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.
reticular lamina
Contains reticular fibers (mainly collagen III).
Some type I collagen.
myoepithelial cells
Basket cells.
Pseudostratified.
Function: wound healing????? need to check
gland formation
All begin as an epithelial ingrowth.
All retain keratin expression.
typical products of merocrine secretion
mucus
zymogens
lysozymes
sweat
holocrine secretion: phenotypic progression of cells from base to duct
Cell borders disappear.
Nucleus degenerates.
Cytoplasmic droplets coalesce.
connective tissue functions
1) structural integrity of tissues and organs.
2) mechanical properties: tensile and compressive properties.
3) provides environment for differentiation and residence for immune cells.
4) facilitates exchange of metabolites, electrolytes, and water.
5) energy storage (white adipose).
6) heat production (brown adipose)
7) repair and restoration of tissue architecture following damage
cells of connective tissues (general, overarching categories)
Indigenous cells.
Immigrant cells.
indigenous cells
Arise within the CT.
Mesenchymal cells. Fibroblasts. Adipocytes. Osteogenic cells and derivatives. Chondrogenic cells and derivatives.
mesenchymal cells
multipotent stem cells that can differentiate into:
myocytes, adipocytes, chondrocytes, osteoblasts, neurons.
stellate appearance with lots of space
fibroblasts
Most common cell in most CTs.
Synthesize ECM components.
Capacity to differentiate into myofibroblasts (in normal and wound healing conditions).
Lots of RER, highly synthetic.
white adipose tissue
Uniocular.
Nuclei pushed to periphery.
brown adipose tissue
Multiocular,
Lots of mitochrondria gives brown appearance.
immigrant cells
Originate from hematopoietic stem cells in bone marrow.
Macrophages, mast cells, lymphocytes, plasma cells.
macrophages
Immigrant cell.
Derived from blood monocytes.
Scavenge debris, immune system functions, inflammation.
Lumpy, not “attractive”
mast cells
Immigrant cell.
Derived from bone marrow precursor.
Central nucleus with cytoplasm packed with granules.
Granules contain heparin and histamine –> stain dark purple.
mast cells in severe allergic reactions
IgE receptors.
Degranulate –> release heparin/histamine.
Leads to anaphalaxis.
lymphocytes
Immigrant cells.
Subsets of B and T cells.
Can be anywhere (wander).
Dark nuclei (takes up most of space in cell). Little cytoplasm.
plasma cells
Immigrant cells.
Differentiated B-lymphocytes.
Synthesize antibodies.
Found in loose CT.
Eccentric nuclei.
Clockface chromatin.
Abundant golgi, RER.
connective tissue components
Cells.
ECM fibers.
ECM ground substance.
connective tissue ECM fibers
Fibrillar collagen.
Nonfibrillar collagen.
Elastic fibers.
fibrillar collagens (number and location)
I - nearly everywhere
II - cartilage mostly
III - mainly organs
V, XI, XXIV, XXVII - restricted locations
type I collagen
Most abundant protein in body.
Scar tissue, keloids.
type II collagen
Abundant in hyaline cartilage.
In many organs during development, adult eye/ear.
type III collagen
RETICULAR FIBERS.
Highly branched.
Visualization requires silver stain.
In lymphoid organs, liver, skin.
non-fibrillar collagens
28+ types.
Basement membrane (IV).
Fibril-associated.
Require special techniques to localize.
elastic fibers
Microfibrilin forms a scaffold.
Elastin is added.
Elasticity due to cross-links.
marfan syndrome
Fibrillin-1 mutation.
Aneurisms due to inelastic arteries.
Excess TGF-B causes most of the symptoms.
cutis laxa
Mutation in elastin leads to wrinkled, loose skin.
Internal organs may be affected in severe cases.
ground substance
Proteoglycans, glycosaminoglycans, glycoproteins.
Characteristics:
1) highly charged (sulfates)
2) compressive resistance
3) limited protein components –> poor staining qualities
4) permits nutrient/gas exchange
dense regular CT
In tendons, ligaments. Fibroblasts are main cell type. Collagen fivers organizes refular. Little ground substance. Nuclei organized in same position.
dense irregular CT
Type I collagen.
Nuclei in different directions.
Irregular, wavy collagen fibers.
loose connective tissue
More ground substance (allows for more diffusion).
Fibroblasts, elastic fibers, collagen, endothelial cells.
elastic tissue
Elastic fibers can be parallel or randomly arranged.
Need silver stain to distinguish elastic fibers.
reticular tissue
TYPE III branched collagen.
Supports channels in liver, lymph nodes, spleen.
blood components
Formed elements (cells, platelets). Plasma proteins (albumins, globulins, fibrinogen). Plasma (wastes, nutrients, gases, hormones, electrolytes).
major functions of blood
1) transport (gases, nutrients, wastes, hormones).
2) protection (immune, clotting).
3) homeostasis (pH, body temp, electrolyte balance).
romanowsky staining
stains blood
erythrocytes
Biconcave disc (large SA for gas exchange). 7.5 um diameter. From immature reticulocytes. Live ~4 months. Cleared from spleen.
reticulocytes
Immature predecessors of RBCs.
Still contain ribosomes.
Erythropoietic activity.
granulocytes
Neutrophils (60-70%)
Eosinophils (2-4%)
Basophils (<1%)
agranulocytes
Lymphocytes (25-33%)
Monocytes (3-8%)
neutrophils
Granulocyte. 60-70% Short lifespan. Nucleus w/ 3-5 lobes. Barr body sometimes visible. Phagocytosis. Exocytose DNA --> sticky, traps bacteria.
eosinophils
Granulocyte. 2-4% Lifespan: days to weeks. Bilobed nuclei. Bright red. Phagocytosis. Release granules.
basophils
Granulocyte.
<1%
Bilobed nucleus, sometimes obscured by granules.
Usually in BLOOD (mast cells in CT, looks similar).
IgE receptors help with allergic reactions.
lymphocytes
Agranulocyte. 25-33%. In blood, CT, epithelia. Little cytoplasm. T-cells and B-cells.
T-cells
essential for cell-mediated immunity
B-cells
essential for humoral immunity via antibody production.
monocytes
Agranulocyte. 3-8% Give rise to macrophages. Largest. Large horseshoe nucleus.
platelets
Thrombocytes.
Fragments from megakaryocytes.
Less abundant than RBCs.
Functions: aggregate to seal vessel damage; facilitate clot formation
type IV collagen
Sheet forming.
Basal and external lamina.
type VII collagen
Linking/anchoring.
Anchors fibrils in dermis.
Ehlers-Danlos Syndrome (EDS)
Defect in collagen synthesis.
Causes aortic rupture, hyperextensible joints, hyperelastic skin.
cartilage (general)
Collagen II. Sulfated proteoglycans. Net negative charge (basophilic). Avascular. Aneural. Chondrocytes in isogenous groups.
hyaline cartilage
TM: very basophilic.
Abundant sulfated proteoglycans.
Perichondrium at edges (but not at articular surfaces).
Appositional and interstitial growth.
osteoarthritis
Progressive wear/tear of hyaline cartilage at articular surface.
rheumatoid arthritis
Autoimmune.
Destruction of hyaline cartilage.
elastic cartilage
Isogenous groups, TM.
Elastic fibers surround cells.
Perichondrium.
Interstitial/appositional growth.
Similar to hyaline, but in addition: type II collagen, reticular fibers.
fibrocartilage
TM not obvious. Wavy collagen fibers (type I) --> eosinophilic. NO perichondrium. Has fibroblasts. Intertstitial growth.
woven bone
Immature bone.
Disorderly arrangement of collagen.
Not as strong.
Osteoblasts, osteocytes, calcified cartilage.
compact bone
Lamellar bone. Haversian systems. Concentric lamellae. Interstitial lamellae. Periosteum and Endosteum.
spongy bone
Lamellar bone.
Contains lamellae.
Endosteum only.
No Haversian canals bc nutrients can diffuse.
ground section
No organic tissue.
Air spaces (formerly organic) are dark.
Fine detail visible.
decalcified section
No mineralized tissue.
Stains well with H & E.
Fine detail less visible,
Howship’s lacunae
space where osteoclast degraded bone.
osteoporosis
bone degradation > formation
Estrogen causes increased resorption.
osteogenesis imperfecta
Mutation in type I collagen.
Sharpey fibers
the periosteum entering into the lamellar bone
endochondral bones
Long bones,
Bones of thorax,
Vertebrae,
Pelvis
membrane bones
flat bones in skull
endochondral ossification (general)
Cartilage template for bone deposition.
Initial bone deposited is woven, non-lamellar bone.
Remodeling to form spongy/compact bone.
endochondral ossification - steps
Chondrocytes hypertrophy.
Cartilage is calcified, killing chondrocytes.
Dead chondrocytes make it porous, allowing for blood vessels to enter.
Periosteal bone collar formed de novo.
New bone deposited on calcified cartilage forms primary ossification center.
Secondary ossification center is formed, then epiphyseal plate.
regions of epiphyseal growth plate
Resting.
Proliferation (stacks of coins).
Hypertrophic.
Calcification (chondrocytes die, triggering calcification).
when does bone remodeling occur?
Developmentally.
Throughout life (in response to stressors).
Fracture repair.
compact bone remodeling
Osteoclasts excavate a channel.
Osteoblasts line the outside of the channel, and fill in new bone to the center.
Some osteoblasts get trapped and become osteocytes.
bone remodeling - development
Haversian systems don’t develop until remodeling.
All bone starts as spongy bone, then some fills in and becomes compact.
spongy bone remodeling
Removal of bone by osteoclasts (not a channel).
New bone by osteoblasts.
New bone is lamellar, but not Haversian.
intramembranous ossification
No cartilage template.
Condensed mesenchyme lease to de novo bone formation.
Initial bone deposited is woven bone.
Remodeling to compact and spongy bone.
