tissue basics + epithelial tissue

tissues

a group of specialized cells along with an extracellular matrix to perform a certain function

histology

microscopic study of tissues

epithelial tissue

any tissue immediately touching air or fluid

functions of epithelial tissue

protecting underlying structures, acting as a barrier, allowing passage of substances, absorbing and secreting substances

epithelial tissue heals and gets nutrients via

diffusion

properties of epithelial tissue

cells are tightly packed, has multiple surfaces, is avascular, richly innervated, highly regenerative and has little extracellular matrix

epithelial tissue is highly regenerative due to

high mitotic rate

apical/free surface

the surface of the epithelium in contact with air or fluid

basal surface

thin underlying structure beneath the apical layer

basement membrane

porous and selectively permeable layer under the basal surface made of basal and reticular lamina. creates new cells and migrates them

lateral surface

the side of the cell that connects adjacent cells

classifications of epithelial tissue based on cell shape

squamous, cuboidal, columnar

squamous

flat, scalelike

cuboidal

about equal in height and width

columnar

more taller than wide

transitional

can change based on circumstances

simple epithelium

single layer

stratified epithelium

multiple layers

pseudostratified epithelium

looks stratified but isnt

simple squamous epithelium

are thin, primarily for filtration and rapid diffusion

simple cuboidal epithelium

good for absorption, secretion, and movement of substances

simple columnar epithelium

good for diffusion, thicker and have goblet cells that secrete mucus for protection

pseudostratified columnar epithelium

has goblet cells that move along tiny hairs called cilia

stratified squamous epithelium

can be keratinized or non keratinized, meaning the cytoplasm is replaced with the protein keratin which is harder and offers more protection

stratified cuboidal epithelium

secretes absorbs and protects

stratified cuboidal epithelium

protects and absorbs

transitional epithelium

cuboidal when not stressed, squamous when under stress

free surface modifications

smooth, fold, microvilli, cilia, transitional

cell connection

allow things to pass and communicate with each other

cell connection types

desmosome, hemidesmosome, tight junction, adhesion belts, gap junction

desmosome

allows cells to stretch

hemidesmosome

allows cells to stretch from the basement membrane

tight junction

hold cells together but enables permeability

adhesion bells

anchor cells to each other

gap junction

have channels to allow cells to communicate