EPITHELIAL TISSUE
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Transcript of EPITHELIAL TISSUE
EPITHELIAL TISSUE
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
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
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
Classification of epithelial tissue
• CELL SHAPE• Squamous (SKWA mus )• Cuboidal• columnar
• CELL ARRANGEMENT
• Simple• stratified
TYPES OF EPITHELIAL
• Simple squamous• Simple cuboidal epithelium• Simple columnar• Pseudostratified columnar / pseudostratified
ciliated columnar• Stratified squamous epithelium• Stratified cuboidal / columnar• Transitional eipthelium
SIMPLE SQUAMOUS
• Thin single layer• Rests on basement membrane• Functions: filtration, exchange• Location: walls of capillaries, air sacs • Forms serous (SIR –us) membranes •
»
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
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
PSEUDOSTRATIFIED COLUMNAR
• Cells are of different heights
• Cell nuclei are of different lengths
• Function: absorption, excretion
Pseudostratified ciliated columnar
• Lines respiratory tract
• Mucus traps small debris
• Cilia propel the mucus upward
• Move oocytes through the uterine tubes
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.
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
STRATIFIED CUBOIDAL / COLUMNAR
• Rare in body
• Found mainly in ducts of large glands
TRANSITIONAL EIPTHELIUM
• Found in the lining of the urinary bladder, ureters, and part of the urethra
• Tissue can stretch
Glandular Epithelium
• Makes up glands
• The cells in the glands produce a secretion
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
CELL CONNECTIONS
• Adhesion junction
• Tight junction
• Gap junction
CELL MEMBRANE CONTINUED
• Plasma membrane
• Short chains of sugars– plycoproteins– glycolipids
• Cell identity markers
BODY MEMBRANES
• Epithelial membranes– cutaneous membrane - skin– mucous membrane– serous membrane
• Connective tissue membranes– synovial membranes
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
MUCOUS MEMBRANES CONTINUED
• Functions– Protection
• Traps dust
• Prevents destruction of stomach lining by acid
– lubrication– can be modified for absorption or secretion
SEROUS MEMBRANES
• Simple squamous epithelium on a layer of connective tissue
• Lines body cavities that do not open to the exterior
• occurs in pairs
PAIRS OF SEROUS MEMBRANES
• Parietal
• Visceral
• Serous fluid
• Names– peritoneum– pleura– pericardium
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_frames