Bruise attains greenish discoloration by: September 2003
**Question:** Bruise attains greenish discoloration by: September 2003
**Core Concept:** The process of hemolysis and the development of green discoloration in a bruise.
**Why the Correct Answer is Right:**
Bruises occur due to the rupture of blood vessels, leading to the release of hemoglobin from red blood cells into the surrounding tissue. Hemoglobin is composed of two subunits - globin and heme. Heme contains iron (Fe) which can bind to oxygen (O2) and is responsible for the characteristic red color of a fresh bruise. However, as the bruise ages, oxygen levels decrease, and the heme-iron starts to react with other molecules present in the tissue, such as bilirubin, which is a breakdown product of hemoglobin. This reaction results in the formation of methemoglobin, a non-functional form of heme that lacks the ability to bind oxygen. Methemoglobin has a greenish-blue color, leading to the greenish discoloration observed in older bruises.
**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because it does not address the underlying mechanism of hemolysis and methemoglobin formation that leads to green discoloration in a bruise.
B. This option could be partially correct as hemoglobin breakdown does occur in bruises. However, it does not explain the formation of methemoglobin and the resulting greenish discoloration.
C. This option is incorrect because it does not focus on the process of hemolysis and the formation of methemoglobin.
D. This option is incorrect because it does not address the mechanism of green discoloration in bruises caused by heme-iron reactions.
**Clinical Pearl:**
The greenish discoloration in a bruise is a result of hemolysis and the formation of methemoglobin, a non-functional form of hemoglobin with a greenish-blue color. This phenomenon is particularly noticeable in older bruises, making it an important clinical point for recognizing the age of a bruise and estimating its duration. Understanding this process can aid in clinical diagnosis and estimation of the time since injury.