Epithelial Cells & Tissues Flashcards
properties of tissue
group/s of cells whose type, organisation + architecture are integral to function
cells, ECM + fluid
what is the extracellular matrix
material deposited by cells - “insoluble” part of extracellular environment
fibrillar proteins embedded in hydrated gel
may be poorly or highly organised
what are the 5 main cell types
connective tissue
contractile tissue
haematopoietic
neural
epithelial
types of tumors (6)
carcinomas - epithelial
sarcomas - mesenchymal (connective tissue and muscle)
leukaemias - haematopoietic
lymphomas - lymphomas
neuroblastomas - neurones
gliomas - glial
epithelial functions
transport, absorption, secretion, protection
two main criteria of epithelial classification
shape (squamous, cuboidal, columnar)
layering (simple, stratified, pseudostratified)
simple squamous epithelium + 3 examples
form thin epithelium that allows exchange to occur
e.g
lung alveolar (air sac) epithelium
mesothelium (lining major body cavities)
endothelium lining blood vessels and other blood spaces
simple cuboidal epithelium + 1 example
mainly in linings of ducts
e.g lining the kidney collecting ducts
simple columnar epithelium + 1 example
surfaces involved in absorption and secretion of molecules
e.g enterocytes lining the gut
keritinizing vs non-keritinizing
keratinizing epithelium form thick layers that protect underlying tissues for various physical and chemical insults
e.g. heat, cold, solvents (alcohol), abrasion, etc
no nuclei visible in surface cell layers in keritinizing epithelium
keritinizing stratified squamous epithelium + 1 example
produce keratin + die = thicker, stronger + protective
lose cellular organelles and nuclei
not visible under light microscopy
e.g epidermis
non-keritinizing stratified squamous epithelium + 5 examples
do not undergo keratinisation
retain nuclei + organelles
e.g. epithelium lining the mouth, oesophagus, anus, cervix and vagina
pseudo-stratified epithelium + 2 examples
appears to be multi-layered but surface cells all have contact with basal lamina
e.g.
airway (trachea and bronchi) epithelium
various ducts in the urinary and reproductive tracts
methods used by solutes to cross membranes
gases + hydrophobic molecules = diffuse across the lipid bilayer
most molecules = passive/active using proteins
what is cell polarisation
when cell organelles + membrane proteins are organised to give the cell directionality
absorptive epithelium
apical:
brush border + cells arranged as villi = more SA
BB = active transporters and channels = more uptake
many mitochondria
baso:
passive transport
(absorb things into bloodstream e.g intestinal brush border absorbs nutrients)
secretory epithelium - exocrine
secretion into a duct or lumen
organelles are arranged for secretion from the apical plasma membrane
secretory epithelium - endocrine
into the bloodstream
secrete their contents to the basal aspect
vesicles positioned so contents have close access to blood circulation
epithelial cell proliferation
constant replacement of lost cells by proliferation of stem cells
balance between proliferation + death is key to maintaining tissues
example of too little proliferation
e.g inhibition of stem cell proliferation in intestinal crypts due to chemotherapy leading to gastro-intestinal disturbances
example to too much proliferation
leads to overproduction of tissue as rate of cell loss isn’t sufficient to maintain normal tissue volume
benign tumours such as adenomas can form - high risk of mutation into malignant
proliferation at epidermis
cells of basal layer of stratified squamous epithelia divide + migrate up to replace cells lost from surface
while migrating - undergo differentiation that leads to flattening + keratinising
hyperproliferation of epithelia of epidermis
increased cell numbers + thickening of cell layers
what can cause hyperproliferation of epithelia of epidermis
continuous or repeated pressure + abrasion
infectious agents such as papilloma virus (hijack cell machinery + induce increased proliferation e.g warts)
cell turnover summary
cell loss = cell production ==> steady state
cell loss > cell production ==> reduction in tissue mass
cell loss < cell production ==> increased tissue mass
