1. Electrocardiography Lesson 1: Heart Structure and Function49
Electrocardiography
Lesson 1:
Heart Structure and Function

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

3. The Heart Review 3

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

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

6. 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

7. 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

8. 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

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

10. 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

11. 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

12. 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

13. Conduction System of the Heart13

14. 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 beats per minute 14

15. 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

16. Questions? 16