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Specialized Epithelium Dr. Amal Abd El hafez Assistant Professor of Histopathology 0  Learning Objectives At the end of this lecture, you will be able to: Enumerate the types of specialized epithelium Know t...

Specialized Epithelium Dr. Amal Abd El hafez Assistant Professor of Histopathology 0  Learning Objectives At the end of this lecture, you will be able to: Enumerate the types of specialized epithelium Know the different classifications of the glands. Define myoepithlium Define neuroepithlium Mention examples for each type of specilazed epithlium 0  Specialized Epithelium Definition: Group of epithelial cells that are modified to become specialized in certain function e.g secretion (glandular epithelium), contraction (myoepithelium) or act as a receptor (neuroepithelium) 0  II- Glandular Epithelium Definition: Epithelial cells that are modified to secrete 0 Classification of glands 0  Classification according to the presence or absence of ducts 1. Exocrine glands: formed of 2 parts: Secretory portion (acini) Excretory portion (duct system) that carries secretions outside the gland 2.Endocrine glands: formed of group of secretory cells but, no duct system, their secretion (hormones) diffuse into blood though fenestrated capillaries. 3.Mixed glands: composed of 2 parts, the exocrine part (duct) & endocrine part (no duct) e.g pancreas 0  Classification of Exocrine glands According to A-Number of cells: 1-Unicellular glands: e.g. Goblet cells. 2-Multicellular glands: e,g parotid gland & lacrimal glands. Any gland 0  II-Glandular Epithelium Multicellular 0  II-Glandular Epithelium According to: B- Mode (mechanism) of secretion: cellular changes after secretion 1-Merocrine: minimal changes occurs (secretions stored in vesicles and reach lumen via exocytosis) [e.g. sweat gland, goblet cells]. 2-Apocrine: Apical part of the cell is pinched off during secretion [e.g. mammary gland]. 3-Holocrine: the whole cell is destroyed during secretion and is replaced with another cell [e.g. sebaceous gland]. 0 0 According to: II-Glandular Epithelium C-Type (nature) of secretion: 1-Serous glands: e.g. Exocrine pancreas and the parotid gland. 2- Mucous: e.g. Goblet cells, labial gland ,Brunner’s tracheal glands. 3-Mucoserous gland: e.g sublingual & submandibular gland 0 According to: D-The shape (branching) of the duct: 1- Simple: if all the secretory cells of an exocrine gland discharge (drain) into one duct 2-Compound: if each group of secretory cells discharges into its own duct. These ducts unite into single large duct that ultimately drain to the surface. i.e multiple ducts drain into single one 0  According to: E-The shape of the secretory unit: 1-Tubular glands: tube like 2-Alveolar (acinar) glands: sac like 3-Tubuloalveolar (tubuloacinar) glands Since all exocrine glands are composed of a secrectory part and a duct system, they are classified into:- 0 0  III. Myoepithelium Definition: Myoepithelial cells are contractile epithelial cells. Also, called basket cells Sites: Between the basal lamina and the basal surface of secretory or ductal cells of exocrine glands. 0 Criteria: 1. Stellate shaped cells with many processes cradling the secretory pieces (octopus like) 2. Connected to each other and to the epithelial cells by gap junctions and desmosomes. 3.Contains cytoplasmic actin filaments, myosin and cytokeratin filaments. Function: Contract around the secretory portion of the gland → squeezing its contents outside the gland. 0  III- Neuroepithelium Definition: Epithelial cells specialized to act as a receptor so, associated with special sense organs. Examples: 1. Taste buds: in tongue for gustation (taste) 0  III-The Neuroepithelium 2. Organ of Corti: In inner ear for hearing 3. Macula & crista ampullaris: In inner ear for equilibrium 4. Rods & cones In eye for vision 5.Olfactory epithelium: In nose for olfaction (smell) 0  RECOMMENDED REFERENCES, WEBSITES Junqueira's Basic Histology: Text and Atlas, Thirteenth Edition 2013 ISBN-13: 978-0071780339 ISBN-10: 0071780335 Edition: 13th The histology tutor: http://www2.yvcc.edu/histology zoomer/HistologyTutorials/hi stology_tutorials.htm 0