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 •

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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

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