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