Histology: Epithelial tissue Epithelial Tissue is presented in two forms: 1. Covering Epithelia: 2. Glandular Epithelia:
1. Simple Epithelium: contain only one layer of cells. 2. Stratified Epithelium: contain more than one layer.
Simple Epithelium is classified according to the morphology of the cell into: 1. Simple Squamous Epithelium 2. Simple Cuboidal Epithelium 3. Simple Columnar Epithelium 4. Pseudo stratified Epithelium
2. Stratified Epithelium: contain more than one layer. Stratified Epithelium is classified according to the morphology of the cell into: Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium/ Urothelium
2. Glandular Epithelia: I) exocrine II) endocrine III) Classification
Stratified Squamous Epithelium (Non keratinized( Stratified epithelium is named for the shape of the cells forming the outermost layers. Stratified squamous epithelium consists of many layers of cells, making this tissue relatively thick. Cells nearest the free surface are flattened the most, whereas those in the deeper layers, where cell division occurs, are cuboidal or columnar. As the newer cells grow, older ones are pushed farther and farther outward, where they flatten
Stratified squamous epithelium lines the oral cavity, esophagus, vagina, and anal canal. In these parts, the tissue is not keratinized; it stays soft and moist, and the cells on its free surfaces remain alive.
H&E stain of biopsy of normal esophagus showing the stratified squamous cell
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2-Stratified Squamous (keratinized) Epithelium Stratified Squamous (keratinized) Epithelium is similar to stratified squamous (Non keratinized) Epithelium except that the superficial layers are composed of dead cells whose nuclei and cytoplasm have been replaced with keratin. (epidermis of skin). 14
The outermost layer of the skin (epidermis) is stratified squamous epithelium. As the older cells are pushed outward, they accumulate a protein called keratin, then harden and die. This keratinization produces a covering of dry, tough, protective material that prevents water and other substances from escaping from underlying tissues and blocks chemicals and microorganisms from entering.
the stratified squamous cell epithelium squamous epithelial surface, referred to as the epidermis. The layer of keratin here is named the stratum corneum
Stratified Squamous (keratinized) 17
3-Stratified Cuboidal Epithelium Stratified cuboidal epithelium which contains multiple layers of cuboidal cells, lines the ducts of sweat glands. 19
3-Stratified Cuboidal Epithelium 20
4-Stratified Columnar Epithelium It's composed of more than one layer of cells and the superficial layer is columnar in shape. This epithelium is found only in a few places of the body,
Stratified Columnar Epithelium
Urinary Epithelium Epithelial type is urinary epithelium Unlike pseudo stratified epithelium, this is a true stratified form. As the name implies, it's found only in the urinary tract. This image is from the urinary bladder, which is lined with it.
Notice that the cells in the deep layers are cuboidal to columnar; that those of the topmost layer are larger, pale and washed out looking, with small nuclei; and that the border is "scalloped." These are the definitive characteristics of this epithelial type
The urinary bladder has to expand and contract as the amount of stored urine increases or decreases. The epithelium you see here is in a bladder that's contracted (because it's empty).to accommodate this change in organ volume, the lining epithelium has to have extra membrane so that when the bladder is distended, the cells aren't stretched and torn.