Heart

1. Heart The heart pumps blood, which creates pressure, and circulates oxygen, nutrients, and other substances.

2. Heart Information • Cardiology is the study of the heart • In the embryo, the heart begins to beat at 4 weeks • The heart beats 100,000 times a day • The heart is located in the thoracic cavity between the lungs, and above the diaphragm.

3. Cont. • Is located mediastinally within chest • The location makes CPR possible • Is about the size of the person’s closed fist • The heart is composed of cardiac muscle

4. Pericardial Membranes The pericardium is a triple layered sac that surrounds and protects the heart 2 portions • Fibrous- (pericardial sac) tough, loose fitting sac that prevents stretching, provides protection • Serous- delicate membrane that forms double layers around heart a. parietal b. epicardium

6. Pericardial Membranes • Serous fluid, which prevents friction as the heart beats, is between the parietal and epicardium layers of pericardium • Pericarditis is the inflammation of this fluid

7. Layers of the heart • Fibrous • Parietal • Epicardium- outermost • Myocardium- responsible for pumping (heart muscle) • Endocardium- provides smooth lining for inside of heart

9. 4 chambers of the heart • Right atrium • Left atrium • Right ventricle • Left ventricle The two superior chambers are the left/right atrium The two inferior chambers are the left/right ventricle

10. Cont. • Auricle- are found on each atria and increase size and volume (ear shaped) • Coronary sulcus- are external grooves that separate the atria from the ventricles, and contain coronary blood vessels

11. Myocardium is the muscle of the heart • The chambers are lined with endocardium, which is a smooth tissue that prevents abnormal blood clotting

12. The interatrial septum is an internal wall that separates the atria • The interventricular septum is an internal wall that separates the ventricles • Fossa ovalis- remnant of fetal heart opening found in right atrium

13. Right Atrium • Receives blood from the upper body by way of the superior vena cava and receives blood from the lower body by way of the inferior vena cava. • The tricuspid valve prevents the backflow of blood into the right atrium

14. Right ventricle • When the right ventricle contracts, the tricuspid valve closes, and the blood is pumped to the lungs through the pulmonary artery • The flaps of the pulmonary semilunar valve close to prevent the backflow of blood into the right ventricle

15. Right ventricle • The right ventricle has columns of myocardium(muscle) called papillary muscles. • The chordea tendineae, extend from the papillary muscle to the flaps of the tricuspid • The chordea tendineae prevent the inversion of the tricuspid valve

16. Left atrium • The left atrium receives blood from the lungs, by way of four pulmonary veins. • This blood then flows into the left ventricle through the bicuspid valve • The bicuspid valve prevents backflow of blood from the left ventricle to the left atrium when the left ventricle contracts. • Another function is to produce the hormone ANH (atrial natriuretic hormone) which lowers blood pressure

17. Left ventricle • The walls of the left ventricle are thicker than those of the right ventricle, which enables the left ventricle to contract more forcefully. • The left ventricle pumps blood to the body through the aorta, the largest artery of the body.

18. Left ventricle • The chordae tendineae anchor the bicuspid valve of the left ventricle • At the junction of the aorta and the left ventricle is the aortic semilunar vavle. • The aortic semilunar valve closes when the left ventricle relaxes, to prevent the backflow of blood from the aorta to the left ventricle

20. Heart summary • The heart is really a double, or two sided pump. • The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs to pick up oxygen and release carbon dioxide. • The left side of the heart receives oxygenated blood from the lungs and pumps it to the body. • Both pumps work simultaneously, both atria contract together, followed by the contraction of both ventricles.

21. Coronary circulation • Coronary circulation is the flow of blood through the vessels of the myocardium • Coronary arteries supply blood • Coronary veins drain (greater, middle) • Ischemia- when part of the myocardium is deprived of blood

22. Coronary vessels • Prolonged ischemia will create an infarct, and an area of necrotic (dead) tissue. Commonly known as a heart attack.

23. Cardiac OutPut • Cardiac Output is the amount of blood pumped by a ventricle in 1 minute • Stroke Volume is the amount of blood pumped per beat • Starling’s Law of the Heart states that the more cardiac muscles are stretched, the more forcefully they contract

24. Cardiac cycle • Cardiac cycle is the simultaneous contraction of the two atria, followed .20 second later by the simultaneous contraction of the ventricles. • 1% of cardiac muscle fibers become autorhythmic cells (generate action potentials) • These cells form the conduction system for the heart

25. Cardiac Conduction pathway • SA node- found in right atria • AV node- found in atria septum • Bundle of His- found between atria and ventricles • Purkinje fibers- found in apex of ventricles

26. Cardiac cycle • Systole is another term for contraction. • Diastole is another term for relaxation.

27. Heart sounds • Each heartbeat produces four sounds, two are heard lubb-dupp • The first sound lub, the loudest and longest, is caused by the closing of the AV valves. • The second sound dup, is caused by the closure of the aortic and pulmonary semilunar valves.

28. Heart sounds • If any valves do not close properly, an extra sound called a heart murmur may be heard.

29. Heart rate • A healthy adult has a resting heart rate (pulse) of 60 to 80 beats per minute, which is the rate of depolarization of the SA node. • A rate of less than 60 (except for athletes) is called bradycardia; a rate greater than 100 beats is called tachycardia.

30. Heart rate • A child’s normal heart rate may be as high as 100, that of a infant may be as high as 120, and that of a near term fetus as high of a 140 beats per minute. • These higher rates are not related to age, but to rather to size; the smaller the individual the faster the rate.

31. Regulation of heart rate • The medulla of the brain regulates the heart rate; it contains the two cardiac centers, the accelerator, and the inhibitory center. • Pressoreceptors in the aortic sinus detect changes in blood pressure. • Chemoreceptors in the aortic body detect changes in the oxygen content of the blood.

32. Electrocardiogram • A ECG is a recording of action potentials produced by the myocardium during each heart beat • A ECG consist of three waves • P wave-small upward wave, that represents atrial depolarization • QRS complex- represents the depolarization of the ventricles - large Q indicate myocardial infarction - enlarged R indicates enlarged ventricles - flatter T indicates insufficient O2 to heart muscle

33. ECG 3. T wave- represents the repolarization of the ventricles.

34. Risk Factors in Heart Disease • Smoking- Nicotine enters blood stream and constricts small blood vessels, which elevates pressure • Obesity- have extra capillaries in adipose tissue (200 mi), more work • High blood pressure- causes the left ventricle to enlarge

35. Treatments • Hypothermia- slows metabolism and reduces needs of tissue • Heart transplant- 50 to 1 • Cardiac assist - Cardiomyoplasty- wrapping heart in muscle - LVAD- implanted in abdomen - Hemopump- propeller like pump

36. Aging and the heart • Heart muscle becomes less efficient with age. • Atherosclerosis, hypertension, and arrhythmias become more common.

37. Astherosclerosis • Areas where there are a build up cholesterol plaques in the coronary artery. These areas narrow the artery and increase the risk of clot formation, reducing the flow of oxygen. • Predisposing risk are cigarette smoking, diabetes mellitus, and high blood pressure (genetics). • Can be treated with angioplasty or bypass

38. Arrhythmias • Are irregular heartbeats caused by damage to part of the conduction pathway. • Palpitations are non-serious irregular heartbeats, and may result from too much caffeine, nicotine, or alcohol. • Flutter is a very rapid but fairly regular heartbeat. • Fibrillation is a very rapid and uncoordinated ventricular beat that is totally ineffective for pumping blood (V-fib)

39. Rheumatic Fever • An infection caused by Streptococcus bacteria that inflames the heart damaging the valves by stretching