Study the following structures involved in blood circulation: Aorta – Right atrium – Left atrium – Right ventricle – Body tissues. Arrange these structures in the correct sequence to show the pathway of blood in systemic circulation.

here are the answers to Question 4:

4.1. Identify structures labelled A, C.

• A: Aorta
• C: Pulmonary artery

4.2. When you listen to the heart though a stethoscope you hear a (lub-dub) sound.

• (i) Identify which sound is the closing of the atrioventricular valves and which is the closing of the semilunar valves.
  • The "lub" sound is the closing of the atrioventricular valves.
  • The "dub" sound is the closing of the semilunar valves.
• (ii) Explain why these sounds occur. These sounds occur due to the sudden closure of the heart valves, which causes vibrations in the blood and the walls of the heart.

4.3. Study the following structures involved in blood circulation: Aorta – Right atrium – Left atrium – Right ventricle – Body tissues. Arrange these structures in the correct sequence to show the pathway of blood in systemic circulation.
The correct sequence for the pathway of blood in systemic circulation using the given structures is:

• Left atrium $\rightarrow$ Aorta $\rightarrow$ Body tissues $\rightarrow$ Right atrium $\rightarrow$ Right ventricle