FoM:L1 - Epithelia Flashcards
What is epithelial tissue?
thin continuous sheet of cells
What is glandular epithelium?
- formed by downgrowth of epithelium into underlying tissues
- can form secretory glands and ducts
What are the 3 functions of epithelial tissues?
- protection
- barrier between internal and external environment
- allows transport of materials (diffusion, absorption and secretion)
What are 5 characteristics of surface epithelium?
- basal surface of cells rests on basement membrane
- polarity (apical, basal and lateral surfaces)
- Contiguous adhesive (cells joined by intercellular junctions)
- No direct blood supply (diffusion important!)
- High mitotic activity
What is the basement membrane?
thin protein later that lies deep in epithelium, made up of 3 parts
What is the function of the BM? (3 points)
- support and anchor epithelium to tissue
- physical and selective diffusion barrier
- essential for epithelial cell proliferation ansd polarisation
Where are junctions of epithelial cells located?
basal - BM
lateral - other cells
gap junctions allow communication
What are the 3 types of apical specialisations?
Microvilli - increase SA for absorption; made of actin and immobile
Cilia - waft and move things; made of microtubules (9,2) so are mobile
Stereocilia - increase SA for absorption; made of actin and immobile, slightly longer than MV
Where are each of the apical specialisations found? (examples of each)
Microvilli - intestinal epithelium
Cilia - respiratory and uterine tube epithelia
Stereocilia - epididymis and vas deferens
What 2 structural features are used to classify surface epithelium?
- Thickness: simple vs stratified
- Shape: squamous vs cuboidal vs columnar
Give an overview of simple squamous cells
function: barrier, trans-epithelial transport
Location: endothelium (vessels), respiratory air spaces; mesothelium (covers organs)
Give an overview of simple cuboidal cells
Function: barrier; absorption and secretion
Location: kidney tubules, bronchioles, secretary cells of some glands
Give an overview of simple columnar cells
Function: barrier; absorption and secretion
Location: lines GI tract, uterus
Give an overview of stratified squamous cells
Function: protective barrier against wear + tear
Location: skin, lining of oral cavity, oesophagus, vagina
Give an overview of stratified cuboidal/columnar cells
Function: barrier; some secretory/absorptive function
Location: ducts of sweat glands, walls of large ducts
What are pseudo-stratified columnar epithelial cells?
- SIMPLE COLUMNAR epithelium
- appears stratified
- all cells rest on BM
- eg respiratory epithelium
What are transitional epithelium?
- stratified
- only lines lumens of UT
- Change appearance depending on stretch
- relaxed: surface umbrella cells, look rounded
- stretched - thin, squamous like cells
What are the types of gland?
exocrine: link with surface, usually by a duct
endocrine: no connection with surface (no duct) secretions released into tissues
How do exo and endocrine glands secrete?
Exo:
- merocrine; from apical cell surface
- Apocrine; partial loss of apical parts of cells
- Holocrine: entire cell
Endo:
from base of cell
How can glands be classified by secretion?
mucous: glycoproteins and water
Serous: protein and water
Mixed: Both
What is the only unicellular secretory portion?
goblet cells - not grown deeper into tissue
- use stain for secretions to identofy
