Define autolysis, Apoptois and Necrosis and give key features of (a) autolysis and (b) physiological and pathological PDF

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Summary

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Description

Tumours (often accomplished by necrosis) Atrophy (virtually never accompanied by necrosis)

Occurs in a number of conditions

Caseous ( tuberculosis) Liquefaction (brain infarct)

Viral illness e.g hepatitis

Gangrenous

Different types of necrosis

Pathological apoptosis Control on apoptosis is crucial to the process of neoplasia

Fat necrosis Coagulative

Some genes involved in cancer formation (e.g bel-2-oncogenes) may switch off apoptosis, theoretically allowing cells to live forever

Embryogenesis (formation of digits)

Occurs in a number of situations

Menstrual cycle ( endometrial cell loss)

Death of individual cells and tissues after the death of the whole organism

Physiological apoptosis

Breast feeding (reversal of changes in lactating breast after breast feeding is finished

Autolysis

Cells are degraded by post-mortem release of digestive enzymes from cytoplasmic lysosomes

Immune cell development (deletion of immune cells (T cells) that may react with body's own tissues)

Defined as morphological changes that result from cell death within living tissues Death of large number of cells in one area as opposed to selective apoptotic cell death

Cessation of function of tissue or organ Release of cellular enzymes ( can be used as markers)

Initiation of inflammatory response (vital reaction)

Control cell numbers Physiological and embryological processes

Necrosis

Define autolysis, Apoptois and Necrosis and give key features of (a) autolysis and (b) physiological and pathological apoptosis and the different types of necrosis

Apoptosis

Pathological processes (inflammation, cancers)

Results of cell death can include

Synthesis of enzymes needed to cause cell dissolution e.g proteases and nucleases

Normal cells are arranged in close contact and united by cell junctions Priming for apoptosis occurs (enzyme synthesis for dissolution)

Priming

Enzyme activation

Splitting of cell into fragments (apoptotic bodies) Nuclear fragmentation- process only takes a few minutes Apoptotic fragments recognised by adjacent cells which phagocytose them

Endonucleases cleave chromatin, resulting in DNA fragmentation Proteases degrade the cytoskeleton, resulting in cell shrinkage

Nuclear chromatin condenses beneath nuclear membrane

Endonuclease enzymes cleave chromosomes

No structural cellular changes

Stages of apoptosis Stages of apoptosis

Apoptotic cells loose surface specialisation and junctions, shrinking in size

Arrest proliferation and tissue damage

Plasma membrane and organelles remain intact

Fragmentation of the cell

Cell fragmented into apoptotic bodies Each fragment contains viable mitochondria and intact organelles Presence of intact plasma membranes around apoptotic bodies explains absence of any inflammation

Apoptotic fragments are phagocytosed and destroyed by adjacent cells...