What is atresia?

Explanation

### Step-by-Step Solution:

1. **Definition of Atresia**: Atresia is a medical condition characterized by the abnormal absence or closure of an orifice or passage in the body.

2. **Examples of Atresia**:
- **Oral Atresia**: This is a congenital deformity where the ear canal is underdeveloped, leading to hearing issues.
- **Intestinal Atresia**: This condition involves a malformation of the intestine, often resulting from a vascular accident that occurs during fetal development (in utero).
- **Biliary Atresia**: This condition occurs in newborns where the common bile duct, which connects the liver to the small intestine, is blocked, leading to serious digestive issues.
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