Surface Epithelium Flashcards
define contiguous cells
cells that form linings that cover most body surfaces, cavities or tubes
what are functions of epithelial tissue
protection (skin), transcellular transport (with selective permeability), secretion (mucus precursor, hormones), absorption (intestine), sensations (taste buds, retina), immune defense (house cells of immune system, and physical barrier)
describe the structure of epithelial tissue
apical + basal surfaces, tight junctions between cells, resting on basement membrane- attaches epi cells to connective tissue
is there a lot/little extracellular space and matrix in epithelial tissue
little ECM or space
define brush border
fuzzy appearance that villi give epi cells i.e intestine or kidney
define motile cilia
allow movement by pushing substances i.e in trachea mucus
what are the two sections of the basement membrane
basal lamina, lamina reticularis
function of basal lamina?
molecular filter- prevent substances entering epithelium
function of lamina reticularis
fixes lamina densa to underlying connective tissue
which part of the basement membrane is avascular
lamina reticularis
what are the two subsections of the basal lamina
lamina lucinda and lamina densa
how thick are the lamina lucinda and densa
50nm
what are the lamina lucinda and densa made of
lucinda- glycoproteins- laminin and intactin
densa- type 4 collagen
how are epithelial tissue/cells classified?
according to cell layers, morphology and polarity + surface specialisation
two classification categories for number of cell layers
simple or stratified
classification categories for cell morphology
squamous, cuboidal, columnar
classification categories for polarity and surface specialisation
polarised cells- have apical domain and basolateral domain where the apical domain faces a lumen and the basolateral domain is in contact with the basal lamina
write a note on simple squamous epithelium (structure, function, location)
thin single layer of flat cells, rapid diffusion (O2, CO2, fluids, ions), air sacs of lungs, kidney tubules, blood vessel linings
write a note on simple cuboidal epithelium (structure, function, location)
single layer of cube shaped cells- large nucleus. rapid substance diffusion. renal tubules, resp passages, ducts of glands, thyroid glands, covering of ovary
write a note on simple columnar epithelium (structure, function, location)
single layer rectanglular shaped cells- nuclei in basal portion of cell. can have microvilli or cilia on apical plasma membrane. microvilli = small intestine, cilia = uterine tubules/parts of resp tract
what are the three categories of stratified squamous epithelium
kertatinized, non keratinized and parakeratinised
describe keratinized stratified squamous epithelium
these cells are dead and lack nuclei- filled with keratin . resist friction and impermeable to water, i.e outer layers of skin
describe non keratinized stratified squamous epi cells
retain nuclei and are still alive. found in areas where surface must be moist or wet like the mouth or throat, vagina
describe parakeratinised stratified squamous epithelium
surfacemost cells retain their nuclei but are pyknotic meaning the nuclei are undergoing necrosis or apoptosis
stratified cuboidal epi structure and function
two cell layers- lining ducts of sweat glands
stratified columnar epi structure and function
only a few layers and the apical layer is columnar + basal layer is cuboidal. male urethra, cornea, salivary ducts
write a note on transitional epithelium
only in urinary system in linings of kidney, ureter,bladder and urethra .
basal cell layers are cuboidal where apical cell layers are dome shaped when relaxed. apical cells flatten- allow tissue to stretch
