The+Heart+HW3+MC

(1) In which direction does the heart tilt? The heart is tilted so that the apex (the pointed end) is oriented to the left. (2) What is the approximate size of the heart? To approximate the size of your heart, make a fist, then clasp the fist with your opposite hand. (3) Describe the myocardium. It consist largely of cardiac muscle tissue and is serviced by the coronary artery and cardiac vein and not by the blood it pumps. (4) Why do you think a heart attack is sometimes called a myocardial infarction p. 97? Because it occurs when a portion of the heart muscle dies due to lack of oxygen. When a coronary artery is completely blocked, perhaps because of thromboembolism, a heart attack occurs. (5) Describe the pericardium. It surrounds the heart. It’s a thick, membrane sac that supports and protects the heart. The inside of the pericardium secretes a lubrication fluid, and the pericardium slides smoothly over the surface as the heart pumps the blood. (6) Describe the septum. A wall called the septum separates the heart into a right side and a left side. (7) Where are the atria? Describe their walls. They are located in the upper part of the heart as the two upper chambers. They are called the left atrium and the right atrium. Each atrium has a wrinkled, Protruding appendage called an auricle. (8) Where are the ventricles? Describe their walls. They are in the lower part of the heart as the two lower chambers that are thick-walled ventricles called the right ventricle and the left ventricle. (9) Where are the atrioventricular valves? Describe their shape (number of flaps) and various names. They lie between the atria and the ventricles. Strong fibrous strings called chordae tendineae support these valves. The AV valve on the right side is called the tricuspid valve because it has 3 flaps. The AV valve on the left side has two bibicuspid valve because it has 2 flaps. The bicuspid valve is commonly referred to as the mitral valve, because it has a shape like a bishop’s hat, or mitre. The two remaining valves are the semilunar valves, with flaps shaped like half-moons, that lie between the ventricles and their attached vessels. (10) What are the chordae tendinae? They are strong fibrous strings that support the valves. (11) Where are the semilunar valves? Why do they have that name? They are the two remaining valves with flaps shaped like half-moons, that lie between the ventricles and their attached vessels. They are named for their attached vessels. (12) List the path of blood through the heart. The superior vena cava and the inferior vena cava, which carry oxygen-poor blood, enter the right atrium. The right atrium sends blood through an atrioventricular valve (the tricuspid valve) to the right ventricle. The right ventricle sends blood through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk, which carries oxygen-poor blood, divides into two pulmonary arteries, which go to the lungs. Four pulmonary veins, which carry oxygen-rich blood, enter the left atrium. The left atrium sends blood through an atrioventricular valve (the bicuspid valve) to the left ventricle. The left ventricle sends blood through the aortic semilunar valve into the aorta to the body proper. (13) Where does blood go when it leaves the right side of the heart? Blood then goes to the lungs. (14) Where does blood go when it leaves the left side of the heart? The blood goes to the rest of the body. (15) Which side of the heart is stronger? Why? The left side of the heart is stronger because it has a thicker-wall then the right side and it enables blood to be pumped to all the other parts of the body. (16) Why is the heart a double pump? It’s a double pump because the right ventricle of the heart sends blood through the lungs, and the left ventricle sends blood throughout the body. (17) Define systole. It’s the working phase that refers to contraction of the chambers. (18) Define diastole. It’s the resting phase referring to the relaxation of the chambers. (19) How many times does the heart normally contract in a minute? The heart contracts, or beats, about 70 times a minute, and each heartbeat lasts about 0.85 seconds. (20) What causes the "lub" and "dup" of the heart sounds? Lub occurs when increasing pressure of blood inside a ventricle forces the cusps of the AV valve to slam shut. The dup occurs when the ventricles relax, and the blood in the arteries pushes back, causing the semilunar valves to close. (21) What is the sinoatrial node? What does it do? Why is called the pacemaker? It’s a unique cardiac muscle located in the upper dorsal wall of the right atrium. It initiates the heartbeat and automatically sends out an excitation impulse every 0.85 seconds; this causes the atria to contract. It’s called the pacemaker because it usually keeps the heartbeat regular. (22) What is the atrioventricular bundle? Why is the delay important between the SA node and AV bundle? It’s a group of specialized fibers that conduct impulses from the atrioventricular node to the ventricles of the heart. The delay is important because it allows the atria to finish their contraction before the ventricles begin their contraction. (23) What does in ECG measure? An ECG is a recording that measures the electrical changes that occur in myocardium during a cardiac cycle. (24) What triggers the P wave? When the SA node triggers an impulse, the atrial fibers produce an electrical change called the P wave. The P wave indicates that the atria are about to contract. (25) What triggers the QRS wave? The P wave indicates the atria are about to contract. After that, the QRS complex signals that the ventricles are about to contract.