A bands and I bands are found in

Options

A. voluntary muscles
B. involuntary muscles
C. unstriated muscles
D. striated muscles

Answer

**Step-by-Step Solution:**

1. **Identify the Context**: The question asks about A bands and I bands, which are terms related to muscle fibers.

2. **Understand Muscle Fibers**: Muscle fibers are made up of myofibrils. Each muscle fiber consists of many myofibrils, which are the contractile units of muscle.

3. **Components of Myofibrils**: Each myofibril contains myosin and actin filaments. Specifically, there are about 1500 myosin filaments and 3000 actin filaments in each myofibril.

4. **Formation of A and I Bands**:
- **A Bands**: These are dark bands that contain myosin filaments and the overlapping ends of actin filaments. They are called A bands because they are anisotropic to polarized light.
- **I Bands**: These are light bands that consist solely of actin filaments. They are called I bands because they are isotropic to polarized light.

5. **Striated Appearance**: The arrangement of A bands and I bands creates a striated or banded appearance in skeletal muscle tissue. The alternating pattern of light (I bands) and dark (A bands) gives the muscle its characteristic striped look.

6. **Conclusion**: A bands and I bands are found in striated muscle, also known as striped or banded muscle.

**Final Answer**: A bands and I bands are found in striated muscle.

---