Final answer:
The yellow skin tinge in obstructive jaundice is caused by the accumulation of bilirubin, a product of hemoglobin breakdown, due to blockage in the bile ducts, preventing its excretion.
Step-by-step explanation:
The yellow tinge in the skin symptomatic of obstructive jaundice is caused by the accumulation of a substance called bilirubin in the blood and tissue. Obstructive jaundice arises when there is a blockage in the bile duct system, which prevents bilirubin from being excreted from the body. This buildup can occur due to various reasons, including gallstones or tumors that block the bile ducts or due to inflammation.
The concentration of bilirubin in the blood normally does not exceed 1 mg/100ml, but with the onset of obstructive jaundice due to the blocked bile ducts, the concentration can rise, and when it reaches 2 mg/100 ml, the blood cannot hold any more bilirubin, causing it to diffuse into peripheral tissue and give a yellow color to the skin. This condition is known as jaundice or icterus.
In addition to the skin, the sclera of the eyes and mucous membranes may also display a yellowish color, indicating the presence of jaundice. Effective treatment of obstructive jaundice requires addressing the underlying cause of the bile duct obstruction to restore normal bilirubin metabolism and excretion.