Muscles of iris and ciliary body are derived from  

Options

A. mesoderm
B. ectoderm
C. endoderm
D. chordamesoderm

Answer

To determine the origin of the muscles of the iris and ciliary body, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structures**:
- The iris is the colored part of the eye that surrounds the pupil.
- The ciliary body is a circular structure that is an extension of the iris and is involved in the accommodation of the lens.

2. **Understand Muscle Types**:
- The muscles of the iris and ciliary body are smooth muscles. Smooth muscles are involuntary muscles that are not striated and are found in various internal organs.

3. **Embryonic Layers**:
- In embryonic development, there are three primary germ layers: ectoderm, mesoderm, and endoderm.
- **Ectoderm**: The outermost layer, which gives rise to structures such as the skin and nervous system.
- **Mesoderm**: The middle layer, which develops into muscles, bones, and the circulatory system.
- **Endoderm**: The innermost layer, which forms internal organs such as the gut and lungs.

4. **Determine the Origin of the Muscles**:
- The muscles of the iris and ciliary body arise from the mesoderm. Specifically, they are derived from undifferentiated mesenchymal cells in the embryonic mesoderm, which differentiate into myoblasts (muscle precursor cells).

5. **Eliminate Incorrect Options**:
- **Ectoderm**: Incorrect, as it does not give rise to muscle tissue.
- **Endoderm**: Incorrect, as it forms internal organs, not muscles.
- **Chordamesoderm**: This is a specific part of the mesoderm that forms structures like the notochord and is not directly responsible for the muscles of the iris and ciliary body.

6. **Conclusion**:
- The correct answer is that the muscles of the iris and ciliary body are derived from the **mesoderm**.

### Final Answer:
The muscles of the iris and ciliary body are derived from **mesoderm**.