MCQ – 1389

Which of the following structures is NOT located within the triangular interval between the medial border of Scalenus anterior and Longus colli muscles in the root of the neck?

Correct Answer » B Explanation

Anatomical Region Involved:

The triangular interval (also called the scalene triangle or the scalenovertebral triangle) is formed by the following boundaries:

• Medially: Longus colli muscle

• Laterally: Scalenus anterior muscle

• Base/Inferiorly: First part of the subclavian artery

This space lies at the root of the neck, just posterior to the clavicle and first rib, and contains several important structures that pass between the neck and thorax.

✦ Structures Found Within This Triangle:

• Sympathetic Trunk: Runs vertically along the prevertebral fascia, close to the Longus colli muscle – present

• Thoracic Duct: On the left side, it enters the venous angle (junction of internal jugular and subclavian veins) passing through this triangle – present

• Inferior Cervical Ganglion: Located near the transverse process of C7, close to the base of this triangle – present

Internal Carotid Artery:

• The internal carotid artery is a deep continuation of the common carotid artery.

• It lies medial and posterior to the sternocleidomastoid, and ascends within the carotid sheath in the anterior triangle of the neck.

• It does NOT pass through the scalenovertebral (triangular) interval at the root of the neck.
  Therefore, it is NOT located within this triangle.

Why Other Options are Incorrect:

• A. Sympathetic trunk – Present in the triangle, lies just anterior to Longus colli.

• C. Thoracic duct – Present on the left side, passes through the triangle to drain into venous angle.

• D. Inferior cervical ganglion – Present, usually near the base of the triangle near C7.