general pathology: cellular adaptations lorne holland, m.d. [email protected]
TRANSCRIPT
General Pathology:General Pathology:Cellular AdaptationsCellular Adaptations
Lorne Holland, [email protected]
Cellular AdaptationsCellular Adaptations
• Given stressors, cells respond by changing their size, function or composition
• Some of these changes may be, at least initially, beneficial (hypertrophy, hyperplasia, metaplasia)
• Some of these changes are maladaptive (atrophy, hypoplasia)
• Left unchecked, some changes can ultimately lead to cancer (dysplasia)
Hypertrophy- Hypertrophy- “too much “too much nourishment”nourishment”
• Increase in cell size without an increase in the number of cells
• Response to increased demand on a cell to do whatever it does
• Classic example- muscle cells in response to exercise
• Other examples- thyroid in response to hormonal stimulation during puberty
• Pathologic example- myocardial cells in response to chronic, systemic hypertension
Hyperplasia- Hyperplasia- “too much “too much growth”growth”
• Increase in the number of cells without an increase in the size of cells
• Response to increased demand on a cell to do whatever it does
• Classic example- regenerating liver after damage/resection
• Other examples- glandular tissue in breast in response to puberty and pregnancy
• Pathologic example- endometrial tissue due to abnormal/irregular hormonal cycles
Hypertrophy and Hypertrophy and HyperplasiaHyperplasia
• These processes do not have to occur separately
• Usually, both occur though one is by far more predominant
• Classic example- uterine smooth muscle during pregnancy
Atrophy- Atrophy- “no nourishment”“no nourishment”
• Decrease in organ size due to decreased cell size and/or decreased number of cells
• Physiologic- thymus in adulthood, uterus and testes in old age
• Pathologic- disuse, ischemia, starvation
Hypoplasia- Hypoplasia- “little growth”“little growth”
• Could be visually indistinguishable from atrophy
• Once normal or supernormal tissue which regresses is atrophic
• Tissue which never develops to normal size is hypoplastic
• Similar causes of hypoplasia as atrophy
• In the extreme, aplasia “no growth” usually due embryologic failure
Metaplasia- Metaplasia- “changed “changed growth”growth”
• Transformation of one normal cell type into another normal cells type
• Transition of ciliated glandular epithelium to squamous epithelium in respiratory tissue of smokers
• Transition of squamous epithelium to glandular epithelium in esophageal reflux
• Often, though not always a precursor to dysplasia
Dysplasia- Dysplasia- “bad growth”“bad growth”
• Characterized by one or more– Hyperplasia especially with
increased mitotic figures– Decreased differentiation
Dysplasia- Dysplasia- “bad growth”“bad growth”
• Characterized by one or more (cont.)– Atypia (not typical appearance)
•Pleomorphism (more forms)–Variable cell size/shape–Variable nucleus size/shape
•High nuclear to cytoplasm ratio•Hyperchromasia (too much color) of nucleus
Neoplasia- Neoplasia- “new growth”“new growth”
• Unregulated growth of abnormal tissue
• Commonly called a tumor (swelling)• May or may not be cancer,
depending on clinical behavior (malignant vs. benign)
CalcificationCalcification
• Abnormal precipitation of calcium in tissue– Dystrophic due to wear and tear with
“normal” blood calcium concentrations•Atheromatous plaques•Heart valves•Fat necrosis
– Metastatic due to calcium in “normal” tissue with elevated blood calcium concentration•Much less frequent but seen in
hyperthyroidism, hypercalcemia of malignancy
AmyloidAmyloid
• Proteins which layer as B pleated sheets to form fibrillar structures
• Can be highlighted with special stains (Congo red)
• Small amounts can be seen in tissues of “normal” elderly people
AmyloidosisAmyloidosis
• AL amyloid– Due to precipitation of immunoglobulin
light chains produced by abnormal plasma cells
• AA amyloid– Due to precipitation of serum amyloid
protein A produced by liver during inflammation (acute phase reaction)
• Hereditary amyloidosis– Due to genetic defects in proteins which
favor precipitation
AmyloidosisAmyloidosis
• Can effect virtually any organ with clinical symptoms reflective of organ(s) most affected– Predilection for affecting kidneys
(filtering)– Liver and spleen are also often enlarged
Questions?Questions?