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EPITHELIAL TISSUE
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Tissue - group of cells with similar structure and function 4 types –Epithelial –Connective –Muscular –Nervous Organs contain several tissue types –Arrangement determines structure and function
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Epithelial Tissue or epithelium Consists of cells with little extracellular fluid between them Covers body surfaces, lines body cavities, hollow organs, and ducts, and forms glands Functions: protection, absorption, filtration, secretion
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Special Characteristics Cells fit very closely together to form a continuous sheet Cells held together by cell junctions ( true for epithelial cells, some muscles and nerve cells) Apical surface Basement membrane Avascular Has a nerve supply High capacity for renewal by cell division
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Classification of epithelial tissue CELL SHAPE Squamous ( SKW A mus ) Cuboidal columnar CELL ARRANGEMENT Simple stratified
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TYPES OF EPITHELIAL Simple squamous Simple cuboidal epithelium Simple columnar Pseudostratified columnar / pseudostratified ciliated columnar Stratified squamous epithelium Stratified cuboidal / columnar Transitional eipthelium
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SIMPLE SQUAMOUS Thin single layer Rests on basement membrane Functions: filtration, exchange Location: walls of capillaries, air sacs Forms serous (SIR –us) membranes
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SIMPLE CUBOIDAL Single layer Function: secretion and absorption Found in glands and their ducts Ex. Salivary glands, Forms walls of kidney tubules and covers surface of ovaries
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SIMPLE COLUMNAR Single layer of tall cells Function: protection, secretion, absorption Location: lines entire digestive tract from stomach to anus, lining of uterus Contains goblet cells –Forms mucous membranes Contains microvilli – aid in absorption –Small intestines Some may be ciliated
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PSEUDOSTRATIFIED COLUMNAR Cells are of different heights Cell nuclei are of different lengths Function: absorption, excretion
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Pseudostratified ciliated columnar Lines respiratory tract Mucus traps small debris Cilia propel the mucus upward Move oocytes through the uterine tubes
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STRATIFIED Two or more cell layers Names for the type of cells at the apical layer FUNCTION: protection of underlying tissues in areas where there is considerable wear and tear.
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STRATIFIED SQUAMOUS Most common of the stratified Apical area is squamous cells Basement area is cuboidal or columnar Function: protection Found in high friction areas
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STRATIFIED CUBOIDAL / COLUMNAR Rare in body Found mainly in ducts of large glands
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TRANSITIONAL EIPTHELIUM Found in the lining of the urinary bladder, ureters, and part of the urethra Tissue can stretch
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Glandular Epithelium Makes up glands The cells in the glands produce a secretion
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TWO TYPES ENDOCRINE Secretion is released into the blood stream ductless Examples - pituitary, thymus, pineal, thyroid EXOCRINE Secretion is released through a duct on to the body’s surface or into hollow organ Most numerous Goblet cells Examples – sweat/oil glands, glands that make digestive enzymes, mammary glands
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CELL CONNECTIONS Adhesion junction Tight junction Gap junction
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CELL MEMBRANE CONTINUED Plasma membrane Short chains of sugars –plycoproteins –glycolipids Cell identity markers
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BODY MEMBRANES Epithelial membranes –cutaneous membrane - skin –mucous membrane –serous membrane Connective tissue membranes –synovial membranes
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MUCOUS MEMBRANES Composed of epithelium tissue lines all body cavities that open to the exterior –stratified squamous –simple columnar continuously bathed in secretions (mucous) –except urinary mucosae - urine
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MUCOUS MEMBRANES CONTINUED Functions –Protection Traps dust Prevents destruction of stomach lining by acid –lubrication –can be modified for absorption or secretion
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SEROUS MEMBRANES Simple squamous epithelium on a layer of connective tissue Lines body cavities that do not open to the exterior occurs in pairs
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PAIRS OF SEROUS MEMBRANES Parietal Visceral Serous fluid Names –peritoneum –pleura –pericardium
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Internet sites Internet Atlas of Histology –www.med.uiuc.edu/histo/small/atlas/ JayDoc –kumc.edu/instruction/medicine/anatomy/histow eb/ Lumen Histology –Meddean.luc.edu/lumen/MedEd/Histo/frames/h isto_frames
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