Cell Injury

    • Reversible Cell Injury
      • Reversible injury is the ability to heal without permanent damage
        • Hyperplasia is an increase in the number of cells
        • Hypertrophy is an increase in cell size.
        • Atrophy is a decrease in cell size.
        • Metaplasia is an alteration of cell differentiation.
        • Intracellular accumulations are an altered metabolism
      • Hyperplasia can be physiologic or pathologic.
        • Physiologic hyperplasia
          • Hormones may drive hyperplasia (MCQ)
            • pregnant uterus
            • lactating breast
          • Compensatory hyperplasia may occur with tissue damage
            • liver regeneration after partial hepatectomy
            • wound repair
          • Initiation of cell proliferation includes induction of transcription factors and cell cycle proteins.
        • Pathologic hyperplasia
          • a risk factor for neoplasia
          • causes
            • usually due to  excessive hormonal stimulation (eg, PCOD leading to excessive estrogen production), (MCQ)
            • effects of growth factors.
    • Hypertrophy
      • increase in the size of the cell
      • occur due to the synthesis of structural components rather than cellular swelling.
      • It is usually a physiologic process due to increased functional demands
      • placed on the cell
        • hypertrophy of striated muscles from weight lifting
        • cardiac myocyte hypertrophy secondary to systemic hypertension(MCQ)
    • Atrophy is the reduction of cell or organ size.
      • Physiologic atrophy
        • occurs during fetal development (eg, regression of the notochord)
        • occurs throughout life (eg, muscle).
      • Common causes of atrophy include:
        • Decreased workload or denervation (eg, paralysis).
        • Diminished blood supply (eg, atherosclerosis).
        • Inadequate nutrition (eg, marasmus “muscle wasting”).
        • Loss of hormone stimulation (eg, menopause).
        • Aging (build up of cellular waste and DNA damage).
        • Compression (eg, organ compression by expanding tumor).
    • Metaplasia
      • differentiation from one mature cell type to another (MCQ)
      • squamous metaplasia of glandular respiratory epithelium
      • an adaptive response to a hostile environment.
      • usually a change from glandular mucosa to keratin rich squamous mucosa as in squamous metaplasia of ciliated respiratory mucosa because of smoking(MCQ)
      • mitochondria rich oncocytic cells can form(MCQ)
        • apocrine change in breast
        • Hürthle change in thyroid
        • oncocytic change in the salivary glands
      • Barrett esophagus. (MCQ)
        • Metaplasia from squamous to glandular mucosa is unusual
        • a common consequence of chronic reflux esophagitis
      • mechanism is thought to arise from reprogramming of stem cells (reserve cells) from the basal layer (MCQ)
        • eg, squamous metaplasia at the cervical trans- formation zone).
      • Metaplasia increases the patient’s risk for carcinoma
        • lung cancer from smoking(MCQ)
        • esophageal cancer from reflux
    • Intracellular accumulations
      • represent metabolic derangement.
      • Steatosis (fatty change) (MCQ)
        • develops in the liver
        • seen in ethanol , diabetes mellitus, obesity, and pregnancy.
      • Atherosclerosis
      • Immunoglobulin produced in excess in chronically active plasma cells produce round red Russell bodies. (MCQ)
      • Lipofuscin (MCQ)
        • brown pigment
        • derived from lipid peroxidation (MCQ)
        • commonly seen in aged organs.
      • Melanin
        • dark brown pigment ). (MCQ)
        • made in skin, hair, and eye (iris and choroid layer)
      • Hemosiderin
      • a granular brown pigment composed of ferric oxide
      • result from the breakdown of hemoglobin
      • a sign of hemolysis, or disturbed iron metabolism (eg, hemochromatosis). (MCQ)

    Pathophysiology 4 cell injury
    Cell Injury: Reversible Changes
    An animated overview of the reversible changes that take place following cell injury.
    Cellular Injury
    This video covers the basics of injurious agents to cells and how they respond.
    Basic Medical Pathology: Morphological Expressions of Cell Injury
    National Institutes of Health
    Lister Hill National Center for Biomedical Communications
    Overview of Reversible cell injury and necrosis: microscopic morphology
    What do cells look like when they are dying, and what happens to them? these questions are answered in this and the next few videos. This is video #7. cellular swelling, nuclear condensation, apoptotic bodies.