Flashcards in Epithelium Deck (44):
How often does cancer arise from epithelium?
75% of the tim; MAJORITY
Group of cells closely associated in structure and function
The study of tissues
What are the four major types of tissue?
Where are epithelia located?
They COVER or LINE:
a. free surfaces (skin)
b. lining of open cavities (digestive, respiratory systems)
c. lining of closed cavities (ventral body cavity)
d. lining of blood vessels and heart (parietal pericardium (lines heart WALL) visceral pericardium (lines organ itself))}
Skin dips down and make something in it when there is a gland
ex. gland in ear makes ear wax
What are the 4 main function of Epithelia?
1. Protection- against bacterial infections, injury, etc.
2. Absorption- ex. lining of digestive tract; absorbs food into blood vessels that takes food in
3. Filtration- ex: renal-kidney; make urine, some goes out, some stays
4. Secretion- ex. glandular epithelium
*Or any COMBO of the 4
What are the features of epithelial tissue?
-Tightly packed/little extracellular space
- exists as sheets: tight junctions and desmosomes
Top part of cell; often contain microvilli
Bottom part of cell; always attached to basement membrane
Anchoring junction; anchors cells together
Keeps in in tact so it doesn't fall apart
Highly folded EXTENSIONS of the plasma membrane (it IS the membrane) that increases absorption area; brush border
-Beat in/out; stroke to push things away
EX: filter (beat out) mucous out of mouth and catch particles while its going up. (move substances over surfaces)
-not part of the membrane; they go through the cell membrane and ANCHOR in the cytoplasm
What is the structure of cilia?
Core 9+2 microtubule doublets
Basal body (centriole)= 9 microtubule triplets
longer projections from basal body in cilia; cell propels itself
Musinagen inside them that will become mucous; not cilia covering where goblet cell is bc once it makes mucous, it pushes it out of cell
What does it mean if epithelia doesn't sit on basement membrane?
Polarity of epithelia
cell is different all around
-only epithelia have this
-two layers: basal lamina and reticular lamina
Is epithelia vascular or avascular?
Avascular; no blood vessels
-Thin layer; closest to epithelium (secreted BY epithelium)
-non-cellular adhesive layer
-selective filter of materials from blood
-template for wound repair
-Below the basal lamina
-Extracellular network of collagen fibers
How does food get from connective tissue to epithelia if there are no blood vessels in epithelia?
Simple diffusion through capillaries: Blood vessels in connective tissue ----> epithelium; skin is fed from bottom, up
-No blood vessels
-Nutrients by diffusion
-IS innervated (supplied by nerves)
-High mitotic index; one of highest in body
One layer of cells; contains all 3 shapes
multiple layers; may have different shapes but nomenclature (naming) is based upon the cell shape of the free (apical) surface
3 epithelium shapes
Looks stratified but really not; one layer of cells but different heights
-Little protection; good for filtration (allows things to diffuse through them; form/function)
-Lines blood vessels/capillaries
-serosal membrane (ex: mesothelium- inside lining of lung)
How does oxygen get to simple squamous epithelia?
O2 gets absorbed by alveoli in lungs, diffused into capillaries, and since simple squamous is only one cell thick, it absorbs it quickly
What are the most common gasses in air?
N2, O2 (20%), CO2 (1%)
One layer thick of cubes; absorption in kidney (many microvilli)
-Sometimes have cilia, sometimes not; goblet cells for mucous production (mucous=sugar)
-digestive tract, urine tubes, pancreatic duct, oviduct
What kinda of epithelium is in the trachea?
Psuedostratified ciliated columnar epithelia
Stratified squamous epithelium
-MOST COMMON type of stratified epithelium
-protection vs. abrasion
-high mitotic index
-cells shed from apical region
- different layers may have different shapes but name is based off of the free apical (top) surface
-Basal layers: usually not squamous, site of new cell generation
Example of stratified squamous
On apical surface of stratified squamous; water insoluble protein (extra layer on top of skin; NOT in places with moisture like nose, mouth, vagina, etc.)
Why do we need moisture in our noses?
Function is to warm air; warmer it is the faster it diffuses so we humidify it with moisture
-Urethra of male
-some large organ ducts of glands
-2 to 3 cells deep
-Largest ducts of: sweat glands, mammary glands, salivary glands, surrounding eggs