Reversible changes
hypertrophy, hyperplasia, atrophy, metaplasia, dysplasia
hypertrophy
inc in cell size, no new cells
(tissues with cells NOT capable of rep)
due to inc func demand/gfac/hormonal stim (activated growth factors, ion channels, oxygen supply, etc).
can co-exist w/ hyperplasia
Pathologic hypertrophy exp.
increased workload
hypertension
cardiocyte hypertrophy
Physiologic hypertrophy exp.
increased workload
pumping iron
skeletal muscle cell hypertrophy
Hyperplasia
inc in cell # –> inc in tissue/organ mass
(tissue with cells CAPABLE of rep)
exp. proliferation from stem cells, physiologic/pathologic hyperplasia
often co-exists w/ hypertrophy
Pathologic hyperplasia exp.
benign prostatic hyperplasia
Physiological hyperplasia
rapid growth via cell division in endometrial glands/stroma during proliferative phase of menstruation
hyperplasia + hypertrophy exp.
uterus during pregnancy
Atrophy
reduced cell size/organelles (long-term –> also dec in cell #)
dec workload/metabolic activity/protein synthesis
inc pro degrad
inc autophagy
via ischemia, denervation, aging, hormone withdrawal (mammary gland during menopause)
Metaplasia
Replacing cell types
Often adaptive response to stress
Via reprogramming stem cells
exp. respiratory epithelium in smoker (columnar to squamous), barrett’s esophagus during acid reflux (SSNKE –> intestinal columnar)
Dysplasia
Disordered growth/maturation
Response to persistence of injurious influence
*usu regresses upon removal of stimulus
Shares cytological features w/ cancer
exp. cervical dysplasia (SSKNE –> disordered)
General mechanisms of cell injury
Hypoxia vs ischemia
hypoxia–> dec oxygen (Low pO2 in blood), anaerobic E prod can continue
ischemia–> dec oxygen AND substrates (Mechanical obstruction of blood flow), aerobic/anaerobic compromised
Progression of ischemic cell injury
onset
reversible
irreversible
reperfusion injury (inc ROS formation, inflammation, Ca2+ mobilization)
Reversible cell injury (volume)
temporary loss of volume and E regulation
Reversible cell injury (Energy)
Drop in oxygen…
-ATP depletion, inc anaerobic metabolism (dec glycogen stores, inc lactic acid and Pi –> dec intracellular pH –> dec enzyme act)
-Ribosome detachment from RER
Dec protein synthesis
Reversible cell injury (Morphology)
Light microscopy
EM
-inc h2o, dilation of ER, dec glycogen stores, condensed mito, PM blebbing, blunting microvilli, myelin figures
Irreversible cell injury
Serum signs for irreversible cell injury
troponin
myoglobin
CK-MB isoenzyme
lactase dehydrogenase
Irrev cell injury (morphology)
Light
EM
matrix granules
flocculent densities
swelling/rupture
Ischemia/reperfusion injury
cell death after reestab blood flow
MPTP
Uncoupling of oxidative phosphorylation by mitochondrial permeability transition with release of cyt. C to cytosol. (inc [Ca2+]in will cause mitochondrial damage)
*irreversible injury
cytochrome C
pro-apoptotic
Calcium homeostasis
[extracellular Ca] > [intracellular Ca]
Injury –> inc cytoplasmic Ca –> inc damaging enzymes (phospholipases, proteases, endonucleases, ATPase) and opening of MPTP
Injury –> inc cytoplasmic Ca (preferentially taken up by mito) –> depleted ATP prod