Question

To reach the left side of heart, the blood must pass through (a) Lungs (b) Liver (c) Kidneys (d) Sinus venosus

Short answer

The blood must pass through the Lungs to reach the left side of the heart.

Step-by-step solution

Analyze the options

Look at each of the options provided in the question. They include (a) Lungs, (b) Liver, (c) Kidneys, and (d) Sinus venosus. Consider the role of these organs in the blood circulation process.

Knowledge of human circulatory system

Remember that the human circulatory system consists of two main parts: the systemic circulation and the pulmonary circulation. Oxygen-depleted blood returns to the right side of the heart and then is pumped to the lungs where it is re-oxygenated. The blood then returns to the left side of the heart, ready to be pumped to the rest of the body.

Link the knowledge to the provided options

Looking at the options and from the knowledge of the human circulatory system, it's clear that before blood reaches the left side of the heart, it passes through the lungs for re-oxygenation.

Choose the correct answer

Therefore, the correct answer is (a) Lungs.

Key concepts

Blood Circulation

Understanding blood circulation is central to grasping how our bodies function. Blood circulation refers to the continuous movement of blood through the heart and vascular system, providing oxygen and nutrients to every part of the body. It's composed of two key parts: the pulmonary circulation and the systemic circulation.

The heart, acting as a pump, drives this circuit. Deoxygenated blood from the body flows into the right atrium, through to the right ventricle, and is then pumped to the lungs. This is part of pulmonary circulation. After picking up oxygen in the lungs, the blood returns to the left side of the heart, marking the beginning of systemic circulation, which delivers oxygen-rich blood throughout the body.

In essence, without this elegant loop continuously working, our bodily tissues would not receive the life-sustaining substances they need, nor would they be relieved of harmful wastes.

Pulmonary Circulation

The importance of pulmonary circulation lies in its role in oxygenating the blood. Deoxygenated blood travels to the lungs via the pulmonary arteries. Once in the lungs, carbon dioxide is exchanged for oxygen – a process known as gas exchange.

This is vital, as the rest of the body relies on oxygen to carry out cellular respiration, the process that generates the energy needed for cells to work. After the blood is re-oxygenated, it travels back to the heart through the pulmonary veins, entering the left atrium and then progressing to the left ventricle, poised to deliver oxygen-rich blood to the entire body.

Understanding that this segment of circulatory process exclusively involves the lungs and heart is crucial. We can now see why the answer to our exercise question is (a) Lungs - as they are the sole organs involved in pulmonary circulation.

Systemic Circulation

Following pulmonary circulation, systemic circulation is the journey of oxygen-rich blood from the left side of the heart to all parts of the body and back again to the heart. This extensive network allows oxygen and nutrients to reach the cells and organs that keep us alive.

From the left ventricle, blood is pumped out via the aorta, the largest artery in the body. From here, it travels through a series of smaller arteries, arterioles, then to the capillary beds where exchange with the body's tissues occurs. Deoxygenated blood collected from the tissues then makes its way back through venules, veins, and ultimately to the right atrium of the heart via the vena cava, completing the systemic circulation loop.

Thus, systemic circulation encompasses the entire body, excluding the airways and the lungs responsible for the oxygenation process. It's the final phase where the now oxygen-depleted blood begins its journey back to the right side of the heart, and the cycle starts anew.