Which of the following layers of the ovum undergoes changes to prevent polyspermy when sperm contacts with it ?
(a) Corona radiata
(b) Plasma membrane
(c) Zona pellucida
(d) Tunica albuginea

Options

A. Corona radiata
B. Plasma membrane
C. Zona pellucida
D. Tunica albuginea

Answer

To solve the question regarding which layer of the ovum undergoes changes to prevent polyspermy when sperm contacts with it, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Polyspermy**:
- Polyspermy refers to the fertilization of an ovum by multiple sperm cells, which can lead to abnormal development of the embryo.

2. **Identify the Layers of the Ovum**:
- The ovum has several layers, including:
- **Corona Radiata**: A layer of cells surrounding the ovum.
- **Plasma Membrane**: The membrane that encloses the ovum.
- **Zona Pellucida**: A glycoprotein layer surrounding the plasma membrane.
- **Tunica Albuginea**: A fibrous layer that is not directly involved in fertilization.

3. **Cortical Reaction**:
- Upon sperm contact, a process called the cortical reaction occurs. This reaction involves the release of cortical granules from the ovum, leading to changes in the zona pellucida.

4. **Role of the Zona Pellucida**:
- The zona pellucida undergoes changes that create a barrier to prevent additional sperm from entering the ovum after the first sperm has successfully fertilized it.

5. **Conclusion**:
- The layer that undergoes changes to prevent polyspermy is the **Zona Pellucida**.

### Final Answer:
(c) Zona pellucida