Epithelium Flashcards
Aggregated polyhedral cells
epithelial
several types of fixed and wandering cells
connective
elongated contractile cells
muscles
elongated cells with extremely fine processes
nervous
composed of closely aggregated polyhedral cells adhering strongly to one
another and to a thin layer of ECM
epithelial tissue
functions of epithelium
- Covering, lining and protection
- Absorption
- Secretion
- Filtration
a semipermeable filter for substances
reaching epithelial cells from below
basement membrane
2 parts of basement membrane
- Basal lamina
- Reticular Lamina
functions of basement membrane
- Physical support
- Cell attachment
- Filter
- Guides cell migration
separates apical and basolateral membrane domains
tight junctions or zonula occludens
major transmembrane protein of tight junctions or zonula occludens
- Claudin
- Occludin
firmly anchoring a cell to its neighbors
Adherens Junction (Zonula Adherens)
major transmembrane protein of Adherens Junction (Zonula Adherens)
- Cadherin
- Catenin
resembles a single “spot-weld” and does not form a belt around the
cell
Desmosome (Macula Adherens)
provides points of strong intermediate
filament coupling between adjacent cells,
strengthening the tissue
Desmosome (Macula Adherens)
anchors cytoskeleton to the basal lamina
Hemidesmosome
Major transmembrane link proteins of hemidesmosomes
Integrin
Allows direct transfer of small molecules and ions from one cell to
another
Gap Junction (Nexus)
major transmembrane protein of Gap Junction (Nexus)
connexin
function is to increase epithelial cells’
apical surface area for absorption.
MICROVILLI
increase the surface area available for
absorption; a motion-detecting function
STEREOCILIA
long, highly motile apical structures,
larger than microvilli, and containing
internal arrays of microtubules not
microfilaments
Cilia
Classifications of lining epithelia
- Squamous
- Cuboidal
- Columnar
classifications of secretory epithelia
- Endocrine
- Exocrine
are classified according to the number of cell layers and the cell
morphology in the outer layer
Lining epithelia
cell shapes of epithelia
- Squamous
- Cuboidal
- Columnar
layers of epithelia
- Simple
- Stratified
- Pseudostratified
- Transitional
single layer of flat cells with disc-shaped nuclei; molecules can easily pass (diffusion, filtration); Secretes lubricating substances in serosae
simple squamous epithelium
single layer of cube-like cells with large, spherical central nuclei; secretion and absorption
simple cuboidal epithelium
single layer of column-shaped (rectangular) cells with oval nuclei; Absorption, secretion of mucus, enzymes, and other substances
simple columnar epithelial
all cells originate at basement membrane; only tall cells reach the apical surface; may contain goblet cells and bear cilia; nuclei lie at varying heights within cells; gives false impression of stratification; secretion of mucus; propulsion of mucus by cilia
pseudostratified columnar epithelium
Where is pseudostratified columnar epithelium located
ducts of male reproductive tubes and large glands; lines trachea and most pf upper respiratory tract
many layers of cells but the apical part of the tissue is a squamous
epithelium
stratified squamous epithelium
contain the protective protein keratin
keratinized stratified squamous epithelium
forms moist lining of body openings
non-keratinized stratified squamous epithelium
Location of keratinized stratified squamous epithelium
epidermis
Location of non-keratinized stratified squamous epithelium
esophagus, mouth, and vagina
Basal cells usually cuboidal or columnar; Superficial cells dome-shaped or squamous; stretches and permits distension of urinary
bladder
transitional epithelium
Location of transitional epithelium
ureter
urinary bladder
urethra
remain connected with the
surface epithelium
exocrine glands
lose the connection to their
original epithelium and
therefore lack ducts
endocrine glands
most common method of protein or glycoprotein secretion
Merocrine
releases the product and cell debris into the gland’s lumen
Holocrine
release the product together with small amounts of cytoplasm
and cell membrane
Apocrine
