Chapter 1. Adaptation to Cell Injury: Growth Alterations Flashcards
causes of atrophy
- decreased hormone stimulation
- decreased innervation
- decreased blood flow
- decreased nutrients
- increased pressure
mechanisms of atrophy
- shrinkage of cells due to increased catabolism of cell organelles and reduction of cytosol
- organelles and cytosol form autophagic vacuoles, which fuse with primary lysosomes for enzymatic degradation
- undigested lipids are stored as residual bodies (lipofuscin) - loss of cells by apoptosis
what is brown atrophy?
tissue discoloration from lysosomal accumulation of lipofuscin
what are causes of hypertrophy
increase in cell size
- increased workload
- cell enlargement in cytomegalovirus infections
mechanisms of cardiac muscle hypertrophy
induction of genes for synthesis of growh factors, nuclear transcription, and contractile proteins
-increase in cytosol, number of cytoplasmic organelles, and DNA content
causes of hyperplasia
(increase in cell number)
- hormone stimulation
- chronic irritation
- chemical imbalance
- stimulating Ab
- viral infections
what are mechanisms of hyperplasia for the different types of cells?
dependent on regenerative capacity of different types of cells
- labile (stem) cells divide continuously and may undergo hyperplasia as adaptation to cell injury
- stable (resting) cells divide infrequently b/c normally in G0 phase, and need to be stimulated to enter cell cycle
- may undergo hyperplasia or hypertrophy as adaptation to cell injury - permanent (nonreplicating) cells cannot divide, and only undergo hypertrophy
what is Barrett’s esophagus?
metaplasia from squamous to glandular epithelium
- distal esophagus shows increased goblet cells and mucus-secreting cells in response to acid reflux
- increased risk for developing dysplasia
what is intestinal metaplasia?
metaplasia from glandular to other types of glandular epithelium
- pylorus and antrum epithelium show increase in goblet and Paneth cells in response to H. pylori chronic atrophic gastritis
- increased risk for developing dysplasia
what are 2 examples of metaplasia from glandular to squamous epithelium?
- mainstem bronchus epithelium becomes squamous in response to cigarette smoke
- endocervical epithelium develops squamous metaplasia in response to acid pH in vagina
what is an example of metaplasia from transitional to squamous epithelium?
S. hematobium infection causes transitional epithelium to undergo squamous metaplasia
what are mechanisms of metaplasia?
stem cells have array of progeny cells that have different patterns of gene expression
- under normal physiologic conditions, differentiation is restricted
- may result from reprogramming stem cells to use progeny cells with different pattern of gene expression
- -ex: hormones, vitamins, chemical irritants
- may be reversible if irritant removed
what is dysplasia? risk factors?
disordered cell growth that is precursor to cancer
- risk factors are infection, chemicals, UV light, chronic skin irritation, some types of hyperplasia and metaplasia
- sometimes reversible if irritant is removed
what are microscopic features of dysplasia?
nuclear features
-increased mitotic activity with normal mitotic spindles
-increased nuclear size and chromatin
disorderly proliferation of cells with loss of cell maturation as cells progress to surface
coagulation necrosis and mechanism
preservation of structural outline in dead cells
- denaturation of enzymes and structural proteins (intracellular accumulation of lactate or heavy metals, exposure to ionizing radiation
- inactivation of intracellular enzymes prevents autolysis of the cell
coagulation necrosis microscopic features
indistinct outlines of cells within dead tissue with absent nuclei or karyolysis (fading of nuclear chromatin)
how are infarctions related to coagulation necrosis? the types?
gross manifestation of coagulation necrosis secondary to sudden occlusion of a vessel; usually wedge-shaped if dichotomously branching vessels
- pale (ischemic) type: increased density of tissue prevents RBCs from diffusing through necrotic tissue
- hemorrhagic (red) type: loose-textured tissue allows RBCs to diffuse through necrotic tissue
what is dry gangrene?
form of infarction that results from ischemia
-coagulation necrosis is primary type of necrosis present
what are 6 factors influencing whether infarction will occur in tissue?
- size of vessel occluded (unlikely if major branch of pulmonary artery, but likely if thrombus overlies it)
- state of development of collateral circulation
- presence of a dual blood supply
- sudden onset in organ with pre-existing disease
- tissues with high O2 requirement
- rapidity with which a vessel is occluded
liquefactive necrosis and its mechanisms
necrotic degradation of tissue that softens and becomes liquefied
-lysosomal enzymes released by necrotic cells or neutrophils cause liquefaction of tissue
what kind of necrosis is cerebral infarction?
liquefactive, NOT coagulative, as the autocatalytic effect of hydrolytic enzymes generated by neuroglial cells produce cystic space
what is wet gangrene?
dry gangrene with superimposed anerobic infection, like C. perfringens
-leads to acute inflammation, where liquefactive necrosis is primary type of necrosis
what is caseous necrosis and its mechanisms?
variant of coagulation necrosis, but associated with acellular, cheese-like material
-formed by release of lipid from cell walls of M. tuberculosis and systemic fungi after immune destruction by macrophages
what are microscopic features of a granuloma?
acellular material in the center surrounded by activated mcrophages, CD4 helper T cells, and multinucleated giant cells
