Epithelial Histology Flashcards
three major morphological characteristics of epithelial tissue types
number of cell layers - simple or stratified
cell shape - flat, square, or rectangular
keratinization - keratinizing or non-keratinizing
Name the eight types of epithelial tissue.
simple squamous, simple cuboidal, simple columnar, stratified squamous, transitional, ciliated pseudostratified, stratified cuboidal, stratified columnar
simple squamous epithelium
make out intact sheets sittin on a basement membrane, flattened nuclei, used to pass nutrients from two mediums
simple cuboidal epithelial cells
usually lines ducts, cells look like squares, nuclei look like perfect circles
simple columnar epithelium
cells taller than they are wide, height can vary and nuclei freequency appear elongated in cross-section, commonly found at absorptive surfaces, when occupied by cilia called simple columnar ciliated epithelium
nuclei no longer perfect circle
goblet cells
modified columnar epitheliall cells involved in mucous production and secretion
non-keratinizing stratified squamous epithelium
found vovering certain internal body surfaces such as the oral cavity, basal cells are cuboidal in form but top outermost layer is squamous
color gets paler because less nutrients near the top
keratinizing stratified squamous epithelium
18-30 layers of dead cells compacted on top of each other, prevents dehydration
outermost cells are squamous, filled with hard keratin protein material
dead cells sometimes called corneocytes
stratified cuboidal
quite rare, layers of cuboidal cells, outer cells do not flatten out
stratified columnar epithelium
rare, in salivary gland, lack of cilia and no basal bodies
transitional epithelium
mainly found in bladder, important characteristic is the dome-like appearance of the outer layer of cells, able to stretch out when needed, nuclei start to become larger toward apical side
also has plaque-like structure at the apical end
pseudo-stratified epithelium
round nuclei and goblet cells, every cell has a direct connection to the basement membrane
presence of cilia, basal body easy to recognize
found in larger airways of the respiratory system
specializations of the apical surface
microvilli, cilia, and stereocilia
specialization of the lateral domain
tight junctions, adherens junctions, desmosomes, gap junctions
specializations of the basal domain
hemidesmosome
microvilli
hard to resolve at the light microscope level, actin-filled extensions from the apical surface of epithelial cells in tissues like the gut
called brush border when cells have a plethora of these structures, important for absorption by increasing apical membrane surface area
cilia
mucrotubule based cell surface extension, formed by 9 outer microtubule doublets and 2 inner singlets called the axoneme
used to move materials over the apical surface
non-motile cilia have a distinct 9+0 arrangement
basal body is the large proteniacious mass at the bottom of cilia
sterocilia
more closely related to microvilli, very thin, long extensions of the apical surface and contain actin filaments at their core
likely to increase absorptive surface where they are formed
terminal bars
apical junctional complexes of simple epithelial cells
poorly resolved group of junctional complexes present at the apical aspect of the lateral membrane domain
tight junctions
also known as zonula occludens
act as a barrier or gate to the passage of materials from the lumen into the connective tissue, also has fence function to prevent the free flow of membrane proteins from the apical to the basolateral membrane domain
exist in simple and stratified epithelia (outer layer)
adherens junction
also known as zonula adherens
small gap between contacting membranes filled by extracellular domains of adhesion molecules called cadherins
dense cytoplasmic plaque to which actin microfilaments can be found
work to adhere cells together and is involved in tissue morphogenesis as well as cell-cell comunication
desmosome
also known as the macula adherens
cadherins in intercellular space bind to each other, connected to a keratin network in the intracellular space
gives stretching ability to cells, main function is adhesion
also have a role in signaling between contacting cells
gap junctions
complex provides direct pore between two closely apposed membranes and allows the passage of small molecules between cells
primarily involved in cell-cell communication
six connexin molecules make one connexon and two connexons interact to form a gap junction
allows through molecules less than 1 kDa
hemidesmosome
engaged keratin network though molecular organization
link epithelial cells to the BM
transmembrane receptors involved in signaling
exocrine gland
secretion onto a body surface via a duct
merocrine
cells secrete product via exocytosis
apocrine
secretion is surrounded by a thin layer of cytoplasm within vesicles of cell membrane
holocrine
cell contents are sloughed off as part of secretion
endocrine
secretion into the blood stream via adjacent capillaries, endocrine glands have no ducts
paracrine
secretion affects nearby cells, glands are unicellular
unicellular glands
gland is made up of one cell such as goblet cells
tubular glands
secretory epithelial cells arranged in a tube that also serves as a duct
acinar glands
have a duct with a secretory cluster of cells at the end of an acinus, acini are serous (contain a watery section) or mucous
three types of gland arrangement
simple tubular, brancehd tubular, compound
parenchyma
the functioning epithelial component of glands or organs
stroma
the supporting connective tissue framework of glands or organs
