Which of the following is not exclusively supplied with involuntary muscles ?

Options

A. Muscular coats of blood vessels
B. Muscles of the ducts of glands
C. Muscles of iris
D. Muscles of urethra

Explanation

To determine which of the following options is not exclusively supplied with involuntary muscles, we need to analyze each option in terms of the type of muscle present.

### Step-by-Step Solution:

1. **Understand the Types of Muscles**:
- **Involuntary Muscles**: These muscles are not under conscious control. They include smooth muscles (found in visceral organs) and cardiac muscles (found in the heart).
- **Voluntary Muscles**: These muscles are under conscious control and are primarily skeletal muscles.

2. **Analyze Each Option**:
- **Option 1: Muscular Cord of Blood Vessels**:
- Blood vessels are surrounded by smooth muscles that control the diameter of the vessels (vasoconstriction and vasodilation). These muscles are involuntary.

- **Option 2: Ducts of the Glands**:
- The ducts of glands also contain smooth muscles that help in the secretion process. These muscles are involuntary.

- **Option 3: Muscles of the Iris**:
- The iris muscles control the size of the pupil and respond to light intensity. These muscles are also involuntary.

- **Option 4: Urethra**:
- The urethra has two types of sphincters:
- **Internal Urethral Sphincter**: Made of smooth muscle and is involuntary.
- **External Urethral Sphincter**: Made of skeletal muscle and is under voluntary control.

3. **Conclusion**:
- Among the options, the urethra is the only structure that contains both involuntary (internal sphincter) and voluntary (external sphincter) muscles. Therefore, the correct answer is **Option 4: Urethra**.

### Final Answer:
**The urethra is not exclusively supplied with involuntary muscles.**

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