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1. heart Maria immaculata iwo, sf, itb

2. 2010 The Heart  The heart is located in the thoracic cavity between the lungs, within the mediastinum.  It is a hollow, cone-shaped, muscular organ, about the size of a fist.  The base (the widest part) of the heart is superior to its apex (the pointed tip), which rests on the diaphragm.  Also, the heart is on a slant; the base is directed toward the right shoulder, and the apex points to the left hip.  The base is deep to the second rib, and the apex is at the level of the fifth intercostal space. maria immaculata iwo, sf itb

3. Size and Location, Position of the Heart and Associated Blood Vessels • Size: Nine (9) inches long x three (3) inches wide. Locatedwithin the mediastinum, bordered laterally by the lungs, posteriorly by the backbone, and anteriorly by the sternum.  Base attached to several large blood vessels and lies beneath the second rib. • Apex at the fifth intercostal space maria immaculata iwo, sf itb

5. As the heart pumps the blood through the pulmonary and systemic vessels, it performs these functions: 1. keeps O2-poor blood separate from O2-rich blood; 2. keeps the blood flowing in one direction — blood flows away from and then back to the heart in each circuit; 3. creates blood pressure, which moves the blood through the circuits; 4. regulates the blood supply based on the current needs of the body maria immaculata iwo, sf itb

6. The heart is called double pump. - Pulmonary circuit - Systemic circuit  The right side of the heart pumps blood through vessels of the pulmonary circuit. The left side of the heart pumps blood through vessels of the systemic circuit.  Gas exchange occurs as blood passes through lung (pulmonary) capillaries.  Gas exchange and nutrient- for-waste exchange occur as blood passes through tissue (systemic) capillaries. In this illustration, red vessels carry O2-rich blood, and blue vessels carry O2-poor blood.

7. Wall of the Heart The wall of the heart consists of three layers.  an outer: epicardium or visceral pericardium  a middle: myocardiumthick is composed of cardiac muscle tissue.  an inner: endocardium  External to the epicardium is the double-layeredparietalpericardium, composed of an inner serous membrane and an outer fibrous membrane. • The pericardial cavity, lies between the epicardium and parietal pericardium containing pericardial fluid • Fluid secreted by the serous membranes reduces friction, enabling the heart to move freely within the pericardial sac. maria immaculata iwo, sf itb

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9. Anterior view of exterior heart anatomy

10. Chambers and valves of the heart The heart has four hollow chambers • The upper (superior): • thin-walled chambers, the left and right atria, which receive blood returning to the heart. • Atria send blood into the adjacent ventricles. • The lower (inferior), • thick-walled chambers are the left and right ventricles, which pump blood into the arteries leaving the heart. • the left ventricle has a thicker wall than the right ventricle; • the right ventricle pumps blood to the lungs, which are nearby. • The left ventricle pumps blood to all the other parts of the body.  Internally, the atria are separated by the interatrial septum, and the ventricles are separated by the interventricular septum.  Therefore, the heart has a left and a right side. maria immaculata iwo, sf itb

11. The heart has 4 valves: • two atrioventricularvalves • two semilunar valves. The Atrioventricular valves  The valves prevent a backflow of blood from the ventricles into the atria during systole - the contraction phase of the heart cycle.  The cusps have thin cords, the chordae tendineae, that anchor them to papillary muscles on the walls of the ventricles and prevent the valve cusps from being forced into the atria during contraction. The tricuspid av-valve, has three flaps or cusps and occurs between the right atrium and ventricle. The mitral or bicuspid av-valve has only two cusps, and occurs between the left atrium and ventricle. maria immaculata iwo, sf itb

12. The semilunar valves the pulmonary semilunar valve  located at the base of the pulmonary artery the aortic semilunar valve  located at the base of the aorta  They each have three cusps  Prevent the backflow of blood from the arteries into the ventricles during diastole - the relaxation phase of the heart cycle. maria immaculata iwo, sf itb

13. Internal heart anatomy Semilunar valve Bicuspid (mitral) valve (AV valve) Tricuspid valve (AV valve) Intraventricular septum

14. Coronary Circuit Cardiac muscle fibers and the other types of cells in the wall of the heart are not nourished by the blood in the chambers; Instead, these cells receive nutrients and rid themselves of wastes at capillaries embedded in the heart wall.  coronary arteries, the left and right coronary arteries, branch from the aorta just beyond the aortic semilunar valve. • Each of these arteries branches then rebranches  encircled by small arterial blood vessels  capillary bed in the heart  the coronary veins (specifically called cardiac veins). • The cardiac veins enter a coronary sinus, • The coronary sinus enters the right ventricle. maria immaculata iwo, sf itb

15. Coronary Circuit Disorders • Heart diseases are especially associated with atherosclerosis, a degenerative disorder of arterial walls. First, soft masses of fatty materials, particularly cholesterol, accumulate in the arterial wall.  Further changes result in plaque, protrusions that interfere with blood flow. If the coronary artery is partially occluded (blocked) by atherosclerosis, the individual may suffer from ischemic heart disease.  the person experiences insufficiency during exercise or stress.  This may lead to angina pectoris, chest pain that is often accompanied by a radiating pain in the left arm. The blood may clot in an unbroken blood vessel, particularly if plaque is present  thromboembolism is present when a blood clot breaks away from its place of origin and is carried to a new location. Thromboembolism leads to heart attacks when the embolus blocks a coronary artery and a portion of the heart dies due to lack of oxygen. Dead tissue is called an infarct, and therefore, a heart attack is termed a myocardial infarction.

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18. Physiology of the Heart The physiology of the heart pertains to its pumping action— that is, the heartbeat. It is estimated that the heart beats two and-a-half billion times in a lifetime, continuously recycling some 5 liters (L) of blood to keep us alive. In this section, we will consider what causes the heartbeat, what it consists of, and its consequences. maria immaculata iwo, sf itb

19. Conduction System of the Heart  The conduction system of the heart is a route of specialized cardiac muscle fibers that initiate and stimulate contraction of the atria and ventricles.  The conduction system is said to be intrinsic, meaning that the heart beats automatically without the need for external nervous stimulation.  The conduction system coordinates the contraction of the atria and ventricles, so that the heart is an effective pump.  Without this conduction system, the atria and ventricles would contract at different rates. maria immaculata iwo, sf itb

20. Conduction System of the Heart The SA node is called the pacemaker because it usually keeps the heartbeat regular. maria immaculata iwo, sf itb

21. Nodal system, • intrinsic conducting system Components • Sinoatrial (S-A) Node (pacemaker) • Atrioventricular node • (A-V node) • A-V bundle • (Bundle of His) • right and left bundle branches • down, the branches • give rise to enlarged Purkinje fibers Sinoatrial (SA) node (AV) node AV bundle Left bundle branch Right bundle branch Purkinje fibers maria immaculata iwo, sf itb

22.  An area other than the SA node can become the pacemaker when it develops a rate of contraction that is faster than the SA node.  This site, called an ectopic pacemaker, may cause an extra beat, if it operates only occasionally, or it can even pace the heart for a while. • Caffeine and nicotine are two substances that can stimulate an ectopic pacemaker. A rate of fewer than 60 heartbeats per minute is called bradycardia, and more than 100 heartbeats per minute is called tachycardia. Another type of arrhythmia is fibrillation, in which the heart beats rapidly but the contractions are uncoordinated.  heart block maria immaculata iwo, sf itb

23. Electrocardiogram (ECG) • Impulse transmission through the conduction system generated electrical currents that can be detected on the body's surface. • A graph that records the electrical activity of the myocardium during • a cardiac cycle is called an electrocardiogram, or ECG. • An ECG consists of a set of waves: •  the P wave, •  a QRS complex, •  a T wave.

25. P-Wave • Indicates atrial depolarization. • The spread of the impulse from the S-A node through the two atria. • the atria are going to be in systole and that the atrial myocardium is about to contract. • QRS-Wave or Complex • Represents ventricular depolarization • the spread of the electrical impulse through the ventricles. • Shortly after the QRS wave begins, the ventricles undergo contraction. • T-Wave • Indicates ventricular repolarization maria immaculata iwo, sf itb

26. Cardiac Cycle and Heart Sounds  A cardiac cycle includes all the events that occur during one heartbeat.  On average, the heart beats about 70 times a minute, although a normal adult heart rate can vary from 60 to 100 beats per minute.  The right and left sides of the heart beat independently of one another, but actually, they contract together.  First the two atria contract simultaneously; then the two ventricles contract together.  The term systole refers to contraction of heart muscle, and the term diastolerefers to relaxation of heart muscle.  During the cardiac cycle, atrial systoleis followed by ventricular systole. maria immaculata iwo, sf itb

27. three phases of the cardiac cycle Phase 1: Atrial Systole. Phase 2: Ventricular Systole. Phase 3: Atrial and Ventricular Diastole. maria immaculata iwo, sf itb

28. Phase 1: Atrial Systole. - Time 0.15 sec. - During this phase, both atria are in systole (contracted), while the ventricles are in diastole (relaxed). - Rising blood pressure in the atria forces the blood to enter the two ventricles through the AV valves. - At this time, both atrioventricular valves are open, and the semilunar valves are closed. maria immaculata iwo, sf itb

29. Phase 2: Ventricular Systole. - Time 0.30 sec. - During this phase, both ventricles are in systole (contracted), while the atria are in diastole (relaxed). - Rising blood pressure in the ventricles forces the blood to enter the pulmonary trunk leading to the pulmonary arteries and aorta through the semilunar valves. - At this time, both semilunar valves are open, and the atrioventricular valves are closed. maria immaculata iwo, sf itb

30. Phase 3: Atrial and Ventricular Diastole. - Time 0.40 sec. - During this period, both atria and both ventricles are indiastole (relaxed). - At this point, pressure in all the heart chambers is low. - Blood returning to the heart from the superior and inferior vena cava and the pulmonary veins fills the right and left atria and flows passively into the ventricles. - At this time, both atrioventricular valves are open, and the semilunar valves are closed. maria immaculata iwo, sf itb

31. Phase 3: atrial & ventricular diastole Phase 1: atrial systole Phase 2: ventricular systole maria immaculata iwo, sf itb

32. Heart Sounds • A heartbeat produces the familiar “LUB-DUP” sounds as the chambers contract and the valves close. • Lub sound • The first heart sound, “lub,” is heard when the ventricles contract and the atrioventricular valvesclose. • This sound lasts longest and has a lower pitch. • Dup sound • The second heart sound, “dup,” is heard when the relaxation of the ventricles allows the semilunar valves to close. • The third sound seems to be caused by the vibration of the ventricular walls and the atrio-ventricular valve cusps during systole. maria immaculata iwo, sf itb

33. Heart murmurs,  which are clicking or swishing sounds heard after the “lub,” are often due to ineffective valves. • These leaky valves allow blood to pass back into the atria after the atrioventricular valves have closed, or back into the ventricles after the semilunar valves have closed. • A trained physician or health professional can diagnose heart murmurs from their sound and timing. • It is possible to replace the defective valve with an artificial valve. maria immaculata iwo, sf itb

34. Cardiac Output • Cardiac output (CO) • is the volume of blood pumped out of a ventricle in one minute. • Cardiac output is dependent on two factors: • heart rate(HR),which is the beats per minute; • stroke volume(SV),which is the amount of blood pumped by a ventricle each time it contracts. • The CO of an average human is 5,250 ml (or 5.25 L) per minute, which equates to about the total volume of blood in the human body. • Each minute, the right ventricle pumps about 5.25 L through the pulmonary circuit, while the left ventricle pumps about 5.25 L through the systemic circuit. maria immaculata iwo, sf itb

35. Heart Rate • A cardioregulatory center in the medulla oblongata of the brain can alter the heart rate by way of the autonomic nervous system (ANS) • Parasympathetic motor impulses conducted by the vagus nerve cause the heart rate toslow, • Sympatheticmotor impulses conducted by sympathetic motor fibers cause the heart rate to increase. • The cardioregulatory center is under the influence of the cerebrum and the hypothalamus. • when we feel anxious, • the sympathetic motor nerves are activated, and the adrenal medulla releases the hormones norepinephrine and epinephrine.  The result is an increase in heartbeat rate. maria immaculata iwo, sf itb

36.  Activities such as yoga and meditation lead to activation of the vagus nerve, which slows the heartbeat rate. • low body temperature  slows the rate. • proper electrolyte concentrations are needed to keep the heart rate regular. • Exercise? maria immaculata iwo, sf itb

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39. Stroke Volume • SV - which is the amount of blood that leaves a ventricle, depends on the strength of contraction. • The degree of contraction depends on • the blood electrolyte concentration • the activity of the autonomic system. maria immaculata iwo, sf itb

40. Venous Return Venous return is the amount of blood entering the heart by way of the vena cava (right side of heart) or pulmonary veins (left side of heart). Any event that decreases or increases the volume or speed of blood entering the heart will affect the strength of contraction—called Starling’s Law. • A slow heart rate allows more time for the ventriclesto fill and therefore increases the strength of contraction. • A low venous return, as might happen if there is blood loss, decreases the strength of contraction. • Exercise increases the strength of contraction because skeletal muscle contraction puts pressure on the veins and speeds venous return. maria immaculata iwo, sf itb

43. Regulation of blood pressure and volume • Bottom: • When the blood sodium (Na) level is low, a low blood pressure causes the kidneys to secrete renin. Renin leads to the secretion of aldosterone from the adrenal cortex. Aldosterone causes the kidneys to reabsorb Na, and water follows, so that blood volume and pressure return to normal. • Top:When the blood Na is high, a high blood volume causes the heart to secrete atrial natriuretic hormone (ANH). ANH causes the kidneys to excrete Na, and water follows. The blood volume and pressure return to normal. maria immaculata iwo, sf itb