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Chapter 20

Chapter 20. Cardiovascular System: The Heart. Cardiovascular System: The Heart. Fxns of the heart Size, Shape, & Location of the heart Anatomy of the heart Route of blood flow thru the heart Histology Electrical Properties Cardiac Cycle Mean Arterial BP Regulation of the heart

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Chapter 20

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  1. Chapter 20 Cardiovascular System: The Heart AP2 Chap. 20: Cardio Syst-Heart

  2. Cardiovascular System: The Heart • Fxns of the heart • Size, Shape, & Location of the heart • Anatomy of the heart • Route of blood flow thru the heart • Histology • Electrical Properties • Cardiac Cycle • Mean Arterial BP • Regulation of the heart • Heart & Homeostasis • FX of aging on the heart AP2 Chap. 20: Cardio Syst-Heart

  3. Cardiovascular System • Heart is actually 2 pumps: • 1st pump receives O2poor blood from the body and pumps it to the lungs • Pulmonary Circulation • 2nd pump receives O2rich blood from the lungs and pumps it to the body • Systemic Circulation Fig. 20.1 pg 679 AP2 Chap. 20: Cardio Syst-Heart

  4. I. Functions of the Heart AP2 Chap. 20: Cardio Syst-Heart

  5. I. Fxns of the heart Pg 680 Figure 20.2a • Generating BP (blood pressure) • Contractions of the ♥ generate the BP, wh/ is responsible for blood mvment thru vessels • Routing Blood • ♥ is the interchange between pulmonary & systemic circulation, thus insuring better oxygenation of bld going to tissues • Insuring One-Way blood flow • Valves of the heart are 1-way thus insuring no backflow • Regulating Blood Supply • As metabolic needs of the tissues D the heart can D rate & force of contraction to aid the tissues AP2 Chap. 20: Cardio Syst-Heart

  6. II. Size, shape, & location of the ♥ AP2 Chap. 20: Cardio Syst-Heart

  7. II. Size, shape, & location of the ♥ Front View Pg 684 Figure 20.5 a • ~ size of a closed fist, shaped like a blunt cone • Lies obliquely within the mediastinum with its base directed back and superior & apex coming forward inferiorly to the left. Posterior View Pg 685 Figure 20.5 c AP2 Chap. 20: Cardio Syst-Heart

  8. III. Anatomy of the ♥ Pericardium Heart Wall External Anatomy & Coronary Circulation Heart Chambers & Valves AP2 Chap. 20: Cardio Syst-Heart

  9. III. Anatomy of the heart: Pericardium • A sac surrounding the heart made of 2 layers that can also be called the pericardial sac. • It can D in size to accommodate more fluid or D in heart size • Fibrous Pericardium • Aids in holding the heart in place • Serous Pericardium • Reduces friction as the heart beats and is made up of 3 regions: • Parietal Pericardium • Lies just under & Lines #1 • Pericardial Cavity • Lies between a) & c) filled with pericardial fluid • Helps reduce friction as heart moves in the pericardial sac • Visceral Pericardium • Lines the exterior surface of the heart Pg 681 Figure 20.3

  10. III. Anatomy of the Heart: Heart Wall Pg 682 Figure 20.4 • Has 3 main layers: • Epicardium • Outermost layer that protects from friction • Myocardium • Middle layer responsible for contraction • Endocardium • Innermost layer & protects from friction created by flowing blood • Simple squamous epi over CT • Heart valves are modified Endocardium • Atria (top chambers) • Mainly smooth w/some raised areas called pectinate muscles that are separated by smooth parts by a ridge called cristae terminalis • Ventricles (bottom chambers) • Have large ridges called trabeculae carneae

  11. III. Anatomy of the Heart: External Anatomy & Coronary Circulation Right Auricle Left Auricle There is also a posterior Interventricular Sulcus AP2 Chap. 20: Cardio Syst-Heart

  12. III. Anatomy of the Heart: External Anatomy & Coronary Circulation These veins come from the body with O2 poor blood and empty into the right atrium + Coronary Sinus These veins come from the lungs with O2 Rich blood and empty into the left atrium.

  13. III. Anatomy of the Heart: External Anatomy & Coronary Circulation These arteries exit the heart carrying O2 poor blood to the lungs This major arteryexits the heart carrying O2 rich blood to the body.

  14. III. Anatomy of the Heart: External Anatomy & Coronary Circulation Blood flow to the coronary blood vessels isn’t continuous. • Cardiac Muscle contracts blood vessels get compressed & blood doesn’t readily flow • Cardiac Muscle relaxes  Blood vessels aren’t compressed & blood flow thru the coronary blood vessels resumes AP2 Chap. 20: Cardio Syst-Heart

  15. III. Anatomy of the Heart: External Anatomy & Coronary Circulation Major Arteries (A) supplying heart tissue • Lie within the coronary sulcus & interventricular sulci. • Rt. & Lt. Coronary Arteries (CA) • Major A’s supplying blood to heart • Exit the aorta just as it leaves the heart and lie w/in the coronary sulcus • Right is smaller in diameter than left • Branches of the Rt.CA • Rt. Marginal A • Supply bld to lat’l wall of the rt ventricle • Post’rInterventricular A. • Supplies bld to the posterior & inferior region of the heart • Branches of the Lt.CA • Ant. Interventricular A • Supplies most of the ant. heart • Left Marginal A • Supplies bld to the lat. lt. ventricle • Circumflex A • supplies most of the posterior heart. Pg 685 Figure 20.6a

  16. III. Anatomy of the Heart: External Anatomy & Coronary Circulation Pg 685 Figure 20.6a Major veins (V) draining the heart tissue • Great Cardiac V • Major vein draining the tissue on the left side of the heart • Small Cardiac Vein • Drains the right margin of the heart • Both empty into the Coronary Sinus • Empties into the right atrium AP2 Chap. 20: Cardio Syst-Heart

  17. Interatrial Septum • piece of tissue that separates L from R atrium • Foremen Ovale/ Fossa Ovalis • Ovale, an opening between the atria in a embryo & fetus to bypass pulmonary circulation that seals and forms the Ovalis III. Anatomy of the heart: Chambers & Valves Right Atrium • Upper R chamber • 3 openings: • Superior Vena Cava • Drains upper body • Inferior Vena Cava • Drians Lower Body • Coronary Sinus • Drains the Heart Pg 686 Figure 20.7 • Left Atrium • Upper L chamber • 4 uniform openings: • Pulmonary Veins • 2 from each lung • Drains lungs after getting O2

  18. Interventricular Septum • Thick muscular piece of tissue that separates L from R ventricle • Each ventricle has 1 large, superiorly placed outflow route near midline III. Anatomy of the heart: Chambers & Valves Right Ventricle • Lower R chamber • Opens to the pulmonary trunk Pg 686 Figure 20.7 • Left Ventricle • Lower L chamber • Opens to the aorta

  19. Pulmonary Valve Between the R ventricle and the Pulmonary Trunk • Aortic Valve Between L ventricle and the Aorta III. Anatomy of the heart: Chambers & Valves Semilunar Valves • Composed of 3 pocket like semilunar cusps/flaps the free inner borders meet in the center of the arteries to block blood flow.

  20. Tricuspid Valve Between the R atrium and R ventricle 3 cusps/flaps • Bicuspid Valve Between the L atrium and L ventricle 2 cusps/flaps III. Anatomy of the heart: Chambers & Valves Atrioventricular Valves • Composed of cusps/flaps allow blood to flow from atrium to the ventricles but because of design help to prevent back flow

  21. Blood pushing out of the ventricle causes enough pressure to push the semilunar valves open while at the same time causing the atrioventricular valves to seal with the help of the chordae tendineae and the papillary muscle. As the ventricle relaxes the semilunar valves get sucked back effectively sealing them while the atrioventricular valves open • Chordae Tendineae • Strong CT strings that connect to the cusps of AV-valves • Papillary Muscle • Cone-shaped muscular pillars, that contract when V contract & prevent flaps from protracting Pg 687 Figure 20.9

  22. IV. Route of blood flow thru the heart AP2 Chap. 20: Cardio Syst-Heart

  23. Figure 20.10 Pg 688 AP2 Chap. 20: Cardio Syst-Heart

  24. Cardiac Cycle • Arteries: • Carries blood away from the heart • Veins: • Carries blood toward the heart • BLUE: • Deoxygenated blood • RED • Oxygenated blood AP2 Chap. 20: Cardio Syst-Heart

  25. Lung Tissue Body Tissue Left Atrium Right Atrium Left Ventricle Right Ventricle AP2 Chap. 20: Cardio Syst-Heart

  26. Bicuspid Valve Tricuspid Valve Aortic Semilunar Valve Pulmonary Semilunar Valve AP2 Chap. 20: Cardio Syst-Heart

  27. Pulmonary Arteries Aorta Coronary Arteries Aorta Inferior Vena Cava Pulmonary Veins Pulmonary Trunk Superior Vena Cava Coronary Sinus AP2 Chap. 20: Cardio Syst-Heart

  28. Body Tissue Inferior Vena Cava • Deoxygenated blood drains into the Right atrium via the: • The inferior vena cava drains the lower body tissue • The superior vena cava drains the upper body tissue • The coronary sinus drains the heart tissue Superior Vena Cava Coronary Sinus

  29. Right Atrium • The right atrium fills with deoxygenated blood AP2 Chap. 20: Cardio Syst-Heart

  30. Right Atrium Tricuspid Valve • Deoxygenated blood goes from the right atrium thru the tricuspid valve into the right ventricle.

  31. Right Ventricle • The right ventricle fills with deoxygenated blood

  32. Pulmonary Semilunar Valve Pulmonary Trunk Right Ventricle • Deoxygenated blood is squeezed from the right ventricle thru the pulmonary semilunar valve into the pulmonary trunk.

  33. Pulmonary Arteries Lung Tissue Pulmonary Trunk • The pulmonary trunk splits into the right and left pulmonary arteries carrying deoxygenated blood in to the right and left lungs respectively to pick up oxygen and drop off carbon dioxide.

  34. Lung Tissue • In the lungs CO2 is exchanged for O2 AP2 Chap. 20: Cardio Syst-Heart

  35. Lung Tissue Left Atrium Pulmonary Veins • The right and left pulmonary veins carry the newly oxygenated blood back to the left atrium from the right and left lungs respectively.

  36. Left Atrium • Theleft atrium fills with freshly oxygenated blood.

  37. Left Atrium Bicuspid Valve Left Ventricle • The oxygenated blood is pumped from the left atrium thru the bicuspid valve into the left ventricle.

  38. Left Ventricle • Theleft ventricle fills with freshly oxygenated blood.

  39. Aorta Aortic Semilunar Valve Left Ventricle • Oxygenated blood is squeezed from the left ventricle thru the aortic semilunar valve into the aorta.

  40. Aorta Coronary Arteries Body Tissue Aorta Aortic Semilunar Valve • The aorta splits into the right and left coronary arteries carrying oxygenated blood to the heart tissue.

  41. Aorta Coronary Arteries Body Tissue Aorta • Then the aorta continues to carry the oxygenated blood to the body tissues.

  42. V. Histology Heart Skeleton Cardiac Muscle Conducting System AP2 Chap. 20: Cardio Syst-Heart

  43. V. Histology: Heart Skeleton • Consists of a plate of fibrous CT that serves 3 purposes: • Supports both the semilunar & atrioventricular valves to insure they don’t collapse • Acts as electrical insulation between the atria & ventricles • Acts as a point of attachment for cardiac muscle Figure 20.11 Pg 690 AP2 Chap. 20: Cardio Syst-Heart

  44. V. Histology: Cardiac Muscle (CM) Figure 20.11 Pg 690 • CM cells joined by intercalated disks that allow action potentials to move directly from 1 cell to the next, thus cardiac muscle cells fxn as a unit • Intercalated disks are a combo of desmosomes (wh/hold cells together) & gap junctions (wh/allow for cell to cell communication) • CM cells have a slow onset as well as period of contraction due to Ca2+ mvmt along myofibrils. • Has a good blood supply to support aerobic respiration • ATP prod’d with: • Glucose, Fatty Acids, Lactic Acid • CM doesn’t develop O2-debt • Elongated, branching cells w/ 1 or 2 centrally located nuclei. • Like skeletal muscle actin & myosin are organized to form sarcomeres. Arrangement of both the Smooth ER & transverse tubules varies but fxns essentially the same.

  45. V. Histology: Conducting System (CS) • Consists of modified CM-cells that form 2 nodes & a conducting bundle. (both of which are made up of small diameter cells to slow action potential) • SA-Node • AV-Node • SA-node initiates action potentials that spread across the atria & cause them to contract • At the AV-node action potential slows allowing atria to complete contraction & ventricles to fill • Next it follows along the AV bundle, Rt & Lt bundle branches & Purkinje fibers. • This causes the contraction of the ventricles from the apex of the heart toward the base • SA-node •  • AV-node •  • AV bundle •  • Rt & Lt Bundle braches •  • Purkinje fibers

  46. V. Histology: Conducting System (CS) • The CS of the heart consists of modified CM-cells that form 2 nodes & a conducting bundle. • SA-Node medial to the opening of the superior vena cava • A.k.a. Pacemaker (generates spontaneous action potentials) • AV-Node- medial to the tricuspid valve SA-node AV-node AV bundle Rt & Lt Bundle braches Purkinje fibers

  47. VI. Electrical Properties Action potentials Autorhythmicity of cardiac muscle Refractory periods of cardiac muscle Electrocardiogram AP2 Chap. 20: Cardio Syst-Heart

  48. VI. Electrical Properties • CM have a resting membrane potential (RMP) • Depends on the permeability of the PM • Low permeability to Na+ and Ca2+ • Higher permeability to K+ • Once their threshold is reached….an Action Potential results AP2 Chap. 20: Cardio Syst-Heart

  49. VI. Electrical Properties: Action Potentials Permeability D’s during and action potential in CM • Depolarization Phase • Voltage-Gated (VG) Na+ channels open (Na+ rushes in) • VG K+ channels close (K can’t get out) • VG Ca2+ channels begin to open (Ca2+ goes in) • Early Repolarization & Plateau Phase • VG Na+ channels close (Na+ can’t get in) • Some VG K+ channels open causing “early” repolarization • K+ goes out in a rush • VG Ca2+ channels are open, prod’ing the plateau by further slowing repolarization (Ca2+ coming in) • Final Repolarization Phase • VG Ca2+ channels close • Many VG K+ channels open Action potentials in CM last longer than in SM SM 2 ms CM 200-500ms

  50. VI. Electrical Properties: Action Potentials • Gap junctions w/in intercalated disks do allow action potentials to transfer between CM-cells, but they do slow the rate of the action potential between them. • Calcium-induced calcium release (CICR) • Movement of the Ca2+ into the cell stimulates the release of Ca2+ from the sarcoplasmic reticulum • Ca2+ binding facilitates the interaction between actin & myosin to produce the contraction of CM. AP2 Chap. 20: Cardio Syst-Heart

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