Epithelial TissuesEpithelial Tissues

Tissues – IntroductionTissues – Introduction a group of similar cells specialized to a group of similar cells specialized to

carry on a particular functioncarry on a particular function tissue = cells + extracellular matrixtissue = cells + extracellular matrix

– nonliving portion of a tissue that supports nonliving portion of a tissue that supports cellscells

4 types4 types– epithelial = protection, secretion, absorptionepithelial = protection, secretion, absorption– connective = support soft body parts and connective = support soft body parts and

bind structures togetherbind structures together– muscle = movementmuscle = movement– nervous = conducts impulses used to help nervous = conducts impulses used to help

control and coordinate body activitiescontrol and coordinate body activities

Epithelial Tissues Epithelial Tissues CharacteristicsCharacteristics free surface open to the outside free surface open to the outside

or an open internal spaceor an open internal space basement membrane anchors basement membrane anchors

epithelium to underlying epithelium to underlying connective tissueconnective tissue

lack blood vesselslack blood vessels readily divide (ex. skin healing)readily divide (ex. skin healing) tightly packed with little tightly packed with little

extracellular spaceextracellular space

Epithelial Epithelial ClassificationsClassifications classified based on shape and # classified based on shape and #

of cell layersof cell layers shapeshape

– squamous = thin, flat cellssquamous = thin, flat cells– cuboidal = cube-shaped cellscuboidal = cube-shaped cells– columnar = tall, elongated cellscolumnar = tall, elongated cells

numbernumber– simple = single layersimple = single layer– stratified = 2 or more layersstratified = 2 or more layers

Epithelial LocationsEpithelial Locations cover body surfaces, cover and cover body surfaces, cover and

line internal organs, and compose line internal organs, and compose glandsglands– skin cells, cells that line the stomach skin cells, cells that line the stomach

and small intestine, inside of your and small intestine, inside of your mouthmouth

Simple squamous Simple squamous epitheliumepithelium a single layer of thin, flattened cellsa single layer of thin, flattened cells

– look like a fried egglook like a fried egg easily damagedeasily damaged common at sites of filtration, common at sites of filtration,

diffusion, osmosis; cover surfacesdiffusion, osmosis; cover surfaces air sacs of the lungs, walls of air sacs of the lungs, walls of

capillaries, linings of blood and capillaries, linings of blood and lymph vesselslymph vessels

Simple cuboidal Simple cuboidal epitheliumepithelium single layer of cube-shaped cellssingle layer of cube-shaped cells

– centrally located nucleuscentrally located nucleus secretion and absorptionsecretion and absorption surface of ovaries, linings of surface of ovaries, linings of

kidney tubules, and linings of kidney tubules, and linings of ducts of certain glandsducts of certain glands

Simple columnar Simple columnar epitheliumepithelium single layer of cells that are longer single layer of cells that are longer

than they are widethan they are wide– nucleus located near basement mem.nucleus located near basement mem.

ciliated or nonciliatedciliated or nonciliated some have microvillisome have microvilli goblet cells = secrete mucusgoblet cells = secrete mucus absorption, secretion, protectionabsorption, secretion, protection linings of the uterus, stomach, and linings of the uterus, stomach, and

intestineintestine

Pseudostratified Pseudostratified columnar epitheliumcolumnar epithelium appear stratified b/c nuclei are at appear stratified b/c nuclei are at

2 or more levels2 or more levels– NOT stratified b/c all cells touch NOT stratified b/c all cells touch

basement mem.basement mem. ciliatedciliated goblet cellsgoblet cells protection, secretion, movement protection, secretion, movement

of mucusof mucus linings of respiratory systemlinings of respiratory system

Stratified squamous Stratified squamous epitheliumepithelium many layers of flattened cellsmany layers of flattened cells named based on appearance of named based on appearance of

top layer of cellstop layer of cells protectionprotection outer layers of skin, linings of oral outer layers of skin, linings of oral

cavity, throat, vagina, and anal cavity, throat, vagina, and anal canalcanal

Stratified cuboidal Stratified cuboidal epitheliumepithelium 2 or 3 layers of cuboidal cells2 or 3 layers of cuboidal cells protectionprotection linings of larger ducts of linings of larger ducts of

mammary glands, sweat glands, mammary glands, sweat glands, salivary glands, and pancreassalivary glands, and pancreas

Stratified columnar Stratified columnar epitheliumepithelium protection and secretionprotection and secretion vas deferens, part of the male vas deferens, part of the male

urethra, parts of the pharynx urethra, parts of the pharynx (throat)(throat)

Transitional epitheliumTransitional epithelium can stretchcan stretch distensibility (stretching), distensibility (stretching),

protectionprotection inner lining of urinary bladder and inner lining of urinary bladder and

linings of the ureters and part of linings of the ureters and part of urethraurethra

Glandular epitheliumGlandular epithelium cells that are specialized to cells that are specialized to

produce and secrete substances produce and secrete substances into ducts or into body fluidsinto ducts or into body fluids

gland = 1 or more cuboidal or gland = 1 or more cuboidal or columnar cellcolumnar cell

secretionsecretion salivary glands, sweat glands, salivary glands, sweat glands,

endocrine glandsendocrine glands

Exocrine vs. Endocrine Exocrine vs. Endocrine exocrine = secrete sub. into ducts exocrine = secrete sub. into ducts

that open onto surfacesthat open onto surfaces– skin or linings of digestive tractskin or linings of digestive tract

endocrine = secrete sub. into endocrine = secrete sub. into tissue fluid or bloodtissue fluid or blood– hormoneshormones

Exocrine glandsExocrine glands merocrine = release watery, merocrine = release watery,

protein-rich fluid by exocytosisprotein-rich fluid by exocytosis– salivary glands, sweat glandssalivary glands, sweat glands

apocrine = lose small portions of apocrine = lose small portions of their cell body during secretiontheir cell body during secretion– mammary glands, ear waxmammary glands, ear wax

holocrine = entire cell lysis holocrine = entire cell lysis (breaks apart) during secretion(breaks apart) during secretion– sebaceous glands of the skinsebaceous glands of the skin

Serous vs. MucousSerous vs. Mucous serous = typically watery with serous = typically watery with

lots of enzymeslots of enzymes– lubricationlubrication

mucous = mucusmucous = mucus– digestive and respiratory systemsdigestive and respiratory systems– protectionprotection