Epithelia Flashcards
(20 cards)
What does “epi” mean?
“On top of “ in Greek
What is epithelia ?
The tissue that cover and line the interior and exterior surfaces of the body
What is simple squamous epithelium?
Composed of single layers of cells.
Flat and plate-like.
Allows passage of materials through diffusion.
Eg. Alveoli in lungs, blood vessels
What is simple cuboidal epithelium ?
Single layer of cube-like cells.
Large, spherical, central nuclei.
Secrete and absorb.
Eg. Thyroid follicles, renal tubules
What is simple columnar epithelium ?
Single layer of columnar cells (tall and slender)
Oval shaped nuclei
Secrete and absorb
Eg. Digestive tract, fallopian tubes
What is stratified squamous epithelium?
Classification is based on the shape of the cells at the top layer.
There are two types: keratinised and non-keratinised.
Most suited for areas under constant abrasion.
What is stratified squamous keratinised epithelium?
Keratinisation is a process by which the cytoskeleton of cells in the top layer becomes tightly condensed with keratin.
Mechanically strong, dead cells.
What is pseudostratified epithelium ?
It appears to be stratified but is actually a single layer of cells.
Often ciliated.
All cells are in contact with the extracellular matrix.
What is transitional epithelium ?
A type of stratified epithelium.
It can change shape:
Cuboidal when relaxed
Squamous when stretched
Describe glandular epithelium structure
Epithelium grows as a tube unto underlying tissue, forming specialised secretory gland structures- exocrine glands
What are tight junctions ?
Connections found between epithelial tissue that form a tight seal to prevent leakage of water soluble molecules through gaps between cells.
Forces material to passage through the cells rather than between the cells.
Eg. BBB
What are anchoring junctions ?
They form strong mechanical attachments between cells.
They are built around transmembrane proteins called cadherin.
Main types:
Adherens
Desmosomes
Hemidesmosomes
What are adherens junctions ?
Each cadherin molecule is attached to actin filaments.
Cell to cell.
Maintain tissue shape and support.
What are desmosomes ?
Cadherins interact with cytoplasmic plaque that provide the anchor for intermediate filaments.
Provide good tensile strength to the epithelial sheet.
What is pemphigus ?
An autoimmune disease
Autoantibodies attack the cadherin in desmosomes which causes cells to become separated, the epidermis to become detached, which forms blisters
What are hemidesmosomes ?
Cell to basal membrane interaction.
Integrins linked to intermediate filaments
Connects cells to connective tissues.
What are gap junctions ?
Bridge a narrow gap between plasma membranes of adjacent cells.
Made of connexin proteins which align with neighbouring cells to form connexons.
Allow small molecules and electrical connections to pass directly between cells.
Describe cell polarity
Top surface= apical
Bottom surface= basal
Where does the epithelia sit ?
On top of the basement membrane
What is a carcinoma ?
A malignant tumour derived from epithelium
