1. Cardiovascular System Northwest Rankin High School Human A&P

2. Introduction 2  The cardiovascular system consists of the heart and vessels (arteries, capillaries and veins.)  A functional cardiovascular system is vital for supplying oxygen and nutrients to tissues and removing wastes from them.  Deoxygenated blood is carried by the pulmonary circuit to the lungs, while the systemic circuit sends oxygenated blood to all body cells. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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4. Size of Heart  The heart is about the size of a person’s fist.  It is hollow, cone shaped and weighs less than one pound.

5. Location of Heart  Behind the sternum and is flanked on either side by the lungs.  The heart rests on the diaphragm and the pointed apex of the heart is directed toward the left hip.  The superior part of the heart is pointing towards the right shoulder.

6. Walls of the Heart  The heart is enclosed by a double sac called pericardium. The visceral pericardium, or epicardium tightly hugs the heart. The parietal pericardium is the outside layer that anchors the heart to the surrounding structures (diaphragm and sternum). Between the pericardial layers is a fluid to reduce friction.

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8. Layer of the Heart Wall  Epicardium – outside layer  Made of connective and epithelial tissue  Houses blood and lymph capillaries as well as the coronary arteries  Myocardium – middle layer  thick layers of cardiac muscle  Endocardium –the inside layer  Very smooth  Made of connective and epithelial tissue  Contains Purkinje fibers

10. Chambers of the heart  The heart has 4 chambers 2 atria  Superior chambers  Receive blood returning to the heart  Thin walls 2 ventricles  Inferior chambers  Pump blood to the body and to the lungs  Thick walls A septum divides the atrium and ventricles on each side.

12. Valves of the heart  Valves prevent backflow of blood in the heart.  The valves open and close in response to pressure changes in the heart

14. Atrioventricular (AV) Valves  Each side of the heart has an AV valve to ensure one way flow of blood  There are two AV valves: Biscuspid (mitral) valve – LEFT AV valve with 2 cusps, between the left atria and ventricle Tricuspid valve – RIGHT AV valve with three cusps located between the right atria and ventricle  Each AV valve cusps attach to chordae tendinae which are attached to papillary muscles.

15. AV Valves  The AV valves open during heart relaxing and close when the heart contracts to prevent blood from returning to the atria.  When the heart is relaxed and blood is passively filling its chambers, the AV- valve flaps hang limply into the ventricles. As the ventricles contract, the pressure begins to rise and forces the valves closed. This prevents backflow into the atria when the ventricles are contracting.

17. Semilunar Valves  Each side of the heart also has a semilunar valve to further ensure one way flow of blood  There are also two semilunar valves Pulmonary – in the pulmonary artery leaving the heart to the lungs. Aortic – in the aortic arch leaving the heart to the body.

18. Semilunar Valves  The semilunar valves open during heart contraction and close to prevent backflow into the ventricles when relaxing.  When the ventricles are contracting and forcing blood out of the heart, the cusps are forced open and flattened against the wall of the arteries by the tremendous force of rushing blood. Then when the ventricles relax the blood begins to flow backward toward the heart, and the cusps fill with blood, closing the valves.

20. Heart functions as a double pump  Pulmonary circulation – right side of heart to the lungs and back to the left side of the heart. It’s only function is to carry blood to the lungs for gas exchange and then to return it to the heart.  Systemic circulation – left side of the heart through the body tissues and back to the right side of the heart. It supplies oxygen and nutrient rich blood to all body organs.

22. Path of Blood through the Heart 22 1. Blood low in oxygen returns to the right atrium via the venae cavae and coronary sinus. 2. The right atrium contracts, forcing blood through the tricuspid valve into the right ventricle. 3. The right ventricle contracts, closing the tricuspid valve, and forcing blood through the pulmonary valve into the pulmonary trunk and arteries. 4. The pulmonary arteries carry blood to the lungs where it can rid itself of excess carbon dioxide and pick up a new supply of oxygen. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24. 24 5. Freshly oxygenated blood is returned to the left atrium of the heart through the pulmonary veins. 6. The left atrium contracts, forcing blood through the left bicuspid valve into the left ventricle. 7. The left ventricle contracts, closing the bicuspid valve and forcing open the aortic valve as blood enters the aorta for distribution to the body. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Path of Blood through the Heart

26. Blood Supply to the Heart 26  The first branches off of the aorta, which carry freshly oxygenated blood, are the right and left coronary arteries that feed the heart muscle itself.  Branches of the coronary arteries feed many capillaries of the myocardium.  Cardiac veins drain blood from the heart muscle and carry it to the coronary sinus, which empties into the right atrium. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

27. Heart Actions  The cardiac cycle consists of the atria beating in unison (atrial systole) followed by the contraction of both ventricles, (ventricular systole) then the entire heart relaxes for a brief moment (diastole). It includes events of one complete heartbeat, during which both atria and ventricles contract and then relax. (0.8 seconds) or 75 times a minute Common terms: Systole-Ventricle contraction; Diastole- Ventricle relaxation 27 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

28. Cardiac Cycle  During the cardiac cycle, pressure within the heart chambers rises and falls with the contraction and relaxation of atria and ventricles.  When the atria fill, pressure in the atria is greater than that of the ventricles, which forces the A-V valves open.  Pressure inside atria rises further as they contract, forcing the remaining blood into the ventricles 28 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

29. Cardiac Cycle  When ventricles contract, pressure inside them increases sharply, causing A-V valves to close and the aortic and pulmonary valves to open.  As the ventricles contract, papillary muscles contract, pulling on chordae tendinae and preventing the backflow of blood through the A-V valves. 29 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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31. Heart Sounds  Heart sounds are due to vibrations in heart tissues as blood rapidly changes velocity within the heart.  Heart sounds can be described as a "lubb- dupp" sound. The first sound (lubb) occurs as ventricles contract and A-V valves are closing. The second sound (dupp) occurs as ventricles relax and aortic and pulmonary valves are closing 31 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. http://www.smm.org/heart/lessons/lesson4.htm

32. Controlling systems of the heart  Without a controlling system, the heart would be an inefficient pump  There are two controlling systems Intrinsic Conduction System Autonomic nervous system

33. Intrinsic Conduction System  Specialized cardiac muscle tissue conducts impulses throughout the myocardium and comprises the intrinsic conduction system. It is not found anywhere else in the body It causes heart muscle depolarization in only one direction from the atria to the ventricles  The Intrinsic Conduction System consists of an SA node (pacemaker), an AV node, the AV bundle (bundle of His) and bundle branches, and the Purkinje fibers

34. SA Node  A self-exciting mass of specialized cardiac muscle called the sinoatrial node (S-A node or pacemaker), located on the posterior right atrium, generates the impulses for the heartbeat. 34 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

35. AV Node  Impulses spread next to next grouping of cells, it contracts, and impulses then travel to the junctional fibers leading to the atrioventricular node (A-V node) located in the septum.  Junctional fibers are small, allowing the atria to contract before the impulse spreads rapidly over the ventricles. 35 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

37. Bundle of His and Purkinje fibers  From the AV Node signals spread to the AV bundle (Bundle of His)  And then the branches of the A-V bundle give rise to Purkinje fibers leading to papillary muscles  These fibers stimulate contraction of the papillary muscles at the same time the ventricles contract. 37 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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40. Electrocardiography: ECG  All the activity of the heart produces electrical waves we can measure. The measurement is typically represented as a graph called an electrocardiogram (ECG)  The typical ECG has three recognizable waves P wave: small and signals the depolarization of the atria immediately before they contract QRS complex: results from the depolarization of the ventricles, complicated shape; precedes the contraction of the ventricles T wave: results from currents flowing during the repolarization of the ventricles

41. http://health.howstuffworks.com/heart1.htm

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43. Regulation of the Cardiac Cycle  The amount of blood pumped at any one time must adjust to the current needs of the body  The SA node is innervated by branches of the sympathetic and parasympathetic divisions, so basically the autonomic system of the CNS controls heart rate. Sympathetic impulses increase the speed of heart rate. Heart rate is decreased by parasympathetic impulses 43 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

44. Cardiac control center  The cardiac control center of the medulla oblongata maintains a balance between the sympathetic and parasympathetic divisions of the nervous system in response to messages from baroreceptors which detect changes in blood pressure.  Impulses from the cerebrum or hypothalamus may also influence heart rate, as do body temperature and the concentrations of certain ions. 44 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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46. Heart Sounds  Lub-dup- pause Lub: closing of the AV valves, longer and louder sound Dub: closing of the semilunar valves at the end of systole, shorter and sharper sound

47. Blood Vessels 47  The blood vessels (arteries, arterioles, capillaries, venules, and veins) form a closed tube that carries blood away from the heart, to the cells, and back again.  Large arteries leave heart (aorta) THEN to smaller arteries THEN to arterioles THEN to capillary beds THEN to venules THEN to veins THEN to larger veins (inferior and superior vena cavae) that dump blood back into heart. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

48. Anatomy of Blood Vessels  Arteries and veins have 3 layers Tunica intima – forms slick surface to decrease friction of blood flow Tunica media – smooth muscle and elastic tissue. Tunica media is thick in arteries and relatively thin in veins Tunica externa – the outermost tunic basically supports and protects the vessels  Capillaries have only one layer: tunica intima

49. Anatomy of Arteries  Arteries are strong, elastic vessels adapted for carrying high-pressure blood.  All the major arteries of the systemic circulation are branches of the aorta, which leaves the left ventricle  Arteries are capable of vasoconstriction as directed by the sympathetic impulses; when impulses are inhibited, vasodilation results.  Arteries become smaller as they divide and give rise to arterioles.

51.  Anatomy of Capillaries 51  Capillaries are the smallest vessels, consisting only of a layer of endothelium through which substances are exchanged with tissue cells.  Capillary permeability varies from one tissue to the next, generally with more permeability in the liver, intestines, and certain glands, and less in muscle and considerably less in the brain (blood-brain barrier).  Precapillary sphincters can regulate the amount of blood entering a capillary bed and are controlled by oxygen concentration in the area. If blood is needed elsewhere in the body, the capillary beds in less important areas are shut down Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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53.  Exchanges in the Capillaries 53  Blood entering capillaries contains high concentrations of oxygen and nutrients that diffuse out of the capillary wall and into the tissues.  Plasma proteins remain in the blood due to their large size.  Hydrostatic pressure drives the passage of fluids and very small molecules out of the capillary at this point.  At the venule end, osmosis, due to the osmotic pressure of the blood, causes much of the tissue fluid to return to the bloodstream.  Lymphatic vessels collect excess tissue fluid and return it to circulation. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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56. Anatomy of Veins  Veins have the same three layers as arteries but the walls are thinner, their lumens are larger, and they are equipped with valves. These modifications reflect low-pressure nature of veins. The valves prevent the backflow of blood.  The major veins of the systemic circulation ultimately converge on one of the venae cavae. All veins above the diaphragm drain into the superior vena cava, and those below the diaphragm drain into the inferior vena cava. Both venae cavae enter the right atrium of the heart  Varicose veins are caused by incompetent valves in the veins. It is common in the obese and people who stand for long hours

58. Blood Pressure 58  Blood pressure is the force of blood against the inner walls of blood vessels anywhere in the cardiovascular system, although the term "blood pressure" usually refers to arterial pressure. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

59.  Arterial Blood Pressure 59  Arterial blood pressure rises and falls following a pattern established by the cardiac cycle.  During ventricular contraction, arterial pressure is at its highest (systolic pressure).  When ventricles are relaxing, arterial pressure is at its lowest (diastolic pressure).  The surge of blood that occurs with ventricular contraction can be felt at certain points in the body as a pulse Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

60. 60  Arterial pressure depends on heart action, blood volume, resistance to flow, and blood viscosity.  Heart Action Heart action is dependent upon stroke volume and heart rate (together called cardiac output); if cardiac output increases, so does blood pressure.  Blood Volume Blood pressure is normally directly proportional to the volume of blood within the cardiovascular system. Blood volume varies with age, body size, and gender. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Factors that Affect Arterial Pressure

61. 61  Peripheral Resistance Friction between blood and the walls of blood vessels is a force called peripheral resistance. As peripheral resistance increases, such as during sympathetic constriction of blood vessels, blood pressure increases.  Blood Viscosity The greater the viscosity (ease of flow) of blood, the greater its resistance to flowing, and the greater the blood pressure. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Factors that Influence Arterial Pressure

62. 62 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

63. Control of Blood Pressure 63  Blood pressure is determined by cardiac output and peripheral resistance. The body maintains normal blood pressure by adjusting cardiac output and peripheral resistance. Cardiac output depends on stroke volume and heart rate, and a number of factors can affect these actions. Other factors, such as emotional upset, exercise, and a rise in temperature can result in increased cardiac output and increased blood pressure.

64. Control of Blood Pressure 64 The volume of blood that enters the right atrium is normally equal to the volume leaving the left ventricle.  If arterial pressure increases, the cardiac center of the medulla oblongata sends parasympathetic impulses to slow heart rate.  If arterial pressure drops, the medulla oblongata sends sympathetic impulses to increase heart rate to adjust blood pressure.

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