Question

A person has a total blood volume of 5 L. Out of this total, assume that 4 L is contained in the systemic circulation and 1 L in pulmonary circulation. The cardiac output of the person is 5 L.min$^{-1}$. Time taken for a drop of blood to go from right ventricle to left ventricle is _________ s.

• A. 60
• B. 20
• C. 15
• D. 12

Hint:

The time for blood to flow through a circuit can be found by dividing the volume of blood in that circuit by the cardiac output. Remember to convert units properly, especially between minutes and seconds.

Answer 1

The Correct Option is D

We are given the following data:
- Total blood volume = 5 L
- Systemic circulation = 4 L
- Pulmonary circulation = 1 L
- Cardiac output = 5 L/min
Step 1: Understand the problem.
Cardiac output is the total amount of blood pumped by the heart per minute. This blood is distributed between the systemic and pulmonary circulations. The drop of blood travels from the right ventricle to the left ventricle through the pulmonary circulation. The time taken for a drop of blood to travel from the right ventricle to the left ventricle is the time it takes to complete one cycle through the pulmonary circulation. This time is given by: \[ \text{Time} = \frac{\text{Volume of blood in pulmonary circulation}}{\text{Cardiac output}}. \] Step 2: Substitute the values.
We know that the volume of blood in the pulmonary circulation is 1 L, and the cardiac output is 5 L/min. Thus, the time is: \[ \text{Time} = \frac{1 \, \text{L}}{5 \, \text{L/min}} = \frac{1}{5} \, \text{minutes}. \] Step 3: Convert to seconds.
Since 1 minute = 60 seconds, we convert the time to seconds: \[ \text{Time} = \frac{1}{5} \times 60 = 12 \, \text{seconds}. \] Step 4: Conclusion.
Therefore, the time taken for a drop of blood to go from the right ventricle to the left ventricle is 12 seconds, which corresponds to option (D).