Muscular System

Description

Posterior trunk musculature is organized from the cervical region through the lumbar spine, with the trapezius spanning from the external occipital protuberance and nuchal ligament inferiorly to the scapular spine and acromion. Lateral to the vertebral column, the deltoid caps the glenohumeral region while the infraspinatus occupies the infraspinous fossa deep to the scapular spine, blending laterally toward the greater tubercle via the rotator cuff tendon. Inferiorly, the latissimus dorsi sweeps superolaterally from the thoracolumbar fascia and iliac crest toward the intertubercular sulcus of the humerus, with the erector spinae group running longitudinally in paired columns immediately adjacent to the spinous processes. Posterior brachium detail includes the triceps brachii, positioned proximal to the elbow and posterior to the humerus. A posterior view like this matters because it frames how scapular position and thoracolumbar posture are controlled by the interplay between trapezius, latissimus dorsi, and the spinal extensors, and it makes the line of pull easy to teach without relying on cross sections. Rotator cuff dysfunction often presents as altered scapulothoracic rhythm, and appreciating the infraspinatus in relation to the posterior deltoid helps explain external rotation weakness and posterior shoulder pain patterns. Small asymmetries are common. This is also the anatomic backdrop for common injection and surgical corridors, including a posterior deltoid approach to the shoulder and midline posterior exposure over the paraspinal muscles. Use this illustration in myology and kinesiology courses, posture and gait modules in physical therapy curricula, and figures for textbooks or patient education explaining rotator cuff pathology, scapular dyskinesis, or paraspinal strain. It also reads well in orthopedic and sports medicine slide decks where you need a clean posterior map of muscle bellies, fiber direction, and regional relationships. Anatomical accuracy verified by SciePro's Medical Advisory Board.