**Question:** A 22-year-old woman is admitted to the emergency department in an unconscious state. The nurse takes a radial pulse to determine the heart rate of the patient. This pulse is felt lateral to which tendon?

A. Flexor Pollicis Longus Tendon
B. Abductor Pollicis Longus Tendon
C. Flexor Digitorum Profundus Tendon
D. Flexor Digitorum Superficialis Tendon

**Correct Answer:** D. Flexor Digitorum Superficialis Tendon

**Core Concept:**
In the human body, the radial artery is a branch of the brachial artery. It runs adjacent to the posterior interosseous nerve and posterior interosseous artery, which are both found within the spiral canal formed by the interosseous membrane. The spiral canal is located lateral to the Flexor Digitorum Superficialis (FDS) tendon in the forearm.

**Why the Correct Answer is Right:**
The radial pulse is felt lateral to the Flexor Digitorum Superficialis (FDS) tendon because it lies adjacent to the radial artery, which is the site where the pulse is palpated to determine the heart rate in patients. Palpating the radial pulse allows clinicians to assess the heart rate and cardiovascular status of a patient.

**Why Each Wrong Option is Incorrect:**
A. Flexor Pollicis Longus Tendon: This tendon is located more medial than the radial artery and pulse.
B. Abductor Pollicis Longus Tendon: This tendon is also located more medial than the radial artery and pulse.
C. Flexor Digitorum Profundus Tendon: This tendon is located more medial than the radial artery and pulse.

**Clinical Pearl:**
Palpating the radial pulse is a vital clinical skill for assessing a patient's cardiovascular status. It is essential for determining the heart rate, assessing circulatory status, and detecting potential cardiovascular abnormalities, such as hypotension, hypertension, or arrhythmias.

**Why Each Wrong Option is Incorrect:**
A. Flexor Pollicis Longus Tendon: This tendon is located more medial than the radial artery and pulse.
B. Abductor Pollicis Longus Tendon: This tendon is also located more medial than the radial artery and pulse.
C. Flexor Digitorum Profundus Tendon: This tendon is located more medial than the radial artery and pulse.

**Why the Correct Answer is Right:**
D. Flexor Digitorum Superficialis Tendon: The FDS tendon is located more lateral to the radial artery and pulse, making it the correct option for palpating the radial pulse.