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Chapter 11

Chapter 11. The Cardiovascular System. Introduction. The cardiovascular system consists of heart, blood vessels, and blood Sends blood to Lungs for oxygen Digestive system for nutrients CV system also circulates waste products to certain organ systems for removal from the blood.

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Chapter 11

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  1. Chapter 11 The Cardiovascular System

  2. Introduction • The cardiovascular system consists of heart, blood vessels, and blood • Sends blood to • Lungs for oxygen • Digestive system for nutrients • CV system also circulates waste products to certain organ systems for removal from the blood

  3. Functions of the Heart • Generating blood pressure • Routing blood • Heart separates pulmonary and systemic circulations • Ensuring one-way blood flow • Heart valves ensure one-way flow • Regulating blood supply • Changes in contraction rate and force match blood delivery to changing metabolic needs

  4. The Heart: Structures • Cone-shaped organ about the size of a loose fist • In the mediastinum • Extends from the level of the second rib to about the level of the sixth rib • Slightly left of the midline

  5. The Heart: Structures (cont.) • Heart is bordered: • Laterally by the lungs • Posteriorly by the vertebral column • Anteriorly by the sternum • Rests on the diaphragm inferiorly

  6. Size, Shape, Location of the Heart • Size of a closed fist • Shape • Apex: Blunt rounded point at the bottom pointing towards left hip. • Base: Flat part at opposite of end of cone • Located in thoracic cavity in mediastinum

  7. Coverings of the Heart: Anatomy • Pericardium – a double-walled sac around the heart composed of: • A superficial fibrous pericardium • A deep two-layer serous pericardium • The parietal layer lines the internal surface of the fibrous pericardium • The visceral layer or epicardium lines the surface of the heart • They are separated by the fluid-filled pericardial cavity that helps to minimize friction during heart beats.

  8. Pericardial Layers of the Heart Figure 18.2

  9. Heart walls: Epicardium (visceral layer) Outermost layer Fat to cushion heart Myocardium Middle layer Primarily cardiac muscle Actually contracts Endocardium Innermost layer Thin and smooth Stretches as the heart pumps The Heart: Structures (cont.) Click for Larger View

  10. Four chambers Two atria Upper chambers Left and right Separated by interatrial septum Two ventricles Lower chambers Left and right Separated by interventricular septum The Heart: Structures (cont.) • Atrioventricular septum separates the atria from the ventricles Click for View of Heart

  11. The Heart: Structures (cont.) • Tricuspid valve – prevents blood from flowing back into the right atrium when the right ventricle contracts • Bicuspid valve – prevents blood from flowing back into the left atrium when the left ventricle contracts • Pulmonary valve – prevents blood from flowing back into the right ventricle • Aortic valve – prevents blood from flowing back into the left ventricle Click for View of Heart

  12. Location of Heart Valves

  13. Heart Valves

  14. The Heart: Blood Flow Oxygenated blood out to body Deoxygenated blood in from body Oxygenated blood in lungs Deoxygenated blood out to lungs Atria Contract Ventricles Contract

  15. Right Atrium TricuspidValve Right Ventricle PulmonaryValve Lungs Body AorticSemilunarValve BicuspidValve Left Ventricle Left Atrium The Heart: Blood Flow (cont.)

  16. Systemic and PulmonaryCirculation

  17. Myocardial Thickness and Function Thickness of myocardium varies according to the function of the chamber Atria are thin walled, deliver blood to adjacent ventricles Ventricle walls are much thicker and stronger • right ventricle supplies blood to the lungs (little flow resistance) • left ventricle wall is the thickest to supply systemic circulation

  18. Thickness of Cardiac Walls Myocardium of left ventricle is much thicker than the right.

  19. Pathway of Blood Through the Heart and Lungs Figure 18.5

  20. Right atrium contracts Tricuspid valve opens Blood fills right ventricle Right ventricle contracts Tricuspid valve closes Pulmonary semilunar valve opens Blood flows into pulmonary artery Left atrium contracts Bicuspid valve opens Blood fills left ventricle Left ventricle contracts Bicuspid valve closes Aortic semilunar valve opens Blood pushed into aorta The Heart: Cardiac Cycle • One heartbeat = one cardiac cycle • Atria contract and relax • Ventricles contract and relax

  21. Cardiac Cycle

  22. The Heart: Cardiac Cycle (cont.) • Influenced by • Exercise • Parasympathetic nerves • Sympathetic nerves • Cardiac control center • Body temperature • Potassium ions • Calcium ions

  23. The Heart: Heart Sounds • One cardiac cycle – two heart sounds (lubb and dubb) when valves in the heart snap shut • Lubb – First sound • When the ventricles contract, the tricuspid and bicuspid valves snap shut • Dubb – Second sound • When the atria contract and the pulmonary and aortic valves snap shut • Third heart sound (occasional) • Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

  24. Group of structures that send electrical impulses through the heart Sinoatrial node (SA node) Wall of right atrium Generates impulse Natural pacemaker Sends impulse to AV node Atrioventricular node (AV node) Between atria just above ventricles Atria contract Sends impulse to the bundle of His Bundle of His Between ventricles Two branches Sends impulse to Purkinje fibers Purkinje fibers Lateral walls of ventricles Ventricles contract Link to Diagram The Heart: Cardiac Conduction System

  25. Electrocardiogram • Action potentials through myocardium during cardiac cycle produces electric currents than can be measured • Pattern • P wave • Atria depolarization • QRS complex • Ventricle depolarization • Atria repolarization • T wave: • Ventricle repolarization

  26. Heart Excitation Related to ECG Figure 18.17

  27. Cardiac Arrhythmias • Tachycardia: Heart rate in excess of 100bpm • Bradycardia: Heart rate less than 60 bpm • Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration • Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

  28. Alterations in Electrocardiogram

  29. Events during Cardiac Cycle

  30. Mean Arterial Pressure (MAP) • Average blood pressure in aorta • MAP=CO x PR • CO is amount of blood pumped by heart per minute • CO=SV x HR • SV: Stroke volume of blood pumped during each heart beat • HR: Heart rate or number of times heart beats per minute • Cardiac reserve: Difference between CO at rest and maximum CO • PR is total resistance against which blood must be pumped

  31. Chapter 18, Cardiovascular System Cardiac Output: Example • CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat) • CO = 5250 ml/min (5.25 L/min)

  32. Strongest of the blood vessels Carry blood away from the heart Under high pressure Vasoconstriction Vasodilation Arterioles Small branches of arteries Aorta Takes blood from the heart to the body Coronary arteries Supply blood to heart muscle Blood Vessels: Arteries and Arterioles

  33. Blood under no pressure in veins Does not move very easily Skeletal muscle contractions help move blood Sympathetic nervous system also influences pressure Valves prevent backflow Venules Small vessels formed when capillaries merge Superior and inferior vena cava Largest veins Carry blood into right atrium Blood Vessels: Veins and Venules

  34. Blood Vessels: Capillaries • Branches of arterioles • Smallest type of blood vessel • Connect arterioles to venules • Only about one cell layer thick • Oxygen and nutrients can pass out of a capillary into a body cell • Carbon dioxide and other waste products pass out of a body cell into a capillary

  35. Apply Your Knowledge ANSWER: C Match the following: __ Tricuspid valve A. Two branches; sends impulse to Purkinje fibers __ Bicuspid valve B.Covering of the heart and aorta __ Pericardium C. Between the right atrium and the right ventricle __ SA node D. In the lateral walls of ventricles __ Bundle of His E. Natural pacemaker __ Purkinje fibers F. Between the left atrium and the left ventricle F B E A D Good Job!

  36. Apply Your Knowledge How do arteries control blood pressure? ANSWER: The muscular walls of arteries can constrict to increase blood pressure or dilate to decrease blood pressure. Correct!

  37. Gross Anatomy of Circulatory System

  38. Chapter 18, Cardiovascular System Coronary Circulation • Coronary circulation is the functional blood supply to the heart muscle itself • Collateral routesensure blood delivery to heart even if major vessels are occluded

  39. Coronary Circulation: Arterial Supply Figure 18.7a

  40. Chapter 18, Cardiovascular System Coronary Circulation: Venous Supply Figure 18.7b

  41. Circle of Willis = Cerebral Arterial Circle = Ring of vessels surrounding pituitary gland - supplies cerebrum and cerebellum Brain can receive blood from carotids or vertebrals (significance?) ic v Fig 22.13

  42. Circle of Willis

  43. Pulmonary Circuit Right ventricle into pulmonary trunk to pulmonary arteries to lungs Return by way of 4 pulmonary veins to left atrium Fig 22.9

  44. Major Systemic Arteries • The Systemic Circuit • Contains 84% of blood volume • Supplies entire body: except for pulmonary circuit • Supplies entire body: • except for Figure 21-20

  45. Systemic Arteries • Blood moves from left ventricle: • into ascending aorta

  46. The Aorta • The ascending aorta: • rises from the left ventricle • curves to form aortic arch • turns downward to become descending aorta • Branches of the Aortic Arch deliver blood to head and neck: • brachiocephalic trunk • left common carotid artery • left subclavian artery

  47. The Common Carotid Arteries • Carry blood to head and neck • Each common carotid divides into: • external carotid artery-Supplies structures of: Neck, lower jaw, face • internal carotid artery-Enters skull and divides into: opthalmic artery, anterior cerebral artery, middle cerebral artery

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