University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

285

Pages:

2
Author:

Mariam A. A.

Intro to Pathology Define cellular adaptations as hyperplasia, hypertrophy, atrophy, and metaplasia & give examples of their causes. Hyperplasia: ↑ cell no., growth factors, ↑ mitosis Physiological: Hormonal (uterus in pregnancy), after partial resection Pathological: Compensatory (liver after partial resection), hormonal (endometrium due to excess estrogen) Hypertrophy: ↑ cell size, ↑ no. of cells Physiological: Compensatory (heart after aortic stenosis) Pathological: Increased workload (skeletal muscle use, weightlifting), hormonal (uterus in pregnancy) Atrophy: ↓ in no. of cells Physiological: Cells during embryonic life Pathological: Disuse (after injury), denervation, aging, malnutrition Metaplasia: Replacement of one cell type with another Physiological: Squamous epithelium in the bronchi of smokers Pathological: Glandular epithelium to squamous epithelium in the cervix Cellular Adaptations Metaplasia: Mature differentiated cell type replaced by a cell type more suited to the new environment Dysplasia: Abnormal arrangement of cells Reversible if stimulus is removed May progress to neoplasia Example: Squamous metaplasia in epithelial tissue → GERD Columnar to squamous in esophagus Cell Injury Apoptosis: Programmed cell death Active process Shrinkage, membrane blebbing, nuclear fragmentation Necrosis: Cell death due to irreversible injury Passive process Swelling, rupture, inflammation Cellular aging: Loss of replication capacity Stem cells are an exception Senescence disease: Telomeres shorten progressively → ↓ cell division Telomerase lengthens telomeres Found in stem cells and cancer cells Telomerase overcomes restriction on cell replication capacity Cell injury is reversible if limits of adaptive response are not exceeded; cell is exposed to harmful agents or stress only to a sub-lethal degree