As the blood coagulum clot becomes older the fibrin filaments shrink

As the blood coagulum clot becomes older the fibrin

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As the blood coagulum (clot) becomes older, the fibrin filaments shrink. Consequently the coagulum gets smaller and rose-coloured (pink) water, namely serum, is squeezed out. Blood takes approximately 5 minutes to coagulate. Inflammation Damaged tissue releases chemical substances or matter, e.g. histamines. Substances such as histamine cause vasodilation of capillaries. Increase in blood supply to the area. Temperature rises as a result of increase in blood supply. Permeability of capillaries increases plasma and leukocytes move to area. It causes tissue to swell a condition known as oedema. Plasma contains: Chemical substances such as interferon, compliment and interleucin Phagocytes Antibodies Phagocytes ingest antibodies, pathogens and dead cells. Fibrinogen -is available should blood coagulation be necessary. Wound healing Fibroblasts appear and form collagen (a fibrous protein that bonds with a polysaccharide to form lesion tissue). (Vit. C is necessary for the formation of collagen) After approximately 14 days the masses of fibres are reorganised in bundles. Blood-vessels begin to form through the wound carry food and O 2 to tissue. Epidermis cells remove waste materials in wound and form a new skin surface. Scab falls off. [22] 4. Phagocytosis: Definition: It is the process through which some leukocytes take in and consume large molecules, micro-organisms, dead cells and waste material. The leukocytes responsible for this are known as phagocytes. Phagocytes, together with the skin and other non-specific mechanisms, form the first line of defence.
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Study unit 7 108 Types of phagocytes: 1. Neutrofils: Are able to push / press through walls of capillaries; move around in intercellular spaces. 2. Macrophages : Initially known as monocytes when in blood for 30 40 hours. The monocytes then move to tissues (particularly the liver, spleen and lymphatic nodes) where the cells are known as mactophages. Sometimes the macrophages remain in one place where they line the blood spaces in the organs. These cells encase and consume foreign particles and micro-organisms. They can take in larger particles as neutrofils, e.g. old red blood corpuscles and malaria parasites (=eukaryotes), which are much larger cells than bacteria (=prokaryotes). They can also retain indigestible particles in the cells for long periods of time. Neutrofils and macrophages form the reticulo-endothelium system in the human body. How phagocytes function: 1. Opsonisation of antigen (e.g. bacteria by covering bacteria with compliment ( 20 proteins that are activated by bacterial infection) or antibodies involved in specific immune response. 2. Phagocytes possess receptors on cell surface membranes that fit onto the opsonins and are therefore brought to the bacteria in order to absorb or take in and consume the bacteria.
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  • Spring '16
  • Ambani Mudau
  • Phylum, Windelspecht

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