State whether the following statement is true or false.
In the cells that line the lumen of the small intestine, gap junctions keep materials from the digestive tract from slipping between the cells and entering the tissues.
A. True
B. False

Answer

To determine whether the statement is true or false, we need to analyze the roles of gap junctions and tight junctions in the cells lining the lumen of the small intestine.

### Step-by-Step Solution:

1. **Understanding Gap Junctions**:
- Gap junctions are specialized intercellular connections that allow for communication between adjacent cells. They consist of protein channels that enable the transfer of ions and small molecules.
- **Hint**: Remember that gap junctions are primarily for communication and do not seal spaces between cells.

2. **Understanding Tight Junctions**:
- Tight junctions, on the other hand, are structures that seal the spaces between epithelial cells. They prevent the passage of materials between cells, effectively controlling what enters the tissues from the lumen.
- **Hint**: Think of tight junctions as barriers that prevent leakage, while gap junctions allow for signaling.

3. **Analyzing the Statement**:
- The statement claims that gap junctions prevent materials from slipping between the cells in the small intestine. However, this is not accurate.
- **Hint**: Identify which type of junction is responsible for sealing and preventing material movement.

4. **Conclusion**:
- Since tight junctions are responsible for preventing materials from passing between cells in the small intestine, the statement is false.
- Therefore, the correct answer is **B. False**.

### Final Answer:
B. False