Problem 6 - Campbell Biology

Question

A molecule of \(\mathrm{CO}_{2}\) released into the blood in your left toe can be exhaled from your nose without passing through which of the following structures? (A) the pulmonary vein. (C) the right atrium. (B) the trachea. (D) the right ventricle.

Step-by-Step Solution

Answer

B: the trachea

Step 1: Understanding the Exercise

Identify the path that a molecule of \(\text{CO}_2\) takes from a toe to being exhaled through the nose.

Step 2: Path of \(\text{CO}_2\) in the Bloodstream

Trace the path: From the toe, \(\text{CO}_2\) travels through veins to the right atrium of the heart.

Step 3: Heart Chambers and Lungs

From the right atrium, it moves to the right ventricle, then gets pumped to the lungs via the pulmonary artery.

Step 4: From the Lungs to Exhalation

In the lungs, \(\text{CO}_2\) is exchanged for \(\text{O}_2\) and then travels through the pulmonary veins to the left atrium, from where it is pumped to the left ventricle and then to the rest of the body. It exits the body by moving through the bronchi, the bronchioles, and the trachea.

Step 5: Identifying the Structure Not Involved

Compare the given structures: A) pulmonary vein, B) trachea, C) right atrium, D) right ventricle. Based on the path outlined, the \(\text{CO}_2\) molecule does not travel through the trachea when it's in the bloodstream; it only passes the trachea when it is in gaseous form in the lungs.

Step 6: Conclusion

The molecule of \(\text{CO}_2\) does not pass through the trachea while circulating through the blood.

Key Concepts

Circulatory System

The circulatory system is essential for transporting substances, like carbon dioxide (CO2), throughout your body.
It involves the heart, blood, and blood vessels.
When a molecule of CO2 is released into the blood in your left toe, it travels through veins to reach the heart.
Veins carry deoxygenated blood, containing CO2, back to the heart.
Let's break down how this system works:

• Veins: These are blood vessels that return deoxygenated blood to the heart. They have valves that prevent backflow.
• Arteries: These carry oxygen-rich blood away from the heart.
• Capillaries: Tiny blood vessels where gas exchange occurs between blood and tissues.

As the CO2 molecule travels through the veins, it first reaches the right side of the heart. This leads us to the next topic: heart chambers.

Heart Chambers

The heart has four chambers: two atria and two ventricles. They are critical for pumping blood throughout your body.
Here's how they function:

• Right Atrium: Receives deoxygenated blood from the body, including CO2 from your toe.
• Right Ventricle: Pumps this deoxygenated blood to the lungs through the pulmonary artery.
• Left Atrium: Receives oxygen-rich blood from the lungs through the pulmonary veins.
• Left Ventricle: Pumps oxygenated blood to the rest of the body.

Once the CO2 molecule enters the right atrium, it moves to the right ventricle.
The right ventricle then pumps the CO2 to the lungs, where it is exchanged for oxygen (O2). The blood, now rich in O2, moves to the left atrium and then to the left ventricle, from where it is pumped to the body.

Respiratory System

The respiratory system is where CO2 is finally exchanged for O2 and exhaled.
This system includes structures like the lungs, bronchi, bronchioles, and the trachea.
Here's how they work together:

• Lungs: Main organs for gas exchange, where CO2 is expelled and O2 is absorbed.
• Bronchi: Two main air passages that branch from the trachea into each lung.
• Bronchioles: Smaller branches of the bronchi that lead to alveoli.
• Alveoli: Tiny sacs in the lungs where gas exchange occurs.
• Trachea: The windpipe that conducts air to and from the lungs.

CO2 is carried to the lungs by blood via the pulmonary artery.
In the alveoli, CO2 is exchanged for O2 and then exhaled through the bronchioles, bronchi, and finally, the trachea.
This path shows us that CO2 does not pass through the trachea while in the bloodstream; it only travels through the trachea once it is in gaseous form in the lungs, ready to be exhaled.