epithelia III A Flashcards
Glands of the body are derived from _____.
epithelial tissue
Glands are found _______.
in many sites of the body, often associated with the epithelia of body surfaces and cavities, and as components of specific organs.
The primary function of glands is ______
secretion of either specific bioactive molecules (e.g. hormones), complex fluids (e.g. mucous, sweat), or both.
There are two major types of epithelial glands:
- Exocrine glands that secrete materials onto epithelia-lined surfaces or the outside world.
- Endocrine glands that secrete substances into the blood stream
Glands secrete their substances in one of two general ways.
(1) Exocytosis
(2) holocrine glands
Exocytosis:
most common mechanism
also called merocrine or apocrine glands.
holocrine glands
Total cell disintegration, which leads to the entire cellular contents becoming part of the secretion;
–less common
holocrine glands examples:
the secretion of oily sebum onto hair and skin
Exocrine glands secrete materials onto the _____.
apical side of epithelial surfaces
exocrin are generally:
multicellular
Some epithelial cells in the lining of internal passageways function as ____
unicellular glands secreting materials directly onto those surfaces (e.g. goblet cells).
All multicellular exocrine glands have two main components:
- secretory units
2. ducts
The Secretory units are:
clumps of secretory epithelial cells, which produce and secrete the bulk of the secretion.
Secretory units can be organized into:
bowl or flask-shaped lobules called alveoli or acini, and are called alveolar or acinar glands, or they may be organized into tubes, and are called tubular glands.
Some glands have both tubular and alveolar character and are called ______.
tubuloalveolar
Some glands can have:
a single secretory unit or they may have multiple branched units
Ducts are:
tubular structures that emanate from the secretory units.
Ducts function as:
passageways to conduct secretions to their destinations, although their epithelia can also modify the secretion content by secretory and ion transport properties of duct cells.
Glands that possess a single duct are classified as _______.
simple glands, whereas those with multiple branched ducts are called compound glands.
Further subclassifications exist reflecting whether the glands is coiled, and whether the secretory units are multilobed (branched) or not.
exocrine glands of the body “tubes” (alimentary canal, respiratory, and urogenital systems) are of three general types:
- mucous
- serous
- mixed
mucous:
from which a viscous glycoprotein-rich fluid is produced
serous:
from which a watery fluid, containing salts and some specific proteins, is produced
mixed:
from which both kinds of secretions are produced.
secretory epithelial cells of these glands secrete materials _____
unidirectionally from their apical surface (with the exception of holocrine secretion)
Endocrine glands have _____
no ducts and secrete substances to the blood stream.
Endocrine glands produce
mostly specific hormones that act over relatively long distances to control tissue function.
Endocrine glands are generally organized as
clumps or chords of cells that are embedded with and surrounded by connective tissue containing extensive capillary networks.
Blood capillaries are imbedded in
connective tissue on the other side of the epithelial basal lamina.
hormone molecules must cross the _______ to reach the blood stream.
basal surface and basal lamina of the epithelium (and finally the basal lamina and endothelial layer of the capillary)
each endocrine clump is surrounded by
a basal lamina.
most endocrine cells secrete hormone molecules from the _____ membrane
basolateral
