Electrocardiography Lesson 1: Heart Structure and Function 49 Electrocardiography Lesson 1: Heart Structure and Function

Lesson Objectives Upon completion of this lesson, students should be able to … Define and spell the terms for this chapter.

The Heart Review 3

Critical Thinking Question Trace the blood flow through the heart. 4

Function of the Cardiovascular System To carry oxygen from the lungs to all the tissues of the body

Function of the Cardiovascular System Deoxygenated blood then circulates through the body and discharges carbon dioxide, the waste product of cell metabolism, from the lungs Blood circulates throughout the body and returns from the general circulation by way of the superior and inferior vena cava, to the right atrium, moving in one direction through the heart

Function of the Cardiovascular System When the right atrium is full, the atrium contracts and blood is pumped into the right ventricle through the tricuspid valve

Function of the Cardiovascular System On filling, blood is pumped by contraction of the right ventricle through the semilunar valves into the pulmonary artery going to the lungs There, blood is oxygenated and returned to the left atrium through the four pulmonary veins When that chamber is full, it contracts and blood is squeezed into the left ventricle through the mitral (bicuspid) valve In the left ventricle, blood enters the aortic semilunar valve and moves into all parts of the body except the lungs

Function of the Cardiovascular System Blood travels to all parts of the body via the aorta and then goes into all other arteries

Function of the Cardiovascular System Heart muscle receives supply of oxygen and nutrients through the coronary artery system Blood that flows through the heart to the body is not used for energy for the heart tissues

Function of the Cardiovascular System As blood leaves the left ventricle rich with oxygen it enters immediately into aorta and the coronary arteries to supply the heart muscle Deoxygenated blood returns to the general circulation through the cardiac veins which empty into the coronary sinus in the right atrium

Heart Valves Act as gates to prevent the backward flow of blood Open and shut in response to the changing pressure brought about by cardiac contraction and relaxation

Conduction System of the Heart 13

Conduction System of the Heart The SA Node normally serves as the pacemaker of the heart If the SA Node fails, other areas may serve as the pacemaker as well AV Node: will generate slower rates (40-60 beats per minute) Bundle of His: will generate rates less than 40 beats per minute Purkinje system: will also generate rhythms in an emergency SA Node: Normal resting rate of 60-80 beats per minute 14

Heart Sounds Associated with Abnormal Conditions Heart murmurs, caused by: Damaged valves Regurgitation or back flow of blood through a valve High flow rates All of which cause a kind of turbulence Gallops or galloping rhythm An abnormal rhythm indicated by three distinct sounds in each heartbeat similar to the sounds of a galloping horse 15

Questions? 16