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Chapter 11: Cardiovascular System

Chapter 11: Cardiovascular System. The Cardiovascular System. A closed system of the heart/blood The heart pumps blood It is no more than a transportation pump Blood vessels allow blood to circulate throughout the body MILES of blood vessels – intricate network

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Chapter 11: Cardiovascular System

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  1. Chapter 11: Cardiovascular System

  2. The Cardiovascular System • A closed system of the heart/blood • The heart pumps blood • It is no more than a transportation pump • Blood vessels allow blood to circulate throughout the body • MILES of blood vessels – intricate network • At all times, blood is contained within the vessels or heart • Function: • Deliver oxygen and nutrients and re”move” carbon dioxide and other waste products

  3. The HEART • Location • Thorax: between the lungs & inferior to the mediastinum • Orientation • Apex (5cm) is pointed toward the left hip • Superior surface lies on the diaphragm • Base (9 cm) is towards the right shoulder • Lies anterior to the vertebral column, posterior to the sternum • Size • About the size of your fist • Weighs less than 1 pound • Shape • Hollow & cone shaped

  4. The HEART

  5. The HEART

  6. The HEART • Pericardium • Double walled sac containing the heart & the roots of the greater vessels • Two walls: fibrous pericardium & serous pericardium • Functions to protect the heart & lubricate the heart • Fibrous pericardium is loose and superficial • Functions: • Protect the heart • Anchor the heart to its surrounding structures (diaphragm & greater vessels) • Prevents overfilling of the heart with blood • Serous membrane (pericardium) is deep to the fibrous pericardium and composed of two layers • Visceral pericardium • Next to heart; also known as the epicardium • Parietal pericardium • Outside layer that lines the inner surface of the fibrous pericardium • Serous fluid fills the space between the layers of pericardium • The fluid is pale yellow, translucent, & benign in nature (“functionless)

  7. The HEART: Heart wall Three layers • Epicardium • Outside layer • This layer is the visceral pericardium • Produces pericardial fluid • Connective tissue layer • Lubricates the motion between the inner and outer layers of the pericardium • Often infiltrated with fat, in older people • Myocardium • Middle layer • Mostly cardiac muscle – arranged in circular/spiral bundles • This arrangement is what links all the structures of the heart together • Collagen & elastin connective tissues form the fibrous skeleton of the heart • Creates additional support where the great vessels issue from the heart/around the heart valves • Over time, these area become “stretched out” from the continual stress of blood pumping • Connective tissue cannot carry electrical impulses - limits the direct spread of action potential across cardiac tissue

  8. The HEART: Heart wall • Endocardium • Inner layer • Endothelium • Thin, white sheet of epithelial tissue • Lines the entire surface of the circulatory system, down to the interior surfaces of the capillaries • Label it all!

  9. The Chambers of the Heart • Right and left side act as separate pumps • Four chambers & two major separations • Atria • Thin walled & small  blood just flows down • Receiving chambers: blood enters the heart • Right atrium: receives deoxygenated blood from: • Superior vena cava • Returns blood from the body that is superior from the diaphragm • Inferior vena cava • Returns blood from the body that is inferior from the diaphragm • Coronary sinuses • Collects blood that drains from the myocardium itself • Left atrium: receives oxygenated blood from: • Left & right pulmonary veins • This makes up most of the heart’s base • Transports blood back to the heart, from the lungs

  10. The Chambers of the Heart Atria • The right and left atria are separated by the interatrial septum • Fossa ovalis: small shallow depression that marks where the foramen ovale had existed in the fetal heart • Auricles: small “flaps” that increase atrial volume – distinguishing feature of atria • Bundles of muscle in atria are specifically called pectinate muscles – look like they have been “raked with a comb”

  11. The Chambers of the Heart • Ventricles • Makes up most of the mass of the heart • Discharging chambers: blood leaves the heart • Right ventricle: pumps deoxygenated blood to the lungs through the pulmonary arteries • Makes up most of the anterior surface of the heart • Left ventricle: pumps (propels) oxygenated blood through the aorta out through the body (systemic circulation) • Makes up most of the posteroinferior surface • Trabeculae carneae:irregular ridges in the internal walls of the muscle layer – “crossbars” • Papillary muscles: conelike muscle bundles • Play a role in valve function

  12. The HEART

  13. The Heart: Septa • Interventricular septum • Separates the two ventricles • Interatrial septum • Separates the two atria

  14. The Heart: Types of circulation • Systemic circulation • Blood flows from the left side of the heart through the body tissues and back to the right side of the heart • Left side of the heart – systemic circuit pump • Blood leaves the left side of the heart to smaller arteries attached to body tissues to provide nutrients and gases. • Pulmonary circulation • Blood flows from the right side of the heart to the lungs and back to the left side of the heart • Right side of the heart – pulmonary circuit pump • Starts as Oxygen poor/carbon dioxide rich blood in the right atrium/ventricle • OPPOSITE: Pulmonary veins carry OXYGEN RICH blood back to the L.A.

  15. The Heart: Types of circulation • Coronary circulation • Shortest circulation within the body • Blood flow within the vessels of the heart itself • Ensures adequate oxygen supply for the heart muscle itself to function • The vessels are the coronary arteries & cardiac veins • Coronary arteries are the only source of blood supply for the actual myocardium • Myocardium is too thick to allow for diffusion of nutrients and gases • Delivery of nutrients and gases are specifically accomplished by the left and right coronary arteries (arising from the base of the aorta)

  16. The Heart: Types of circulation • Coronary circulation • The left C.A. runs towards the left side of the heart, branching into the interventricular artery, supplies blood to the interventricular septum & the anterior walls of both ventricles • Then, that blood travels to the posterior walls of the left ventricle via the circumflex artery. • The right C.A. runs along the right side of the heart, branching in two: • Marginal artery serves the myocardium of the lateral part of the right side of the heart • Posterior interventricular artery runs to the heart apex and supplies the posterior ventricular walls

  17. The Heart: Types of circulation • Coronary circulation • Arterial supply of the heart varies considerably • Each person can have different anastomoses (merging points) of arteries • These create different networks/routes of blood delivery to the heart • This also explains how arterial blockages don’t always stop the heart from working completely, unless. • Complete blockage of a coronary artery leads to tissue death and heart attack • Coronary arteries provide pulsing, intermittent blood flow to the heart • Actively deliver blood when the heart is relaxed • Ineffective when the ventricles are contracting • Compressed by the contracting heart muscles • Entrances to the coronary arteries are partly blocked by the flaps of the open aortic semilunar valve • Even though the heart only represents 1/200 of body weight, it requires 1/20 of blood supply • With the left ventricle using most of that blood supply

  18. The Heart: Valves • Valves allow blood to only flow in one direction (prevent backflow) • Four valves: • Between the atria & ventricles: AV valves • Anchored in place by chordae tendinae: “heart strings” • Open during heart relaxation and closed during ventricular contract • Bicuspid (mitral): left side of the heart • Tricuspid: right side of the heart • Between ventricles & an artery: semilunar valves • Closed during heart relaxation & open during ventricular contract • Pulmonary semilunar valve: between the right ventricle & the pulmonary artery • Aortic semilunar valve: between the left ventricle & the aorta

  19. The Heart: Greater Vessels • Arteries: • Aorta: leaves the left ventricle • Brings oxygenated blood out to the body • Pulmonary artery: leaves the right ventricle • Brings deoxygenated blood to the lungs • Veins • Superior & inferior vena cava: enters the right atrium • Brings deoxygenated blood into the heart • Pulmonary veins (there are four): enters the left atrium • Brings oxygenated blood into the heart

  20. Pathway of Blood flow • Superior & Inferior venae cavae bring blood into the right atrium • From the right atrium, blood travels through the tricuspid valve to the right ventricle • Blood leaves the right ventricle, passing through the semilunar valve into the pulmonary trunk • The pulmonary trunk splits into the left/right pulmonary arteries that carry blood into the lungs

  21. Pathway of Blood flow • Oxygen is picked up and carbon dioxide is dropped off • Oxygen rich blood travels back to the heart through the four pulmonary veins • Blood enters the left atrium, travels through the bicuspid valve into the left ventricle • From the left ventricle, blood leaves the heart via the aortic semilunar valve and ultimately the aorta – allowing the blood to travel through the body. • Simple, no?

  22. Coronary Circulation • Blood in the heart chambers does not nourish the myocardium • The heart has its own nourishing circulatory system consisting of • Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood • Cardiac veins—drain the myocardium of blood • Coronary sinus—a large vein on the posterior of the heart, receives blood from cardiac veins • Blood empties into the right atrium via the coronary sinus

  23. Electrical Conduction of the Heart

  24. Electrical Conduction of the Heart • Intrinsic conduction system (nodal system) • Heart muscle cells contract, without nerve impulses, in a regular, continuous way • Special tissue sets the pace • Sinoatrial node = SA node (“pacemaker”) • Impulse generating tissue that keeps the regular contractions of the heart • It’s a group of cells called myocytes positioned by the top of the right atrium • It’s a muscle cell that contains some parts of the contractile unit • Atrioventricular node = AV node, is at the junction of the atria and ventricles • Serves as a “backup” for the SA node (pacemaker) • Ensures there is a mild delay (0.12 seconds) in the contraction of ventricles to ensure that there is actually enough blood to pump out of the ventricles

  25. Electrical Conduction of the Heart • Special tissue sets the pace (continued) • Atrioventricular bundle = AV bundle (bundle of His), is in the interventricular septum • Transmits impulses from the AV node to the apex of the heart • Purkinje fibers extend out of the AV bundle • This bundle of cells is important because it’s regular rate of impulse messaging is 40-60 beats per minute • Bundle branches are in the interventricular septum • Purkinje fibers spread within the ventricle wall muscles • Distribute the impulses to the walls of ventricles actually allowing cardiac muscle contraction to happen • Atrial fibrillation: the muscles of the atria “quiver” instead of regularly contract • Physiological cause: overwhelming, disorganized impulses from the SA node or AV node miscommunication • Increases stroke risk up to 7x because blood may pool in atria or clot

  26. Electrical Conduction of the Heart • Contraction is initiated by the sinoatrial node • Sequential stimulation occurs • Force cardiac muscle depolarization in one direction—from atria to ventricles • Once SA node starts the heartbeat • Impulse spreads to the AV node • Then the atria contract • At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers • Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract

  27. Heart Contraction • Tachycardia—rapid heart rate over 100 beats per minute • Bradycardia—slow heart rate less than 60 beats per minutes

  28. The Cardiac Cycle • Atria contract simultaneously • Atria relax, then ventricles contract • Systole = contraction • Usually describes left ventricle contraction: cardiomyocytes • Diastole = relaxation • Happens after systole; allows the heart to refill with blood • Cardiac cycle—events of one complete heart beat • Mid-to-late diastole—blood flows from atria into ventricles • Ventricular systole—blood pressure builds before ventricle contracts, pushing out blood • Early diastole—atria finish refilling, ventricular pressure is low

  29. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Ventricularejection phase Isovolumetricrelaxation Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Early diastole The Cardiac Cycle http://www.sumanasinc.com/webcontent/animations/content/bloodpressure.swf

  30. The Heart: Cardiac Output • Cardiac output (CO) • Amount of blood pumped by each side (ventricle) of the heart in one minute • Stroke volume (SV) • Volume of blood pumped by each ventricle in one contraction (each heartbeat) • Usually remains relatively constant • About 70 mL of blood is pumped out of the left ventricle with each heartbeat • Heart rate (HR) • Averages: 75 beats per minute • CO = HR  SV • CO = HR (75 beats/min)  SV (70 mL/beat) • CO = 5250 mL/min • Starling’s law of the heart—the more the cardiac muscle is stretched, the stronger the contraction • Changing heart rate is the most common way to change cardiac output

  31. Regulation of Heart Rate • Increased heart rate • Sympathetic nervous system is stimulated • Crisis • Low blood pressure • Hormones • Epinephrine – released in stressful situations (adrenaline) • Thyroxine – used to increase metabolism • Exercise • Decreased blood volume • Decreased heart rate • Parasympathetic nervous system is activated in reaction to a sympathetic stimulation • High blood pressure or blood volume • Decreased venous return

  32. Blood Vessels • Transport blood to the tissues and back • Carry blood away from the heart • Arteries • Arterioles • Exchanges between tissues and blood • Capillary beds • Return blood toward the heart • Venules • Veins

  33. Blood Vessels: Microscopic Anatomy • Three layers (tunics) • Tunica intima • Endothelium – one layer of cells • Have direct contact with blood • Tunica media • Smooth muscle • In larger arteries, there may be elastic tissue • Controlled by sympathetic nervous system • Tunica externa • Mostly fibrous connective tissue (collagen) • Anchors blood vessels to body organs

  34. Differences between arteries & veins • Walls of arteries are the thickest • Lumens of veins are larger • Larger veins have valves to prevent backflow • Skeletal muscle “milks” blood in veins toward the heart • Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue • Most arterial blood is pumped by the heart

  35. Capillaries • Capillary beds consist of two types of vessels • Vascular shunt—vessel directly connecting an arteriole to a venule • True capillaries—exchange vessels • Oxygen and nutrients cross to cells • Carbon dioxide and metabolic waste products cross into blood

  36. Major Arteries • Aorta • Largest artery in the body • Leaves from the left ventricle of the heart • Regions of the Aorta • Ascending aorta—leaves the left ventricle • Left & right coronary arteries leave here to supply blood to the heart • Aortic arch—arches to the left • Thoracic aorta—travels downward through the thorax • Abdominal aorta—passes through the diaphragm into the Abdominopelvic cavity

  37. Major Arteries • Arterial branches of the aortic arch (BCS) • Brachiocephalic trunk splits into the • Right common carotid artery • Right subclavian artery • Left common carotid artery splits into the • Left internal and external carotid arteries • Left subclavian artery branches into the • Vertebral artery • In the axilla, the subclavian artery becomes the axillary artery  brachial artery  radial and ulnar arteries • http://zircon.mcli.dist.maricopa.edu/arle/LabelingExercisesII/activityApplet7.html

  38. Major Arteries • Arterial branches of the thoracic aorta • Intercostal arteries supply the muscles of the thorax wall • Other branches of the thoracic aorta supply the • Lungs (bronchial arteries) • Esophagus (esophageal arteries) • Diaphragm (phrenic arteries)

  39. Major Arteries • Arterial branches of the abdominal aorta • Celiac trunk is the first branch of the abdominal aorta. Three branches are • Left gastric artery (stomach) • Splenic artery (spleen) • Common hepatic artery (liver) • Superior mesenteric artery supplies most of the small intestine and first half of the large intestine • Left and right renal arteries (kidney) • Left and right gonadal arteries • Ovarian arteries in females serve the ovaries • Testicular arteries in males serve the testes • Lumbar arteries serve muscles of the abdomen and trunk

  40. Major Arteries • Arterial branches of the abdominal aorta • Inferior mesenteric artery serves the second half of the large intestine • Left and right common iliac arteries are the final branches of the aorta • Internal iliac arteries serve the pelvic organs • External iliac arteries enter the thigh  femoral artery  popliteal artery  anterior and posterior tibial arteries

  41. Major Arteries

  42. Major Veins • Superior and inferior vena cava enter the right atrium of the heart • Superior vena cava drains the head and arms • Inferior vena cava drains the lower body • Veins draining into the superior vena cava • Radial and ulnar veins  brachial vein  axillary vein • These veins drain the arms • Cephalic vein drains the lateral aspect of the arm and empties into the axillary vein • Basilic vein drains the medial aspect of the arm and empties into the brachial vein • Basilic and cephalic veins are jointed at the median cubital vein (elbow area)

  43. Major Veins • Veins draining into the superior vena cava • Subclavian vein receives • Venous blood from the arm via the axillary vein • Venous blood from skin and muscles via external jugular vein • Vertebral vein drains the posterior part of the head • Internal jugular vein drains the dural sinuses of the brain • Left and right brachiocephalic veins receive venous blood from the • Subclavian veins • Vertebral veins • Internal jugular veins • Brachiocephalic veins join to form the superior vena cava  right atrium of heart • Azygous vein drains the thorax

  44. Major Veins • Veins draining into the inferior vena cava • Anterior and posterior tibial veins and fibial veins drain the legs • Posterior tibial vein  popliteal vein  femoral vein  external iliac vein • Great saphenous veins (longest veins of the body) receive superficial drainage of the legs • Each common iliac vein (left and right) is formed by the union of the internal and external iliac vein on its own side • Right gonadal vein drains the right ovary in females and right testicle in males • Left gonadal vein empties into the left renal vein • Left and right renal veins drain the kidneys • Hepatic portal vein drains the digestive organs and travels through the liver before it enters systemic circulation • Left and right hepatic veins drain the liver

  45. Major Veins

  46. Arterial Supply of the Brain • Internal carotid arteries divide into • Anterior and middle cerebral arteries • These arteries supply most of the cerebrum • Vertebral arteries join once within the skull to form the basilar artery • Basilar artery serves the brain stem and cerebellum • Posterior cerebral arteries form from the division of the basilar artery • These arteries supply the posterior cerebrum • Circle of Willis • Anterior and posterior blood supplies are united by small communicating arterial branches • Result—complete circle of connecting blood vessels called cerebral arterial circle or circle of Willis

  47. Arterial Supply of the Brain

  48. Pulse • Pulse • Pressure wave of blood • Monitored at “pressure points” in arteries where pulse is easily palpated • Pulse averages 70–76 beats per minute at rest

  49. Variations in Blood Pressure • Normal human range is variable • Normal • 140–110 mm Hg systolic • 80–75 mm Hg diastolic • Hypotension • Low systolic (below 110 mm HG) • Often associated with illness • Hypertension • High systolic (above 140 mm HG) • Can be dangerous if it is chronic

  50. Factors that affect blood pressure • BP is blood pressure • BP is affected by age, weight, time of day, exercise, body position, emotional state • CO is the amount of blood pumped out of the left ventricle per minute • PR is peripheral resistance, or the amount of friction blood encounters as it flows through vessels • Narrowing of blood vessels and increased blood volume increases PR • BP = CO  PR

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