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A&P -The Cardiovascular System
The cardiovascular system consists of two circuits - the pulmonary circuit and the systemic circuit. In the pulmonary circuit, deoxygenated blood is pumped from the right side of the heart to the lungs where it receives oxygen and returns to the left side of heart. In the systemic circuit, oxygenated blood is pumped from the left side of the heart through the aorta to the entire body, then returns to the right side of the heart. The heart is made up of four chambers - two upper atria which collect blood and two lower ventricles which pump blood out of the heart. It is surrounded and protected by membranes and contains valves that allow blood to flow in only one direction.
A&P -The Cardiovascular System
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- 2. Location of theheart Size: • Size of a fist and weighs less than 1 lb. Location: • Mediastinum • Rests on the diaphragm • 2/3 of the heart lies left of the midline • Apex – directed anteriorly, inferiorly, and left • Base – posteriorly, superiorly, and left
- 3. Outer Layers ofthe Heart Pericardium: • Double-layered sac that anchors and protects heart Parietal pericardium: • membrane around heart’s cavity Visceral pericardium: • membrane on heart’s surface
- 4. Pericardium Pericardium • The membranethat surrounds and protects the heart • Two Main Parts: • Fibrous Pericardium • Serous Pericardium
- 5. Outer Layers ofthe Heart
- 6. Pericardium Fibrous Pericardium: • Superficiallayer • Composed of tough inelastic dense irregular connective tissue • Resembles a bag that rests on and attaches to the diaphragm • Prevents over stretching of the heart • Provides protection from the mediastinum
- 7. Pericardium Serous Pericardium • Deeperand thinner layer of the pericardium Two Layers: • Parietal Layer • Visceral Layer (aka: epicardium) • Adheres to the surface of the heart Pericardial Fluid • Between parietal and visceral layers • Thin film fluid • Slippery secretion of the pericardial cells provides lubrication for the heart as it expands and contracts • Prevents pericardial friction
- 8. Parietal pericardium • Partof the Serous Pericardium • Outer layer of the serous pericardium • In contact with the superfical layer called – the fibrous pericardium
- 9. Layers of theHeart Wall 3 Layers of the Heart Wall Superficial to deep: 1. Epicardium 2. Myocardium 3. Endocardium
- 10. Layers of theHeart Wall Epicardium: • Outer most layer • Transparent surface layer of heart (outside) • Remember: • this is also the visceral layer of the pericaridum • Composed of delicate, smooth slippery connective tissue
- 11. Layers of theHeart Wall Myocardium • (myo=muscle) • Cardiac Muscle Tissue • Makes up the bulk of the heart • Responsible for heart contraction – pumping action • Striated like skeletal muscle • Involuntary action – autonomic nervous system Summary: • The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES) and connected to form the contractile pump to generate blood flow
- 12. Layers of theHeart Wall Endocardium • (Endo=within) • Provides the smooth lining for the chambers of the heart • Covers the values of the heart • Continuous with the blood vessels of the heart The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are similar to the endothelial cells
- 13. Layers of theHeart Wall
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- 15. Chambers of theHeart 4 Chambers of the Heart: • Left atrium (LA) • Right atrium (RA) • Left ventricle (LV) • Right ventricle (RV)
- 16. Chambers of theHeart Atria • (atria = entry hall) • Two superior chambers (Left and Right Atria) • Blood returns to the heart into the atria Right Atrium Left Atrium Receives Un-oxygenated (O2-) Blood From: • Superior Vena Cava • Inferior Vena Cava Receives Oxygenated (O2+) Blood From: • Pulmonary Veins
- 17. Chambers of theHeart The Atria: • Upper portion of heart (the base) • Holding chambers for returning blood • Small, thin walled • Less muscular than the ventricles • Contracts to push blood into ventricles Interatrial septum: separates right and left atria
- 18. Chambers of theHeart Ventricles • Lower portion of the heart (the apex) • Pumping chambers • The ventricles contract to push blood out of the heart • Large muscular chambers that collect and expel blood received from an atrium • Thick muscular, strong walled • Contract forcefully to propel blood out of heart Interventricular septum: separates right and left ventricles
- 19. Chambers of theHeart Right Ventricle • Pumps Deoxygenated blood received from the body via the Right Atrium into the Pulmonary artery • The Pulmonary Artery is the passageway for deoxygenated blood to travel into the lungs to receive oxygen Left Ventricle • Pumps Oxygenated blood into the systemic circulation through the Aorta • Some blood from the aorta flows into the coronary arteries to supply the heart with oxygenated blood • Left ventricle works harder than the right…pumps blood throughout the system
- 20. Chambers of theHeart
- 21. VALVES OF THEHEART
- 22. Valves of theHeart • 4 values of the heart • 2 on the right side / 2 on the left side • Atrioventricular valves (AV): • Between atria and ventricles • 2 Atrioventticular (One Right: Tricuspid / One Left: Bicuspid) • Semilunar valves: • Pulmonary: base of pulmonary trunk (right side) • Aortic: base of aorta (left side) • Valves are structures that permit One Way Blood Flow
- 23. Valves of theHeart Tricuspid Valve: • Right Side of the Heart • One of two atrioventricular valves, which separates the atria and ventricular chambers - • Separates Right Atrium from Right Ventricle • Blood passes through the tricuspid valve from the right atrium to the right ventricle • Tri - has three leaflets and three papillary muscles • Opens during atria systole (contraction) permitting blood to enter the right ventricle
- 24. Valves of theHeart Pulmonary Valve (aka: Pulmonic Valve) • Right side of the heart • Semilunar value (semi = half, luna moon shaped), which has three cusps • Pulmonary valve opens in ventricular systole, when the pressure in the right ventricle rises above the pressure in the pulmonary artery • Resides between right ventricle the pulmonary artery • Deoxygenated blood is pumped from the right ventricle through the Pulmonary value and the pulmonary artery to the lungs to receive oxygen
- 25. Valves of theHeart • Pulmonary Valve
- 26. Valves of theHeart Bicuspid Valve (Aka: Mitral Valve) • Left side of the Heart • Atrioventricular valve – separates the atria and ventrriculuar chambers • During diastole, the mitral valve opens as a result of increased pressure from the left atrium • Opening facilitates the passive flow of blood from the left atria into the left ventricle • The apical pulse is heard from the bicuspid valve closing
- 27. Valves of theHeart Chordae tendineae • On the bicuspid valve chordae tendinea are attached to both leaflets • Thus, when the left ventricle contracts, the intraventricular pressure forces the valve to close • The cordea tendineae are the tendons that keep the leaflets together and prevent the valve from opening in the wrong direction (regurgitation – back into the atria)
- 28. Valves of theHeart Bicuspid Valve OPEN • Blood flows from LA into LV. • Aortic semilunar valve is closed. • Tension on chordae tendineae is low. Bicuspid Valve CLOSED • Blood flows from LV into aorta. • Aortic semilunar valve is open. • Tension on chordae tendineae is high.
- 29. Valves of theHeart Aortic Valve • Semi-lunar valve • Open when pressure in the ventricles exceeds pressure in the arteries • During ventricular systole: Pressure rises in the left ventricle When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens Blood exits the left ventricle and is pumped into the aorta When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close
- 30. Valves of theHeart
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- 32. Circulation Pulmonary circuit: • Rightside of the heart: • Oxygen poor blood is received from the body • Blood is O2 poor, CO2 rich • Blood is transported from the Right Side of the Heart (right atrium and right ventricle) to the lungs via the Pulmonary Artery, where blood receives oxygen and release CO2
- 33. Circulation Pulmonary Circuit Right Atrium: •receives blood from 3 sources: • Superior vena cava • Inferior vena cava • Coronary Sinus Superior vena cava: • Returns blood from above diaphragm (head, neck, thorax, upper limbs) Inferior vena cava: • Returns blood from below diaphragm cavity and lower limbs coronary sinus: • Returns blood from myocardium
- 34. Circulation Pulmonary Circuit Right Ventricle •Receives oxygen poor blood from the right atrium via the tricuspid valve (atrioventricular valve) • Opens into the pulmonary trunk Pulmonary trunk: • Splits into right and left pulmonary arteries Pulmonary arteries: • Transports O2 poor blood away from heart to lungs to receive oxygen and release Co2
- 35. Circulation Pulmonary Circuit Summary •Pulmonary circulation is the half portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart (left atrium). • Pulmonary circulation the flow of blood from the right ventricle through the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen, and back through the pulmonary vein to the left atrium.
- 36. Circulation Systemic circuit Left Sideof the Heart • Pumps oxygenated blood from the left ventricle of the heart to body (organs, tissues, muscles) • Blood is O2 rich
- 37. Circulation Systemic circuit Left Atrium: •There are 4 openings caused by the pulmonary veins returning oxygenated blood from the lungs Left Ventricle: • Receives O2+ blood from left atrium via the mitral valve aorta • Thicker myocardial walls than the right ventricle • Contracts more forcefully to eject blood against systemic pressure (systemic vascular resistance) • Pumps blood into the aorta via the semi-lunar aortic vlavles Aorta: carries blood from left ventricle to body (system)
- 38. Circulation 1. Right Atrium- receives O2- blood from body 2. Tricuspid valve – opens and permits blood to flow into the Right ventricle 3. Right Ventricle - contracts and pumps blood through the Pulmonary semilunar valve to the Pulmonary trunk 4. O2- blood travels through the Pulmonary arteries to the lungs 5. Lungs – oxygenate blood 6. Pulmonary veins return oxygenated blood to the Left Atrium 7. Left Atrium – receives O2+ blood from the lungs 8. Bicuspid valve – valve opens and permits blood to drain into the Left Ventricle 9. Left Ventricle copntracts and pumps oxygenated blood to the - Aortic semilunar valve 10. Aorta 11. Body
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- 42. Coronary Circulation Coronary Arteries: •Supply the myocardium with oxygenated blood • Originate from base of aorta • While the heart is contracting little blood flows through the coronary arteries, squeezed shut due to myocardial expansion • Blood is received to the myocardia when the heart relaxes • Blockage of the coronary arties from thrombosis result in ischemia and cause the heart muscle cells (myocardia) to die
- 43. Coronary Circulation Two CoronaryArties: Right Coronary Artery • Marginal Branch • Supplies the myocardium of the right ventricle with oxygenated blood Left Coronary Artery • Left Anterior Descending (LAD) • Circumflex Branch • Supplies oxygenated blood to the myocardial walls of the Left Ventricle and Atrium
- 44. Coronary Circulation Coronary Veins CoronarySinus • Most blood drains from the coronary sinus located in the coronary sulcus on the posterior side of the heart • Veins that carry deoxygenated blood to the coronary sinus: • Great cardiac vein • Middle cardiac vein • Small cardiac vein • Anterior cardiac vein
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- 47. Cardiac Muscle Structural Proteins: •Like skeletal muscle, the primary structural proteins of cardiac muscle are actin and myosin, however, in contrast to skeletal muscle, cardiac muscle cells may be branched instead of linear and longitudinal. • T-Tubules • Another difference between cardiac muscle and skeletal muscle is that the T-tubules in the cardiac muscle are larger, broader and run along the Z-Discs. • There are also fewer T-tubules in comparison with skeletal muscle
- 48. Cardiac Muscle Intercalated discs •Junctions between cardiac muscles • Contain many gap junctions which permit one cardiac muscle fiber to touch the cytoplasm of another • Intercalated discs also support the rapid spread of action potentials and the synchronized contraction of the myocardium Gap Junctions • Allow muscle action potential to conduct from one cardiac muscle fiber to another
- 49. Cardiac Muscle Calcium • Incontrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur • Like skeletal muscle, the initiation and upshoot of the action potential in ventricular muscle cells is derived from the entry of sodium ions across the sarcolemma • However, an inward flux of extracellular calcium ions through sustains the depolarization of cardiac muscle cells for a longer duration • This allows for proper filling of the ventricles with blood from the atria
- 50. Cardiac Muscle Autorhythmic fibers •The myocardium contract without impulses sent from the nervous system • This ability is automaticity (self excitable) • The source of electrical activity in the heart is conducted by a network of specialized cardiac muscle fibers that generate action potentials to trigger heart contractions Pacemaker – • establishes rhythm of electrical stimulation Conduction system – • Ensures that cardiac chambers are stimulated in a coordinated manner
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- 53. The Conduction System SinoatrialNode (SA Node) • The 1st major node • The pacemaker of the heart • Located in the Right Atrium • Superior wall of the Right Atrium • Excitation of the heart begins with the SA Node • Composed of a mass of pacemaker potential auto-rhythmic myocardial cells • Sets the pace of heart contractions • (60 – 100 BPM)
- 54. The Conduction System ArtioventricularNode (AV Node) • The 2nd major node • Action potential are received from the SA Node via gap junctions and arrive at the AV node • The AV node is an area of specialized tissue between the atria and the ventricles • A wave of excitation spreads out from the sinoatrial node through the atria along specialized conduction channels to activate the AV node • The SA node delays impulses by approximately 0.12s • This delay in the cardiac pulse ensures that the atria have ejected their blood into the ventricles • 40 – 60 BPM
- 55. The Conduction System Bundleof His • 3rd major conduction location • A collection of heart muscle cells specialized for electrical conduction • Transmits the electrical impulses received from the AV node • The Bundle of His is located between the atria and the ventricles • Splits into the left and right bundle branches • Only site where action potentials conduct from the atria and ventricles • From the Bundle of His the impulse then is transmitted to the Purkinje fibers
- 56. The Conduction System Purkinjefibers • Specialized muscle fibers in the heart that relay impulses from the atrioventricular bundle to the ventricles • During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both the left and right bundle branch to the myocardium of the ventricles • This causes the muscle tissue of the ventricles to contract
- 57. The Conduction System 1.SA node 2. AV node (atrioventricular) 3. AV bundle 4. Right and Left Bundle branches 5. Purkinje fibers
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- 60. Cardiac Action Potentials ActionPotentials in Cardiac Muscle • Caused by the SA Node Depolarization phase: • Na+ channels open very fast • Ca2+ channels open Plateau phase: • Period of sustained depolarization, caused by the opening of the Ca2+ channels opening • Na+ channels close • Some K+ channels open • Ca2+ channels remain open
- 61. Cardiac Action Potentials Repolarizationphase: - K+ channels are open - Ca2+ channels close • Plateau phase prolongs action potential by keeping Ca2+ channels open. • In skeletal muscle action potentials take 2 msec, in cardiac muscle they take 200-500 msec.
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- 64. ECG P wave: • Atriadepolarization • Represents the electrical impulse originating the SA node and spreading through the atria • This is called Arterial Depolarization • 0.11 seconds ( < 3 small boxes) • Presence of P wave signifies that the impulse originated in the SA node QRS complex: • Ventricular depolarization T wave: • Repolarization of ventricles
- 65. ECG QRS complex: • Ventriculardepolarization • Ventricles contract • QRS complex measures < 0.12 seconds • If the QRS complex is prolonged conduction is impaired within the ventricles. • This can occur with bundle branch blocks
- 66. ECG T Wave • VentricularRepolarization • Ventricles Relax P-Q Interval • Time required for the action potential to travel through the atria, AV node, Bundle Branches, Perkinje fibers S-T Segment • Time when the ventricular myocardial fibers are depolarized during the plateau period
- 68. Cardiac Cycle Atrial Systole •Depolarization of the SA node causes systole (contraction) – (P wave) Ventricular Systole • Ventricular depolarization causes contraction (QRS) Relaxation Period • Ventricular diastole – repolarization (T wave) • Blood flows back into the atria • Aortic and Pulmonic Valves close
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- 71. Cardiac Output Cardiac Output= (Stoke Volume) x (Heart Rate) Stroke Volume • The volume of blood pumped from the left ventricle of the heart with each contraction (approximately 15 mL)
- 72. Cardiac Output Preload • Alsoknown as: End diastolic volume (EDV) • Stroke volume is intrinsically controlled by preload (the degree to which the ventricles are stretched prior to contracting). • An increase in the volume or speed of venous return will increase preload • Frank–Starling law of the heart • Preload is equal to end diastolic volume • Caused by: • venous return • Duration of ventricular diastole
- 73. Cardiac Output Afterload • Alsoknow as Systemic Vascular Resistance • The pressure the ventricle must exceed to eject blood • Afterload is readily broken into components: • Aortic pressure • The pressure the ventricle must over come to eject blood • The greater the afterload the greater the ventricles must work to eject blood (think of after load as increased blood pressure in the system)