Pigment Accumulation Pigments produced inside the body are referred to as
pigments, while
those introduced into the body from the environment are referred to as
.
pigments.
Generally exogenous pigments are harmless, causing no change in cell function. involves the injection of a pigment into the dermis of the skin. The pigment, or ink, is chosen to be harmless and inorganic so that they are not broken down once inside the cells. Tattoos are used for identification purposes and are seen most commonly on the inside of the top lip in racehorses. Occasionally an accumulation of an exogenous pigment can be indicative of disease. When inhaled, carbon enters the epithelial cells of the respiratory tract giving the lungs a blue-black appearance. This is known as , as it was commonly seen in individuals and animals working in coalmines. A similar pigmentation is seen in the lungs of those who smoke cigarettes. The carbon irritates the respiratory epithelium, causing an inflammatory immune reaction. The epithelium reacts by the excessive production of secretions such as mucus and by the deposition of collagen. The excessive secretion causes a non-infective pneumonia, while the collagen results in hardening and fibrosis of the lungs. The result is compromised inflation of the lungs, and a reduction in the gas exchange between the alveoli and the pulmonary circulation. Conditions such as emphysema, pneumonia, and chronic bronchitis are linked to the presence of carbon in the lung tissue.
There are two categories of endogenous pigments.
1. Pigments that are of blood origin 2. Pigments that are not.
The , which is found inside RBC’s. We can most clearly see the haematogenous pigments when we consider the development and maturation of a hematoma (bruise). Initially the area of injury is red-blue due to the accumulation of blood from broken blood vessels. The damaged vessels form a clot leaving blood trapped in the intracellular space of the tissue. Phagocytes arrive at the site of injury and begin breaking down the trapped blood components. The metabolites of haemoglobin degradation are the pigments seen in a bruise as it ages. pigments are derived from the molecule First haemoglobin is broken down into biliverdin , then into bilirubin and finally haemosiderin . Each pigment has a distinctive colour. Biliverdin has a colour, while bilirubin is . Haemosiderin is a colour. Some diseases involving damage to the liver or extensive breakdown of RBC’s result in a condition called . This is when there is an excess of bilirubin in the blood causing the tissues to become stained a yellow brown. Bilirubin is normally broken down in the
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