Types
Glands can be divided into 2 groups:
- Endocrine glands — are glands that secrete their products through the basal lamina into the blood stream and lack a duct system.
- Exocrine glands — secrete their products through a duct or directly onto the apical surface, the glands in this group can be divided into three groups:
- Apocrine glands — a portion of the secreting cell's body is lost during secretion. Apocrine gland is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion.
- Holocrine glands — the entire cell disintegrates to secrete its substances (e.g., sebaceous glands)
- Merocrine glands — cells secrete their substances by exocytosis (e.g., mucous and serous glands). Also called "eccrine".
The type of secretory product of an Exocrine gland may also be one of three categories:
- Serous glands — secrete a watery, often protein-rich product.
- Mucous glands — secrete a viscous product, rich in carbohydrates (e.g., glycoproteins).
- Sebaceous glands — secrete a lipid product.These glands are also known as oil glands.
Read more about this topic: Gland
Famous quotes containing the word types:
“As for types like my own, obscurely motivated by the conviction that our existence was worthless if we didn’t make a turning point of it, we were assigned to the humanities, to poetry, philosophy, painting—the nursery games of humankind, which had to be left behind when the age of science began. The humanities would be called upon to choose a wallpaper for the crypt, as the end drew near.”
—Saul Bellow (b. 1915)
“He types his laboured column—weary drudge!
Senile fudge and solemn:
Spare, editor, to condemn
These dry leaves of his autumn.”
—Robertson Davies (b. 1913)
“The bourgeoisie loves so-called “positive” types and novels with happy endings since they lull one into thinking that it is fine to simultaneously acquire capital and maintain one’s innocence, to be a beast and still be happy.”
—Anton Pavlovich Chekhov (1860–1904)