**Question:** Pre-auricular sulcus is seen in?

A. Eustachian tube
B. Parotid salivary gland
C. Temporal bone
D. Auricle

**Core Concept:**

The pre-auricular sulcus is a prominent groove found on the anterior surface of the temporal bone, located superior to the tragus and inferior to the facial nerve canal. It is a key landmark in various clinical and radiological examinations, as it represents the course of the facial nerve (CN VII) and the Eustachian tube.

**Why the Correct Answer is Right:**

The correct answer is D, auricle (also known as the pinna). The pre-auricular sulcus is part of the anatomy of the auricle and temporal bone. It is located on the anterior surface of the temporal bone and marks the course of the facial nerve and the Eustachian tube.

**Why Each Wrong Option is Incorrect:**

A) Eustachian tube (option A) is a part of the middle ear, connecting the tympanic cavity with the pharynx. It is not related to the pre-auricular sulcus.

B) Parotid salivary gland (option B) is located inferior to the facial nerve canal and does not form a sulcus on the temporal bone.

C) Temporal bone (option C) is the bony structure that houses the middle ear and inner ear, but it does not contain the pre-auricular sulcus.

**Clinical Pearl:**

The pre-auricular sulcus is a crucial landmark for assessing the integrity of the Eustachian tube and the facial nerve during clinical examinations, as well as interpreting radiological images. Understanding the anatomy of the pre-auricular sulcus helps in making a proper clinical diagnosis and treatment decisions regarding ear and facial nerve disorders.