| Line 390: |
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| | from cells or pooled from lipoproteins in crystalline form( cholesterol clefts )as a result of | | from cells or pooled from lipoproteins in crystalline form( cholesterol clefts )as a result of |
| | haemorrhage or tissue damage. | | haemorrhage or tissue damage. |
| − | 4. Mucoid ( mucinous, myxomatous ) degeneration - changes in epithelial tissue
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| − | or ground substance (matrix) produced by fibroblasts in connective tissue..
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| − | This is an extracellular phenomenon of some specific cells. They tend to show a bluish tinge
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| − | in H&E stained sections.
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| − | a. Epithelium - specifically the goblet cells of wet mucous membranes and the mucous
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| − | glands themselves. It is a beneficial reaction and is not really degeneration, but an increased
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| − | production of mucin. Their secretions are important as lubricants and protective substances
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| − | 19
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| − | soothing inflamed surfaces, entrapping and diluting harmful agents, carrying specific
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| − | antibodies against infectious agents, and providing a means for their removal.
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| − | b. Connective tissue - the mucin here forms part of the ground substance between the cells
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| − | ( fibroblasts ) producing it. In some circumstances, there appears to be a disturbance in the
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| − | metabolism of the fibroblasts which produce the mucin and the ground substance takes on a
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| − | bluish hue in H&E sections.
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| − | The common example is the
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| − | mucoid ( myxomatous, myxoid )
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| − | degeneration that occurs in the
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| − | heart valves of middle-aged and
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| − | older dogs. It occurs primarily in the
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| − | mitral valve and is responsible for a
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| − | condition specific for this species
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| − | called endocardiosis.
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| − | It is important and results in slowly
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| − | developing heart failure due to the
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| − | inability of a heart with swollen
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| − | misshapen valves to effectively pump
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| − | blood from the left ventricle out into
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| − | the systemic circulation. A substantial
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| − | portion of the blood passes back into
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| − | the left
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| − | atrium and compromises the filling of the atrium from the pulmonary vein. This leads to
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| − | back pressure on the pulmonary capillaries with oedema formation in the lungs. This
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| − | 20
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| − | reduces the oxygenation of blood leading to exercise intolerance and may be heard as moist
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| − | sounds on auscultation of the lungs. Eventually, this failure of the left side compromises the
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| − | function of the right side and there is also pooling of blood in the venous system i.e. in the liver.
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| | | | |
| | ===Mucoid Degeneration=== | | ===Mucoid Degeneration=== |