Tendon absent in palm is?
**Core Concept**
The palmaris longus tendon is a superficial tendon in the flexor compartment of the forearm, which inserts into the pisiform bone in the wrist and then continues as a long tendon that passes through the palmar aponeurosis to attach to the base of the second and third metacarpals in the palm. The palmaris longus tendon plays a minor role in wrist flexion but is more notable for its presence or absence, which can be used as a marker for genetic variability.
**Why the Correct Answer is Right**
The palmaris longus tendon is often absent or hypoplastic in individuals of European descent, with a reported prevalence of around 10-15%. This condition is usually inherited in an autosomal dominant pattern and is more common in women than men. The absence of the palmaris longus tendon is generally not associated with any functional or clinical significance, but it can be a useful landmark for surgeons during hand surgery.
**Why Each Wrong Option is Incorrect**
* **Option A:** The flexor carpi radialis tendon is not absent in the palm, but rather inserts into the base of the second and third metacarpals, similar to the palmaris longus tendon. However, it is often more prominent and easier to identify.
* **Option B:** The palmaris brevis tendon is a small, superficial tendon in the palmar aponeurosis, but it is not absent in the palm. Instead, it helps to cover the palmar surface of the metacarpal bones.
* **Option C:** The flexor digitorum profundus tendon is a deep tendon in the flexor compartment of the forearm, which inserts into the distal phalanges of the fingers. It is not absent in the palm.
**Clinical Pearl / High-Yield Fact**
The absence of the palmaris longus tendon is a useful marker for genetic variability and can be used as a teaching tool to illustrate the concept of genetic inheritance.
**Correct Answer: D. Palmaris longus**