First external sign of putrefaction is: March 2004
**Core Concept**
The first external sign of putrefaction is a significant clinical indicator of post-mortem changes, which can provide valuable information about the time elapsed since death. Putrefaction is a complex process involving the breakdown of tissues, primarily due to microbial action.
**Why the Correct Answer is Right**
The first external sign of putrefaction is typically the appearance of greenish discoloration around the eyes, known as **conjunctival petechiae**. This occurs due to the release of enzymes from the liver, which break down the hemoglobin in red blood cells, producing biliverdin, a green pigment. As the putrefaction process advances, this discoloration can spread to other areas of the body.
**Why Each Wrong Option is Incorrect**
**Option A:** Rigor mortis, while an early sign of death, is not an external sign of putrefaction. It is a temporary stiffening of the muscles due to the cessation of ATP production.
**Option B:** Livor mortis, or post-mortem hypostasis, is a discoloration of the skin due to the pooling of blood in the lower extremities, but it is not the first external sign of putrefaction.
**Option C:** Algor mortis, or the cooling of the body temperature, is a sign of death, but it is not an external sign of putrefaction.
**Clinical Pearl / High-Yield Fact**
Remember that the sequence of post-mortem changes can provide valuable information about the time elapsed since death. The sequence is typically: algor mortis (cooling), rigor mortis (stiffening), livor mortis (discoloration), and finally, putrefaction (tissue breakdown).
**Correct Answer: B. Livor mortis is the first visible sign of putrefaction.