Chapter 18, Problem 1MC

Summary Introduction

To determine:

The correct occurrence of sequences if semilunar valves are open

(a) 2, 3, 5, 6, (b) 1, 2, 3, 7, (c) 1, 3, 5, 6, (d) 2, 4, 5, 7

____ (1) coronary arteries fill

____ (2) AV valves are closed

____ (3) ventricles are in systole

____ (4) ventricles are in diastole

____ (5) blood enters aorta

____ (6) blood enters pulmonary arteries

____ (7) atria contract

Answer to Problem 1MC

Solution:

(a) 2, 3, 5, 6: The events that occur when the semilunar valves are open are listed as follows:

1. The closing of atrioventricular valves.

2. The ventricles are in the systolic stage.

3. The blood enters the aorta.

4. The blood enters the pulmonary arteries.

Explanation of Solution

The semilunar valve is situated between the left ventricle and aorta of the heart. The opening of the semilunar valves marks the systolic stage. The atrioventricular valves at this stage are closed in order to prevent the backflow of the blood. The blood is pumped to the aorta and the pulmonary artery to distribute it to the different parts of the body.