Anterior Scalenes Beneath the Skin, Gross Anatomy

Description

Running deep to the sternocleidomastoid, the anterior scalene is rendered in profile beneath semi-transparent skin, arising from the anterior tubercles of the transverse processes of C3 to C6 and descending inferolaterally to the scalene tubercle on the first rib. Its belly sits anterior to the middle scalene, forming the anterior boundary of the interscalene interval, while the cervical vertebrae and prevertebral fascia lie immediately medial and posterior. Superiorly, the muscle relates to the lateral base of the skull and mandible seen in the same lateral field; inferiorly, the first rib and upper thoracic cage anchor the line of pull. A small muscle with large consequences. Clinically, this relationship map matters because the subclavian artery and the trunks of the brachial plexus pass between anterior and middle scalene, and hypertrophy or spasm here is a common anatomic contributor to neurogenic thoracic outlet syndrome. The phrenic nerve typically descends on the anterior surface of anterior scalene, so needle placement for an interscalene brachial plexus block or anterior scalene trigger point injection risks hemidiaphragmatic paresis if the trajectory is too anterior or medial. The subclavian vein lies anterior to anterior scalene, a distinction that informs subclavian central venous access and helps explain why arterial puncture occurs when landmarks are misread. Use this lateral neck plate for teaching prevertebral compartment anatomy in gross anatomy, anesthesia, and regional block courses, and for figure support in surgical, pain medicine, or sports medicine content discussing thoracic outlet evaluation, scalene release, or rib-first relationships. It also serves well in patient-facing education where transparent skin clarifies why symptoms can radiate into the upper limb despite a cervical origin. Anatomical accuracy verified by SciePro's Medical Advisory Board.