Anatomy & Physiology 2 Ch. 18 Blood
Erythrocyte Production
2.5 million RBCs are produced per second Average lifespan of about 120 days Development takes 3 to 5 days Iron—key nutritional requirement Lost daily through urine, feces, and bleeding
The Coronary Circulation
5% of blood pumped by heart is pumped to the heart itself through the coronary circulation to sustain its strenuous workload 250 mL of blood per minute Needs abundant O2 and nutrients
Widowmaker
A sudden occlusion of the proximal left anterior descending coronary artery (LAD) has very grave consequences due to the large size of myocardium perfused by the LAD. (an occlusion anecdotally termed "the widow maker" due to its occurrence in elderly males)
How Blood Is Produced
Adult production of 400 billion platelets, 200 billion RBCs, and 10 billion WBCs every day Hemopoiesis—production of blood, especially its formed elements Hemopoietic tissues produce blood cells Red bone marrow produces all seven formed elements
Components and General Properties of Blood
Adults have 4 to 6 L of blood A liquid connective tissue consisting of cells and extracellular matrix Plasma: matrix of blood Clear, light yellow fluid Formed elements: blood cells and cell fragments Red blood cells, white blood cells, and platelets Seven kinds of formed elements 1)Erythrocytes: red blood cells (RBCs) 2)Platelets Cell fragments from special cell in bone marrow Leukocytes: white blood cells (WBCs) Five leukocyte types divided into two categories Granulocytes (with granules) 3)Neutrophils 4)Eosinophils 5)Basophils Agranulocytes (without granules) 6)Lymphocytes 7)Monocytes
Aneurysm
Aneurysm— weak point in an artery or the heart wall Forms a thin-walled, bulging sac that pulsates with each heartbeat and may rupture at any time Dissecting aneurysm: blood accumulates between the tunics of the artery and separates them, usually because of degeneration of the tunica media Most common sites: abdominal aorta,(AAA) renal arteries, and arterial circle at base of brain. Can cause pain by putting pressure on other structures Can rupture causing hemorrhage Result from congenital weakness of the blood vessels or result of trauma or bacterial infections such as syphilis Most common cause is atherosclerosis and hypertension
Angina and Heart Attack
Angina pectoris—chest pain from partial obstruction of coronary blood flow Pain caused by ischemia of cardiac muscle Obstruction partially blocks blood flow Myocardium shifts to anaerobic fermentation, producing lactic acid and thus stimulating pain Myocardial infarction (MI)—sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation Cardiac muscle downstream of the blockage dies Heavy pressure or squeezing pain radiating into the left arm Some painless heart attacks may disrupt electrical conduction pathways, leading to fibrillation and cardiac arrest Silent heart attacks occur in diabetics and the elderly MI responsible for about half of all deaths in the United States
Arteries
Arteries are sometimes called resistance vessels because they have a relatively strong, resilient tissue structure that resists high blood pressure Conducting (elastic or large) arteries Biggest arteries Aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries Expand during systole, recoil during diastole which lessens fluctuations in blood pressure Distributing (muscular or medium) arteries Distributes blood to specific organs Brachial, femoral, renal, and splenic arteries Smooth muscle layers constitute three-fourths of wall thickness Resistance (small) arteries Arterioles: smallest arteries Control amount of blood to various organs Thicker tunica media in proportion to their lumen than large arteries and very little tunica externa
General Anatomy of the Blood Vessels
Arteries carry blood away from heart Veins carry blood back to heart Capillaries connect smallest arteries to veins
The Aorta and Its Major Branches
Ascending aorta Right and left coronary arteries supply heart Aortic arch Brachiocephalic Right common carotid supplying right side of head Right subclavian supplying right shoulder and upper limb Left common carotid supplying left side of head Left subclavian supplying shoulder and upper limb Descending aorta Thoracic aorta above diaphragm Abdominal aorta below diaphragm
Cardiac Arrhythmias
Atrial flutter—ectopic foci in atria Atrial fibrillation Atria beat 200 to 400 times per minute Premature ventricular contractions (PVCs) Caused by stimulants, stress, or lack of sleep Ventricular fibrillation Serious arrhythmia caused by electrical signals reaching different regions at widely different times Heart cannot pump blood and no coronary perfusion Kills quickly if not stopped Defibrillation—strong electrical shock whose intent is to depolarize the entire myocardium, stop the fibrillation, and reset SA nodes to sinus rhythm
Heart Sounds
Auscultation—listening to sounds made by body First heart sound (S1), louder and longer "lubb," occurs with closure of AV valves, turbulence in the bloodstream, and movements of the heart wall Second heart sound (S2), softer and sharper "dupp," occurs with closure of semilunar valves, turbulence in the bloodstream, and movements of the heart wall S3—rarely heard in people over 30; slosh after S1/S2; indicative of heart failure when heard late in life
Neural Control
Baroreflex—an automatic, negative feedback response to changes in blood pressure Increases in BP detected by carotid sinuses Signals sent to brainstem by way of glossopharyngeal nerve Inhibit the sympathetic cardiac and vasomotor neurons reducing sympathetic tone, and excite vagal fibers to the slowing of heart rate and cardiac output, thus reducing BP. Vaso- Vagal Response Decreases in BP have the opposite effect Baroreflexes important in short-term regulation of BP but not in cases of chronic hypertension They work well for adjustments for rapid changes in posture
Varicose Veins
Blood pools in the lower legs in people who stand for long periods stretching the veins Cusps of the valves pull apart in enlarged superficial veins further weakening vessels Blood backflows and further distends the vessels, their walls grow weak and develop into varicose veins Hereditary weakness, obesity, and pregnancy also promote problems Hemorrhoids are varicose veins of the anal canal
Blood Pressure
Blood pressure (BP)—the force that blood exerts against a vessel wall Measured at brachial artery of arm using sphygmomanometer Two pressures are recorded Systolic pressure: peak arterial BP taken during ventricular contraction (ventricular systole) Diastolic pressure: minimum arterial BP taken during ventricular relaxation (diastole) between heart beats Normal value, young adult: 120/75 mm Hg Pulse pressure—difference between systolic and diastolic pressure Important measure of stress exerted on small arteries by pressure surges generated by the heart Hypertension—high blood pressure Chronic is resting BP > 140/90 Consequences Can weaken small arteries and cause aneurysms Hypotension—chronic low resting BP Caused by blood loss, dehydration, anemia BP rises with age Arteries less distensible and absorb less systolic force
Blood Types
Blood types and transfusion compatibility are a matter of interactions between plasma proteins and erythrocytes blood types A, B, AB, and O Blood types are based on interactions between antigens and antibodies Antigens Complex molecules on surface of cell membrane that are unique to the individual Used to distinguish self from foreign matter Foreign antigens generate an immune response Antibodies Proteins secreted by plasma cells Part of immune response to foreign matter Bind to antigens and mark them for destruction Forms antigen-antibody complexes You do not form antibodies against your antigens Agglutinogens -antigens on the surface of the RBC that is the basis for blood typing Agglutinins—antibodies in the plasma that bring about transfusion mismatch Agglutination - when agglutinin binds to agglutinogen, causing clumping of red blood cells
Arteries of the Abdominal and Pelvic Region
Branches of celiac trunk supply upper abdominal viscera—stomach, spleen, liver, and pancreas
Arteries of the Lower Limb
Branches to the lower limb arise from external iliac branch of the common iliac artery
Capillaries
Capillaries—site where nutrients, wastes, and hormones pass between the blood and tissue fluid through the walls of the vessels (exchange vessels) The "business end" of the cardiovascular system Composed of endothelium and basal lamina Absent or scarce in tendons, ligaments, epithelia, cornea, and lens of the eye
Cardiac Output
Cardiac output (CO)—the amount ejected by ventricle in 1 minute Cardiac output = heart rate x stroke volume About 4 to 6 L/min at rest A RBC leaving the left ventricle will arrive back at the left ventricle in about 1 minute Vigorous exercise increases CO to 21 L/min for a fit person and up to 35 L/min for a world-class athlete
Structure of Cardiac Muscle
Cardiocytes—striated, short, thick, branched cells, one central nucleus surrounded by light-staining mass of glycogen Intercalated discs—join cardiocytes end to end Repair of damage of cardiac muscle is almost entirely by fibrosis (scarring) which doesn't contract or transmit electric signals
Overview of the Cardiovascular System
Cardiovascular system Heart and blood vessels Circulatory system Heart, blood vessels, and the blood
Anemia
Causes of anemia fall into three categories Inadequate erythropoiesis or hemoglobin synthesis Iron-deficiency anemia- Lack of Iron for use in erythropoiesis Pernicious anemia-Inadequate vitamin B12 from poor nutrition or lack of intrinsic factor Hypoplastic anemia—slowing of erythropoiesis Aplastic anemia—complete cessation of erythropoiesis Hemorrhagic anemias from bleeding Hemolytic anemias from RBC destruction (ex: sickle-cell anemia, erythroblastosis fetalis) Anemia has three potential consequences Tissue hypoxia and necrosis Patient is lethargic Shortness of breath upon exertion Life-threatening necrosis of brain, heart, or kidney Blood osmolarity is reduced producing tissue edema Blood viscosity is low Heart races and pressure drops Cardiac failure may ensue
Blood Plasma
Centrifuge blood to separate components: Hematocrit - ratio of the volume of red blood cells to the total volume of blood Erythrocytes are heaviest and settle first 37% to 52% total volume White blood cells and platelets 1% total volume Buffy coat- middle layer Plasma The remainder of volume on top 47% to 63% Complex mixture of water, proteins, nutrients, electrolytes, nitrogenous wastes, hormones, and gases Plasma—liquid portion of blood (Above the Buffy Coat) Serum: remaining fluid when blood clots and the solids are removed Identical to plasma except for the absence of fibrinogen Three major categories of plasma proteins Albumins: smallest and most abundant Contribute to viscosity and osmolarity; influence blood pressure, flow, and fluid balance Globulins (antibodies) Provide immune system functions Alpha, beta, and gamma globulins Fibrinogen Precursor of fibrin threads that help form blood clots
Effects of Chemicals
Chemicals affect heart rate as well as neurotransmitters from cardiac nerves Blood-borne adrenal catecholamines (NE and epinephrine) are potent cardiac stimulants Drugs that stimulate heart Nicotine Thyroid hormone Caffeine Electrolytes K+ has greatest chronotropic effect Hyperkalemia—excess K+ in cardiocytes Myocardium less excitable, heart rate slows and becomes irregular Hypokalemia—deficiency K+ in cardiocytes Cells hyperpolarized, harder to stimulate emergency Calcium Hypercalcemia—excess of Ca2+ Decreases heart rate and contraction strength Hypocalcemia—deficiency of Ca2+ Increases heart rate and contraction strength
Circulatory Shock
Circulatory shock—any state in which cardiac output is insufficient to meet the body's metabolic needs Cardiogenic shock: inadequate pumping of heart (MI) Low venous return (LVR): cardiac output is low because too little blood is returning to the heart Neurogenic shock— loss of vasomotor tone, vasodilation Causes from emotional shock to brainstem injury Septic shock Bacterial toxins trigger vasodilation and increased capillary permeability Anaphylactic shock Severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
The Circulatory System
Circulatory system consists of the heart, blood vessels, and blood Cardiovascular system refers only to the heart and blood vessels Functions of circulatory system Transport O2, CO2, nutrients, wastes, hormones, and stem cells Protection Inflammation, limit spread of infection, destroy microorganisms and cancer cells, neutralize toxins, and initiate clotting Regulation Fluid balance, stabilizes pH of ECF, and temperature control
Arteries of the Head and Neck
Common carotid divides into internal and external carotids External carotid supplies most external head structures
Overview of Volume Changes
Congestive heart failure (CHF)—results from the failure of either ventricle to eject blood effectively Usually due to a heart weakened by myocardial infarction, chronic hypertension, valvular insufficiency, or congenital defects in heart structure Left ventricular failure—blood backs up into the lungs causing pulmonary edema Shortness of breath or sense of suffocation Right ventricular failure—blood backs up in the vena cava causing systemic or generalized edema Enlargement of the liver, ascites (pooling of fluid in abdominal cavity), distension of jugular veins, swelling of the fingers, ankles, and feet Left or Right ventricular failure eventually leads to total heart failure
The Conduction System
Coordinates the heartbeat Composed of an internal pacemaker and nervelike conduction pathways through myocardium Generates and conducts rhythmic electrical signals in the following order: Sinoatrial (SA) node: modified cardiocytes Pacemaker initiates each heartbeat and determines heart rate Pacemaker in right atrium near base of superior vena cava Signals spread throughout atria Atrioventricular (AV) node Located near the right AV valve at lower end of interatrial septum Electrical gateway to the ventricles Atrioventricular (AV) bundle (bundle of His) Bundle forks into right and left Bundle branches Branches pass through interventricular septum toward apex Purkinje fibers Nervelike fibers that spread throughout ventricular myocardium
Cor pulmonale
Cor pulmonale: right ventricular failure due to obstructed pulmonary circulation In emphysema, chronic bronchitis, and black lung disease Lung disease restricts pulmonary circulation
Coronary Artery Disease
Coronary artery disease (CAD)—a constriction of the coronary arteries Usually the result of atherosclerosis: an accumulation of lipid deposits that degrade the arterial wall and obstruct the lumen Unavoidable risk factors: heredity, aging, being male Preventable risk factors: obesity, smoking, lack of exercise, anxious personality, stress, aggression, and diet Treatment Coronary bypass surgery Great saphenous vein (footgroin vein) harvested to replace coronary arteries Balloon angioplasty Laser angioplasty
The Major Systemic Veins
Deep veins run parallel to arteries while superficial veins have many anastomoses
Clotting Disorders
Deficiency of any clotting factor can shut down the coagulation cascade Hemophilia—family of hereditary diseases characterized by deficiencies of one factor or another Hematoma—mass of clotted blood in the tissues
Clinical Management of Blood Clotting
Goal—prevent formation of clots or dissolve existing clots Preventing clots Vitamin K is required for formation of clotting factors Coumarin, warfarin (Coumadin)—vitamin K antagonists Aspirin suppresses thrombus formation Other anticoagulants discovered in animal research Medicinal leeches used since 1884 (hirudin) Snake venom from vipers (arvin) Dissolving clots that have already formed Streptokinase: enzyme made by streptococci bacteria Used to dissolve clots in coronary vessels Digests almost any protein Tissue plasminogen activator (TPA): works faster, is more specific, and now made by transgenic bacteria Hementin: produced by giant Amazon leech
Types of Leukocytes
Granulocytes - granules with defense enzymes Neutrophils (60% to 70%): Barely visible granules in cytoplasm Eosinophils (2% to 4%) Large rosy-orange granules Basophils (less than 1%) Large, abundant, violet granules Agranulocytes Lymphocytes (25% to 33%) Variable amounts of bluish cytoplasm Monocytes (3% to 8%) Largest WBC
Veins
Greater capacity for blood containment than arteries Thinner walls, flaccid, less muscular and elastic tissue Collapse when empty, expand easily Have steady blood flow Merge to form larger veins Subjected to relatively low blood pressure Remains 10 mm Hg with little fluctuation venules— smallest veins Even more porous than capillaries so also exchange fluid with surrounding tissues Tunica interna with a few fibroblasts and no muscle fibers Most leukocytes emigrate from the bloodstream through venule walls Medium veins—up to 10 mm in diameter Thin tunica media and thick tunica externa Tunica interna forms venous valves Varicose veins result in part from the failure of these valves Skeletal muscle pump propels venous blood back toward the heart Large veins—larger than 10 mm Some smooth muscle in all three tunics Thin tunica media with moderate amount of smooth muscle Tunica externa is thickest layer Contains longitudinal bundles of smooth muscle Venae cavae, pulmonary veins, internal jugular veins, and renal veins
Position, Size, and Shape of the Heart
Heart located in mediastinum, between lungs Base—wide, superior portion of heart, blood vessels attach here Apex—inferior end, tilts to the left, tapers to point
The Complete Blood Count
Hematocrit Hemoglobin concentration Total count for RBCs, reticulocytes, WBCs, and platelets Differential WBC count RBC size and hemoglobin concentration per RBC
Platelets and Hemostasis— The Control of Bleeding
Hemostasis—the cessation of bleeding Stopping potentially fatal leaks Hemorrhage: excessive bleeding Three hemostatic mechanisms Vascular spasm Platelet plug formation Blood clotting (coagulation) Platelets play an important role in all three
Sickle-Cell Disease
Hereditary hemoglobin defects that occur mostly among people of African descent Caused by a recessive gene that modifies the structure of the hemoglobin molecule (HbS) in oxygen-poor blood RBCs become rigid, sticky, pointed at ends in oxygen-poor blood Clump together and block small blood vessels causing intense pain Can lead to kidney or heart failure, stroke, rheumatism, or paralysis
Hormonal Control
Hormones influence blood pressure Some through their vasoactive effects Some by regulating water balance Angiotensin II—potent vasoconstrictor Raises blood pressure Promotes Na+ and water retention by kidneys Increases blood volume and pressure Atrial natriuretic peptide—increases urinary sodium excretion Reduces blood volume and promotes vasodilation Lowers blood pressure ADH promotes water retention and raises BP Pathologically high concentrations; also a vasoconstrictor Epinephrine and norepinephrine effects Most blood vessels —vasoconstriction Skeletal and cardiac muscle blood vessels —vasodilation
Hypertension—The "Silent Killer"
Hypertension—most common cardiovascular disease affecting about 30% of Americans over 50 "The silent killer" Major cause of heart failure, stroke, and kidney failure Damages heart by increasing afterload Myocardium enlarges until overstretched and inefficient Renal arterioles thicken in response to stress Drop in renal BP leads to salt retention (aldosterone) and worsens the overall hypertension Primary hypertension Obesity, sedentary behavior, diet, nicotine Secondary hypertension—secondary to other disease Kidney disease, hyperthyroidism
Plasma Protein Deficiency
Hypoproteinemia Deficiency of plasma proteins Extreme starvation Liver or kidney disease Severe burns Kwashiorkor Children with severe protein deficiency Fed on cereals once weaned Thin arms and legs Swollen abdomen
Pulmonary Edema
If the left ventricle pumps less blood than the right, the blood pressure backs up into the lungs and causes pulmonary edema
Systemic edema
If the right ventricle pumps less blood than the left, pressure backs up in the systemic circulation and causes systemic edema
During exercise
Increased perfusion of lungs, myocardium, and skeletal muscles Decreased perfusion of kidneys and digestive tract
Veins of the Head and Neck
Internal jugular vein receives most of the blood from the brain Branches of external jugular vein drain the external structures of the head Upper limb is drained by subclavian vein
Erythrocyte Homeostasis
Negative feedback control Drop in RBC count causes kidney hypoxemia Kidney production of erythropoietin stimulates bone marrow RBC count increases in 3 to 4 days Stimuli for increasing erythropoiesis Low levels O2 (hypoxemia) High altitude Increase in exercise Loss of lung tissue in emphysema
Granulocytes
Neutrophils—increased numbers in bacterial infections Phagocytosis of bacteria Release antimicrobial chemicals Eosinophils—increased numbers in parasitic infections, collagen diseases, allergies, diseases of spleen and CNS Phagocytosis of antigen-antibody complexes, allergens, and inflammatory chemicals Release enzymes to destroy large parasites Basophils—increased numbers in chickenpox, sinusitis, diabetes Secrete histamine (vasodilator): speeds flow of blood to an injured area Secrete heparin (anticoagulant): promotes the mobility of other WBCs in the area
Erythroblastosis Fetalis
Occurs if Rh- mother has formed antibodies and is pregnant with second Rh+ child Anti-Rh antibodies can cross placenta and attack fetus's RBCs Prevention RhoGAM given to pregnant Rh- women Binds fetal Rh antigen in her blood so she will not form anti-Rh antibodies
The Heart Wall
Pericardium— double-walled sac (pericardial sac) that encloses the heart Allows heart to beat without friction, provides room to expand, yet resists excessive expansion Anchored to diaphragm inferiorly and sternum anteriorly Parietal pericardium—outer wall of sac Visceral pericardium (epicardium)—heart covering Serous lining of sac turns inward at base of heart to cover the heart surface Pericardial cavity—space inside the pericardial sac filled with 5 to 30 mL of pericardial fluid Pericarditis—inflammation of the membranes Painful friction rub with each heartbeat Epicardium (visceral pericardium) Serous membrane covering heart Adipose in thick layer in some places Coronary blood vessels travel through this layer Myocardium Layer of cardiac muscle proportional to work load Muscle spirals around heart which produces wringing motion Endocardium Smooth inner lining of heart and blood vessels Covers the valve surfaces and is continuous with endothelium of blood vessels Frictionless surface prevents blood clotting
Peripheral Resistance
Peripheral resistance—the opposition to flow that blood encounters in vessels away from the heart Resistance hinges on three variables Blood viscosity ("thickness") RBC count and albumin concentration elevate viscosity the most Decreased viscosity with anemia and hypoproteinemia speed flow Increased viscosity with polycythemia and dehydration slow flow Resistance hinges on three variables (cont.) Vessel length The farther liquid travels through a tube, the more cumulative friction it encounters Pressure and flow decline with distance Vessel radius: most powerful influence over flow Only significant way of controlling peripheral resistance Vasomotion—change in vessel radius Vasoconstriction: by muscular effort that results in smooth muscle contraction Vasodilation: by relaxation of the smooth muscle Arterioles are most significant point of control over peripheral resistance and flow On proximal side of capillary beds and best positioned to regulate flow into the capillaries Outnumber any other type of artery, providing the most numerous control points More muscular in proportion to their diameter Highly capable of vasomotion Arterioles produce half of the total peripheral resistance
Platelet Form and Function
Platelets—small fragments of megakaryocyte cells with long tendrils of cytoplasm (proplatelets) that break off in capillary blood flow forming platelets. Normal platelet count—130,000 to 400,000 platelets/L (micro liter) Functions Stick together to form platelet plugs to seal small breaks Secrete procoagulants or clotting factors to promote clotting
Erythrocyte Disorders
Polycythemia—an excess of RBCs Primary polycythemia (polycythemia vera) Cancer of erythropoietic cell line in red bone marrow RBC count as high as 11 million RBCs/L; hematocrit 80% Secondary polycythemia From dehydration, emphysema, high altitude, or physical conditioning RBC count up to 8 million RBCs/L Dangers of polycythemia Increased blood volume, pressure, viscosity Can lead to embolism, stroke, or heart failure
Heart Rate
Pulse—surge of pressure produced by each heart beat that can be felt by palpating a superficial artery with the fingertips Infants have HR of 120 bpm or more Young adult females average 72 to 80 bpm Young adult males average 64 to 72 bpm Heart rate rises again in the elderly Tachycardia—resting adult heart rate above 100 bpm Stress, anxiety, drugs, heart disease, or fever Loss of blood or damage to myocardium Bradycardia—resting adult heart rate of less than 60 bpm In sleep, low body temperature, and endurance-trained athletes
Quantities of Erythrocytes and Hemoglobin
RBC count and hemoglobin concentration indicate amount of O2 blood can carry Hematocrit (packed cell volume): percentage of whole blood volume composed of RBCs Men 42% to 52% cells; women 37% to 48% cells RBC count Men 4.6 to 6.2 million/L women 4.2 to 5.4 million/L
Erythrocyte Death and Disposal
RBCs lyse in narrow channels in spleen Macrophages in spleen Digest membrane bits Separate heme from globin Globins hydrolyzed into amino acids Iron removed from heme Heme pigment converted to biliverdin (green) Biliverdin converted to bilirubin (yellow) Released into blood plasma (kidneys-yellow urine) Liver removes bilirubin and secretes into bile -Concentrated in gallbladder: released into small intestine; bacteria create urobilinogen (brown feces) Jaundice - Yellowish skin/eyes caused by rapid hemolysis, a liver disease or a bile duct obstruction Urochrome (yellow urine)
Lymphatic System - Function
Return tissue fluid to the blood Specialized lymphatic vessels play a role in intestinal absorption Protection against disease
The Rh Group
Rh agglutinogens discovered in rhesus monkey in 1940 A patient is considered blood type Rh+ if having Rh antigen on RBCs Anti-Rh agglutinins - not normally present but they will form in Rh- individuals exposed to Rh+ blood When does this become an issue? Rh- woman with an Rh+ fetus or Rh- person transfused with Rh+ blood No problems with first transfusion or pregnancy, major problems with second exposure to Rh+ blood
The Valves
Valves ensure a one-way flow of blood through the heart Atrioventricular (AV) valves—control blood flow between atria and ventricles Right AV valve has three cusps (tricuspid valve) & is between RA & RV Left AV valve has two cusps (mitral/bicuspid valve) & is between LA & LV Semilunar valves—control flow into great arteries; open and close because of blood flow and pressure; look like Mercedes symbol Pulmonary semilunar valve: in opening between right ventricle and pulmonary trunk Aortic semilunar valve: in opening between left ventricle and aorta
Valvular Insufficiency Disorders
Valvular insufficiency (incompetence)—any failure of a valve to prevent reflux (regurgitation), the backward flow of blood Valvular stenosis: valve cusps are stiffened and opening is constricted by scar tissue Result of rheumatic fever, autoimmune attack on the mitral and aortic valves Heart overworks and may become enlarged Heart murmur—abnormal heart sound produced by regurgitation of blood through incompetent valves Major reason for valve replacement Mitral valve prolapse: insufficiency in which one or both mitral valve cusps bulge into atria during ventricular contraction Hereditary in 1 out of 40 people May cause chest pain and shortness of breath Can be clinically insignificant to also being a reason for valve replacement surgery.
Hemostasis
Vascular spasm—prompt constriction of a broken vessel Most immediate protection against blood loss Causes Pain receptors Some directly innervate blood vessels to constrict Smooth muscle injury Platelets release serotonin (vasoconstrictor) Endothelium smooth, coated with prostacyclin—a platelet repellant Toxins and environmental poisons (cigarette smoke)can destroy this layer allowing for blood vessel blockages. Platelet plug formation Broken vessel exposes collagen beneath prostacylin allowing the platelet stick forming plug. Coagulation (clotting)—last and most effective defense against bleeding Conversion of plasma protein fibrinogen (a plasma protein) into insoluble fibrin threads to form framework of clot Procoagulants (clotting factors)—usually produced by the liver; are present in plasma Activate one factor and it will activate the next to form a reaction cascade
Regulation of Blood Pressure and Flow
Vasomotion is a quick and powerful way of altering blood pressure and flow Three ways of controlling vasomotion Local control Neural control Hormonal control
Mechanisms of Venous Return
Venous return—the flow of blood back to the heart Pressure gradient Blood pressure is the most important force in venous return 7 to 13 mm Hg venous pressure toward heart Venules (12 to 18 mm Hg) to central venous pressure: point where the venae cavae enter the heart (~5 mm Hg) Gravity drains blood from head and neck Skeletal muscle pump in the limbs Contracting muscle squeezed out of the compressed part of the vein Get up and get your blood moving!
Blood Flow Through the Chambers
Ventricles relax Pressure drops inside the ventricles Semilunar valves close as blood attempts to back up into the ventricles from the vessels AV valves open Blood flows from atria to ventricles Ventricles contract AV valves close as blood attempts to back up into the atria Pressure rises inside of the ventricles Semilunar valves open and blood flows into great vessels
Blood Viscosity and Osmolarity
Viscosity—resistance of a fluid to flow, resulting from the cohesion of its particles (Thickness of fluid) Whole blood 4.5 to 5.5 times as viscous as water Plasma is 2.0 times as viscous as water Osmolarity of blood—the total molarity (e.g., concentration) of those dissolved particles that cannot pass through the blood vessel wall If too high, blood absorbs too much water, increasing the blood pressure If too low, too much water stays in tissue, blood pressure drops, and edema occurs Optimum osmolarity is achieved by the body's regulation of sodium ions, proteins, and red blood cells
Prevention of Inappropriate Clotting
Natural anticoagulants Heparin (from basophils and mast cells) Antithrombin (from liver)
Form and Function-Erythrocytes
Disc-shaped cell with thick rim Gas transport—major function 33% of cytoplasm is hemoglobin (Hb) 280 million hemoglobin molecules on one RBC O2 delivery to tissue and CO2 transport to lungs Carbonic anhydrase (CAH) in cytoplasm Produces carbonic acid from CO2 and water Important role in gas transport and pH balance
Veins of the Abdominal and Pelvic Region
Drains nutrient-rich blood from viscera (stomach, spleen, and intestines) to liver so that blood sugar levels are maintained
Hemoglobin-Erythrocytes
Each Hb molecule consists of: Four protein chains—globins Four heme groups Heme groups Nonprotein moiety that binds O2 to ferrous ion (Fe2+) at its center Globins—four protein chains Two alpha and two beta chains 5% CO2 in blood is bound to globin moiety
Edema
Edema—the accumulation of excess fluid in a tissue Occurs when fluid filters into a tissue faster than it is absorbed
The Electrocardiogram
Electrocardiogram (ECG or EKG) Composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs, and chest P wave SA node fires, atria depolarize and contract Atrial systole begins 100 ms after SA signal QRS complex Ventricular depolarization Complex shape of spike due to different thickness and shape of the two ventricles ST segment—ventricular systole Plateau in myocardial action potential T wave Ventricular repolarization and relaxation
Steps in Atherosclerosis
Endothelium damaged by hypertension, virus, diabetes, or other causes Monocytes penetrate walls of damaged vessels and transform into macrophages Absorb cholesterol and fats to be called foam cells Look like fatty streak on vessel wall Can grow into atherosclerotic plaques (atheromas) Inflammation transforms atheroma into a hardened complicated plaque called arteriosclerosis Bulging mass grows to obstruct arterial lumen
Venous Return and Physical Activity
Exercise increases venous return in many ways Heart beats faster and harder, increasing CO and BP Vessels of skeletal muscles, lungs, and heart dilate and increase flow Increased respiratory rate, increased action of thoracic pump Increased skeletal muscle pump Venous pooling occurs with inactivity Venous pressure not enough to force blood upward Prevented by tensing leg muscles, activate skeletal muscle pump Jet pilots wear pressure suits
Exercise and Cardiac Output
Exercise makes the heart work harder and increases cardiac output Proprioceptors signal cardiac center At beginning of exercise, signals from joints and muscles reach the cardiac center of brain Sympathetic output from cardiac center increases cardiac output Increased muscular activity increases venous return Increases preload and ultimately cardiac output Increases in heart rate and stroke volume cause an increase in cardiac output Exercise produces ventricular hypertrophy Increased stroke volume allows heart to beat more slowly at rest Athletes with increased cardiac reserve can tolerate more exertion than a sedentary person
The Chambers
Four chambers Right and left atria Two superior chambers Receive blood returning to heart Right and left ventricles Two inferior chambers Pump blood into arteries Interatrial septum Wall that separates atria Interventricular septum Muscular wall that separates ventricles
The Pulmonary and Systemic Circuits
Major divisions of circulatory system Pulmonary circuit: right side of heart Carries blood to lungs for gas exchange and back to heart Systemic circuit: left side of heart Supplies oxygenated blood to all tissues of the body and returns it to the heart Left side of heart Fully oxygenated blood arrives from lungs via pulmonary veins Blood sent to all organs of the body via aorta Right side of heart Lesser oxygenated blood arrives from inferior and superior venae cavae Blood sent to lungs via pulmonary trunk
White Blood Cell Form and Function
Least abundant formed element 5,000 to 10,000 WBCs/L Protect against infectious microorganisms and other pathogens
Arterial Supply
Left coronary artery (LCA) branches off the ascending aorta Two branches of LCA that often have blockages Left Anterior Descending (LAD) or Anterior interventricular branch Supplies blood to both ventricles and anterior two-thirds of the interventricular septum Circumflex branch Supplies left atrium and posterior wall of left ventricle Right coronary artery (RCA) branches off the ascending aorta Supplies right atrium and sinoatrial node (pacemaker)
Leukocyte Disorders
Leukopenia—low WBC count: below 5,000 WBCs/L (micro liter) Causes: radiation, poisons, infectious disease Effects: elevated risk of infection Leukocytosis—high WBC count: above 10,000 WBCs/L Causes: infection, allergy, disease Differential WBC count: identifies what percentage of the total WBC count consist of each type of leukocyte Leukemia—cancer of hemopoietic tissue that usually produces an extraordinary high number of circulating leukocytes and their precursors Myeloid leukemia: uncontrolled granulocyte production Lymphoid leukemia: uncontrolled lymphocyte or monocyte production Acute leukemia: appears suddenly, progresses rapidly, death within months Chronic leukemia: undetected for months, survival time 3 years
The Leukocyte Life Cycle
Leukopoiesis—production of white blood cells Circulating WBCs do not stay in bloodstream Granulocytes leave in 8 hours and live 5 days longer Monocytes leave in 20 hours, transform into macrophages, and live for several years Lymphocytes provide long-term immunity (decades), being continuously recycled from blood to tissue fluid to lymph and back to the blood
Lymphatic Pathways
Lymphatic pathways start as lymphatic capillaries that merge to form larger vessels that empty into the circulatory system.
Agranulocytes
Lymphocytes—increased numbers in diverse infections and immune responses Destroy cells (cancer, foreign, and virally infected cells) 3 subtypes with specific functions: "Present" antigens to activate other immune cells Coordinate actions of other immune cells Secrete antibodies and provide immune memory Monocytes—increased numbers in viral infections and inflammation Can leave bloodstream and transform into macrophages Phagocytize pathogens and debris "Present" antigens to activate other immune cells
Introduction to ch.18 blood
Many myths about blood Mysterious "vital force" Drained "bad blood" for medical reasons Hereditary traits were once thought to be transmitted through blood Blood cells were seen with the first microscopes Hematology—the study of blood Recent developments in this field help save lives
Arterial Sense Organs
Sensory structures in the walls of certain vessels that monitor blood pressure and chemistry Carotid sinuses: baroreceptors (pressure sensors) In walls of internal carotid artery Monitors blood pressure—signaling brainstem Decreased heart rate and vessel dilation in response to high blood pressure Carotid bodies: chemoreceptors Oval bodies near branch of common carotids Monitor blood chemistry Mainly transmit signals to the brainstem respiratory centers Adjust respiratory rate to stabilize pH, CO2, and O2 Aortic bodies: chemoreceptors One to three in walls of aortic arch Same function as carotid bodies
Circulatory Routes
Simplest and most common route Heart arteries arterioles capillaries venules veins Passes through only one network of capillaries from the time it leaves the heart until the time it returns Portal system Blood flows through two consecutive capillary networks before returning to heart Between hypothalamus and anterior pituitary In kidneys Between intestines to liver Anastomosis—the point where two blood vessels merge Arteriovenous anastomosis (shunt) Artery flows directly into vein by passing capillaries Venous anastomosis Most common One vein empties directly into another This is the reason vein blockage is less serious than arterial blockage Arterial anastomosis Two arteries merge Provides collateral (alternative) routes of blood supply to a tissue Coronary circulation and around joints
The Cardiac Rhythm
Sinus rhythm—normal heartbeat triggered by the SA node Set by SA node at 60 to 100 bpm Adult at rest is 70 to 80 bpm (vagal tone) At rest, fires every 0.8 second or 75 bpm Each depolarization of the SA node sets off one heartbeat Ectopic focus—another part of heart fires before the SA node Caused by hypoxia, electrolyte imbalance, or caffeine, nicotine, and other drugs Nodal rhythm— if SA node is damaged, heart rate is set by AV node, 40 to 50 bpm Intrinsic ventricular rhythm—if both SA and AV nodes are not functioning, rate set at 20 to 40 bpm Requires pacemaker to sustain life Arrhythmia—any abnormal cardiac rhythm Failure of conduction system to transmit signals (heart block) Bundle branch block Total heart block (damage to AV node)
Arterial Pressure Points
Some major arteries close to surface allow for palpation for pulse and serve as pressure points to reduce arterial bleeding
The Vessel Wall
Tunica interna (tunica intima) Lines the blood vessel and is exposed to blood Endothelium: simple squamous epithelium overlying a basement membrane and a sparse layer of loose connective tissue Acts as a selectively permeable barrier Secretes chemicals that stimulate dilation or constriction of the vessel Normally repels blood cells and platelets that may adhere to it and form a clot When tissue around vessel is inflamed, the endothelial cells produce cell-adhesion molecules that induce leukocytes to adhere to the surface Tunica media Middle layer Consists of smooth muscle, collagen, and elastic tissue Strengthens vessels and prevents blood pressure from rupturing them Vasomotion: changes in diameter of the blood vessel brought about by smooth muscle Tunica externa (tunica adventitia) Outermost layer Consists of loose connective tissue that often merges with that of neighboring blood vessels, nerves, or other organs
Erythrocytes
Two principal functions Carry oxygen from lungs to cell tissues Pick up CO2 from tissues and bring to lungs Insufficient RBCs may kill in minutes due to lack of oxygen to tissues
Stroke volume (SV)
Stroke volume (SV) of about 70 mL of blood is ejected of the 130 mL in each ventricle Amount of blood ejected from 1 ventricle in 1 stroke Ejection fraction of about 54% As high as 90% in vigorous exercise
Arteries of the Upper Limb
Subclavian passes between clavicle and first rib Vessel changes names as it passes to different regions Subclavian to axillary to brachial to radial and ulnar Brachial used for BP and radial artery for pulse
Nerve Supply to the Heart
Sympathetic nerves (increase heart rate) Fibers terminate in SA and AV nodes allowing for an instantaneous increase in heart rate. Parasympathetic nerves (slows heart rate) Fibers come from the Vagus Nerve to SA node and AV node
What happens when the wrong blood type is transfused?
The antibodies of the recipient clump the RBCs of the donor!!! Responsible for mismatched transfusion reaction Agglutinated RBCs block small blood vessels and hemolyze, spilling out their hemoglobin over the next few hours or days Hb blocks kidney tubules and causes acute renal failure
Clotting Disorders
Thrombosis—abnormal clotting in unbroken vessel Thrombus: clot that stays put Most likely to occur in leg veins of inactive people Pulmonary embolism: clot may break free, travel from veins to lungs Embolus—anything that can travel in the blood and block blood vessels a way from its location of origin. Infarction (tissue death) may occur if clot blocks blood supply to an organ (MI or stroke) 650,000 Americans die annually of thromboembolism (traveling blood clots)
Edema Can Lead to:
Tissue necrosis Oxygen delivery and waste removal impaired Pulmonary edema Suffocation threat Cerebral edema Headaches, nausea, seizures, and coma Severe edema or circulatory shock Excess fluid in tissue spaces causes low blood volume and low blood pressure
Brain
Total blood flow to the brain fluctuates less than that of any other organ (700 mL/min.) Seconds of deprivation causes loss of consciousness Four to 5 minutes causes irreversible brain damage Blood flow can be shifted from one active brain region to another Transient ischemic attacks (TIAs)—brief episodes of cerebral ischemia Caused by spasms of diseased cerebral arteries Dizziness, loss of vision, weakness, paralysis, headache, or aphasia Lasts from a moment to a few hours Often early warning of impending stroke Stroke, or cerebral vascular accident (CVA) Sudden death of brain tissue caused by ischemia Atherosclerosis, thrombosis, ruptured aneurysm Effects range from unnoticeable to fatal Blindness, paralysis, loss of sensation, loss of speech common Recovery depends on surrounding neurons, collateral circulation
Capillary Beds
When sphincters open Capillaries are well perfused with blood and engage in exchanges with the tissue fluid When sphincters closed Blood bypasses the capillaries Flows through thoroughfare channel to venule Three-fourths of the body's capillaries are shut down at a given time
The ABO Group
Your ABO blood type is determined by presence or absence of antigens (agglutinogens) on RBCs Blood type A person has A antigens (wave an red "A" flag) Blood type B person has B antigens (wave a yellow "B" flag) Blood type AB has both A and B antigens (wave both "A & B" flags) Blood type O person has neither antigen (wave no flag) Most common: type O Rarest: type AB Universal donor Type O: most common blood type Has no antigens for the recipient's antibodies to attack so can be given to anyone!! Donor's plasma may have both antibodies against recipient's RBCs (anti-A and anti-B) May give packed cells (minimal plasma) Universal recipient Type AB: rarest blood type Has no antibodies to attack A or B antigens
