Question

Figure 16.10 Which of the following statements about the circulatory system is false? a. Blood in the pulmonary vein is deoxygenated. b. Blood in the inferior vena cava is deoxygenated. c. Blood in the pulmonary artery is deoxygenated. d. \(\quad\) Blood in the aorta is oxygenated.

Short answer

The false statement is a. 'Blood in the pulmonary vein is deoxygenated.' The pulmonary vein actually carries oxygenated blood from the lungs to the heart.

Step-by-step solution

Identify the functions of blood vessels

In the human body, the circulatory system consists of blood vessels that can be categorized into arteries and veins. Arteries carry blood away from the heart, and in most instances, this blood is oxygenated. On the other hand, veins return blood to the heart and usually have deoxygenated blood.\n\nThe pulmonary circulation is an exception, where the terms vein and artery are opposite. In this case, the pulmonary artery carries deoxygenated blood from the heart to the lungs to get oxygenated, while the pulmonary vein returns the now oxygenated blood back to the heart.

Analyze the given statements

Statement a mentions that 'Blood in the pulmonary vein is deoxygenated'. However, the pulmonary vein carries oxygenated blood from the lungs to the heart which is contrary to the given statement. Therefore, this statement is false.\n\nStatement b states that 'Blood in the inferior vena cava is deoxygenated.' The inferior vena cava indeed carries deoxygenated blood from the lower part of the body back to the heart, so this statement is true.\n\nStatement c expresses that 'Blood in the pulmonary artery is deoxygenated.' Yes, the pulmonary artery transports deoxygenated blood from the heart to the lungs to be oxygenated, so this statement is accurate.\n\nStatement d asserts that 'Blood in the aorta is oxygenated.' This is correct since the aorta is the main artery that carries oxygenated blood from the heart to the rest of the body. Hence, this statement is true.

Key concepts

Blood Vessels

The circulatory system in our body relies on an extensive network known as blood vessels, which includes arteries and veins. Each type serves a different function:

• Arteries: These vessels primarily transport oxygen-rich blood from the heart to various parts of the body. They are crucial in delivering essential nutrients and oxygen that our organs and tissues need to function.
• Veins: Veins are responsible for bringing blood back to the heart. Typically, this blood is low in oxygen as it has traveled through the body, delivering oxygen and collecting metabolic waste products.

It's interesting to note that despite these general roles, there are exceptions, especially in the pulmonary system, where the oxygenation status of blood changes dramatically.

Pulmonary Circulation

Pulmonary circulation is a unique circuit within the larger circulatory system where arteries and veins reverse their usual roles regarding the oxygen content of the blood they carry. Within pulmonary circulation, deoxygenated blood is carried by the pulmonary artery from the heart to the lungs. This is an exception because arteries usually carry oxygenated blood. In the lungs, blood picks up oxygen, becoming rich in it, and releases carbon dioxide. After this vital exchange, the now oxygen-rich blood returns to the heart via the pulmonary vein. This reversal of roles is critical for oxygenating the blood so it can be pumped out to the rest of the body.

Oxygenated and Deoxygenated Blood

Understanding the difference between oxygenated and deoxygenated blood is key to grasping how the circulatory system works.

• Oxygenated blood: This type of blood flows mainly through the arteries (with the notable exception of the pulmonary veins) and is rich in oxygen. After leaving the lungs, it's pumped by the heart to tissues and organs through arteries such as the aorta.
• Deoxygenated blood: Low in oxygen content, this blood travels through veins (except for the pulmonary arteries) toward the heart, ready to be sent to the lungs for oxygen exchange and carbon dioxide removal.

By contrasting these two states, we can better appreciate the complex but beautifully systematic way blood circulates, nourishing the body and removing waste.