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34 Cards in this Set
- Front
- Back
Definition of cell death |
Irreversible loss of cell's ability to maintain independence form environment |
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Two major forms of cell death |
apoptosis necrosis |
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Necrosis vs. Apoptosis |
Necrosis - cellular/tissue death in living organism Apoptosis - energy dependent process for deletion of unwanted individual cell |
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Name six different types of necrosis |
Coagulative Colliquative Caseous Gangrenous Fibrinoid Fat |
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Coagulative necrosis - defintion |
Denaturation of intracytoplasmic proteins
Dead tissue will initially become firm and swollen but later soft (e.g. venticular rupture after MI)
Typically occur in ischaemic injury (NOT the brain) |
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Colliquative necrosis - definition |
Seen in brain, probably due to lack of supporting stoma Necrotic brain tissue liquefies Glial reaction at periphery with cyst formation occurs eventually |
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Caseous necrosis - definition |
Typically in TB Macroscopically cheese-like Microscopically structureless |
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Gangrenous necrosis - definition |
Necrosis with putrefaction of tissues due to certain bacteria e.g. clostridia, strep Tissue is black due to iron sulphide from degraded Hb |
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Fibrinoid necrosis - definition |
Associated with malignant hypertension Necrosis of arteriole SM wall with seepage of plasma into tunica media and deposition of fibrin Smudgy eosinophilic appearance on H+E sections |
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Fat necrosis - definition |
Direct trauma to adipose tissue and extracellular liberation of fat Enzymatic lysis of fat by lipase, splitting fat into fatty acid which combines with Ca to precipitate as soaps |
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Function of apoptosis |
Morphogenesis (elimination of cells in embryonal development) Removal of cells which have undergone DNA damage Removal of virally infected cells Tolerance to self-antigens by removing autoreactive T cells |
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Four mediators of apoptosis and function |
p53 - tumour suppressor gene which checks integrity of genome prior to mitosis. Switches cells with damaged DNA into apoptosis
BCL-2 - inhibits apoptosis. bcl-2 is overexpressed in neoplasia
fas (cd 95) - plasma membranee receptor which when activated is coupled to the activation of intracellular proteases
Caspases - present in all cells and unless inhibited will lead to apoptosis |
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Describe process of apoptosis |
Cell shrinkage + chromatin condensation --> membrane blebbing --> continued blebbing + nuclear collapse -->apoptotic body formation --> lysis of apoptotic bodies |
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Disease of increased apoptosis |
HIV Neurodegenerative diseases |
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Disease of decreased apoptosis |
Neoplasia Autoimmune disease |
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regeneration vs repair |
Regeneration - total healing of wound with restitution of original tissue in their usual amounts, arrangements and normal function
Repair - original tissue is not totally regenerated defect is made good to a variable extent by scar tissue
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Describe different levels of potential for cell renewal |
Labile cells - good capacity for regeneration e.g. surface epithelial cells continuously being replaced from deeper layers e.g. skin oesophagus, vagina
Stable cells - replaced by mitotic division of mature cells and lost cells rapidly replaced e.g. liver, renal rubular epithelium
Permanent cells - never divide in post natal life e.g. nerve cells, myocardial cells |
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Summary of process of repair of tissue |
Fibrinous exudate --> removal of fibrin and dead tissue and phagocytes --> migration of fibroblasts and capillaries forming granulation tissue --> replacement of exudate by vascularised fibrous tissue --> collagen rich scar |
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What is granulation tissue |
Combinatino of capillary loops and myofibroblasts |
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Process of granulation |
Angiogenesis Migration and proliferation of fibroblasts (secrete collagen and matrix component) Fibroblasts become myofibroblasts by acquiring muscle filaments Wound contraction |
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Describe healing by 1st intention |
Healing by 1st intention (incised surgical wound) - Edges of incision apposed - Fibrin sticks edges together - Capillaries bridge tiny gaps - Fibroblasts invade fibrin network - After 10 days wound is strong, suture removed, remodelling occurs
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Describe healing by 2nd intention |
Healing by 2nd intention e.g. wound left open (e.g. infected) or tissue loss e.g. trauma - Phagocytes remove any debris - Formation of granulation tissue at base of wound - Myofibroblasts cause wound contraction - Centripetal growth of epithelium from edges to cover defect - Tissue deficit eventually made good by scar issue |
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Name 2 abnormalities of skin healing |
Keloid = Excessive fibroblast proliferation and collagen production Collagen deposition beyond and above the wound itself
Hypertorphied scar - wound broad and riased, does not extend beyond wound. Usually settles spontaneously in up to 18 months |
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Nam the seven ladders of the reconstructive ladder |
Primary closure Delayed primary closure Split-thickness skin graft Full thickness skin graft Local/random pattern flap Regional/pedicled flap Free flap |
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Definition of graft |
Composed of skin but may contain variety of tissue incl. skin, cartilage, tendon, bone or combination of above NOT transferred with own vascular supply and depends on formation of new vascular system at new site |
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Name different types of graft |
autograft - own tissue Allograft - e.g. cadaver bone xenograft - e.g. animal tendon |
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Full thickness skin graft vs split thickness |
full thickness - epidermis and all of dermis split thickness - epidermis and variable thickness of dermis |
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Mechanism of skin graft |
Adherence - fibrin bonds graft to recipient site, occurs in <12 hours Plasmic imbibition - graft absorbs essential nutrients from recipient site, occurs at 24-48 hours Inosculation - revascularisation of the graft via growth of vascular buds, occurs at 48-72 hours |
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Common donor sites for split skin grafts
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thighs buttocks upper arms |
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Which takes better at recipient site - split vs full thickness skin graft and why? |
Split as thinner helping survive imbibition process |
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Which one results in more contraction at recipient site - split vs full thickness skin graft |
split thickness |
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Common donor sites for full thickness skin graft |
Groin pre/post auricular area Supraclavicular region |
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Definition of flap |
unit of tissue transferred with own blood supply |
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What are flaps used for? |
- large defect - places where graft would produce poor cosmetic outcome e.g. face - where base of defect would not support a graft e.g. bare bone, exposed tendon or poorly vascularised bed |