Molecules produced within one tissue but regulating a different tissue of the same organ are called paracrine factors.

Here's why:

* Paracrine: This term describes signaling where a molecule is released from a cell and acts on a nearby target cell within the same tissue or organ.

* Autocrine: In contrast, autocrine signaling involves a cell releasing a molecule that acts on itself.

* Endocrine: Endocrine signaling involves the release of hormones into the bloodstream, which can travel long distances to reach their target cells.

Example:

In the digestive system, the stomach produces gastrin, a paracrine factor that stimulates the release of gastric acid by the stomach lining. This is an example of paracrine signaling within the same organ.

Key takeaway: Paracrine factors play a crucial role in coordinating the activities of different tissues within an organ, ensuring proper function and homeostasis.