**Core Concept:** The lateral border of the tongue is a crucial anatomical landmark that can provide information about the underlying teeth. The presence of indentations or grooves on the tongue's lateral border is known as lingual grooves or fissures, and they are associated with the corresponding teeth.

**Why the Correct Answer is Right:** The correct answer, option D (fissured tongue), refers to the condition where the lateral border of the tongue has visible grooves or fissures. This condition is caused by the fusion defect between the primary and secondary germ layers during embryonic development, leading to the incomplete formation of papillae on the tongue surface. The fissured tongue is commonly associated with a normal dentition, and the fissures correspond to the teeth, providing information about the teeth present in the mouth.

**Why Each Wrong Option is Incorrect:**

A. Uvula (adenoids): The uvula is a small, pink, mucous membrane pendulum located at the posterior end of the soft palate and is unrelated to the lateral border of the tongue.

B. Tongue enlargement: Tongue enlargement refers to tongue hypertrophy, which is unrelated to the presence of lingual fissures.

C. Tongue ulcer: Tongue ulcer is a localised area of erosion, inflammation, or infection on the tongue, which is not related to the formation of lingual fissures.

D. Fissured tongue: This is the correct answer, as mentioned above, explaining the condition where the lateral border of the tongue has visible grooves or fissures, corresponding to teeth and providing information about the dentition.

**Clinical Pearl:** The presence of lingual fissures can serve as a clinical guide to identify the number and arrangement of teeth in patients with unknown dentition, especially in cases where the patient cannot effectively communicate their dental status. Additionally, the fissured tongue may be considered a variant of normal anatomy in the absence of any associated symptoms or complications.