3rd extensor compament of wrist contains tendon of
**Core Concept**
The 3rd extensor compartment of the wrist is one of the nine extensor compartments that contain tendons of the extensor muscles of the forearm. These compartments are anatomically arranged in a specific order to facilitate optimal function of the wrist and hand.
**Why the Correct Answer is Right**
The 3rd extensor compartment of the wrist contains the tendon of the extensor pollicis longus (EPL) muscle. The EPL muscle originates from the posterior surface of the ulna and inserts into the base of the distal phalanx of the thumb. The tendon of the EPL muscle passes through the 3rd extensor compartment, which is bounded by the tendons of the extensor pollicis brevis (EPB) and abductor pollicis longus (APL) muscles.
**Why Each Wrong Option is Incorrect**
* **Option A:** The 1st extensor compartment contains the tendon of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscles, not the 3rd compartment.
* **Option B:** The 2nd extensor compartment contains the tendon of the extensor carpi radialis brevis (ECRB) muscle, not the 3rd compartment.
* **Option C:** The 4th extensor compartment contains the tendon of the extensor digitorum (ED) muscle, not the 3rd compartment.
**Clinical Pearl / High-Yield Fact**
The 3rd extensor compartment is a common site for injuries and tendonitis, particularly in individuals who perform repetitive activities involving the thumb, such as musicians or athletes.
**Correct Answer: D. EPL**