epithelium Flashcards
(28 cards)
do epithelial tissues contain blood
they do not contain blood, they are avascular
tight junctions:
individual sealing strands, transmembrane, two key protiens involved are claudins and occludins. found in intestine and bladder. function: prevents harmful substances from passing between cells. keeps cell polarity by preventing protiens from getting between apical and basal surfaces. is electrically tight.
adherens junctions
they have a plaque layer of proteins on the inside of the cell to join actin to cadherins. Cadherine (the gap between the cells), catenins (links the cadherin to actin). more basal then in tight junctions. adherens junctions prevent cell seperation from tension forces in contractions
desmosome junctions
lateral wall. have plaque like adherens junctions. cadherin spans the gap and binds to desmoplakin. links the cell surface to keratin. keratin spans from one desmosome to another. they bind muscle cells and cardiac cells of the heart to prevent pulling apart
gap junctions
direct connection between cells. 2 hemichannels make up gap junctions. allows up to -1kDa small molecules through
hemidesmosome
connects epithelia to basement membrane. links cellular basal intermediate filament (keratin) to basement membrane. integrin fills the gap NOT cadherin. links th laminin in the basal membrane and to keratin in the cytoplasm
basement membrane - found between the connective tissue and epithelium.
Basal lamina - secreted by epithelial cells, contains collagen, laminin, glycoprotiens, other proteoglycans
reticular lamina - produced by cells of the connective tissue called fibroblasts and contains proteins such as fibronectin and collagen
functions of basement membrane
- supports the above epithelium
- provides a surface where epithelial cells migrate during growth and wound healing
- acts as a physcial barrier
- filters substances in the kidney
two types of epithelial tissue:
- covering and lining epithelia
- otuer covering (skin some organs)
- inner lining (blood vessels) - glandular epithelia
- secretes glands into the body and outside the body onto skin
covering and lining epithelia: simple epithelia
single layer of cells, secretion, absorption, filteration
covering and lining epithelia: stratified
two or more layers, protective
covering and lining epithelia: pseudostratified
appears to have multiple layers but all the cells touch the basement membrane, but not all touch the apical surface
shapes:
squamous: flat thin (allows passage by diffusion)
cuboidal: tall and wide (secretion, absorption)
columnar: more tall than wide (secretion absorption)
Transitional: a stratified epithelium where cells can change shape from cuboidal to flat depending on the organ shape (allows stretch esp for urinary bladder)
simple epithelium (single layer)
-simple squamous
-simple cuboidal
-simple columnar (ciliated -and non-ciliated)
stratified epithelia (two or more layers)
-stratified squamous (keratinised and non-keratinised)
-stratified cubiodal
-stratified columnar
-transitional
pseudostratified (appears multiple layers but is one layer)
pseudostratified columnar (ciliated and non-ciliated)
simple squamous epithelium (filteration, diffusion, secretion)
- most delicate epithelium
- where there is filteration
in kidney, diffusion in lung, and secretion where slippery surface needed - thin flat and not identical
- subtypes: mesothelium lines pericardial, pleural, peritoneal cavities
- endothelium lines inside of heart, blood and lymphatic vessels
other locations, inside eye, cavity linings, inside heart
simple cuboidal epithelium (tall and wide and one layer)
where there is secretion and absorption
cuboidal boxes
subtypes are: Nil
locations: pancreas ducts, parts of kidneys, smaller ducts of many glands
simple columnar epithelium
rectangular, nuclei is elongated and near the base of cell
has more cytoplasm so more organelles
more metabolically active than squamous
can be non ciliated simple columnar epithelium
or ciliated simple coumnar epithelium
if no cilia, then nicrovilli is there
non-ciliated simple columnar epithelium
single layer, microvilli on apical surface, have goblet cells around the cell,
lines gut from stomach to anus, ducts of many glands, gall bladder
function:secretion lubrication, absorption
ciliated simple columnar epithelium
single layer, has goblet cells and cillia to move substance around through the cells (cillia look like hairs)
locations: fallopian tubes, spinal cord,
functions: moves mucus and foreign objects or eggs (oocytes)
stratified squamous epithelium
two or more layers
lower layers may look like cubiodal or columnar.
cells furthest from nutrition are thinner and less active
features: located where mechanical or chemical stresses are severe
they protect from microbes.
apical cells are packed with keratin where mechanical stress and dehydration are a major issues - makes the surface tough and waterproof
subtypes:
keratinised (skin dry trauma areas)
non-keratinised (wet trauma areas) mouth, throat, tongue, vagina, anus, esophagus, function: protection from abrasion, defence from microbes, require secretions from glands
psuedo-stratified columnar epithelium
appears to have more layers, all cells touch BM but not apical surface
subtypes:
pseudostratified ciliated columnar:
- found in most upper airways
- secretes mucus and moves it
- cilia on some cells
- secretes mucus from goblet cells
pseudostratified non-ciliated columnar:
- no cilia
- no goblet cells
- found in larger gland ducts, epididymis, male urethra
- absorption and protection
glandular epithelia
glands are single or groups of cells that secrete ducts into ducts, onto a surface or into blood, function: secretion
