Every 100 mL of deoxygenated blood delivers approximately

Options

A. 5 mL of `O_2` to the tissues
B. 5 mL of `CO_2` to the tissues
C. 4 mL of `CO_2` to the alveoli
D. 4 mL of `O_2` to the alveoli

Answer

To solve the question regarding how much gas is delivered by every 100 mL of deoxygenated blood, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Composition of Deoxygenated Blood**:
- Deoxygenated blood is characterized by a higher concentration of carbon dioxide (CO2) and a lower concentration of oxygen (O2). This blood returns from the tissues to the lungs for gas exchange.

2. **Identify the Relevant Options**:
- The options provided are:
- 5 mL of O2 to the tissues
- 5 mL of CO2 to the tissues
- 4 mL of CO2 to the alveoli
- 4 mL of O2 to the alveoli
- Since we are dealing with deoxygenated blood, we can eliminate options that suggest delivery of oxygen (O2) to the tissues or alveoli.

3. **Eliminate Irrelevant Options**:
- The first option (5 mL of O2 to the tissues) can be eliminated because deoxygenated blood does not deliver oxygen.
- The second option (5 mL of CO2 to the tissues) can also be eliminated because deoxygenated blood is returning from the tissues, not delivering CO2 to them.

4. **Focus on Relevant Options**:
- We are left with:
- 4 mL of CO2 to the alveoli
- 4 mL of O2 to the alveoli
- Since deoxygenated blood is returning to the lungs to release CO2 and pick up O2, the relevant option is the one that states CO2 is delivered to the alveoli.

5. **Determine the Correct Answer**:
- Every 100 mL of deoxygenated blood delivers approximately **4 mL of CO2 to the alveoli**. This is the correct answer based on the understanding of the gas exchange process.

### Final Answer:
- Every 100 mL of deoxygenated blood delivers approximately **4 mL of CO2 to the alveoli**.

---