A group of cells with a communal secretory function. Exocrine glands
incorporate a duct, or a system of ducts like tributaries leading to a river, which open onto an external or internal body surface. Some are simple or spiral pits(such as sweat glands in the skin
or those which secrete acid and enzymes into the stomach
) with a few secreting cells in their depths; others vary in size and complexity from the small salivary glands
to the mammary glands
(breasts). Endocrine glands
by contrast are ductless, and secrete hormones directly into the bloodstream. The activity of all glands is regulated by chemical or nervous signals, or both. Molecules in the local environment, or brought by the blood, or released from nerve endings of the autonomic nervous system
bind to cell membrane receptors
, starting a sequence of signals within the cells which results in an increase (or decrease) in extrusion of their own particular secretion.
The nodular enlargements which can be felt under the skin in association with an infection (such as those in the neck with a sore throat) are commonly called swollen ‘lymph glands’, but they are not secretory and are more correctly called lymph nodes
See adrenal glands
; alimentary system
; breasts; hormones
; parathyroid glands
; pituitary gland
A group of cells or a single cell in animals or plants that is specialized to secrete a specific substance. In animals there are two types of glands, both of which synthesize their secretions. Endocrine glands
discharge their products directly into the blood vessels; exocrine glands
secrete through a duct or network of ducts into a body cavity or onto the body surface. Secretory cells are characterized by having droplets (vesicles
) containing their products. See also secretion
In plants glands are specialized to secrete certain substances produced by the plant. The secretions may be retained within a single cell, secreted into a special cavity or duct, or secreted to the outside. Examples are the water glands (hydathodes
) of certain leaves, nectaries (see nectar
), and the digestive glands of certain carnivorous plants.
gland1 / gland/ •
n. an organ in the human or animal body that secretes particular chemical substances for use in the body or for discharge into the surroundings. ∎ a structure resembling this, esp. a lymph node. ∎ Bot. a secreting cell or group of cells on or within a plant structure.gland2 •
n. a sleeve used to produce a seal around a piston rod or other shaft.
Cell or tissue that manufactures and secretes special substances. There are two basic types. Exocrine glands
make such substances as hydrochloric acid, mucus, sweat, sebaceous fluids and enzymes
, and secrete these usually through ducts to an external or internal body surface. Endocrine glands
contain cells that secrete hormones
directly into the bloodstream. See also endocrine system
gland (gland) n.
an organ or group of cells that is specialized for synthesizing and secreting certain fluids, either for use in the body or for excretion. See endocrine gland
, exocrine gland
A cell or group of cells that is specialized for the secretion of a particular substance.