St r a t ifie d squ a m ou s n on k e r a t in ize d e pit h e liu m St r a t ifie d squ a m ou s k e r a t in ize d e pit h e liu m St r a t ifie d colu m n a r e pit h e liu m Tr a n sit ion a l e pit h e liu m Un ice llu la r gla n d Ex ocr in e gla n d
Stratified squamous nonkeratinized epithelium 1.: I t s ce lls for m t h r e e la ye r s:1. St r a t u m ge r m in a t ivu m / ba sa le / cylin dr oce llu la r e Consists of a single row of columnar cells resting on the basal lamina. The intense mitotic activity is responsible for the replacement of the removed cells from the surface. The junction of the epithelium and connective tissue is irregular, the interdigitations of connective tissue called papillae between evagination of the epithelium enhance the adhesion of the two tissue types.
2. Stratum spinosum: Consists of polygonal cells bound together by desmosomes. As a consequence of tissue preparation, the cells decrease in size and remain bound by desmosomes located at the tips of spiny cellular projections; the name of this layer is suggestive for this spine-studded appearance3. Stratum planocellulare: Flattened cells that retain their nuclei.Location: Oral cavity, esophagus Vagina The corneal epithelium
Str. lumen planocellulareepithelium Str. spinosum Str. germinativum
Layers:1 .Stratum basale (germinativum): For m e d by colu m n a r ce lls pr e se n t in g in t e n se m it ot ic activity2.Stratum spinosum: Polygon a l ce lls a r e a lik e t h ose of t h e n on k e r a t in ize d epithelium.3.Stratum granulosum: Con sist s of fla t t e n e d ce lls w it h ba soph ilic k e r a t oh ya lin granules.4.Stratum lucidum: Tr a n slu ce n t , t h in la ye r of e osin oph ilic ce lls la ck in g n u cle i.5.Stratum corneum: Keratinized nonnucleated cells, horny cells, that are continuously shed at the surface.Location: the epidermis of the skin
epithelium Str. corneum Str. lucidum Dermis Str. granulosum Str. spinosum Hypodermis Str. germinativum
Stratified cuboidal epithelium: present in the duct of the sweat gland.Urothelium/ transitional epithelium:Layers:1. Columnar cell layer2. Polygonal cells/ pear-shaped cells3. Domelike facet cells, also called umbrella cellsLocation: Renal pelvis Urinary bladder Upper part of the urethra
The superficial layer consists of columnar cells, while cuboidal or smaller columnar cells are present in the basal layer.Location: The bulbous part of the male urethra Conjunctiva Interlobular excretory ducts of glands
I t is for m e d by ce lls spe cia lize d t opr odu ce a flu id se cr e t ion .Type s of gla n du la r e pit h e lia : En docr in e glands: ductless glads, their secretion is picked up and transported by the bloodstream, or diffuses into the surrounding extracellular fluid and acts on the neighbouring target cells (paracrine effect). Their secretions are called hormones. Ex ocr in e glands: usually present ducts through which the secretory product passes to reach the surface.
Ge n e r a l st r u ct u r e of t h e e x ocr in e gla n d: Secretory portion (acinus): its shape may be acinar, tubular, tubuloacinar. Duct: it is unbranched in simple glands, and repeatedly branched in compound glands. Cla ssifica t ion of t h e e x ocr in e gla n ds a ccor din g t o t h e ir position: endoepithelial, exoepithelial.Cla ssifica t ion of t h e e x ocr in e gla n ds a ccor din g t o t h echemical nature of the secretion: Serous glands: tight lumen, secretory cells with basophilic cytoplasm and round nuclei Mucinous glands: large lumen, the flattened cell nuclei are situated in the basal portion of the cell. The cells appear clear in HE staining because of the mucin garnules. Demilunes of Gianuzzi: serous cells are attached to the mucinous secretory portion, forming serous demilunes.
Cla ssifica t ion of t h e e x ocr in e gla n ds a ccor din g t o t h e m e ch a n ism of se cr e t ion : Merocrine mechanism: the secretion product is present in granules sorrounded by membranes, and it is released by exocitosis. E.g.: salivary glands. Apocrine mechanism: the secretion is eliminated together with the apical portion of the cytoplasm. E.g.: release of the lipid component of the secretion in lactating mammary gland. Holocrine mechanism: the entire secretory cell tranforms in secretion. E.g.: sebaceous gland.
Demilune of Gianuzzi Mucinous acini Serous aciniDuctus salivaris
Receives external stimuliHair cells It is composed of modified epithelial cells, whichin the represent a transitionorgan of between epithelial and nerveCorti cells. Classification of the cells of the neuroepithelium: Primary sensory cell (neuroepithel cell): presents process. E.g.: cells of the olfactory epithelium Secondary sensory cell (neuroepithel cell): does not present processes, stimuli pass on neural ganglia. E.g.: taste buds, hair cells of the internal ear
It is composed of cells that containLayer of thepigmented epithelial granules of melanin.cells E.g.: stratum pigmentosum retinae