The glands that secrete hormones comprise the endocrine signaling system. The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell (autocrine or intracrine signalling) or nearby cells (paracrine signalling).
A fen is one of the main types of wetland, the others being grassy marshes, forested swamps, and peaty bogs. Along with bogs, fens are a kind of mire. Fens are usually fed by mineral-rich surface water or groundwater.
Noun. 1. marsh-low-lying wet land with grassy vegetation; usually is a transition zone between land and water; thousands of acres of marshland; the fens of eastern England.fenland, marshland, fen. salt marsh-low-lying wet land that is frequently flooded with saltwater.oun. 1. marsh-low-lying wet land with grassy vegetation; usually is a transition zone between land and water; thousands of acres of marshland; the fens of eastern England.