Hole s Essentials of Human Anatomy & Physiology

Transcription

1 Hole s Essentials of Human Anatomy & Physiology David Shier Jackie Butler Ricki Lewis Created by Dr. Melissa Eisenhauer Head Athletic Trainer/Assistant Professor Trevecca Nazarene University Amended by John Crocker Chapter 13 1

2 Chapter 13 Cardiovascular System 2

3 Introduction A. The cardiovascular system consists of 1. Heart 2. Blood vessels a) Arteries b) capillaries c) veins B. Supplies oxygen and nutrients to tissues C. Removes wastes from tissues D. The pulmonary circuit carries deoxygenated blood to the lungs E. The systemic circuit sends oxygenated blood to all body cells 3

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5 Structure of the Heart A. Hollow, cone-shaped, muscular pump within the thoracic cavity B. Size and Location 1. Average adult heart is 14 cm long and 9 cm wide 2. Lies in the mediastinum under the sternum 3. Apex extends to the fifth intercostal space 5

6 A. Coverings of the Heart 1. Pericardium encloses the heart 2. It is made of two layers: a) Tough outer connective tissue fibrous pericardium b) Surrounds a more delicate visceral pericardium (epicardium) that surrounds the heart c) At the base of the heart, the visceral pericardium folds back to become the parietal pericardium that lines the fibrous pericardium d) Between the parietal and visceral pericardia is a potential space (pericardial cavity) filled with serous fluid 6

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8 A. Wall of the Heart 1. Epicardium a) b) c) d) Outermost layer Made up of connective tissue and epithelium Houses blood and lymph capillaries and coronary arteries Same as the visceral pericardium 2. Myocardium a) Middle layer b) Thickest layer c) Consists of cardiac muscle 3. Endocardium a) b) c) d) Inner layer Smooth Made up of connective tissue and epithelium Continuous with the endothelium of major vessels joining the heart 8

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10 A. Heart Chambers and Valves 1. The heart has four internal chambers: a) Two atria on top 1) receive blood returning to the heart 2) thin walls 3) ear-like auricles projecting from their exterior b) Two ventricles below 1) The thick-muscled 2) Pumps blood to the body 10

11 1. A septum divides the atrium and ventricle on each side 2. Each also has an atrioventricular (A-V) valve to ensure one way flow of blood a) Right A-V valve (tricuspid) b) Left A-V valve (bicuspid or mitral valve) c) Have cusps to which chordae tendinae attach d) Chordae tendinae attach to papillary muscles in the inner heart wall 1) Contract during ventricular contraction 2) Prevent the backflow of blood through the A-V valves 11

12 1. The superior and inferior vena cavae bring blood from the body to the right atrium 2. The right ventricle has a thinner wall than does the left ventricle because it must pump blood only as far as the lungs rather than the entire body 3. Pulmonary valve a) At the base of the pulmonary trunk leading to the lungs b) Prevents a return flow of blood to the ventricle 4. The left atrium receives blood from 4 pulmonary veins 5. The left ventricle a) Pumps blood into the entire body through the aorta b) Guarded by the aortic valve c) Prevents backflow of blood into the ventricle 12

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14 A. Skeleton of the Heart 1. Rings of dense connective tissue surround the pulmonary trunk and aorta to provide attachments for the heart valves and fibers 2. These tough rings prevent dilating of tissue in this area 14

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16 A. Path of Blood through the Heart 1. Blood low in oxygen returns to the right atrium via a) Venae cavae b) Coronary sinus 2. The right atrium contracts 3. Blood forced through the tricuspid valve into the right ventricle 4. The right ventricle contracts, closing the tricuspid valve 5. Blood forced through the pulmonary valve into the pulmonary trunk and arteries 16

17 1. Pulmonary arteries carry blood to the lungs where it: a) Rids itself of excess carbon dioxide b) Picks up a new supply of oxygen 2. Freshly oxygenated blood is returned to the left atrium of the heart through the pulmonary veins 3. The left atrium contracts 4. Blood forced through the left bicuspid valve into the left ventricle 5. The left ventricle contracts closing the bicuspid valve 6. Aortic valve is forced open 7. Blood enters the aorta for distribution to the body 17

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19 A. Blood Supply to the Heart 1. The first branches off of the aorta a) Right and left coronary arteries b) Feed the heart muscle itself c) Carry freshly oxygenated blood 2. Branches of the coronary arteries feed capillaries of the myocardium 3. Heart requires a continuous supply of freshly oxygenated blood 4. Smaller branches of arteries often have anastomoses as alternate pathways for blood 5. Cardiac veins a) Drain blood from the heart muscle b) Carry it to the coronary sinus c) Coronary sinus empties into the right atrium 19

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22 Heart Actions A. Cardiac cycle consists of 1. Atria beating in unison (atrial systole) 2. Followed by the contraction of both ventricles, (ventricular systole) 3. Then the entire heart relaxes for a brief moment (diastole) 22

23 A. Cardiac Cycle 1. Pressure within the heart chambers rises and falls with contraction and relaxation of atria and ventricles 2. When atria fill pressure in the atria is greater than that of the ventricles forcing the A-V valves open 3. Pressure inside atria rises further as they contract forcing the remaining blood into the ventricles 4. When ventricles contract pressure inside them increases sharply a) A-V valves forced closed b) aortic and pulmonary valves forced open c) papillary muscles contract pulling on chordae tendinae and prevent the backflow of blood through the A-V valves 23

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25 A. Heart Sounds 1. Due to vibrations in heart tissues as blood rapidly changes velocity within the heart 2. Heart sounds can be described as "lubb-dupp" 3. The first sound (lubb) occurs as ventricles contract and A-V valves are closing 4. The second sound (dupp) occurs as ventricles relax and aortic and pulmonary valves are closing 25

26 A. Cardiac Muscle Fibers 1. A mass of merging fibers that act as a unit is called a functional syncytium 2. One exists in the atria (atrial syncytium) 3. One in the ventricles (ventricular syncytium) 26

27 A. Cardiac Conduction System 1. Specialized cardiac muscle tissue conducting impulses throughout the myocardium 2. A self-exciting mass of specialized cardiac muscle called the sinoatrial node (S-A node or pacemaker) is located on the posterior right atrium 3. S-A node generates the impulses for the heartbeat 4. Impulses spread next to the atrial syncytium and it contracts 27

28 1. Impulses travel to the junctional fibers a) Junctional fibers are small b) Lead to atrioventricular node (A-V node) in the septum c) Allow the atria to contract before the impulse spreads rapidly over the ventricles 2. Branches of the A-V bundle give rise to Purkinje fibers leading to papillary muscles 3. These fibers stimulate contraction of the papillary muscles at the same time the ventricles contract 28

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30 A. Electrocardiogram 1. Record of the electrical changes that occur during a cardiac cycle 2. The first wave, the P wave, corresponds to the depolarization of the atria 3. The QRS complex corresponds to the depolarization of ventricles and hides the repolarization of atria 4. T waves end the ECG pattern and corresponds to ventricular repolarization 30

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32 A. Regulation of the Cardiac Cycle 1. The amount of blood pumped at any one time must adjust to the current needs of the body (more is needed during strenuous exercise) 2. The S-A node is innervated by branches of the sympathetic and parasympathetic divisions a) CNS controls heart rate b) Sympathetic impulses increase heart rate c) Parasympathetic impulses decrease heart rate 32

33 1. Baroreceptors detect changes in blood pressure and signal medulla oblongata 2. The cardiac control center of the medulla oblongata maintains a balance between the sympathetic and parasympathetic divisions 3. Impulses from the cerebrum or hypothalamus may also influence heart rate 4. Body temperature and the concentrations of certain ions may influence heart rate as well 33

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35 Blood Vessels A. Form a closed tube B. Carry blood away from the heart, to the cells, and back again C. Consist of 1. Arteries 2. Arterioles 3. Capillaries 4. Venules 5. Veins 35

36 A. Arteries and Arterioles 1. Arteries a) Strong, elastic vessels b) Adapted for carrying high-pressure blood 2. Arteries become smaller as they divide and give rise to arterioles 3. The wall of an artery consists of a) Endothelium b) Tunica media (smooth muscle) c) Tunica externa (connective tissue) 4. Vasoconstriction directed by the sympathetic impulses 5. Vasodilation results when impulses are inhibited 36

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38 A. Capillaries 1. Capillaries are the smallest vessels 2. Consist of only of a layer of endothelium through which substances are exchanged with tissue cells 3. Capillary permeability varies from one tissue to the next a) Generally more permeability in: 1) Liver 2) Intestines 3) certain glands b) Less permeability in: 1) Muscles 2) Brain (blood-brain barrier) 38

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40 1. The pattern of capillary density also varies from one body part to the next. 2. Areas with a great deal of metabolic activity have higher densities of capillaries 3. Precapillary sphincters a) Controlled by oxygen concentration in the area b) Regulate the amount of blood entering a capillary bed c) If blood is needed elsewhere in the body the capillary beds in less important areas are shut down 40

41 A. Exchanges in the Capillaries 1. Blood entering capillaries contain: a) High concentrations of oxygen and nutrients b) Diffuse through capillary walls into the tissues c) Diffusion driven by hydrostatic pressure 2. Plasma proteins remain in the blood due to their large size 3. Osmotic pressure of the blood causes much of the tissue fluid to return to venules 4. Lymphatic vessels collect excess tissue fluid and return it to circulation 41

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43 A. Venules and Veins 1. Venules leading from capillaries merge to form veins that return blood to the heart. 2. Veins a) Do not carry high-pressure blood b) Thinner and less muscular than arteries c) Have the same three layers as arteries 1) Endothelium 2) Tunica media (smooth muscle) 3) Tunica externa (connective tissue) d) Flap-like valves prevent backflow of blood e) Function as blood reservoirs 43

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45 Blood Pressure A. Blood pressure is the force of blood against the inner walls of blood vessels B. The term "blood pressure" usually refers to arterial pressure 45

46 A. Arterial Blood Pressure 1. Arterial blood pressure rises and falls following a pattern established by the cardiac cycle a) During ventricular contraction, arterial pressure is at its highest (systolic pressure) b) When ventricles are relaxing, arterial pressure is at its lowest (diastolic pressure) 2. The surge of blood that occurs with ventricular contraction can be felt as a pulse 46

47 A. Factors that Influence Arterial Blood Pressure 1. Heart action a) Dependent upon Stroke volume and heart rate (together called cardiac output) b) Increased cardiac output increases increased blood pressure 2. Blood volume a) Normally directly proportional to blood pressure b) Varies with age, body size, and gender 3. Resistance to flow a) Friction between blood and walls of blood vessels is peripheral resistance b) Peripheral resistance increases blood pressure increases 4. Blood viscosity a) Greater the viscosity greater resistance b) Greater resistance higher blood pressure 47

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49 A. Control of Blood Pressure 1. Blood pressure is determined by cardiac output and peripheral resistance 2. The body maintains normal blood pressure by adjusting cardiac output and peripheral resistance 3. Cardiac output depends on a) stroke volume and heart rate b) a number of factors can affect these actions 4. Blood volume entering the right atrium ~ the volume leaving the left ventricle 49

50 1. The cardiac center of the medulla oblongata responds to arterial blood pressure a) Arterial pressure increases parasympathetic impulses to slow heart rate are sent b) Arterial pressure drops sympathetic impulses to increase heart rate are sent 2. Emotional upset, exercise, and increased temperature can result in increased cardiac output and increased blood pressure 3. The vasomotor center of the medulla oblongata can adjust the sympathetic impulses to smooth muscles in arteriole walls, adjusting blood pressure 50

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52 1. CO2, O2, and H+ can affect peripheral resistance 2. Venous Blood Flow a) Partially the result of heart action b) Contractions of skeletal muscle squeeze blood back up veins one valve at a time c) Breathing movements and vasoconstriction of veins d) Differences in thoracic and abdominal pressures draw blood back up the veins 52

53 Paths of Circulation A. Pulmonary circuit 1. Blood from the right ventricle to the pulmonary arteries 2. To the lungs and alveolar capillaries 3. Pulmonary veins lead from the lungs to the left atrium B. Systemic circuit 1. The aorta and its branches lead to all body tissues 2. Veins return blood to the right atrium 53

54 Arterial System A. The aorta is the largest artery B. Principal Branches of the Aorta 1. Ascending aorta a) Right and left coronary arteries b) Lead to heart 2. Principal branches of the aortic arch a) Brachiocephalic b) Left common carotid c) Left subclavian arteries 54

55 1. Descending aorta (thoracic aorta) gives rise to many small arteries to the thoracic wall and thoracic viscera 2. Branches of the abdominal aorta: a) Celiac b) Superior mesenteric c) Suprarenal d) Renal e) Gonadal f) Inferior mesenteric g) Common iliac 55

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57 A. Arteries to the Head, Neck, and Brain 1. Include branches of the subclavian and common carotid arteries 2. Vertebral arteries a) Supply the vertebrae and their associated ligaments and muscles b) Unite to form a basilar artery which ends as two posterior cerebral arteries in the cranial cavity 3. Posterior cerebral arteries help form the circle of Willis providing alternate pathways through which blood can reach the brain 57

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59 1. The right and left common carotid arteries diverge into a) External carotid b) Internal carotid arteries 2. Near the base of the internal carotid arteries are the carotid sinuses 3. Carotid sinuses contain baroreceptors to monitor blood pressure 59

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61 A. Arteries to the Shoulder and Upper Limb 1. The subclavian artery continues into the arm where it becomes the axillary artery 2. In the shoulder region, the axial artery becomes the brachial artery 3. The brachial artery gives rise to the ulnar and radial arteries 61

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63 A. Arteries to the Thoracic and Abdominal Walls 1. Branches of the thoracic aorta and subclavian artery supply the thoracic wall with blood 2. Branches of the abdominal aorta and other arteries supply the abdominal wall with blood 63

64 A. Arteries to the Pelvis and Lower Limb 1. At the pelvic brim, the abdominal aorta divides to form the common iliac arteries that supply the pelvic organs, gluteal area, and lower limbs 2. The common iliac arteries divide into internal and external iliac arteries a) Internal iliac arteries supply blood to pelvic muscles and visceral structures b) External iliac arteries lead into the legs, where they become femoral, popliteal, anterior tibial, and posterior tibial arteries 64

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66 Venous System A. Veins return blood to the heart after exchange of substances in the tissues B. Venous Pathways 1. Larger veins parallel the courses of arteries and are named accordingly 2. Smaller veins take irregular pathways and are unnamed 3. Veins from the head and upper torso drain into the superior vena cava 4. Veins from the lower body drain into the inferior vena cava 5. The vena cavae merge to join the right atrium 66

67 A. Veins from the Head, Neck, and Brain 1. The jugular veins drain the head 2. Unite with the subclavian veins to form the brachiocephalic veins 67

68 A. Veins from the Upper Limb and Shoulder 1. The upper limbs are drained by superficial and deep veins 2. Major superficial veins a) Basilic veins b) Cephalic veins 3. The major deep veins include a) Radial b) Ulnar c) Brachial d) Axillary veins 68

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70 A. Veins from the Abdominal and Thoracic Walls Tributaries of the brachiocephalic and azygos veins drain the abdominal and thoracic walls B. Veins from the Abdominal Viscera 1. Blood draining from the intestines a) Enters the hepatic portal system b) Flows to the liver then into general circulation 2. The liver processes the nutrients absorbed during digestion and removes bacteria 70

71 1. Hepatic veins drain the liver 2. Gastric veins drain the stomach 3. Superior mesenteric veins lead from the small intestine and colon 4. Splenic vein leaves the spleen and pancreas 5. Inferior mesenteric vein carries blood from the lower intestinal area 71

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73 A. Veins from the Lower Limb and Pelvis 1. Deep and superficial veins drain the leg and pelvis 2. Deep veins include a) Anterior and posterior tibial veins b) Unite into the popliteal vein and femoral vein 3. Superficial veins include: a) Small saphenous veins b) Great saphenous veins 4. These veins all merge to empty into the common iliac veins 73

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