If a molecule of CO2 released into the blood in your left toe is exhaled from your nose, it must pass through all of the following except a. the pulmonary vein. b. the trachea. c. the right atrium. d. the right ventricle.

Verified step by step guidance

1. Identify the path of blood flow and gas exchange in the body: Blood carrying CO2 travels from the body tissues to the heart, then to the lungs for gas exchange, and back to the heart to be pumped to the rest of the body.
2. Understand the role of the heart chambers and major vessels: The right atrium and right ventricle are involved in pumping deoxygenated blood (high in CO2) from the body to the lungs. After gas exchange in the lungs, oxygenated blood (low in CO2) returns to the left side of the heart.
3. Recognize the function of the pulmonary vein: The pulmonary vein carries oxygenated blood from the lungs back to the left side of the heart, specifically to the left atrium. It does not carry high CO2 blood.
4. Analyze the options given in the question: Since the pulmonary vein carries only oxygenated blood from the lungs to the heart, it does not transport CO2-rich blood from the body tissues.
5. Conclude the correct answer: The molecule of CO2 released from your left toe would not pass through the pulmonary vein on its way to be exhaled from your nose. Therefore, the correct answer is 'a. the pulmonary vein.'

Key Concepts

Respiratory System Anatomy

The respiratory system includes structures such as the trachea, bronchi, and lungs, which facilitate the exchange of gases. When CO2 is released into the blood, it travels from the tissues to the lungs, where it is expelled during exhalation. Understanding the pathway of air and blood flow through these structures is crucial for tracing the movement of CO2.

Circulatory System Pathway

The circulatory system transports blood throughout the body, including the heart's chambers: the right atrium and right ventricle. Blood returning from the body, rich in CO2, enters the right atrium, moves to the right ventricle, and is then pumped to the lungs via the pulmonary artery. This pathway is essential for understanding how CO2 is transported to the lungs for exhalation.

Gas Exchange Process

Gas exchange occurs in the alveoli of the lungs, where CO2 is exchanged for oxygen. This process is vital for maintaining the body's pH balance and ensuring that oxygen is available for cellular respiration. Recognizing how CO2 moves from the blood into the alveoli and is then exhaled helps clarify the question regarding the pathway of CO2 from the toe to the nose.