Two cells which are in direct contact can send signal to each other across gap junction. For cells which are not in direct contact, there is a number of ways through which these cells communicate, these basically include: paracrine signalling and endocrine signalling. In paracrine signalling, a cell secrete a chemical substance which have effect on a nearby cell while in endocrine signalling, hormones are released into the circulatory system, which convey them to the target cells.
