Exam 1 Flashcards
Adaptations to cell injury
- Metaplasia: convert to different cell type
- Intracellular accumulations: engulfed material or inability to secrete
- Atrophy: same cell number, smaller cells – was normal size previously
- Hypotrophy: organ doesn’t grow to adult size d/t developmental problem
- Hypertrophy: same cell number, larger cells
- Hyperplasia: increase in cell number
Two options for a cell after experiencing irreversible injury
- ) Necrosis
2. ) Apoptosis
Types of cell injury
- Reversible injury: stress to cell that is mild and transient and cell is able to return to homeostasis
- Irreversible injury: stress to cell that is severe and progressive resulting in cell death via necrosis or apoptosis
What are the etiologies of cell injury?
- Hypoxia
- Physical agents, trauma
- Chemical agents, drugs
- Infectious agents
- Immunologic rxns
- Genetic defects
- Nutritional imbalances
List 5 mechanisms that lead to cell injury
- ) influx of Ca/loss of Ca homeostasis
- ) mitochondrial damage
- ) depletion of ATP
- ) accumulation of ROS/oxidative stress
- ) defects in membrane permeability
- These ultimately lead to damage to MPD: membrane, proteins/cytoskeleton and DNA
Describe how influx of Ca/loss of Ca homeostasis leads to cellular injury
1.) Influx of Ca / loss of Ca homeostasis: injury leads to Ca influx into cell = activation of cellular enzymes (phospholipases, proteases, endonucleases, ATPases) and increases mitochondrial permeability = membrane damage, nuclear damage and decreased ATP production
Describe how mitochondrial damage leads to cellular injury
2.) Mitochondrial damage: increase Ca2+, oxidative stress and phospholipase/sphingomyelin pathways lead to damage to mitochondrial membranes resulting in decreased H+ potential to drive production of ATP via ATP synthase enzymes
Describe how depletion of ATP leads to cellular injury
- ) Depletion of ATP: chemical injury (eg. Cyanide) and hypoxia lead to decreased oxidative phosphorylation leading to decreased ATP cellular levels =
a. ) no energy for Na/K pump = high Na in cell = osmotic changes, h2o into cell = cellular and organelle swelling
b. ) no energy for Ca pump = increased Ca in cell = enzyme activation
c. ) increased anaerobic glycolysis = decreased glycogen, increased lactic acid = decreased pH and clumping of nuclear chromatin
d. ) detachment of ribosomes = decreased protein synthesis
Describe how accumulation of ROS/oxidative stress leads to cellular injury
- ) Accumulation of ROS/oxidative stress: normal metabolism = formation of ROS. Inability to clear ROS = formation of bonds quickly and non-specifically = altered structure of proteins, nucleic acid and lipids
a. ) Lipids: double bonds of unsat FAs are attacked by ROS = formation of lipid peroxides = formation of more lipid peroxides in membranes. Free radicals are normally scavenged by Vitamin E in membrane.
b. ) Proteins: side chains are oxidized, disulfide bonds are formed = altered structure/function
c. ) DNA: ROS interaction with thymine causes single-stranded breaks in DNA = accumulation of mutations
Describe how defects in membrane permeability leads to cellular injury
- ) Defects in membrane permeability = inability to maintain concentration gradients, functional compartmentalization via:
a. ) membranes damaged from ROS via lipid peroxidation
b. ) Ca entry into cell = phospholipase activation = phospholipid degradation in membrane. Also protease activation = cytoskeletal damage.
c. ) Lack of ATP = no reacylation of phospholipids/diminished synthesis of phospholipids = cell membrane cannot be repaired
Compare and contrast morphologic appearance of cell with reversible cell injury and a cell with irreversible cell injury
- Reversible:
a. ) Swelling ER, mitochondria
b. ) Membrane blebs
c. ) Clumping chromatin - Irreversible:
a. ) ER swelling with detachment of ribosomes
b. ) Lysosome rupture
c. ) Myelin figures (protein/lipid swirls)
d. ) Nuclear condensation: pyknosis
e. ) Swollen mitochondria with amorphous densities
List the types of subcellular alterations that can occur in cell injury with respect to the following organelles: lysosomes, ER, mitochondria, cytoskeleton, nucleus
- Lysosomes: swelling and lysing
- ER: swelling and ribosome detachment
- Mitochondria: swelling, amorphous densities
- Cytoskeleton: degradation
- Nucleus: clumping of chromatin, condensation of nuclear material, lysing of nuclear material
Discuss free radical induced injury in terms of: a.) mechanism of production of free radicals, b.) protective mechanisms against free radical injury
a. ) Mechanism of production:
- Radiation, toxins, reperfusion = production of superoxide (o2dot-), hydrogen peroxide (h2o2) and hydroxide (OHdot)
b. ) Protective mechanisms against injury
- SOD (superoxide dismutase in mitochondria) converts o2dot- to h2o2
- Glutathione peroxidase (in mitochondria) converts OHdot to h2o2
- Catalase (in peroxisomes) converts h2o2 into h2o and o2
Two types of cell death. Which is pathologic and which is physiologic?
- Necrosis: resulting from exogenous or endogenous damage to cellular membrane resulting in leaking cellular contents. Not controlled by the cell and doesn’t occur via signaling or activation of genes. Accompanies inflammation. Always pathologic.
- Apoptosis: external/internal cell damage leads to programmed cell death resulting in cell fragmentation and phagocytosis. No leaking of cellular contents. Does not accompany inflammation. Is physiologic or pathologic.
Typical cytoplasmic and nuclear changes that accompany necrosis
- Cytoplasmic: eosinophilia (reddening), glassy appearance (d/t proteins) and vacuolation
- Nuclear: pyknosis (condensation), karyorrhexis (breaking apart) and karyolysis (dissolving)
Types of necrosis. Common sites/tissues and reasons for occurrence. Microscopic/gross appearance.
- ) Coagulative:
- microscopic = outline of cell preserved, no nuclei
- gross = firm tissue
- Sites: tissues with CT network (most organs except for brain)
- Reason: ischemia (eg. MI), hypoxia, reperfusion injury - ) Liquefaction:
- microscopic loss of cells and tissue lacking CT network, amorphous granular
- gross: liquid, pus
- Sites: tissues lacking CT network or where enzymatic digestion of tissue via neutrophils occurred
- Reason: ischemia, pyogenic bacteria infection - ) Caseous: accumulation of mononuclear cells creating granuloma
- microscopic: accumulation of mononuclear cells surrounding amorphous, granular eosinophilic debris
- gross: grayish, white/yellow, soft, crumbly, cheesy
- Sites: areas where infectious organism resides and cannot be broken down by immune system leading to chronic inflammation and granuloma formation
- Reason: TB and certain fungi (esp histoplasmosis) - ) Enzymatic/Fat:
- microscopic: material in necrotic fat cells = eosinophilic (pink), calcium/FA deposit areas are basophilic (purple)
- gross: white and chalky
- Sites: areas of fat
- Reason: in areas where enzymes are activated and act on surrounding fat, fatty acids react with calcium and are saponified - ) Fibrinoid: looks fibrin like
- microscopic: intensely eosinophilic (pink) vascular walls
- gross: ?
- Sites: blood vessel walls
- Reason: vasculitis/injury of blood vessels (eg. Ag/ab complex formation – Type III hypersensitivity) - ) Gangrenous
- Sites: limb or bowel
- Reason: loss of circulation d/t various pathologies including PVD, atherosclerosis, diabetes
- Wet: gangrene superimposed with bacterial infection
- Dry: no bacterial infection
Myocardial infarction results in what type of necrosis
- Coagulative
Abscesses are an example of what type of necrosis
- Liquefaction necrosis
Acute appendicitis is an example of what type of necrosis
- Liquefaction necrosis
Cerebral infarction/stroke results in what type of necrosis
- Liquefaction necrosis
TB results in what types of necrosis
- Caseous necrosis
Pancreatitis results in what type of necrosis
- Enzymatic/Fat necrosis
Necrosis of lower limbs (feet and toes) is usually what type of necrosis
- Gangrenous necrosis
Discuss the mechanisms causing reperfusion injury
- Reperfusion = restoral of blood flow/oxygenation to tissue.
- Large amount of ROS production (superoxide, hydroxide, lipid peroxide and peroxynitrite (ONOO-)). These ROS species disrupt lipids, proteins and DNA. Production exceeds degradation.
- Expression of cytokines and CAMs = accumulation of neutrophils = induction of further injury
- Activation of complement
Examples of apoptosis that is pathologic
- CA/tumor-induced cell death
- Anti-CA and other drugs
- Radiation
- Extreme temps
- Transplant rejection
- Atrophy after duct obstruction
- Viral diseases
Mechanisms of apoptosis induction and pathways (and enzymes involved)
- Cell injury (growth factor withdrawal, DNA damage, protein misfolding) initiates mitochondrial (intrinsic) pathway. Outside factors initiate death receptor (extrinsic) pathway.
1. ) Intrinsic: +Bax, Bak = pro-apoptotic factors dimerization = formation of channels in mitochondrial membrane = permeability of cytochrome c = +executioner caspases
2. ) Extrinsic: Fas (CD95)/TNF receptor interaction = +adaptor proteins = executioner caspases - Executioner caspases activate endonucleases and breakdown cytoskeleton directly. This leads to blebbing and formation of apoptotic bodies which are digested by phagocytes
P53 function
- DNA damage = P53 activation = pro-apoptotic factors (Bax/Bad) = apoptosis
Bax/Bad function
- Pro-Apoptosis factors
Bcl-2/Bcl-x function
- Anti-apoptotic factors preventing leakage of cytochrome c and blocking pro-apoptotic factors
Compare and contrast necrosis and apoptosis from changes to: cell size, nucleus, plasma membrane, cellular contents, adjacent inflammation
- Necrosis: enlarged/swelling, pyknosis-karyorrhexis-karyolysis, disrupted, enzymatic digestion of tissue d/t cellular contents leakage, inflammation
- Apoptosis: reduced/shrinkage, fragmentation/round nucleosome, intact PM, no leakage of cellular contents-apoptotic bodies contain contents, no inflammation
Viral infection leads to what type of cell death
- Necrosis (low energy, antibody against viral antigens and activation of complement)
- Apoptosis (activation of p53, granzymes by CTL = caspase activation)
Describe the different mechanisms of injury d/t chemicals such as: CCl4, acetaminophen, cyanide, phalloidin, paclitaxel and alkylating agents
- CCl4: metabolite CCl3dot reacts with PM and ER
- Acetaminophen: metabolite quinone reacts with protein, DNA and causes oxygen stress = liver necrosis
- Cyanide: target = cytochrome in mitochondria
- Phalloidin: targets cytoskeleton
- Paclitaxel: targets cytoskeleton preventing cell replication
- Alkylating agents: targets DNA
What is hypertrophy? Physiologic or pathologic? Etiology? Mechanism of development? Examples
- Increase in cell size and therefore size of organ
- Both physiologic or pathologic
- Etiology: increased functional demand
- Mechanisms:
a. ) Increase production of cellular contents – proteins, myofilaments, DNA, organelles
b. ) 3 types of signals: mechanical triggers (stretch), vasoactive agents, growth factors/hormones = hypertrophy - Examples: weight lifting, pregnant uterus (with hyperplasia) = physiologic. Cardiomegaly (d/t HTN, aortic valve dz), individual fiber hypertrophy following MI = pathologic.
What is hyperplasia? Physiologic or pathologic? Etiologies? Mechanism of development? Examples.
- Increased number of cells
- Physiologic or pathologic
- Etiology: constant stimulus, persistent injury, functional capacity needed
- Mechanisms:
a. ) result of GF-driven proliferation of mature cells
b. ) increase in output of new cells from tissue stem cells - Example: female breast at puberty, lactating breast, proliferative endometrium (menses, pregnancy) liver damage/resection = physiologic. Endometrial hyperplasia d/t E and P imbalance, BPH (d/t high androgens), Graves’ disease (enlarged thyroid)
What is atrophy? Physiologic or pathologic? Etiologies? Mechanism of development? Examples.
- Reduced cell size, therefore reduction in organ size
- Physiologic or pathologic
- Etiologies: disuse atrophy, denervation atrophy, decreased blood supply/senile atrophy, inadequate nutrition, loss of endocrine stimulation, pressure/tissue compression
- Mechanisms:
a. ) decreased protein synthesis and increased protein degradation
b. ) degradation via ubiquitin-proteasome pathway
c. ) autophagy (self-eating) - Example: pathogenic = Alzheimer’s, particularly frontal, cryptorchidism, vascular insufficiency to organ resulting from severe atherosclerosis, muscular dystrophy
What is metaplasia? Physiologic or pathologic? Etiologies? Mechanism of development? Examples.
- Reversible change in one differentiated cell type to another cell type
- Pathologic (step towards Cancer), function lost
- Etiology: stress/chronic inflammation caused replacement of cell with cell better able to handle stress
- Mechanisms: via cytokines, growth factors and ECM components
a. ) Stem cells undergo differentiation
b. ) Undifferentiated mesenchymal cells undergo reprogramming - Examples
a. ) Bronchi in smokers: ciliated Co cells to strat squamous
b. ) Columnar to squamous: Barrett’s esophagus
c. ) Larynx in smokers
d. ) CT metaplasia: formation of cartilage, bone or adipose in tissue not usually containing these component. Eg. Bone in muscle after intramuscular hemorrhage
What is dysplasia?
- Disordered growth commonly seen in squamous epithelium following chronic injury
- Morphology: variations in size, shape of cell, disorderly arrangement, nuclear changes
Primary vs secondary lysosomes
- Primary = small membrane-bound vesicles budding from Golgi apparatus
- Secondary (aka phagolysosomes) = primary lysosomes fusing with pinocytotic/phagocytotic vesicles
Heterophagy vs autophagy
- Heterophagy: materials from EC environment taken up through endocytosis. Primary lysosome, phagolysosome and residual bodies seen.
- Autophagy: lysosomal digestion of cell’s own components – why? Damaged/senescent organelles, cellular remodeling/differentiation, atrophy. Primary lysosome, autophagic vacuole and residual body seen.
What are residual bodies?
- Material (lipids and other material) that remains in lysosomes undigested, eg. Lipofuscin, carbon particles
What induces SER hypertrophy?
- Drugs (barbiturates: P450 system)
Three categories of intracellular accumulations
- ) Normal endogenous substance: produced at normal or increased rate, but metabolism inadequate to remove
- ) Normal/abnormal endogenous substance: accumulates secondary to genetic/acquired defects in metabolism, packaging, transport or secretion
- ) Abnormal exogenous substance deposited in cells which cannot remove it
Mechanisms that lead to intracellular accumulations
- Abnormal metabolism
- Alterations in protein folding/transport
- Deficiency of enzymes
- Inability to degrade phagocytosed particles
Steatosis and fatty infiltration. Causes, pathogenesis, organs involved, histologic appearance, result?
- Definition = abnormal accumulations of TGLs within parenchyma of liver, heart, muscle and kidney
- Causes: toxins, protein malnutrition, DM, obesity, anoxia, alcohol – most common = alcohol and DM
- Pathogenesis: defect at any step in FA metabolism (FFAs to FA, FA to ketone/phospholipid/CE, apoprotein to lipoprotein)
- Appearance = fat vesicles/vacuoles in tissue
In what disorders does one see cholesterol/CE accumulation
- Atherosclerosis: foam cells within intimal layer of aorta and larger arteries, cholesterol clefts = crystallization of lipids in EC space
- Xanthomas (acquired/hereditary hyperlipidemia): foam cells
- Inflammation, necrosis: phagolysosomes accumulate from neighboring cells
- Cholesterolosis in GB: foam cells
- Niemann-Pick dz, type C (lysosomal storage dz)
In what disorder(s) are cholesterol clefts seen?
- Atherosclerosis, these just represent crystallization of lipids in EC space
How do protein accumulations appear histologically? Causes? Where?
- Hyaline: pink droplets in cytoplasm, can be extracellular; Russell bodies (excessive Igs by plasma cells); Mallory body (aka alcoholic hyaline: in alcoholic liver disease as a result of injury to cytoskeletal filaments in liver cells)
- Causes:
a. ) proteinuria (reabsorption of proteins in proximal renal tubules)
b. ) synthesis of excessive protein
c. ) defects in protein folding
Where are Russell bodies seen? What are they characteristic of?
- Plasma cells. They represent excessive Igs (immunoglobulin) protein synthesis
Where are Mallory bodies found? What are they characteristic of?
- aka alcoholic hyaline: in alcoholic liver disease as a result of injury to cytoskeletal filaments in liver cells
Describe the process of protein folding. What defects lead to abnormal folding? Response by cell to misfolded proteins?
- ) Nascent peptides associates with chaperones (heat-shock proteins), which ensures folding to mature protein
- ) Heat-shock protein can direct protein to correct intracellular location
- Abnormal folding results from low energy stores, genetic mutations, viral infections, chemicals, UV, heat, free radicals etc.
- Cellular response to misfolded
a. ) Increase synthesis of chaperones
b. ) Decreased translation of proteins
c. ) Activation of ubiquitin-proteasome pathway
d. ) Activation of caspases for cellular apoptosis
What is ER stress?
- Protein folding demand exceeds protein folding capacity leads to apoptosis
Examples of defects in protein folding
- ) alpha-1-antitrypsin deficiency
- ) Neurodegenerative diseases
- ) Proteinopathies, protein-aggregation diseases (eg. Amyloidosis)
Describe hyaline changes in cell
- Glassy, pink homogenous appearance on H&E
- Intracellularly = protein droplets in kidney, Russell bodies, Mallory alcoholic hyaline, viral inclusions
- Extracelluarly = collagenized scar, damaged glomeruli, hyaline arteriosclerosis, atherosclerosis, amyloid
What is the appearance of glycogen accumulation? Causes?
- Clear cytoplasmic vacuoles
- Causes: abnormalities in metabolism of glucose or glycogen, eg. DM, glycogen storage diseases (type III, Pompe’s dz)
Most common exogenous pigment
- Carbon
Examples of exogenous pigments. Location, color?
- Carbon (coal dust): black, acquired via inhalation, picked up by macrophages transported to lymph nodes
- Tattooing: various color, stored in dermal macrophages
What is anthracosis?
- Darkened lymph nodes and lung tissue representing carbon accumulation in macrophages
Examples of endogenous pigment. Color, location?
- Lipofuscin/lipochrome: brown-yellow wear/tear pigment representing lipids/phospholipids derived from lipid peroxidation that accumulates in heart, liver and brain and is associated with aging, atrophy. Is marker of past free radical injury. Perinuclear in EM, brown in gross specimen. This is non-injurious pigment.
- Melanin: brown-black pigment formed in melanocytes formed by enzymatic oxidation of tyrosine in epidermis, protective against UV. Can accumulate in basal keratinocytes or dermal macrophages. Non-injurious pigment.
- Iron/hemosiderin: golden yellow-brown pigment (with H&E, blue with Prussian blue stain) representing aggregates of ferritin micelles. Seen in macrophages, bone marrow, spleen and liver where RBC breakdown occurs. Hemosiderosis results from hemochromatosis. Can be injurious in hemochromatosis.
- Bilirubin: yellow pigment found in bile, derived from hemoglobin breakdown without iron. Jaundice results in excess bilirubin. Underlying condition causes this.
What is hemosiderosis? Hemochromatosis? Causes? Result?
- Hemosiderosis: systemic overload of hemosiderin/iron in many organs and tissues resulting from increase absorption of dietary iron, impaired use, hemolytic anemias, transfusions. Systemic condition = hemochromatosis. Hemosiderosis is what is seen at tissue level. Condition can lead to liver fibrosis, heart failure and DM.
Compare dystrophic and metastatic calcification. What are these? Etiology and pathogenesis? Morphologic appearance? Sites and associated diseases?
- Calcification: abnormal deposition of calcium salts with other substances
- Dystrophic: local process occurring in injured or dying tissue with normal serum calcium. Cause: organ dysfunction, atherosclerosis (plaques), aging, damaged heart valves, necrosis. Sites/diseases: aortic valves (atherosclerosis), atherosclerosis plaques in vasculature, breast carcinoma, stomach wall.
- Metastatic: process occurring anywhere in body with hypercalcemia. Cause: CA destroying bone, high PTH levels (d/t parathyroid adenoma, SCCarcinoma of lung), vitamin-D disorder (sarcoid, increased intake vit D, renal failure (secondary hyperparathyroidism). Site: any, mainly in blood vessel interstitium, kidneys, lungs, gastric mucosa. Can get heterotopic bone in foci of calcification.
Inflammation definition
- local rxn of vascularized tissue to injury
Time frame of inflammation: acute, subacute and chronic
- Acute: 0-2 days
- Subacute: 2-14 days
- Chronic: >14 days
Typical cell types involved in acute inflammation
- Neutrophils
Typical cell types involved in chronic inflammation
- Mononuclear cells (agranulocytes) = monocytes, macrophages, lymphocytes, plasma cells
- Granuloma cells (epithelioid and giant cells)
- Fibroblasts
Predominant cell type in allergic reactions and parasitic infestations
- Eosinophils
List the 6 cardinal signs and symptoms of inflammation and briefly describe the underlying causes
- Heat: increased blood flow to site
- Redness: increased blood flow to site
- Swelling: accumulation of fluid and cells
- Pain: pressure of fluid, effect of mediators
- Loss of function: secondary to above effects
- Systemic changes: release of humoral factors
Major causes of acute inflammation
- Biological: infection, immunologic injury, tissue death
- Physical: trauma/injury, thermal extremes, ionizing radiation
- Chemical: poisons, drugs
Compare and contrast serous, fibrinous and suppurative acute inflammation
a. ) Serous: water, protein-poor fluid seen in peritoneal, pleural or pericardial cavities
b. ) Fibrinous: water, large amounts of protein including fibrin seen in severe injury and inflammation of body cavities
c. ) Suppurative: purulent/pus containing water, proteins and neutrophils with necrotic cells seen in pyogenic bacterial infections
What is ulceration?
- local defect/excavation produced by sloughing off of inflammatory necrotic tissue only on skin or mucosa (GU/GU/mouth)