EPITHELIAL TISSUE

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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 (SKWA 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
  bodys 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/histoweb/
• Lumen Histology
• Meddean.luc.edu/lumen/MedEd/Histo/frames/histo_fra
  mes