1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 50

2. The Circulatory System

3. Blood Type of connective tissue composed –Fluid matrix called plasma –Formed elements Functions of circulating blood 1.Transportation 2.Regulation 3.Protection 3

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5. Blood plasma 92% water Contains the following solutes –Nutrients, wastes, and hormones –Ions –Proteins Albumin Fibrinogen –If removed, plasma is called serum 5

6. Formed elements Red blood cells (erythrocytes) –About 5 million per microliter of blood –Hematocrit is the fraction of the total blood volume occupied by red blood cells –Mature mammalian erythrocytes lack nuclei –RBCs of vertebrates contain hemoglobin Pigment that binds and transports oxygen 6

7. Formed elements White blood cells (leukocytes) –Less than 1% of blood cells –Larger than erythrocytes and have nuclei –Can migrate out of capillaries into tissue fluid –Types Granular leukocytes –Neutrophils, eosinophils, and basophils Agranular leukocytes –Monocytes and lymphocytes 7

8. Formed elements Platelets Cell fragments that pinch off from larger cells in the bone marrow Function in the formation of blood clots 8

9. Formed elements All develop from pluripotent stem cells Occurs in the bone marrow Erythropoietin stimulates the production of erythrocytes (erythropoiesis) 9

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11. Invertebrate Circulatory Systems Nature of the circulatory system in multicellular invertebrates is directly related to the size, complexity, and lifestyle of the organism No circulatory system –Sponges and most cnidarians utilize water from the environment as a circulatory fluid Gastrovascular cavity –Nematodes Use the fluids of the body cavity for circulation Small or long and thin 11

12. Invertebrate Circulatory Systems Larger animals require a separate circulatory system for nutrient and waste transport Open circulatory system –No distinction between circulating and extracellular fluid –Fluid called hemolymph Closed circulatory system –Distinct circulatory fluid enclosed in blood vessels and transported away from and back to the heart 12

13. 13 Vertebrate Circulatory Systems

14. Amphibian heart –3-chambered heart 2 atria and 1 ventricle –Separation of the pulmonary and systemic circulations is incomplete –Amphibians living in water obtain additional oxygen by diffusion through their skin –Reptiles have a septum that partially subdivides the ventricle, thereby further reducing the mixing of blood in the heart 14

15. Vertebrate Circulatory Systems Mammals, birds, and crocodilians –4-chambered heart –2 separate atria and 2 separate ventricles –Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs –Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps it to rest of the body 15

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17. The Cardiac Cycle Heart has two pairs of valves –Atrioventricular (AV) valves Maintain unidirectional blood flow between atria and ventricles Tricuspid valve = On the right Bicuspid, or mitral, valve = On the left –Semilunar valves Ensure one-way flow out of the ventricles to the arterial systems Pulmonary valve located at the exit of the right ventricle Aortic valve located at the exit of the left ventricle 17

18. The Cardiac Cycle Valves open and close as the heart goes through the cardiac cycle Ventricles relaxed and filling (diastole) Ventricles contracted and pumping (systole) “Lub-dub” sounds heard with stethoscope –Lub – AV valves closing –Dub – closing of semilunar valves 18

19. Right ventricle 1. The atria contract. Diastole “Lub” 1. 2. 3. 4. 5. “Dup” DiastoleSystole Pressure (mm Hg) 0 25 0.101.00.90.80.60.70.50.40.30.2 50 75 100 125 Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

20. The Cardiac Cycle Heart contains “self-excitable” autorhythmic fibers Most important is the sinoatrial (SA) node –Located in wall of right atrium –Acts as pacemaker –Autonomic nervous system can modulate rate 20

21. The Cardiac Cycle Each SA depolarization transmitted –To left atrium –To right atrium and atrioventricular (AV) node AV node is only pathway for conduction to ventricles –Spreads through atrioventricular bundle –Purkinje fibers –Directly stimulate the myocardial cells of both ventricles to contract 21

22. The Cardiac Cycle Electrical activity can be recorded on an electrocardiogram (ECG or EKG) –First peak (P) is produced by depolarization of atria (atrial systole) –Second, larger peak (QRS) is produced by ventricular depolarization (ventricular systole) –Last peak (T) is produced by repolarization of ventricles (ventricular diastole) 22

23. Seconds R T wave 1 sec +1 0 Purkinje fibers Left atrium Right atrium Purkinje fibers AV bundle SA node (pacemaker) AV node AV bundle Interventricular septum Left and right bundle branches 1. The impulse begins at the SA node and travels to the AV node. Internodal pathway AV 2. The impulse is delayed at the AV node. It then travels to the AV bundle. P wave Millivotts Q S Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 23

24. Seconds R T wave 1 sec +1 0 Purkinje fibers AV bundle Interventricular septum 3. From the AV bundle, the impulse travels down the interventricular septum. Left and right bundle branches 5. Finally reaching the Purkinje fibers, the impulse is distributed throughout the ventricles. 4. The impulse spreads to branches from the interventricular septum. P wave Millivotts 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Q S

25. The Cardiac Cycle Right and left pulmonary arteries deliver oxygen-depleted blood from the right ventricle to the right and left lungs Pulmonary veins return oxygenated blood from the lungs to the left atrium of the heart 25

26. The Cardiac Cycle Aorta and all its branches are systemic arteries, carrying oxygen-rich blood from the left ventricle to all parts of the body –Coronary arteries supply oxygenated blood to the heart muscle Blood from the body drains into the right atrium –Superior vena cava drains upper body –Inferior vena cava drains lower body 26

27. The Cardiac Cycle Arterial blood pressure can be measured with a sphygmomanometer Systolic pressure is the peak pressure at which ventricles are contracting Diastolic pressure is the minimum pressure between heartbeats at which the ventricles are relaxed Blood pressure is written as a ratio of systolic over diastolic pressure 27

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29. Characteristics of Blood Vessels Blood leaves heart through the arteries Arterioles are the finest, microscopic branches of the arterial tree Blood from arterioles enters capillaries Blood is collected into venules, which lead to larger vessels, veins Veins carry blood back to heart 29

30. Characteristics of Blood Vessels Arteries and veins are composed of four tissue layers –Endothelium, elastic fibers, smooth muscle, and connective tissue –Walls too thick for exchange of materials across the wall Capillaries are composed of only a single layer of endothelial cells –Allow rapid exchange of gases and metabolites between blood and body cells 30

31. 31 Characteristics of Blood Vessels

32. Arteries and arterioles –Larger arteries contain more elastic fibers in their walls than other blood vessels Recoil each time they receive blood from the heart –Contraction of the smooth muscle layer of the arterioles results in vasoconstriction Greatly increases resistance and decreases flow Chronic vasoconstriction can result in hypertension –Relaxation of the smooth muscle layer results in vasodilation Decreasing resistance and increasing blood flow to an organ 32

33. Characteristics of Blood Vessels Capillaries –Every cell in the body is within 100 micrometers (μm) of a capillary –Although each capillary is very narrow, so many of them exist that the capillaries have the greatest total cross-sectional area of any other type of vessel Slows blood flow to allow for exchange with extracellular fluid 33

34. Characteristics of Blood Vessels Veins and venules –Thinner layer of smooth muscles than arteries –Venous pump helps return blood to heart Skeletal muscle contractions and one- way venous valves 34

35. The Lymphatic System Consists of lymphatic capillaries, lymphatic vessels, lymph nodes, and lymphatic organs (spleen and thymus) Excess fluid in the tissues drains into blind-ended lymph capillaries Lymph passes into progressively larger vessels with one-way valves Eventually drains into subclavian veins 35

36. Cardiovascular Diseases Leading cause of death in the United States Atherosclerosis –Accumulation of fatty material within arteries –Impedes blood flow Arteriosclerosis –Arterial hardening due to calcium deposition 36

37. Cardiovascular Diseases Heart attacks (myocardial infarctions) –Main cause of cardiovascular deaths in U.S. –Insufficient supply of blood to heart Angina pectoris (“chest pain”) –Warning sign that the blood supply to the heart is inadequate but is still sufficient to avoid myocardial cell death Stroke –Interference with blood supply to the brain 37

38. Blood Flow and Blood Pressure Cardiac center of the medulla oblongata modulates heart rate Blood pressure increases with blood volume Blood volume is regulated by four hormones –Antidiuretic hormone (ADH) –Aldosterone –Atrial natriuretic hormone –Nitric oxide (NO) 38

39. Blood Flow and Blood Pressure Blood pressure increases with blood volume Blood volume is regulated by four hormones –Antidiuretic hormone (ADH) –Aldosterone –Atrial natriuretic hormone –Nitric oxide (NO) 39