Histology- Epithelial cells Flashcards
How small can a light microscope see?
as small as .2 microns
2 types of light microscopy and difference
fluorescence- fluorescent probe
confocal- particular plane (can’t see plane above or below, thin almost 2-D image)
Which type of microscope can view living or dead cells?
light
Which type of microscope uses tissues that are frozen in liquid nitrogen, coated in gold, and dead?
electron
4 steps of tissue prep for light microscope?
1.) fixation: chemicals cross-link proteins and inactivate degradation enzymes
2.) dehydration and clearing: with alcohol solutions
3.) infiltration and embedding- waxxed and hardened
4.) trimming: sliced thin, transparent
loaded with dye to improve visualization (staining)
What is it called when cells are stained with fluorescent antibodies that bind to a very specific molecular structure?
immunohistochemistry
Which 2 dyes are usually done together in light microscopy and what colors are they? Basophilic or acidophilic?
hematoxylin-dark blue- basophilic
eosin-pink-acidophilic
What stain is great at showing glycogen and glycoproteins, as well as cytosol, mucous, and some ECM?
PAS- periodic acid-Schiff stain
Which stain is used to see proteins and+ charged molecules?
eosin
Which stain is used to see DNA, - charged molecules and nuclei?
hematoxylin
Trichrome stains which areas what color?
conn. tissue=blue
nuclei=dark red/purple
cytoplasm=red/pink
Functions of epithelial cells?
protection, transport, secretion
Is epithelium vascular?
no
Simple squamous epi. location and function?
lungs, heart, blood vessels, lymph vessels
diffusion, filtration, secretion
EXCHANGE EPITHELIUM
Simple cuboidal epi. location and function?
ducts, secretory portions of small glands, kidney
secretes, absorbs
TRANSPORT EPITHELIUM
Simple columnar epithelium?
ciliated tissues, bronchioles, uterine tubes, microvili
absorbs, secretes mucous and enzymes
CILIA= MOTILITY
MICROVILI=increase surface area
Difference between simple and stratefied?
simple=1 layer
strat= more than 1
Pseudostratified columnar epi. location? function?
ciliated, bronchi, trachea, resp. tract
secretes mucous
Stratified squamous epi, location, function?
esophagus, mouth, vagina, SKIN
protects against abraision
Transitional epi. Location? function?
bladder, urethra, ureters
stretch of urinary organs
CHEMICAL PROTECTION from urine
Function:
1.) actin
2.) int. filaments
3.) microtubules
1.) shape, motility (actors have nice shape and move on stage)
2.) structural “strength” (Des is an int. student filled with strength and doing K)
3.) polarity, cell division, cilia (microdick could cause polarity and division in a relationship)
What kind of conn. tissue are desmin and keratin?
int. filaments
Tight junctions
1.) location
2.) functions
1.) apical aspect of almost ALL epithelial cells. gut, brain, skin, resp. tract. CLOSEST to lumen
2.) barrier, regulate movement, est. polarity, direct memb. proteins
Most common proteins in tight junctions?
Claudins (small molecules)
Occludin
junctional adhesion molecules (JAM) (permeability)
ZO-proteins (interaction)
(These guys are TIGHT but Claud, Occy and JAM are all trans. But their friend ZO, says NO, and is still in the closet with his skeletons, but introduces them to his skeletons)
What are found immediately below TJs?
adherens junction
In order to stay TIGHT, junctions must have adherens!
Adheren key proteins
Cadherin and catenin (beta-catenin=signal OR connect with cadherin)
We must adhere to the rules. Cad is trans and has an cat that must stay inside who likes fish skeletons.
Why is regulation of adherens via cadherin, beta-cadherin and catenin important in regulating would healing?
Can send signals for more cadherin to be made to bridge the gap between epithelial cells. You can lose outer connection (cadherins) but catenins will go signal for new cells and cell division.
Which junctions circle the entire apical aspect of a columnar or cuboidal epi. cell? Which attaches to certain spots only?
Adheren and tight
Desmosomes
Which provides more structural stability to the cell? Des or Ad?
Desmosomes
Which type of filaments do desmosomes connect? Example?
intracellular intermediate filaments. Keratin
Adherens and desmosomes both have what kind of “linking” protein? Hemidesmosome has which kind?
claudin-like
integrin
Which linking protein binds to a component of the basement membrane known as laminin? And DOES NOT bind to adjacent cell
Integrin
Integrin and laminin are linked!
Do hemidesmosomes have important intracellular signaling functions? Tight? Adherin? Desmosomes?
No, yes, yes , yes
What do hemidesmosomes link to?
intracellular intermediate filaments
What are examples of columnar epithelial cells that possess motile cilia?
uterine tubes
respiratory epithelium
What structure do cilia have?
9 + 2 (9 microtubules (axoneme) with a central doublet)
Almost all cells have one primary ______
cilia. Non-motile cilia, 9 mt structures but no central doublet. very long (much longer than mv)
When is the primary cilia very important?
development of embryo, sensing fluid movements, sensing growth factors
What does connective tissue proper include?
loose and dense conn. tiss
Which has more collagen, dense irregular or loose conn, tiss? Which has more ground substance? More cells?
dense irregular, loose, loose
Difference in collagen between reg./irreg. conn tiss?
regular has collagen oriented in one particular direction. irreg. is random dispersion
What is collagen synthesized by?
fibroblasts
Function of Type I collagen? Location?
resists tension, multiple triple helices bound together to form fibrils, and fibrils are organized to form fibre.
Bone and dense CT
Function of Type II collagen? Location?
resists pressure and absorbs shock
cartilage
Function of Type III collagen? Location?
reticular fibers, loose conn. tissue.
Type I, II, III collagens are known as what?
fibrillar collagens
Where does type IV collagen form?
basement membrane that connects epithelial and conn. tiss. layers
cross-linked “net” with laminin and proteoglycans
2 major components of ground substance?
multi-adhesive glycoproteins
proteoglycans
3 part structure of proteoglycans?
1.) polymer of hyaluronic acid (GAG)
2.) linking proteins attached to the hyl. acid polymer
3.) shorter GAG chains attached to linking proteins
What is the link between collagens and glycoproteins?
proteoglycans
Are proteoglycans highly hydrated? Why?
Yes, -OH groups of the carbs of GAGs
Proteoglycans can store ________
growth factors
Apical layers are made of?
keratin
What protein helps compact keratin and attract water, aiding in skin moisturization?
filaggrin
FILL A GRIN with moisture and keratin
What junctions are modified when we age? How?
loss of hemidesmosomes
mod of desmosomes
TIGHT junctions remain
Result: Net result – the “outside” surface of the skin is flattened layers of dead “bags” of keratin and filaggrin linked by tight junctions
What brings nutrients and exchanges gases and wastes?
Capillary loops extending from papillary dermis, in the dermal layer
Where is dermal vasculature found?
dermal layer
What condition has itchy papules and plaques on face and scalp, elbows, knees, wrists, and worsens in response to allergen exposure? What’s happening ?
atopic dermatitis, due to subtle abnormalities in filaggrin impair ability of apical strata to retain moisture. Tight junctions become more permeable
Sequence of events for atopic dermatitis?
Impaired skin barrier–> repeated introduction of antigens to immune cells that reside in the epidermis and the dermis –> recruitment of other, particular immune cells into the dermis and epidermis from the blood stream –> a specific type of inflammation (type 2) that causes excessive histamine release into the skin –> chronic swelling and itch with further antigen exposure
What kind of structure is the intestinal mucosa made from? Function?
simple columnar epithelium with prominent apical microvili. Absorption of nutrients
Goblet cells do what?
secrete mucous
What is the bed of highly vascularized loose conn. tiss.? What does it do?
lamina propria
absorption of nutrients and water from across the epi. cell into blood.
Which layer are immune cells present?
lamina propria
What are the finger-like projections of epi. and lamina propria, in the intestines?
villus
In the intestinal mucose, there are 2 routes through the epithelium:
Which is BETWEEN adjacent enterocytes and what type of junction regulates it?
Which is THROUGH enterocytes, across cell membrane and regulated by what?
paracellular, tight junctions
transcellular, membrane proteins
What is the component in gluten that celiacs have an immune response to?
gliadin
Paracellular route that may allow gliadin into the lamina propria, causing Celiac Disease?
paracellular route 1:
Gliadin binds to a protein (FYI – chemokine receptor CXCR3)
signaling cascade that causes release of a signalling protein called zonulin
Zonulin release leads to phosphorylation of ZO proteins
disassembly of claudin and occludin proteins at the tight junction
leakage of gliadin into the immune cell-containing lamina propria
