Cardiac muscle occurs in

Options

A. Epicardium
B. Endocardium
C. Myocardium
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding the Layers of the Heart:**
- The heart consists of three main layers: the epicardium, myocardium, and endocardium.
- Each layer has a specific structure and function.

2. **Analyzing the Epicardium:**
- The epicardium is the outermost layer of the heart.
- It serves as a protective layer but does not contain cardiac muscle tissue.
- Therefore, cardiac muscle does not occur in the epicardium.

3. **Analyzing the Endocardium:**
- The endocardium is the innermost layer of the heart.
- It lines the chambers of the heart and covers the heart valves.
- Similar to the epicardium, the endocardium does not contain cardiac muscle tissue.

4. **Identifying the Myocardium:**
- The myocardium is the middle layer of the heart and is primarily composed of cardiac muscle tissue.
- This layer is responsible for the heart's contractile function, allowing it to pump blood throughout the body.
- Cardiac muscle fibers (cardiomyocytes) are found in the myocardium, making it the correct answer.

5. **Conclusion:**
- Based on the analysis of the three layers, the correct answer to the question "Cardiac muscle occurs in" is the myocardium.

**Final Answer:**
Cardiac muscle occurs in the myocardium.

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