Multi-unit smooth muscle is seen in

Options

A. Stomach
B. Intestine
C. Urinary bladder
D. Large blood vessel

Answer

### Step-by-Step Solution:

1. **Understanding Multi-Unit Smooth Muscle**:
- Multi-unit smooth muscle is a type of smooth muscle where the muscle fibers are organized in a way that they function independently rather than as a single unit. This means that each muscle fiber can contract separately, allowing for fine control of muscle contraction.

2. **Characteristics of Multi-Unit Smooth Muscle**:
- These muscles have very little gap junctions between the fibers, which means that when a signal is sent, it does not spread from one fiber to another. Instead, each fiber responds to stimulation individually.

3. **Locations of Multi-Unit Smooth Muscle**:
- Multi-unit smooth muscle is typically found in structures that require precise control. Common locations include:
- Large blood vessels: The smooth muscle in the walls of large arteries and veins is multi-unit, allowing for regulation of blood flow and pressure.
- The iris of the eye: This muscle controls the size of the pupil.
- The arrector pili muscles: These are small muscles attached to hair follicles that cause hair to stand up.

4. **Eliminating Other Options**:
- Stomach: The muscles in the stomach are not multi-unit smooth muscles; they are more of a single-unit type, allowing for coordinated contractions for digestion.
- Intestine: Similar to the stomach, the intestines also have smooth muscle that works in a coordinated manner, not independently.
- Urinary Bladder: The bladder contains transitional epithelium, which is not classified as multi-unit smooth muscle.

5. **Conclusion**:
- Based on the characteristics and locations of multi-unit smooth muscle, the correct answer to the question "Multi-unit smooth muscle is seen in" is **large blood vessels**.