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Exploring the Anatomy and Function of the Human Heart

Dive into the intricate details of the heart's structure and its vital role in circulation the body. Learn about the cardiac cycle, blood flow pathways, and the electrical conduction system. Discover fascinating facts about the heart's pumping capacity and the complexity of its functions.

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Exploring the Anatomy and Function of the Human Heart

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  1. The Heart

  2. The Heart • Heart pumps over 1 million gallons per year • Over 60,000 miles of blood vessels

  3. I. Layers of Heart Wall • Pericardium • protects and anchors the heart, prevents overstretching • Myocardium • cardiac muscle layer is the bulk of the heart • Endocardium • chamber lining & valves

  4. II. Structures of the Heart Left common carrotid Left subclavian artery Brachiocephalic trunk aorta left pulmonary artery Superior vena cava Mitral/bicuspid pulmonary semi-lunar Right atrium Left atrium Right pulmonary vein Aortic semi-lunar tricuspid Chordae tendinae myocardium Papillary muscle Left ventricle inferior vena cava Interventricular septum Right ventricle Descending aorta

  5. III. Blood Circulation • Two closed circuits, the systemic and pulmonic • Pulmonary circulation • Right atrium pumps blood through the tricuspid valve to the right ventricle • Right ventricle pumps blood through the pulmonary semi-lunar valve to pulmonary trunk • pulmonary trunk branches into left and right pulmonary arteries • Pulmonary arteries carry blood to lungs for exchange of gases • Which gases and in what direction? • Oxygenated blood returns to the heart through the pulmonary veins into the left ventricle

  6. Blood Circulation (con’t) • Systemic circulation • Left atrium pumps blood though the mitral valve (bicuspid) to the left ventricle • Why is this valve replaced the most often? • left ventricle pumps oxygenated blood through the aortic semi-lunar valve into aorta • Why is the myocardium of this chamber the thickest? • Aorta branches into many arteries that travel to organs • Arteries branch into many arterioles in tissue. • Arterioles branch into thin-walled capillaries for exchange of gases and nutrients • Deoxygenated blood begins its return in venules • Venules merge into veins and return to right atrium via the vena cavas

  7. IV. Blood Flow Off Descending Aorta • Commoncarotid artery (left) • First branch coming off of the aorta and it carries blood to head and brain • Returns through jugularveins to superiorvenacava • Left & right Subclavian arteries carries blood to the arms and the subclavian veins return blood to the superior vena cava.

  8. Blood flow off Descending Aorta (2) • Celiac artery carries blood to stomach, spleen and liver • Portal vein leads to the liver and leaves through the hepatic (liver) vein to inferior vena cava. • Superior mesenteric artery carries blood to the small intestine, which in turn connects to the portal vein. • This way all materials entering the blood stream from the digestive tract are sent directly to the liver for detoxification.

  9. Blood flow off Descending Aorta (3) • Inferior mesenteric artery leads to large intestine (and small, but mostly large) • Large intestine leads to internal iliac vein (hypogastric) that connects to the inferior vena cava • The Iliac arteries branches to supply blood to reproductive and excretory organs, as well as the legs • Blood returns through iliac veins to inferior vena cava

  10. HEART QUESTIONS • How many times will your heart beat in 80 years? • How much blood is pumped with each heart beat?

  11. V. Cardiac Cycle • Atrial diastole • both atria fill with blood • atrioventricular valves are open and the semilunar valves are closed • 75% of ventricular filling occurs now • lasts about 0.7 seconds • Atrial systole • atria contract forcing the remaining 25% of the blood into the ventricles • lasts about 0.1 seconds

  12. Cardiac Cycle (2) • Ventricular diastole • ventricles are relaxing • lasts about 0.5 seconds • Ventricular systole • ventricles are contracting • blood is being forced into the aorta and pulmonary arteries. • the semilunar valves are open and the atrioventricular valves are closed. • lasts about 0.3 seconds

  13. VI. Cardiac Conduction System • Impulse originates in sinoatrial node (SA node or pacemaker) which is located in the superiorregion of the right atrium. • Impulse spreads across both atria which causes them to contract at the same time. • The impulse reaches atrioventricular node (AV node) located at the top of the right ventricle.

  14. Cardiac Conduction System (con’t) • From the AV node the impulse passes through the atrioventricular bundle node to (Bundle of His). • The Bundle of His branches off into right and left bundle branches. • The impulse now flows through the many branches of the Purkinje fibers which pass deep into the ventricular myocardium.

  15. Pacemaker Bundle of His AV node Purkinje fibers

  16. VII. Electrocardiogram-ECG or EKG • Action potentials of all active cells can be detected and recorded • The machine amplifies electrical impulses generated by your muscles. • 4 basic parts to analyze: • P wave • P to Q interval • QRS complex • T wave

  17. VIII. ECG Analysis • Parameters • Horizontal Axis • Measures time of duration. • Each box or mm = 0.04 seconds • Vertical Axis • Measures voltage or amplitude • Each box or mm = 0.1 mV

  18. P-Wave • Depolarization of the atria (atrial systole) • Amplitude of P-Wave should be less than 0.2 mV to 0.3 mV • Duration of P-Wave should be less than 0.11 seconds

  19. QRS Complex • Atria repolarization (atrial diastole) • Ventricle depolarization (ventricular systole) • Amplitude should be greater than 0.5 mV in leads 1, 2, or 3 • Measured from tip of R to bottom of S • Duration should be less than 0.12 secs.

  20. T-Wave (isoelectric) • Repolarization of ventricles (ventricular diastole) • Amplitude should be less than 0.5 and greater than 1/10 of R wave for that segment. • T-wave should be on the isoelectric line • Duration not a concern • T-wave should be in the same direction as the R-wave

  21. P-Q Interval • Measured from beginning of P to beginning of Q. • Between 0.12 and 0.2 second duration. • Too long indicates AV block.

  22. ST Segment • Amplitude should be isoelectric • If depressed more than 2 mm indicates ischemic heart. • Most often caused by atherosclerosis. • Duration should be between 0.13 - 0.16 sec.

  23. Heart Rate • HR= 60/(R to R Interval in seconds)

  24. Cardiac Cycle

  25. Regulation of Heart Rate

  26. I. Cardiac Output (CO) • The amount of blood the heart pumps in 1 minute. • stroke volume (SV) = amount of blood pumped per beat

  27. II. Influences on Stroke Volume • Preload (affect of stretching heart muscle) • Frank-Starling Law of Heart • The longer the filling time, the greater the stretch of cardiac muscle • more muscle is stretched, greater force of contraction • This explains why athletes have lower resting heart rates but the same cardiac output • more blood more force of contraction results • Contractility • autonomic nerves, hormones, Ca+2 or K+ levels • Afterload • amount of pressure created by the blood in the way • high blood pressure creates high afterload

  28. III. Control Centers for Heart Rate • Two centers found in the medulla • Cardioacceleratory center • has a sympathetic nerve (cardioaccelerator nerve) that connects to the SA node of the heart. • Cardioinhibitory center • has a parasympathetic nerve (vagus nerve) that connects to the SA node of the heart.

  29. IV. Factors that effect heart rate • Blood Pressure (BP) • Carotid Sinus Reflex: • As the BP in the carotid sinus rises the walls of the carotid sinuses stretch (baroreceptors) • Stretching increases stimulation of the glossopharyngeal nerve, which leads to the cardioinhibitory center in the medulla. • The inhibitory center stimulates the Vagusnerve which slows down the heart rate • Therefore a drop in HR, produced a drop in CO, which produced a drop in blood pressure, that reduced the amount of stretch in the carotid sinus. • What happens if there is a drop in blood pressure in the carotid sinus?

  30. Factors that effect heart rate (con’t) • Aortic reflex (regulates BP to rest of body) • Right Atrial (Bainbridge) reflex • There are baroreceptors located in the right atrium and in the superior and inferior vena cavas. • When these are stimulated heart rate increases. • Why increase heart rate instead of decrease?

  31. Factors that effect heart rate (con’t) • Chemical Factors • CO2 • increases heart rate • Adrenaline (epinephrine) • increases heart rate • Ca 2+ • increases heart rate • Na+ and K+ • lower heart rate

  32. Factors that effect heart rate (con’t) • Other factors • Sex • females have higher heart rates • Age • older-slower • Exercise • increase • person who exercises regularly has a lower resting heart rate than one who doesn't - called Bradycardia • Temperature • Higher temperature, higher heart rate

  33. Cardiovascular Disease (CVD) In the U.S.—1 million deaths/year

  34. I. Coronary heart disease (56%) • Cause • Slow build up of fatty plaque (atherosclerosis) along the walls of the coronary blood vessels which reduces blood flow to heart • The drop in O2 levels (ischemia) causes a angina which could lead to myocardial infarction.

  35. B. Diagnosis • Outward symptoms of a heart attack: • pain in chest and left arm • cyanosis of lips • nausea • dizziness • shortness of breath • cold sweat • denial

  36. Diagnosis (con’t) • Exercise ECG • ST Depression • Problems with PR interval • Angiogram • A catheter is inserted into femoral artery of pelvis and worked into the aorta. • Then dye is injected through catheter. • A fluoroscope will show the dye pathway. • Any narrowing or blockages will show up on the fluoroscope.

  37. C. Treatment • Bypass surgery • remove a vein from the leg and use it to bypass a blockage in heart vessel • stop heart and put on a heart lung machine • Angioplasty (see angiogram) • Catheter with specialized tip is positioned where the coronary artery is narrowed or blocked. • Use syringe to blow up catheter’s balloon (fig. 20-14, page 599). • Balloon presses the plaque up against the walls of the vessel.

  38. By-pass Graft

  39. Coronary Angioplasty

  40. CVD • Stroke 20% • The interruption of blood flow to the brain • Causes • thrombus vs. embolus • atherosclerosis (has no symptoms) • aneurysm-broken blood vessel

  41. Stent in an Artery • Maintains patency of blood vessel

  42. CVD • Hypertension 7% • Chronic high blood pressure • More common in black males than white. • Myocardial degeneration 5% • Heart muscle degenerates • Arteriosclerosis 4% • Hardening of the arteries • Rheumatic fever 2% • Childhood disease that damages heart valves

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