Histology 1 Flashcards
hematoxylin
Basophilic.
Darker purple.
eosin
Eosinophilic.
Light pink.
Periodic-acid Schiff (PAS)
Stains molecules rich in carbohydrates (glycoproteins, proteoglycans).
Silver stains
Stains reticular fibers, nerve cell processes.
toluidine blue
Basic dye.
Mast cells.
size of RBC
7.5 um
general features of epithelium
Form contiguous sheets.
Adhere to each other by using specialized cell-cell junctions.
Adhere to underlying CT via basement membrane.
Avascular.
Renewal by stem cells.
Derived from ectoderm, mesoderm, endoderm.
Free apical surface.
Apical-basal polarity.
Cytokeratins.
functions of epithelium
1) protection
2) surface transport
3) absorption
4) secretion
5) sensory reception
6) trans-epithelial transport
simple
1 layer.
Specialized for absorption/secretion.
stratified
2 or more layers.
Withstands wear/tear.
simple squamous epithelium: function
Specialized for filtration, diffusion, osmosis, secretion
simple squamous epithelium: location
Lines heart, blood vessels, lymph vessels (endothelium).
Lines body cavities and mesentary (mesothelium).
Lines Bowman’s capsule, and lung alveoli.
SSKE: location
In wear-prone areas (epidermis).
SSKE: structure of apical layer
Stratum corneum on apical surface (layer of dead tissue).
Squamous epithelial cells underwent apoptosis.
Keratin rich.
Nuclei and organelles are absent.
SSNKE: location
Less wear-prone areas (oral cavity, esophagus, anal canal, vagina)
Simple Cuboidal Epithelium: function
Specialized for secretion/absorption.
Simple Cuboidal Epithelium: location
Kidney tubules, glandular ducts, ovaries, thyroid glands.
Stratified Cuboidal Epithelium: function
Provide protection.
Secretion.
Stratified Cuboidal Epithelium: location
Found in ducts like sweat, mammary, salivary.
Simple Columnar Epithelium: function
Specialized for secretion/absorption.
May be ciliated (uterus).
Simple Columnar Epithelium: location
Uterus.
Intestine (brush border of microvili for absorption.
Stratified Columnar Epithelium: function
Secretion/protection.
Stratified Columnar Epithelium: location
Rare.
Ocular conjunctiva.
Pharynx, anus, male urethra.
Pseudostratified Epithelium: structure
All cells touch the basement membrane.
Not all cells reach the apical surface.
Pseudostratified Epithelium: function
Specialized for protection.
Cilia for movement of debris.
Goblet cells for secretion.
Transitional Epithelium: location
Only in urinary system (renal pelvis, ureter, bladder)
Transitional Epithelium: function
Specialized for stretching/contraction to hold variable volumes.
Protects against toxic urine.
Resists diffusion of water (prevent dilution of urine).
umbrella cells
In transitional epithelium/urothelium.
Basal extensions penetrate between other cells.
endocrine glands
Secrete into blood.
Hormone is delivered to part of body.
Exocrine gland (general)
secrete into an organ or body system via ducts
classification of exocrine cells
1) number of cells: uni/multicellular
2) duct system: simple, compound
3) terminal secretory pieces: tubular, acinar
4) secretion: serous, mucous
5) mode of secretion
serous secretion
Watery, serum-like.
Contain enzymes/precursors, antimicrobials.
mucus
Viscous, sticky.
Aid in lubrication, trapping pathogens.
mucus with H & E
Stain poorly in H&E (look very light).
Clear cytoplasm.
Flat nuclei.
serous with H & E
Stain well (dark purple).
Abundant RER.
Round nucleus.
merocrine secretion
Secrete by exocytosis.
Only the product is released.
Zymogens, sweat, mucus, lysozymes.
Goblet cells.
apocrine secretion
Decapitation of apical portion.
Part of cytoplasm and plasma membrane are released.
Ex: mammary glands.
holocrine secretion
Apoptosis of secreting cell.
Releases whole cell’s content.
Stem cells at basal lamina divide to replace.
Ex: sebaceous glands.
breast cancer
Originates from mammary glands.
Most common: lobular carcinomas – from cells that line the milk-producing secretory lobules.
Less common: ductal carcinomas – from epithelial cells that line the ductal system.
cystic fibrosis
Caused by malfunctioning of CFTR.
CFTR is found in apical membrane of epithelial cells (lungs, liver, pancreas, skin, reproductive tract).
Normally CFTR moves Cl- out of cell to the covering mucus –> Na+ follows and increases electrolyte concentration in mucus –> pulls water out –> increases fluidity of mucus.
W/o CFTR, ions are imbalanced and mucus is viscous.
Mucus builds up in lungs and blocks airways, causing severe infections.
Blocks ducts of pancreas, causing malabsorption of fat/protein.
Reduced sodium absorption in sweat ducts causes saltier sweat.
Upsets balance of minerals in blood, causing dehydration, increased heart rate/BP, fatigue, heat stroke, death.
zonula occludens
Tight junctions. Regulate apical border seal. Create apical/basolateral domains. Provides a selective permeability barrier. Regulate paracellular transport. Promote transcellular transport. Proteins: claudin, occludin, actin.
zonula adherins
Calcium dependent.
Continuous with actin cytoskeleton.
Resists mechanical stress.
Transduce signals from adjacent cells and ECM.
Mediate folding and other 3D shapes of epithelia.
gap junctions (macula communicans)
Pore-forming complex comprised of connexins/connexons.
Facilitates transcellular movement of metabolites, 2nd messengers, ions.
Location: widespread in epithelia, smooth/cardiac muscle, neurons, etc
basal lamina
Physical support for epithelia.
Comprised of type IV collagen, laminin, nidogen.
2 parts: lamina lucida, lamina densa.
Connects to reticular lamina.
cytokeratins are classified as:
intermediate filaments.
All epithelial cells express cytokeratins
zonula occludens: principal components
Major integral membrane proteins: claudins, occludins
Cytoskeleton proteins: actin
sonula adherens: principal components
Integral membrane protein: E-cadherins.
Cytoskeleton proteins: actin
gap junctions
Punctuate intercellular channels. Approximation to syncytium. Function in electrical synapses. Found in many tissues. Channels form as adjacent connexons align between cell membranes.
Connexons
Made up of 6 connexins (tetraspan integral membrane proteins). Form channels (gap junctions).
basement membrane
Basal lamina AND reticular lamina.
Anchoring fibrils: collagen VII.
Functions: physical support, selective permeability.
basal lamina
Lamina lucida AND lamina densa.
Type IV collagen.