Cellular Adaptations and Gangrene PDF

Gangrene Definition: necrosis of big tissue with superadded putrefaction, black, foul-smelling appearance. Pathogenesis: The Necrosed tissue infected with putrefactive organisms infection. Hemoglobin (released from hemolyzed red blood cells) + hydrogen sulfide H2S (produced by bacteria)--...

Gangrene Definition: necrosis of big tissue with superadded putrefaction, black, foul-smelling appearance. Pathogenesis: The Necrosed tissue infected with putrefactive organisms infection. Hemoglobin (released from hemolyzed red blood cells) + hydrogen sulfide H2S (produced by bacteria)-------------- Iron sulfide ( black in color ) responsible for the dark coloration of the tissue. a. Dry gangrene: Part affected: only occurs on the skin surface. It is particularly liable to affect the limbs, especially the toes. Cause: arterial obstruction. People with impaired peripheral blood flow, such as diabetics. Grossly: dry, shrunken and dark reddish-black, resembling mummified flesh. Dry gangrene Offered by Prof.Orr  b- Wet gangrene: Part affected: Commonly in small intestine, appendix, lung, and uterus, also in limbs. Cause: Both arterial and venous obstruction The tissue is infected with saprophytic microorganism for example (Clostridium perfringens or Bacillus fusiformis). Grossly: wet swollen, foul-smelling, black or green. Systemic manifestation: The toxic products formed by bacteria are absorbed, causing systemic manifestation of septicemia and finally death. Moist gangrene  c. Gas gangrene: Part affected: deep contaminated wounds in which there is considerable muscle damaged by gas formation bacteria. Gross lesion: swollen obviously, gas bubbles formation. The infection rapidly spreads and there is associated severe toxemia. Only occasionally in civilian practice but is a serious complication of war wounds. Cellular Adaptations in Disease  Overview Adaptability of cells to an altered environment – Physiological and pathological stimuli Changes in growth pattern – hypertrophy, Hyperplasia, atrophy, metaplasia  Why is this important? Extremely common responses in diseases Certain adaptations in growth act as a fertile ground for the later development of neoplasia - cancer formation… Nomenclature is used in clinical work. Cellular Adaptations to Stress Changes in growth pattern 1. Hypertrophy 2. Hyperplasia 3. Atrophy 4. Metaplasia  1- Hypertrophy Hyper = excess trophy = nourishment Def.: Abnormal increase in the size and weight of an organ or tissue due to increase in the size of its cells. Cause: increase functional demand of tissue. Types of hypertrophy: 1- Physiological hypertrophy e.g Pregnant uterus, muscular exercise. 2- Pathological hypertrophy: may be a- Compensatory. b- Adaptive.  Physiological hypertrophy Skeletal muscle hypertrophy in response to exercise  Types of Pathological Hypertrophy 1- Compensatory 2- Adaptive Occurred in paired organs Occurred in muscular hallo e.g kidney organs above a chronic partial obstruction e.g heart, stomach, bladder, or intestine. If one of the two organ is destroyed or removed The muscles have to contract the other organ becomes more forcibly to overcome enlarged to compensate the obstruction and become hypertrophied.  Adaptive hypertrophy e.g. Left ventricular hyperterophy in case of aortic valvular stenosis.  2- Hyperplasia Hyper = excess plasia = formation Def.: Increase in the size and weight of organ or tissue due to increase in the Number of its component cells. Types of hyperplasia: 1- Physiological hyperplasia e.g In breast and genital organs at puberty. 2- Pathological hyperplasia Causes of Pathological hyperplasia: 1- Compensatory: i.e Hyperplasia of the bone marrow after hemorrhage or excessive hemolysis. 2- Hormonal: i.e Hyperplasia of endometrium and mammary gland produced by injection of estrogens. 3- Irritation: Mechanical, bacterial infection, toxic. 4- Deficiencies: Deficiency of iodine produces hyperplasia of thyroid. 5- Viral: Hyperplasia of epithelium by pox virus  Pathological hyperplasia Normal skin Hyperplasia after trauma RP = rete peg DP = dermal papilla  3- Atrophy A = not ( deprivation) trophy = nourishment Def.: Decrease in the size of a tissue after it has attained its full growth due to decrease in number of constituent cells or decrease in size of individual cells. Types of atrophy: (1) Physiological atrophy: e.g atrophy of thymus. (2) Pathological atrophy Physiological atrophy Atrophy of thymus  Types of Pathological atrophy 1- General Atrophy: - Malnutrition and starvation atrophy - Senile atrophy 2- Localized atrophy (a) Disuse atrophy (b) Pressure atrophy (c) Vascular atrophy (d) Neuropathic atrophy (e) Endocrine atrophy General atrophy 1- Vascular atrophy: Anemia and chronic venous congestion (lack of oxygen and nutrients). 2- Pressure atrophy The long continued pressure on a tissue results in cuts its blood supply. 3- Neurotrophic atrophy: If a trophic nerve is injured, the corresponding muscle atrophies.. 4- Endocrine atrophy: In absence of trophic hormones, the concerned cells atrophied. 5- Disuse atrophy: Refers to changes in muscle after a period of reduced activity. Pathological atrophy A= atrophic skeletal muscle fibres Disuse atrophy  Refers to changes in muscle after a period of reduced activity Other causes of a small organ other than atrophy Hypoplasia: incomplete growth of an organ Hypo = under plasia = formation Agenesis: complete failure of development of an organ in embryogenesis A = not genesis = production Aplasia : the primordium of an organ is created but the organ failed to be formed A = not plasia = formation  4- Metaplasia Met = after plasia = formation Def. : Change of fully differentiated cells into another type of fully Differentiated cells of the same germinal layer to adapt themselves to change in environment or function. Types of metaplasia: 1- Epithelial metaplasia (squamous metaplasia) 2- Connective tissue metaplasia (osseus metaplasia) 1- Epithelial metaplasia: Def.: Metaplasia of columnar or cuboidal epithelium into stratified squamous epithelium. Occurrence: in bronchi, bronchiole, gall bladder and urinary bladder. Causes: 1- Chronic irritation. 2- Avitaminosis A. 2- Connective tissue metaplasia: Def.: Connective tissue may be converted into bone. Occurrence: 1- in the course of healing as in the wall of the abdomen.  Examples of metaplasia Bladder transitional epithelium (T) with metaplasia to squamous epithelium (S) in response to a bladder stone…