The+Heart+NLL

//**The Heart**//

(1) In which direction does the heart tilt? The heart is tilted so that the apex 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 you’re opposite hand. (3) Describe the myocardium. The major portion of the heart is called the myocardium, consists largely of cardiac muscle tissue. (4) Why do you think a heart attack is sometimes called a myocardial infarction p. 97? Because a portion of the heart muscle dies due to a lack of oxygen. (5) Describe the pericardium. The heart us surrounded by the pericardium, a thick, membranous sac that supports and protects the heart. (6) Describe the septum. The septum is a wall, which separates the heart into a right side and a left side. (7) Where are the atria? Describe their walls. The heart has four chambers. The two upper, thin-walled atria are called the right atrium and left atrium. Each atrium has a wrinkled, protruding appendage called an auricle. (8) Where are the ventricles? Describe their walls. The two lower chambers are the thick-walled ventricles, called the right ventricle and the left ventricle. (9) Where are the atroventricular valves? Describe their shape (number of flaps) and various names. Heart valves keep blood flowing in the right direction and prevent its backward movement. The valves that lie between the atria and the ventricles are called the atroventricular valves. The AV valves on the right side is called the tricuspid valve because it has three flaps. The bicuspids valve is commonly referred to as the mitral valve, because it has a shape like a bishop’s hat, or mitre. (10) What are the chordae tendinae? Chordae tendinae are strong fibrous strings that support the valves. (11) Where are the semilunar valves? Why do they have that name? The semilunar valves are named for their attached vessels: The pulmonary semilunar valve lies between the right ventricle and the pulmonary trunk. The aortic semilunar valve lies between the left and ventricle and the aorta. (12) List the path of blood through the heart. The superior vena cava and the inferior vena cava, which carry O2-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 divides into two pulmonary arteries, which go to the lungs. Four pulmonary veins, which carry O2-rich blood, enter the left atrium The left atrium sends blood through an atrioventricular valve (the bicuspid, or mital, 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? The right side sends it 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 after leaving the left side of the heart. (15) Which side of the heart is stronger? Why? The lift side is stronger because it sends blood throughout the entire body. (16) Why is the heart a double pump? Because it has to send blood to the lungs and the rest of the body. (17) Define systole. Systole is the working phase, refers to contraction of the chambers. (18) Define diastole Diastole is the resting phase, refers to 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 last about 0.86 second. A normal adult rate at rest can vary from 60 to 80 beats per minute. (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 ventricle relaxes, and 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? The SA node imitates the heartbeat and automatically sends out an excitation impulse every 0.85 second this cause the atria to slightly contract. The SA node is 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 is a group of specialized fibers that conduct impulses from the atrioventriclal node to the ventricles of the heart. The delay allows the atria to finish their contraction before the ventricles begin their contraction. (23) What does in ECG measure? It is a recording of the electrical changes that occur in the myocardium during the cardiac cycle. (24) What triggers the P wave? The contraction of the atria (25) What triggers the QRS wave? When the ventricles are contracting.