Epithelial Tissues Flashcards
two main categories
covering epithelium & glandular
functions of epithelium
secretion, absorption, filtration, transport, protection, excretion
characteristics of epithelium
cellularity, specialized contacts, polarity, supported by connective tissue, avascular, regeneration
simple squamous epithelium
single layer - used for diffusion and filtration - kidneys, blood vessels
simple cuboidal epithelium
single layer of cubelike cells with large nuclei - secretion & absorption - kidney - ovary
simple columnar
absorption & secretion of mucus - digestive tract (non-ciliated) and ciliated (bronchi & uterus)
stratified squamous epithelium
many layers - protection -epidermis (keratinized) & esophagus (nonkeratinized)
pseudostratified columnar epithelium
single layer - secretion - male’s sperm (nonciliated) & trachea (ciliated)
transitional epithelium
stretches readily and permits distension of urinary organ - lines the ureters
epithelial cell polarity layers:
apical - lateral - basal
Apical domain specialized features
microvilli - sterocilia - cilia
microvilli
cytoplasmic extensions - increase surface area - non motile
stereocilia
long microvilli - non motile - increase surface area
cilia
produce movement - contains axoneme -
junctional complex components
zonula occludens - zonula adherens - macula adherens
Zonula Occludens
tight junction - anchoring junction - diffusion barrier - provides limited resistance to mechanical stress - closest to apical surface
zonula adherens
anchoring junction - provides mechanical stability by linking cytoskeleton with MICROFILAMENTS and use of cadherins
macula adherens
desmosome - anchoring jxn. - provides mechanical stability by use of INTERMEDIATE filaments and cadherins
gap junctions
communicating junctions - connexon of one cell lines up with the connexon of the next cell - allows exchange of ions
basal domain junctions
focal adhesion - hemidesmosome
focal adhesion
anchoring junction - uses microfilaments to anchor cytskeleton to basal lamina - role in signal detection
hemidesmosome
anchoring junction - uses intermediate filaments to link cell to basal lamina - intermediate filaments are attached to integrins
endocrine glands
ductless glands - secrete into interstitial fluid
exocrine glands
secrete their products onto surface directly or through epithelial duct (indirect)
3 different endocrine hormones
circulatory, paracrine, autocrine
circulatory hormones
released into interstitial fluid and picked up by circulatory system
paracrine hormones
hormones do not get into bloodstream - binds to neighboring cell
autocrine hormones
own cell releases hormone and acts on itself
exdocrine glands can be classified by:
cellularity-structure-type of secretion- mode of secretion
exocrine gland type of secretions:
mucous, serous, mixed glands
serous cells
rounded nuclei - protein secreting cells -
mucous cells
produce hydrophilic glycoprotein mucins - cuboidal
exocrine mode of secretion
merocrine glands - holocrine glands - apocrine glands
merocrine glands
exocytosis -
holocrine
cell explodes to release contents
apocrine
pinched off portion of cell is secretion
