Epithelia
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Epithelia - Details
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| 🇬🇧 | 🇬🇧 |
| What epithelia is shown | Stratified columnar |
| What epithelia is shown | Simple squamous |
| Where is simple squamous found | Alveoli epithelia and blood vessel endothelium |
| Where is stratified columnar found | Salivary gland, eyes, urinary tract |
| What epithelia shown | Stratified squamous |
| Features of simple squamous epithelium | Thin, scale-like flat cells Single layer All rest on the basement membrane Nuclei bulge from cell surface |
| Function of simple squamous epithelium | Lubrication to allow movement of viscera Gas exchange ( alveoli ) Barrier ( Bowman's capsule ) Passive transport of water Active transport |
| Where can simple squamous epithelium be found | Lining of blood and lymph vessels (endothelium) Bowman's capsule Loop of henle Inner and middle ear Intercalated pancreatic ducts |
| Features of simple cuboidal | Equal width and height Centrally places round nucleus Rests on basement membrane May or may not feature brush border of microvilli |
| Location of simple cuboidal epithelium | Thyrocytes Mesothelium of ovary Small ducts of many exocrine glands Kidney tubules Respiratory bronchioles |
| Function of simple cuboidal | Secretion Absorption Conduit Barrier Hormone synthesis and mobilisation |
| Features of simple columnar | Rectangular Oval basal nucleus Rests on basement membrane |
| Where is simple columnar found | Small intestine and colon Gallbladder Striated duct of salivary gland |
| Function of simple columnar found | Secretion Absorption Conduit Transport |
| Pseudostratified squamous epithelium features | Some tall some short Nuclei found in basal 2/3rd Some have cilia |
| Psuedostratified squamous epithelium is found where | Nasal cavity, trachea, Bronchi Auditory canal inter lobular duct of parotid gland Lacrimal sac Epididymis Parts of the male urethra |
| Psuedostratified squamous epithelium function | Secretion Absorption Conduit Particle trapping --> cilia associated |
| Stratified squamous epithelium (non-keratinized) features | Arranged in layers Basal cuboidal or columnar cells Flattened cells are replaced by proliferation and differentiation of basal cells |
| Stratified squamous epithelium location ( non-keratinised ) | Oral cavity Oesophagus Larynx Vagina: Secrets glycogen which is a substrate for the formation of lactobacilli Anal canal Surface of cornea |
| Stratified squamous epithelium function | Protects against abrasion and water loss Secretion |
| Stratified squamous epithelium (keratinized) features | 5-6 layers Basal cuboidal cells Upper layer consists of flattened, dead, anuclear, keratinized cells |
| Function of stratified squamous epithelium keratinised | Protects against UV light rays Abrasion and water loss |
| Transitional epithelium features | Relaxed = Appears 4-5 layers thick Basal layer cuboidal Intermediate layer larger, polygonal Surface dome- like/rounded/umbrella shaped |
| Transitional epithelium locations | Renal calyces Ureters Bladder Proximal urethra |
| Transitional epithelium function | Distensibility Protection of underlying tissue from cytotoxic effects of urine |
| What are the different intercellular junctions | Tight junctions ( zona occludens ) Spot junctions ( Demsomes or musculae adherens ) Adheren junctions Hemidesmosomes |
| Features of Tight junctions | AKA zona occludens Basically contain occludens and also connect microfilaments of adjacent cells and aim to control diffusion in apical regions Found closest to the epithelium |
| Features of Adheren junctions | Connect microfilaments of adjacent cells |
| Features of spot junctions | AKA desmosomes or musculae adherens Comprised of integrins and provide continous epithelium Anchored by intermediate filaments |
| Features of hemidesmosomes | Anchors cells the the BM by integrins |
| What are Junctional complexes | These isolate the luminal space from the intercellular space Fluid is moved from e.g. the intestinal lumen into the cell, then into the intercellular space, and finally across the basement membrane into connective tissue and vasculature Cholera can disrupt this complexes leading to increased intestinal permeability |