Final answer:
Tight junctions are responsible for creating a watertight seal between neighboring cells of the lining of the human digestive tract, preventing leakage and maintaining tissue integrity. Therefore, correct answer is a.
Step-by-step explanation:
The junctions between neighboring cells of the lining of the human digestive tract that are very secure and prevent leakage are tight junctions.
These junctions form a watertight seal between two adjacent animal cells, with proteins such as claudins and occludins holding the cells tightly against each other.
This tight adhesion ensures that materials do not leak between the cells. Tight junctions are commonly found in the epithelial tissue that lines internal organs and cavities, and they play a crucial role in maintaining the integrity of those spaces.
For instance, the tight junctions of the epithelial cells lining the urinary bladder are vital in preventing urine from leaking into the extracellular space.
Similarly, in the digestive system, tight junctions prevent the contents of the gut from leaking between cells into the body, which could lead to various medical conditions.