestive tract heart Carotid artery (also subclavian artery to arms) pulmonary aorta mesenteric arteries renal artery iliac artery Figure CO 2 O 2 80 The Systemic Circuit Blood that is oxygen-rich returns from the lungs and is collected in the right atrium. Oxygen-rich blood is sent throughout the body except the lungs

28 The Systemic Circuit Blood leaves the left ventricle, travels through the body and is returned to the heart aorta arteries arterioles capillaries venules s vena cava Figure CO 2 O head and arms 2 jugular Carotid artery (also subclavian (also subclavian from arms) artery to arms) pulmonary artery superior vena cava inferior vena cava hepatic hepatic portal renal iliac CO 2 CO 2 O 2 O 2 CO 2 liver kidneys lungs digestive tract heart O 2 pulmonary aorta mesenteric arteries renal artery iliac artery 82 common carotid artery internal jugular superior vena cava external jugular subclavian artery subclavian renal artery inferior vena cava mesenteric common iliac aorta renal mesenteric artery common iliac artery femoral artery femoral great saphenous Figure The Systemic Circuit Coronary arteries Serve the heart muscle itself since blood from the chambers does not nourish the heart Are the first branches off aorta and lie on the exterior surface of the heart Coronary capillary beds join to form venules Venules converge to form cardiac s which empty into right atrium 84 28

29 The Systemic Circuit A portal system in blood circulation begins and ends in capillaries. Ex: hepatic portal system, associated with the liver Capillaries from the villi of the small intestine pass into venules that join to form the hepatic portal. This carries the blood to a set of capillaries in the liver. 85 Blood Pressure Systolic Pressure results from blood forced into the arteries during ventricular systole. Diastolic Pressure is the pressure in the arteries during ventricular diastole. As blood flows from the aorta into the arteries and arterioles, blood pressure falls. The difference between systolic and diastolic pressure gradually diminishes. In the capillaries, blood flow is slow and fairly even. 86 Velocity and blood pressure are related to vascular cross-sectional area. arteries arterioles capillaries venules s blood pressure Total cross-sectional area of vessels Magnitude velocity Blood Flow Figure

30 Blood Pressure Blood Pressure Measured with sphygmomanometer Pressure cuff determines the amount of pressure required to stop the flow of blood through an artery Normally measured on the brachial artery Located in the upper arm Expressed in millimeters of mercury (mmhg) Consists of two numbers that represent systolic and diastolic pressure respectively Ex: 120/80 88 Blood Pressure Blood pressure in s is low and by itself not enough to move blood back to heart. When skeletal muscles contract they put pressure on s. Valves prevent backflow. Muscle contraction moves blood back to the heart. to heart to heart Figure a. Contracted skeletal muscle pushes blood past open valve. b. Closed valve prevents back ward flow of blood Cardiovascular Disorders Cardiovascular disease (CVD) is the leading cause of death in Western countries. Modern research efforts have resulted in improvements in diagnosis, treatment, and prevention

31 Atherosclerosis Atherosclerosis Plaque is the accumulation of soft masses of fatty materials, such as cholesterol, beneath inner lining of arteries. Plaque interferes with blood flow by protruding into the artery lumen. Plaques can cause clots to form by allowing platelets to accumulate. If clot breaks loose it becomes an embolus If clot remains stationary it is a thrombus 91 coronary artery ulceration lumen of vessel fat cholesterol crystals atherosclerotic plaque Biophoto Associates/Photo Researchers, Inc. Figure 12B 92 Hypertension Hypertension is high blood pressure Affects about 35% of all Americans Another 30% may have prehypertension Usually caused by a narrowing of the arteries Age, body size, athletic conditioning can influence normal variations in blood pressure Under age 45, a pressure above 130/90mm Hg is considered abnormally high In older people, a pressure of 140/95mm Hg is considered abnormally high 93 31

32 Hypertension Hypertension is often called the silent killer. Not detected until a stroke or heart attack occurs Secondary to narrowing of one s arteries from artherosclerosis Pumping blood requires greater pressure in narrowed arteries. Medications used to treat disease vary. Diuretics to reduce blood volume Vasodilators which dilate blood vessels Various medications which improve heart function 94 Heart Valve Disease Heart Valve Disease 90,000 people/year have faulty heart valves repaired or replaced. May be malformed at birth May degenerate due to age or disease Common types include: Stenosis narrowing of the aortic valve opening Mitral valve prolapse thickened leaflets of mitral valve protrude back into ventricle 95 Stroke, Heart Attack, and Aneurysm Stroke is known as cerebrovascular accident An rteriole in the brain bursts or is blocked by an embolus. Lack of O 2 to brain can cause paralysis or death because brain tissue dies. Warning signs include numbness in hands or face, difficulty speaking, and temporary blindness in an eye. Strokes are more common with age

33 Stroke, Heart Attack, and Aneurysm Angina pectoris Coronary artery is partially blocked Squeezing or burning sensation in the chest Heart attack (Myocardial infarction) Vessel becomes completely blocked Portion of the heart muscle deprived of oxygen 97 Stroke, Heart Attack, and Aneurysm Aneurysm - Ballooning of a blood vessel Occurs most often in abdominal aorta or arteries leading to the brain. Atherosclerosis and hypertension can weaken the walls of vessels, leading to an aneurysm. Bursting of blood vessels can be fatal, especially if it occurs in large arteries. A synthetic graft can be used to replaced damage part of vessel. 98 Coronary Bypass Operations Surgery bypasses blocked areas of coronary arteries. Another blood vessel is grafted to the aorta and then to the blocked coronary artery past the point of blockage. The proportion of heart attack patients receiving bypass surgery has decreased over the past decade. Stem cell therapy may be a future treatment for damaged heart tissue. Figure

34 Clearing Clogged Arteries Angioplasty Catheter is placed in clogged artery Balloon attached to catheter is inflated Expansion increases the lumen of the vessel Stents are often placed to keep vessel open as an alternative to simple angioplasty Stents now frequently drug-eluting to inhibit scarring 100 catheter arterial wall stent a. Artery is closed. b. Stent is placed. c. Balloon is inflated. Angioplasty with stent placement Figure Dissolving Blood Clots Medical treatment for thromboembolism often includes the use of tissue plasminogen activator (tpa). Converts plasminogen into plasmin to dissolve blood clots Aspirin reduces stickiness of platelets. Lowers probability that clot will form May be used for patients who have symptoms indicating stroke or angina

35 Heart Transplants and Artificial Hearts Heart transplants are usually successful but shortage of donated hearts remains an issue. LVAD-left ventricular assist device Serves as temporary alternative to heart transplant Tube passes blood from left ventricle to the LVAD Blood is pumped to the aorta 103 Heart Transplants and Artificial Hearts TAH-total artificial heart Generally used only on very ill patients Poor survival rates possibly due to patients poor condition prior to surgery Figure