Which of the following sarcomeres is labeled correctly?

Options

A.
B.
C.
D.

Answer

To determine which sarcomere is labeled correctly, we need to understand the structure of a sarcomere. Here's a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding Sarcomere Structure**:
- A sarcomere is the basic unit of muscle fibers. It contains several key components:
- **Z-line (Z-band)**: The boundary of the sarcomere.
- **Thin filaments**: These are primarily made of actin and are attached to the Z-line.
- **Thick filaments**: These are primarily made of myosin and are located in the center of the sarcomere.
- **M-line**: This is the line in the middle of the sarcomere where thick filaments are anchored.
- **A-band**: This is the region that contains the entire length of the thick filaments (myosin) and overlaps with thin filaments (actin).

2. **Analyzing the Options**:
- We have four diagrams of sarcomeres, and we need to identify which one correctly labels all the components mentioned above.

3. **Comparing Each Diagram**:
- Look for the presence of:
- Z-line
- Thin filaments (actin)
- Thick filaments (myosin)
- M-line
- A-band
- Check if the arrangement and labeling match the correct structure of a sarcomere.

4. **Identifying the Correct Option**:
- After comparing all the options, the first option is found to have the correct labels for Z-line, thick filaments (myosin), thin filaments (actin), and A-band. Therefore, the first option is labeled correctly.

### Final Answer:
The first option is the correct labeling of the sarcomere.

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