Which of the following cell junction is the least permeable and prevents leakage across a tissue ?

Options

A. Tight junctions
B. Adhering junctions
C. Gap junctions
D. Intercalated disc

Answer

To solve the question about which cell junction is the least permeable and prevents leakage across a tissue, we can follow these steps:

### Step 1: Understand the Types of Cell Junctions
- **Tight Junctions**: These junctions are found in epithelial tissues and are known for their ability to prevent leakage between cells. They create a barrier that is impermeable to most substances.
- **Adhering Junctions**: These junctions provide mechanical stability and allow some materials to pass between cells, but they are not impermeable.
- **Gap Junctions**: These junctions allow for communication between cells by permitting the passage of ions and small molecules, which means they are not impermeable.
- **Intercalated Discs**: These are specialized junctions found in cardiac muscle that facilitate communication and contraction between heart cells, but they do not prevent leakage.

### Step 2: Analyze the Functionality of Each Junction
- **Tight Junctions**: Prevent any leakage of substances between cells, maintaining a barrier.
- **Adhering Junctions**: Allow some transfer of materials, not completely impermeable.
- **Gap Junctions**: Facilitate the transfer of ions and small molecules, allowing leakage.
- **Intercalated Discs**: Allow for communication and contraction but do not prevent leakage.

### Step 3: Identify the Correct Answer
From the analysis, we can conclude that the **Tight Junction** is the least permeable junction and effectively prevents leakage across a tissue.

### Final Answer
The correct option is **A, Tight Junction**.

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