Epithelial Tissue Flashcards
What are the features of the apical surface of an epithelial cell?
Exposed
Specialised with: microvilli, cilia
What are the features of the basal surface of an epithelial cell?
Attaches to the basement membrane via:
Integrins
What is the basement membrane?
Thin layer of basal lamina (and reticular fibres) secreted by epithelial cells between them and connective tissue
How do epithelial cells attach to the basement membrane?
Hemidesmosomes and focal adhesions use integrins as transmembrane proteins between the cell and the basement membrane
What are integrins?
Transmembrane proteins that attach cells to the basement membrane and through to the Extracellular Matrix.
Also, facilitate cell migration (immune patrolling) and cell signalling.
How do hemidesmosomes attach to the basement membrane
Hemidesmosomes produce transmembrane proteins (integrins) that interlock and connect cells with the basement membrane
How do focal adhesions attach to the basement membrane?
Focal adhesions anchor Intracellular actin filaments (microfilaments) to transmembrane proteins (integrins) which connect the cell to the basement membrane
What are the features of the lateral surface of an epithelial cell?
Attaches to adjacent cells via:
Tight junctions
Desmosomes
Gap junctions
How do tight junctions attach to adjacent cells?
What purpose does this serve?
Protein complexes fuse the membranes together forming a seal.
Molecules have to pass through cells
How do desmosomes attach to adjacent cells?
What purpose does this serve?
Produces transmembrane proteins (cadherins) that interlock and connect cells (also contain intermediate filaments intracellularly)
Helps strengthen the connections at other junctions and prevent stretching/twisting of cells under stress
How do gap junctions attach to adjacent cells?
What purpose does this serve?
Connexons (lined up transmembrane proteins) form channels between cells
Allows the movement of molecules for cell-to-cell communication
What are the 4 types of simple (single-level) epithelial cells?
Squamous
Cuboidal
Columnar
Psuedostratified
What are the 4 types of stratified (multi-level) epithelial cells?
Squamous
Cuboidal
Columnar
Transitional
Where is simple squamous epithelium found and what is it’s specific function?
Acts as a barrier: endothelium of vascular vessels, Bowman capsule
Secretes lubricating fluid: mesothelium
Active transport/gas exchange: type I pnuemocytes
Where is simple cuboidal epithelium found and what is it’s specific function?
Diffusion and secretion for hormones: thyroid (thyroxine), type II pnuemocytes (surfactant)
Line ducts/follicles for exocrine glands
Where is simple columnar epithelium found and what is it’s specific function?
Contain microvilli for absorption (simple columnar —> villi): alimentary/GI tract
Where is psuedostratified epithelium found and what is it’s specific function?
Traps particle; secretes mucous (goblet cells), wafts cilia (ciliated epithelial cells): respiratory tract
Where is non-keratinised stratified squamous epithelium found and what is it’s specific function?
Reduces water loss (remains hydrated) and protects against abrasion: openings of the skin (mouth, nostrils, anus)
Where is keratinised stratified squamous epithelium found and what is it’s specific function?
Greatly reduces water loss and toxic ingress
Protects against abrasion and microbial colonisation
Found on the outer layers of skin (stratum corneum) - cornified layer of keratin
Where is stratified transitional epithelium found and what is it’s specific function?
Stretches and distends: relaxed (columnar) contracted (squamous)
Protects from toxic chemicals
Found in the urinary tract
What surfaces is epithelium tissue found?
Exterior (skin)
Interior open to the exterior (mucous membranes)
Interior closed to the exterior (serous membranes)
Where are mucous membranes found?
Mucosa of:
Digestive tract
Respiratory tract
Urinary tract
Where are serous membranes found?
Viscera of:
Peritoneum
Pleural sacs
Peritoneum
Describe features of mucous membranes
Single-layered
Inner epithelium lines lumen
Surrounded by lamina propria (connective tissue) and muscularis mucosae
Describe features of a serous membrane?
Double-layered (mesothelium)
Inner epithelium secretes lubricating fluid (for viscera)
Surrounded by lamina propria (connective tissue)
