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The Cardiovascular System: The Heart

The Cardiovascular System: The Heart. Embryology of the Heart. Derived from mesoderm, begins development at 3 rd week of gestation Contraction of the heart begins by day 22 A pair of tubes develop (endothelial tubes), These fuse into the primitive heart atria and ventricles form

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The Cardiovascular System: The Heart

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  1. The Cardiovascular System:The Heart

  2. Embryology of the Heart • Derived from mesoderm, begins development at 3rd week of gestation • Contraction of the heart begins by day 22 • A pair of tubes develop (endothelial tubes), • These fuse into the primitive heart atria and ventricles form • These then assume a “U” shape then an “S” shape • Making “US”

  3. The Heart • Cardiovascular system • heart, arteries, veins and capillaries • 2 major divisions: • 1. Pulmonary circuit - right side of heart • carries deoxygenated blood to lungs • 2. Systemic circuit - left side of heart • supplies oxygenated blood to the body • Cardiology- study of the heart

  4. Cardiovascular System Circuit

  5. Size, Shape and Position • Big a closed fist, males have bigger anatomical hearts • Located in the mediastinum, like a cone on its side between the lungs • Base - broad superior portion of heart • Apex - inferior end, tilts to the left, tapers to point

  6. Pericardium • Pericardium- surrounds heart, keeps your heart in it’s place (like a father-in-law with the gun collection) • Allows heart to beat without friction, room to expand and resists excessive expansion • Pericarditis= inflammation of pericardium, can result in: • Cardiac Tamponade= fluid in the pericardial cavity compressing the heart, can stop the heart beat

  7. Pericardium • Pericardium- Two parts: • 1.) Parietal Pericardium • Two layers: • Fibrous layer- superficial • protects, prevents overstretching, anchors heart • Serous layer- deep • 2.) Visceral Pericardium • Also called the epicardium

  8. Heart Wall • 3 layers of the Heart wall • 1.) Epicardium- outside slippery layer • Also called the visceral pericardium (just to be confusing) • 2.) Myocardium- muscle of heart • 3.) Endocardium- inside the heart, covers chambers, heart valves • The heart can’t get oxygen from the inside. Why?

  9. Heart Chambers • 4 chambers • Right and left atria (= entry halls) • 2 superior, posterior chambers • receive blood returning to heart • Right and left ventricles (= little bellies) • 2 inferior chambers • pump blood into arteries • Left ventricle is thicker, why?

  10. Anterior Anatomy – Atrioventricular sulcus - separates atria, ventriclesAnterior and posterior interventicular sulci - grooves separate ventricles Atrioventricular sulcus

  11. Posterior Heart AnatomyPosterior Interventricular Sulcus- groove separating ventricles

  12. Heart Chambers - Internal • Interatrial septum • wall that separates atria • Pectinate muscles • internal ridges of myocardium in right atrium and both auricles • Interventricular septum • wall that separates ventricles • Trabeculae carneae • internal ridges in both ventricles walls • Chordae tendineae- cords connecting to the tricuspid and mitral valves

  13. Internal Anatomy Anterior Aspect

  14. Heart Valves • Ensure one-way blood flow • Semilunar valves - control flow into great arteries • pulmonary: from right ventricle into pulmonary trunk • aortic: from left ventricle into aorta • Atrioventricular (AV) valves • right AV valve has 3 cusps (tricuspid valve) • left AV valve has 2 cusps (mitral,bicuspid valve) • rat lamb • chordae tendineae - cords connect AV valves to papillary muscles (on floor of ventricles)

  15. The Mitral Valve

  16. Heart Valves

  17. Valve Anatomy • The AV valves, the tricuspid and bicuspid (mitral) valves

  18. AV Valve Mechanics • Ventricles relax, pressure drops, semilunar valves close, AV valves open, blood flows from atria to ventricles • Ventricles contract, AV valves close(papillary m. contract and pull on chordae tendineae to prevent prolapse),pressure rises, semilunar valves open, blood flows into great vessels

  19. Operation of Atrioventricular Valves

  20. Operation of Semilunar Valves

  21. Be the Blood- Drawing

  22. Be the Blood - Discretion I • You (blood) flow into heart in the Superior (S) vena cava and inferior (I) vena cava and then into the right atrium (1) • You pass through the tricuspid (= three points) valves (2) into the right ventricle (3) • You go through the pulmonary semilunar (4) valves into the pulmonary trunk (5) • The pulmonary trunk divides into right and left pulmonary arteries (6) which go to the lungs so that you can be oxygenated

  23. Be the Blood II • You (be the blood!) then flow from the lungs through the pulmonary veins (7) into the left atrium (8) • Through the bicuspid valve (9) to the left ventricle (10) • The left ventricle pumps blood (you) through the aortic semilunar valve (11) into the ascending aorta (12) then to the aortic arch and on to the descending aorta • http://www.youtube.com/watch?v=upctPUa6RhA

  24. Circulation to the Heart • The heart can not get nutrients from inside • Blood vessels must supply the heart muscle this is called the coronary circulation • The arteries of the heart encircle it like a crown • While contacted no blood flows to the heart • When the heart relaxes the blood flows to it • FLOW- Aorta to coronary arteries to coronary veins

  25. Heart Valves 2 ? 1?

  26. Coronary Circulation • Left coronary artery • 1. anterior interventricular artery • supplies interventricular septum + anterior walls of ventricles • 2. circumflex artery • passes around left side of heart in coronary sulcus, supplies left atrium and posterior wall of left ventricle • Right coronary artery • 1. posterior interventricular artery • supplies posterior walls of ventricles • 2. marginal artery • supplies lateral R atrium + ventricle

  27. Coronary Circulation memory aid • Remember: a heart that doesn’t work well will often- LAC RPM • Right Coronary artery gives off the- • Right Posterior Interventricular artery and Marginal artery (RPM) • Left Coronary artery gives off the- • Left Anterior Interventricular artery and the Circumflex artery (LAC)

  28. Coronary Vessels – Anterior---LAC RPM---

  29. Coronary Vessels – Posterior---LAC RPM---

  30. Structure of Cardiac Muscle • Compared to skeletal muscle cardiac muscle is: • Short in length • Branched • One to two nuclei • Has intercalated discs, these contain gap junctions that assist in electrical conduction

  31. Structure of Cardiac Muscle Cell

  32. Metabolism of Cardiac Muscle • Aerobic respiration • Rich in myoglobin and glycogen • Large mitochondria • Organic fuels: fatty acids, glucose, ketones • What should our diets be? • Fatigue resistant

  33. Heart Electrical Conduction • Myogenic - heartbeat originates within the heart • The fundamental rhythm of the heart is automatic and not dependent on the nervous system or endocrine system • This rhythm is due to autorhythmic cells, specialized cardiac muscle fibers that are self-exciting • These cells act as: a Pacemaker… • Setting the rhythm of the entire heart • …and Conduction system • A route for conducting electrical energy throughout the heart muscle

  34. It’s All In The Timing • The chambers of the heart have to be coordinated or the heart will not work • The SA node (sinoatrial node) stimulated first, as the name implies this node causes atria contraction • Next the AV node (atrioventricular node) is stimulated • The impulse then goes to the Bundle of His (Atrioventricular bundle) • The right and left bundle branches goes to the apex of the heart • Finally, conduction myofibers termination is called Purkinje fibers that conduct impulses to the rest of the heart

  35. Cardiac Conduction System Bundle of His

  36. Heart Conduction: Memory Aid • Remember: SAVe HIS Right and Left BUN from PURKing

  37. Cardiac Rhythm • Systole = contraction; diastole = relaxation • Sinus rhythm • set by SA node, adult at rest is 70 to 80 bpm • Ectopic foci - region of spontaneous firing (not SA) • nodal rhythm - set by AV node, 40 to 50 bpm • intrinsic ventricular rhythm - 20 to 40 bpm • Arrhythmia - abnormal cardiac rhythm • heart block: failure of conduction system • bundle branch block • total heart block (damage to AV node)

  38. Electrocardiogram (ECG) • Composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs and chest

  39. ECG Alphabet • The ECG alphabet goes PQRST • P wave- the first wave shown • QRS complex- the middle quibble • T wave- the last wave

  40. Pacemakers • The SA node is the pacemaker of the heart • If the SA node becomes diseased, and heart rate gets too low (<40 BPM) an Artificial Pacemaker can be surgically implanted • Other sites besides the SA node can stimulate the heart, this is called: an Ectopic pacemaker • Triggers of this activity are caffeine, nicotine, that special someone

  41. EKG/ ECG • Cardiac muscle contraction is electrical, the physiology is similar to skeletal muscle (see A&PI) these electrical impulses can be detected on the skin of the chest • Our friend the Aardvark! • This recording is called is called an Electrocardiogram and the machine is called an Electrocardiograph • The ECG tells three things: E- electrical conduction problems in the heart, C- cardiac enlargement, G- Cardiac Damage

  42. Waves of Meaning I • First wave= P wave- atrial Depolarization • Second wave= QRS- ventricular depolarization as the electrical excitement spreads through the ventricles • Repolarization of the atria occurs here but is not seen due to the QRS length • Third wave= T wave- ventricular REploarization

  43. ECG/EKG • Abnormal Waves • Larger P= enlarged atrium • Enlarged R= enlarged ventricles

  44. EKG (ECG) • Time span between waves is called intervals or segments • P-Q interval lengthened- coronary artery disease, rheumatic fever • Q-T interval lengthened- myocardial damage, HEART ATTACK, coronary ischemia or conduction anomalies

  45. ECGs, Normal & Abnormal No P waves

  46. ECGs, Abnormal Extra systole: note the inverted QRS complex, misshapen QRS and T and absence of a P wave preceding this contraction.

  47. ECGs, Abnormal Arrhythmia: conduction failure at AV node No pumping action occurs

  48. Cardiac Cycle • Events in one heartbeat • Systole is contraction, Diastole is relaxation (“Relax? Relax? When I die, then I’ll relax.”) • The cycle consists of systole and diastole of both atria plus systole and diastole of both ventricles

  49. Heart Sounds • Listening to the sounds of the body is called auscultation (= listening), you can hear bowel sounds, breathing, and heart beats with your ear to the patient (old method) or with a stethoscope (modern method) • 4 heart sounds, 2 clinically important (because a stethoscope can hear them): • The first sound is lubb, • First heart sound (S1), louder and longer “lubb”, occurs with closure of AV valves • The second sound is dub • Second heart sound (S2), softer and sharper “dub” occurs with closure of semilunar valves

  50. Lubb- Dub • Lubb- closure of AV valves: • Tricuspid valve • Mitral valve • Dub- closure of the semilunar valves: • Aortic • Pulmonary Dub Dub Lubb Lubb

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