A closed system of the heart/blood. Function: The heart pumps blood. Blood vessels allow blood to circulate throughout the body

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2 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 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

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6 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 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 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 Right and left side act as separate pumps Four chambers & two major separations Atria Thin walled & small à 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 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 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

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13 Interventricular septum Separates the two ventricles Interatrial septum Separates the two atria

14 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 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 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 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 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 Arteries: Aorta: leaves the left ventricle Brings oxygenated blood out to the body Pulmonary artery: leaves the right ventricle Veins Brings deoxygenated blood to the lungs 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 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 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 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

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24 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 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 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 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 Tachycardia rapid heart rate over 100 beats per minute Bradycardia slow heart rate less than 60 beats per minutes

28 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 Ventricular filling Atrial contraction Isovolumetric Ventricular contraction phase ejection phase Isovolumetric relaxation Mid-to-late diastole (ventricular filling) Ventricular systole (atria in diastole) Early diastole

30 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 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 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 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 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 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 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 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 à brachial artery à radial and ulnar arteries LabelingExercisesII/activityApplet7.html

38 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 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 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 à femoral artery à popliteal artery à anterior and posterior tibial arteries

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42 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 à brachial vein à 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 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 à right atrium of heart Azygous vein drains the thorax

44 Veins draining into the inferior vena cava Anterior and posterior tibial veins and fibial veins drain the legs Posterior tibial vein à popliteal vein à femoral vein à 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

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46 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

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48 Pulse Pressure wave of blood Monitored at pressure points in arteries where pulse is easily palpated Pulse averages beats per minute at rest

49 Normal human range is variable Normal mm Hg systolic 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 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

51 Neural factors Autonomic nervous system adjustments (sympathetic division) Renal factors Regulation by altering blood volume Renin hormonal control Temperature Heat has a vasodilating effect Cold has a vasoconstricting effect Chemicals Various substances can cause increases or decreases Diet