Epithelium Flashcards
How often does cancer arise from epithelium?
75% of the tim; MAJORITY
Tissues
Group of cells closely associated in structure and function
Histology
The study of tissues
What are the four major types of tissue?
- Epithelium
- Connective
- Muscle
- Nervous
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))}
Epithelial Gland
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?
- Protection- against bacterial infections, injury, etc.
- Absorption- ex. lining of digestive tract; absorbs food into blood vessels that takes food in
- Filtration- ex: renal-kidney; make urine, some goes out, some stays
- 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
Apical
Top part of cell; often contain microvilli
Basal
Bottom part of cell; always attached to basement membrane
Desmosome
Anchoring junction; anchors cells together
Tight junction
Keeps in in tact so it doesn’t fall apart
Microvilli
Highly folded EXTENSIONS of the plasma membrane (it IS the membrane) that increases absorption area; brush border
Cilia
-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
Flagella
longer projections from basal body in cilia; cell propels itself
Goblet cell
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?
cancer
Polarity of epithelia
cell is different all around
Basement membrane
- only epithelia have this
- two layers: basal lamina and reticular lamina
Is epithelia vascular or avascular?
Avascular; no blood vessels
Basal Lamina
- Thin layer; closest to epithelium (secreted BY epithelium)
- non-cellular adhesive layer
- selective filter of materials from blood
- template for wound repair
Reticular lamina
- Below the basal lamina
- Extracellular network of collagen fibers
Lamina means…
layer
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
Avascularity
Epithelia:
- No blood vessels
- Nutrients by diffusion
- IS innervated (supplied by nerves)
Regeneration
Epithelia:
-High mitotic index; one of highest in body
Simple epithelium
One layer of cells; contains all 3 shapes
Stratified
multiple layers; may have different shapes but nomenclature (naming) is based upon the cell shape of the free (apical) surface
3 epithelium shapes
- squamous; flattened
- cuboidal; height=width
- columnar; height>width
Pseudostratified
Looks stratified but really not; one layer of cells but different heights
pseudo= false
Simple Squamous
- 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%)
Simple cuboidal
One layer thick of cubes; absorption in kidney (many microvilli)
Simple columnar
- 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
SKIN
Keratin
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
Stratified columnar
- Very RARE
- Urethra of male
- some large organ ducts of glands
Stratified cuboidal
- RARE
- 2 to 3 cells deep
- Largest ducts of: sweat glands, mammary glands, salivary glands, surrounding eggs
Transitional Epithelium
(Stratified)
- Urinary bladder *
- Cuboidal on top, columnar on bottom
- Stretches out when bladder is full
