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4. 3  The heart is the organ that supplies blood and oxygen to all parts of the body. It is about the size of a clenched fist, weighs about 10.5 ounces and is shaped like a cone. The heart is located in the chest cavity just posterior to the breastbone, between the lungs and superior to the diaphragm. The heart is surrounded by a fluid filled sac called the pericardium. Blood is pumped away from the heart through arteries and returns to the heart through veins. The major artery of the body is the aorta and the major veins of the body are the vena cavaposteriorsuperiorpericardiumaortavena cava

5. 4  The pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava and the pulmonary arteryproximalaortavena cavapulmonary  Function:  Keeps the heart contained in the chest cavity.  Prevents the heart from overexpanding when blood volume increases.  Limits heart motion.

6. 5  Blood vessels are intricate networks of tubes that transport blood throughout the entire body.  Types of vessels:  Arteries Arteries  Veins Veins  Capillaries Capillaries  Sinusoids Sinusoids

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8. 7 What is the epicardium?  The epicardium is the outer layer of the wall of the heart. It is composed of connective tissue covered by epithelium. The epicardium is also known as the visceral pericardium.epitheliumpericardium  Function:  Provides an outer protective layer for the heart

9. 8  What is the myocardium?  Myocardium is the muscular middle layer of the wall of the heart. It is composed of spontaneously contracting cardiac muscle fibers which allow the heart to contract.cardiac muscle  Function:  Stimulates heart contractions to pump blood from the ventricles and relaxes the heart to allow the artria to receive blood.ventriclesartria

10. 9  What is the endocardium?  The endocardium is the inner layer of the heart. It consists of epithelial tissue and connective tissue.epithelialconnective tissue  Function:  Lines the inner cavities of the heart, covers heart valves and is continuous with the inner lining of blood vessels. valves blood vessels  Purkinje fibers are located in the endocardium. They participate in the contraction of the heart muscle. Purkinje fibers

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12. 11  What are atria?  The heart is divided into four chambers that are connected by valves. The upper two chambers of the heart are called the left atrium and the right atrium.valves  Function:  Right Atrium: Receives blood returning to the heart from the superior and inferior vena cava.vena cava  Left Atrium: Receives blood returning to the heart from the pulmonary veinspulmonary veins

13. 12  What are ventricles?  The heart is divided into four chambers that are connected by valves. The lower two chambers of the heart are called the left ventricle and the right ventricle.valves  Function:  Right Ventricle: Receives blood from the right atrium and pumps it to the pulmonary artery.pulmonary artery  Left Ventricle: Receives blood from the left atrium and pumps it to the aorta.aorta

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15. 14  Valves are flap-like structures that allow blood to flow in one direction. The heart has two kinds of valves, atrioventricular and semilunar valves.

16. 15  The atrioventricular valves are thin structures that are composed of endocardium and connective tissue. They are located between the atria and the ventriclesendocardiumatriaventricles

17. 16  What is the mitral valve?  Valves are flap-like structures that allow blood to flow in one direction. The mitral valve is located between the left atrium and the left ventricle.  Function:  Prevents the back flow of blood as it is pumped from the left atrium to the left ventricle.

18. 17  What is the tricuspid valve?  Valves are flap-like structures that allow blood to flow in one direction. The tricuspid valve is located between the right atrium and the right ventricle.  Function:  Prevents the back flow of blood as it is pumped from the right atrium to the right ventricle.

19. 18  The semilunar valves are flaps of endocardium and connective tissue reinforced by fibers which prevent the valves from turning inside out. They are shaped like a half moon, hence the name semilunar (semi-, -lunar). The semilunar valves are located between the aorta and the left ventricle and between the pulmonary artery and the right ventricle.semi--lunaraortapulmonary artery

20. 19  What is the aortic valve?  Valves are flap-like structures that allow blood to flow in one direction. The aortic valve is located between the left ventricle and the aorta.  Function:  Prevents the back flow of blood as it is pumped from the left ventricle to the aorta.

21. 20  What is the pulmonary valve?  Valves are flap-like structures that allow blood to flow in one direction. The pulmonary valve is located between the right ventricle and the pulmonary artery.  Function:  Prevents the back flow of blood as it is pumped from the right ventricle to the pulmonary artery

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23. 22  What is the sinoatrial node?  The sinoatrial (SA) node is a section of nodal tissue that is located in the upper wall of the right atrium. The SA node is also referred to as the pacemaker of the heart.nodal tissue  Function:  Sets the rate of contraction for the heart.  Spontaneously contracts and generates nerve impulses that travel throughout the heart wall causing both atria to contract.atria

24. 23  The atrioventricular bundle is a bundle of fibers that are located within the septum of the heart.  Function:  Carries cardiac impulses down the septum to the ventricles via the Purkinje fibersventriclesPurkinje fibers

25. 24  What is the atrioventricular node?  The atrioventricular (AV) node is a section of nodal tissue that lies on the right side of the partition that divides the atria, near the bottom of the right atrium.nodal tissueatria  Function:  Delays cardiac impulses from the sinoatrial node to allow the atria to contract and empty their contents first.sinoatrial node  Relays cardiac impulses to the atrioventricular bundleatrioventricular bundle

26. 25  What are Purkinje fibers?  Purkinje fibers are fiber branches that extend from the atrioventricular bundle. Purkinje fibersatrioventricular bundle  Function:  Relays cardiac impulses to the ventricular cells causing the ventricles to contractventricles

27. 26 Cardiac Cycle

28. 27 The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle:cardiac cycle DiastoleDiastole - Ventricles are relaxed. SystoleSystole - Ventricles contract.

29. 28 Cardiac Cycle Image courtesy of MedValetMedValet

30. 29  The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle:  Diastole - Ventricles are relaxed. Diastole  Systole - Ventricles contract Systole

31. 30 Cardiac Cycle Diastole Phase Early Diastole Ventricles relax. Semilunar valves close.valves Atrioventricular valves open.valves Ventricles fill with blood. Mid Diastole Atria and Ventricles are relaxed. Semilunar valves are closed. Atrioventricular valves are open. Ventricles continue to fill with blood. Late Diastole SA nodeSA node contracts. Atria contract. Ventricles fill with more blood. Contraction reaches AV node.AV node

32. 31  The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle:  Diastole - Ventricles are relaxed. Diastole  Systole - Ventricles contract Systole

33. 32 Systol e Contraction passes from AV node to Purkinje fibers and ventricular cells.AV node Purkinje fibers Ventricles contract. Atrioventricular valves close.valves Semilunar valves open.valves Blood is pumped from the ventricles to the arteries. Cardiac Cycle Systole Phase

34. 33  Arteries  Capillaries  Veins

35. 34  Arteries are vessels that carry blood away from the heart. The aorta is the largest artery in the body. It arises from the left ventricle of the heart, forms an arch, then extends down to the abdomen where it branches off into two smaller arteries. Arteriesventricle  Function:  Carries and distributes oxygen rich blood to all arteries. Most major arteries branch off from the aorta, with the exception of the main pulmonary artery.main pulmonary artery  Branches:  (1) Ascending Aorta - Extends from the left ventricle of the heart.

36. 35  The coronary arteries are the first blood vessels that branch off from the ascending aorta.coronary arteries aorta  Function:  Carry oxygenated and nutrient filled blood to the heart muscle

37. 36  Function:  Carries de-oxygenated blood from the right ventricle to the lungs

38. 37  Function:  Brings oxygenated blood from the lungs to the left atrium

39. 38  Function:  Superior Vena Cava: Brings de-oxygenated blood from the head, neck, arm and chest regions of the body to the right atrium.  Inferior Vena Cava: Brings de-oxygenated blood from the lower body regions to the right atrium.