BMED 66 Chapter 14 Heart PDF

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Anatomy is the identification and description of the structures of living things. It is a branch of biology and medicine. The study of anatomy dates back more than 2,000 years , to the Ancient Greeks. There are three broad areas: ... plant anatomy — phytotomy....

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Chapter 14 THE HEART cardiovascular system - major function, transportation -blood as the transport vehicle, the system carries oxygen, digested foods, cell wastes, electrolytes, and many other substances vital to the body’s homeostasis to and from the body cells - propulsive force - the beating heart, a muscular pump equipped with one-way valves - as the heart contracts,it forces blood into a closed system of large and small plumbing tubes (blood vessels) within which the blood circulates Heart - a cone-shaped organ approximately the size of a fist, located within the mediastinum, the medial cavity of the thorax -flanked laterally by the lungs, posteriorly by the vertebral column, and anteriorly by the sternum (Figure 14.1). - apex Its more pointed extends slightly to the left and rests on the diaphragm, approximately at the level of the fifth intercostal space -. Base – broader from which the great vessels emerge, lies beneath the second rib and points toward the right shoulder - right ventricle of the heart forms most of its anterior surface. - pressing just below the left nipple, apical pulse of your beating heart can be felt; can be verified, in an X-ray image within called the Pericardium - a double-walled serous sac in which the heart is enclosed fibrous pericardium - the loosely fitting outer part of the serous sac -this fibrous layer protects the heart and anchors it to surrounding structures, such as the diaphragm and sternum. Serous pericardium - the two-layer below the fibrous pericardium ; a. parietal layer lines the inside of the fibrous pericardium b. visceral layer, or epicardium - At the base of the heart, the parietal layer reflects back to cover the external heart as the -Serous fluid produced by these membranes allows the heart to beat in a relatively frictionless environment. Three layers of the walls of the heart: a. Epicardium - outer layer, which is also the visceral pericardium b. Myocardium - middle layer; thickest layer, mostly of cardiac muscle c. Endocardium - inner lining of the heart that is made of simple squamous epithelium, covers the heart valves and is continuous with the inner lining of the great vessels.

Figure 14.1. Anterior vies of the heart Heart Chambers Four chambers of the heart: a. two superior atria and b. two inferior ventricles (Figure14.1). interatrial or interventricular septum - divides the heart longitudinally depending on which chambers it partitions. atria - are receiving chambers and are relatively ineffective as pumps - the right atrium receives oxygen-poor blood from the body via the superior and inferior venae cavae - Four pulmonary veins deliver oxygen-rich blood from the lungs to the left atrium. - inferior ventricles - form the bulk of the heart, the discharging chambers; force blood out of the heart into the large arteries that emerge from its base - right ventricle pumps blood into the pulmonary trunk, which sends blood to the lungs to be oxygenated - left ventricle discharges blood into the aorta, - aorta - from which all systemic arteries of the body diverge to supply the body tissues; a much longer circuit than the pulmonary circuit, - left ventricle walls are much thicker than those of the right ventricle - heart’s pumping action usually refer to the activity of the ventricles Four Heart Valves - valves enforce a one-way blood flow through the heart chambers a. atrioventricular (AV) valves – between the atrium and ventricle on each side, prevent backflow into the atria when the ventricles are contracting. The b. semilunar (SL) valves - located between a ventricle and a great vessel on each side c. Right atrioventricular (AV) valve (tricuspid valve):Has three cusps (Figure 20.2b) anchored to the papillary muscles of the ventricular wall by cords called

chordae tendineae (literally, “heart strings”). d. Left atrioventricular (AV) valve: (mitral valve or bicuspid valve): Has two cusps anchored to the papillary muscles by chordae tendineae. Pulmonary semilunar valve - Has three cusps located between the right ventricle and the pulmonary trunk. Aortic semilunar valve- Has three pocket-like cusps located between the left ventricle and the aorta. When the heart is relaxing, blood flows passively into the atria and then into the ventricles. At first, the AV valve flaps hang limply into the ventricular chambers, and then they are carried passively toward the atria by the accumulating blood. When the ventricles contract and compress the blood in their chambers, the intraventricular pressure rises, forcing the valve flaps superiorly, which closes the AV valves. The chordae tendineae anchor the flaps in a closed position that prevents backflow into the atria during ventricular contraction. - SL valve cusps are forced open and flatten against the walls of the artery as the ventricles pump their blood into the large arteries during systole. - ventricles relax and blood flows backward toward the heart, the cusps fill with blood, closing the semilunar valves. This prevents the backflow of blood from the great vessels into the ventricles.

Figure 14.2. Frontal section, interior chambers and valves

Pulmonary and Systemic Circulations The heart is a double pump. a. right side serves as the pulmonary circulation pump, sending the carbon dioxide– rich blood entering its chambers to the lungs to unload carbon dioxide and pick up oxygen and then back to the left side of the heart (Figure 20.3). Gas exchange is the sole purpose of the pulmonary circuit. b. second circuit - systemic circulation, carries oxygen-rich blood from the left heart through the body tissues and back to the right heart. It supplies the functional blood supply to all body tissues.

Trace the pathway of blood through the heart by adding arrows to the frontal section diagram (Figure 20.2b). Use red arrows for the oxygen-rich blood and blue arrows for the less oxygen-rich blood.

Figure 14.3. The systemic and pulmonary circuits The heart is a double pump that serves two circulations. The right side of the heart pumps blood through the pulmonary circuit to the lungs and back to the left heart. (For simplicity, the actual number of two pulmonary arteries and four pulmonary veins has been reduced to one each.) The left heart pumps blood via the systemic circuit to all body tissues and back to the right heart. Notice that blood flowing through the pulmonary circuit gains oxygen and loses carbon dioxide. Blood flowing through the systemic circuit loses oxygen and picks up carbon dioxide. Even though the heart chambers are bathed with blood almost continuously, this blood does not nourish the myocardium. The blood supply that nourishes the heart is provided by the right and left coronary arteries. The coronary arteries branch from the base of the aorta and encircle the heart in the coronary sulcus (atrioventricular groove) at the junction of the atria and ventricles. They then branch over the heart’s surface, the

right coronary artery supplying the posterior surface of the ventricles and the lateral aspect of the right side of the heart, largely through its posterior interventricular and marginal artery branches. The left coronary artery supplies the anterior ventricular walls and the laterodorsal part of the left side of the heart via the anterior interventricular artery and the circumflex artery. The coronary arteries and their branches are compressed during systole and fill when the heart is relaxed. The myocardium is drained by several cardiac veins,which empty into the coronary sinus (an enlarged vessel on the backside of the heart). The coronary sinus, in turn, empties into the right atrium. In addition, several anterior cardiac veins empty directly into the right atrium. Cardiac muscle is found in only one place—the heart. Because the heart acts as a blood pump, propelling blood to all tissues of the body, cardiac muscle is very important to life. Cardiac muscle is involuntary, ensuring a constant blood supply. The cardiac cells are arranged in spiral or figure- 8-shaped bundles (Figure 14.4). When the heart contracts, its internal chambers become smaller (or are temporarily obliterated), forcing the blood upward into the large arteries leaving the heart.

Figure 14.4. Cardiac muscle in spiral arrangement Labels: A. Figure 14.1. Anterior view of the heart Left, downward

Right, downward

1. Brachiocephalic trunk

1.aortic arc

2. Superior vena cava

2.left pulmonary artery

3. Right pulmonary artery

3.left pulmonary vein

4. Aorta

4.left atrium

5. Right pulmonary veins

5.left ventricle

6. Right atrium

6.apex

7. Right ventricle 8. Inferior vena cava B. Figure 14.2. Frontal section, interior chambers and valves Left, downward Right, downward

1.Superior vena cava

1.Aorta

2.Right pulmonary artery

2.Left pulmonary artery

3.Right pulmonary vein

3.pulmonary trunk

4. Right atrium

4.left pulmonary vein

5. Fossa ovalis

5. left atrium

6. Right atrio ventricular valve (tricuspid valve)

6. pulmonary semilunar valve

7. Right ventricle

7. left atrio ventricular valve (bicuspid or mitral valve)

8.Inferior vena cava

8. left ventricle 9.endocardium 10.myocardium 11. visceral pericardium (epicardium) 12. interventricular septum

C. Figure 14.3. System and Pulmonary circuits Left, downward Right, Downward 1. Pulmonary arteries 1. Capillary beds of lungs 2. Vena cavae 2. Pulmonary circuit 3.Pulmonary veins 4.Aorta and branches 5.Left ventriclr 6.Systemic circuit

REFERENCES: Marieb, Elaine N. and Keller, Suzanne M. (2018). Essentials of Human Anatomy and Physiology. 12th Edition. Pearson Education South Asia Pte Ltd. Singapore. Marieb, Elaine N. and Brito, Simone (2019). Anatomy and Physiology coloring workbook( A complete study guide). 12th Edition. Pearson Education South Asia Pte Ltd. Singapore...