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Cardiovascular System Anatomy and Physiology
Two children were sitting outside a clinic. One of them was crying very loudly. 2nd Child: Why are you crying? 1st Child: I came here for a blood test. 2nd Child: So? Are you afraid? 1st Child: No. For the blood test, they cut my finger. At this, the second one started crying profusely. The first one was astonished. 1st Child: Why are you crying now? 2nd Child: I came for a urine test!
Overview of Blood Circulation • Blood leaves the heart via arteries that branch repeatedly until they become capillaries • Oxygen (O2) and nutrients diffuse across capillary walls and enter tissues • Carbon dioxide (CO2) and wastes move from tissues into the blood • Oxygen-deficient blood leaves the capillaries and flows in veins to the heart • This blood flows to the lungs where it releases CO2 and picks up O2 • The oxygen-rich blood returns to the heart
Composition of Blood • Blood is the body’s only fluid tissue • It is composed of liquid plasma and formed elements • Formed elements include: • Erythrocytes, or red blood cells (RBCs) • Leukocytes, or white blood cells (WBCs) • Platelets (Thrombocytes) • Hematocrit – the percentage of RBCs out of the total blood volume
Composition of Blood Figure 18.1
Physical Characteristics and Volume • Blood is a sticky, opaque fluid with a metallic taste • Color varies from scarlet (oxygen-rich) to dark red (oxygen-poor) • The pH of blood is 7.35–7.45 • Temperature is 38C, slightly higher than “normal” body temperature • Blood accounts for approximately 8% of body weight • Average volume of blood is 5–6 L for males, and 4–5 L for females
Functions of Blood • Blood performs a number of functions dealing with: • Substance distribution • Regulation of blood levels of particular substances • Body protection
Blood Plasma • Blood plasma contains over 100 solutes, including: • Proteins – albumin, globulins, clotting proteins, and others • Nonprotein nitrogenous substances – lactic acid, urea, creatinine • Organic nutrients – glucose, carbohydrates, amino acids • Electrolytes – sodium, potassium, calcium, chloride, bicarbonate • Respiratory gases – oxygen and carbon dioxide
Erythrocytes (RBCs) • Biconcave discs, anucleate, essentially no organelles • Filled with hemoglobin (Hb), a protein that functions in gas transport • Contain the plasma membrane protein spectrin that: • Gives erythrocytes their flexibility • Allows them to change shape as necessary Figure 18.3
Erythrocyte Function • Erythrocytes are dedicated to respiratory gas transport • Hemoglobin reversibly binds with oxygen and most oxygen in the blood is bound to hemoglobin • Hemoglobin is composed of: • The protein globin, made up of two alpha and two beta chains, each bound to a heme group • Each heme group bears an atom of iron, which can bind one to oxygenmolecule • Each hemoglobin molecule can transport four molecules of oxygen
Erythrocyte Function Figure 18.4a, b
Hormonal Control of Erythropoiesis • Erythropoietin (EPO) release by the kidneys is triggered by: • Hypoxia due to decreased RBCs • Decreased oxygen availability • Increased tissue demand for oxygen • Enhanced erythropoiesis increases the: • RBC count in circulating blood • Oxygen carrying ability of the blood increases
Hormonal Control of Erythropoiesis Figure 18.6
Life Cycle of Red Blood Cells Figure 18.7
Leukocytes (WBCs) • Leukocytes, the only blood components that are complete cells: • Are less numerous than RBCs • Make up 1% of the total blood volume • Can leave capillaries via diapedesis • Move through tissue spaces • Leukocytosis – WBC count over 11,000 per cubic millimeter • Normal response to bacterial or viral invasion
Platelets • Platelets are fragments of megakaryocytes with a blue-staining outer region and a purple granular center • The granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF) • Platelets function in the clotting mechanism by forming a temporary plug that helps seal breaks in blood vessels
White blood cells Platelets Red blood cells
Neutrophil Lymphocyte
Eosinophil Lymphocyte
Neutrophil Basophil Monocyte
6 3 4 2 5 1
Hemostasis • A series of reactions designed for stoppage of bleeding • During hemostasis, three phases occur in rapid sequence • Vascular spasms – immediate vasoconstriction in response to injury • Platelet plug formation • Coagulation (blood clotting)
Blood Typing • When serum containing anti-A or anti-B agglutinins is added to blood, agglutination will occur between the agglutinin and the corresponding agglutinogens • Positive reactions indicate agglutination
Heart Anatomy • Approximately the size of your fist • Location • Superior surface of diaphragm • Left of the midline • Anterior to the vertebral column, posterior to the sternum
Heart Anatomy Figure 19.1
Heart Covering • Pericardial physiology • Protects and anchors heart • Prevents overfilling Figure 19.2
Heart Covering • Pericardial anatomy • Fibrous pericardium • Serous pericardium (separated by pericardial cavity) • Epicardium (visceral layer) Figure 19.2
Heart Wall • Epicardium – visceral layer of the serous pericardium • Myocardium – cardiac muscle layer forming the bulk of the heart • Fibrous skeleton of the heart – crisscrossing, interlacing layer of connective tissue • Endocardium – endothelial layer of the inner myocardial surface
External Heart: Anterior View Figure 19.4b
Atria of the Heart • Atria are the receiving chambers of the heart • Each atrium has a protruding auricle • Pectinate muscles mark atrial walls • Blood enters right atria from superior and inferior venae cavae and coronary sinus • Blood enters left atria from pulmonary veins
Ventricles of the Heart • Ventricles are the discharging chambers of the heart • Papillary muscles and trabeculae carneae muscles mark ventricular walls • Right ventricle pumps blood into the pulmonary trunk • Left ventricle pumps blood into the aorta
Gross Anatomy of Heart: Frontal Section Figure 19.4e
Pathway of Blood through the Heart and Lungs • Right atrium tricuspid valve right ventricle • Right ventricle pulmonary semilunar valve pulmonary arteries lungs • Lungs pulmonary veins left atrium • Left atrium bicuspid valve left ventricle • Left ventricle aortic semilunar valve aorta • Aorta systemic circulation
Pathway of Blood through the Heart and Lungs Figure 19.5
Heart Valves • Heart valves insure unidirectional blood flow through the heart • Atrioventricular (AV) valves lie between the atria and the ventricles • AV valves prevent backflow into the atria when ventricles contract • Chordae tendineae anchor AV valves to papillary muscles
Heart Valves Figure 19.9
Heart Valves • Aortic semilunar valve lies between the left ventricle and the aorta • Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk • Semilunar valves prevent backflow of blood into the ventricles
Heart Valves Figure 19.10
Heart Physiology: Sequence of Excitation • Sinoatrial (SA) node generates impulses about 75 times/minute • Atrioventricular (AV) node delays the impulse approximately 0.1 second • Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)
Heart Physiology: Sequence of Excitation • AV bundle splits into two pathways in the interventricular septum (bundle branches) • Bundle branches carry the impulse toward the apex of the heart • Purkinje fibers carry the impulse to the heart apex and ventricular walls
Heart Physiology: Sequence of Excitation Figure 19.14a
Electrocardiography • Electrical activity is recorded by electrocardiogram (ECG) • P wave corresponds to depolarization of atria • QRS complex corresponds to ventricular depolarization • T wave corresponds to ventricular repolarization • Atrial repolarization record is masked by the larger QRS complex
Electrocardiography Figure 19.16
videos • heart beat electricity • http://medmovie.com/mmdatabase/flash/0007a.swf • ecg • http://medmovie.com/mmdatabase/flash/0038a.swf • all animations • http://science.nhmccd.edu/biol/ap2int.htm#cardio • heart valves • http://www.wellesley.edu/Biology/Courses/111/HeartValves.MOV • visible heart video clips • http://www.visibleheart.com/videoclips.html • arrythmeias • http://medmovie.com/mmdatabase/flash/0078a.swf • heart attack • http://medmovie.com/mmdatabase/flash/0072a_B.swf
Cardiac Cycle • Cardiac cycle refers to all events associated with blood flow through the heart • Systole – contraction of heart muscle • Diastole – relaxation of heart muscle