Muscles of the Anterior Trunk

functions/ attachments

Sternocleidomastoid – Major Action

Flexion of neck (bilateral); rotation of head to opposite side (unilateral)

Sternocleidomastoid – Attachments

Origin: Manubrium of sternum & medial clavicle → Insertion: Mastoid process of temporal bone

Pectoralis Major – Major Action

Flexion, adduction, and medial rotation of humerus at shoulder joint

Pectoralis Major – Attachments

Origin: Clavicle, sternum, costal cartilages of ribs 1–6 → Insertion: Intertubercular groove of humerus

Pectoralis Minor – Major Action

Protraction and downward rotation of scapula

Pectoralis Minor – Attachments

Origin: Ribs 3–5 (anterior surfaces) → Insertion: Coracoid process of scapula

Rectus Abdominis – Major Action

Flexion of vertebral column (trunk flexion)

External Oblique – Major Action

Trunk flexion (bilateral); rotation to opposite side (unilateral)

Internal Oblique – Major Action

Trunk flexion (bilateral); rotation to same side (unilateral)

Serratus Anterior – Major Action

Protraction and upward rotation of scapula

Transversus Abdominis – Major Action

Compression of abdominal contents

Trapezius – Major Action

Elevation, retraction, and upward rotation of scapula; extension of neck

Deltoid – Major Action

Abduction of humerus at shoulder joint

Deltoid – Attachments

Origin: Lateral clavicle, acromion, spine of scapula → Insertion: Deltoid tuberosity of humerus

Latissimus Dorsi – Major Action

Extension, adduction, and medial rotation of humerus at shoulder joint

Latissimus Dorsi – Attachments

Origin: Spinous processes T7–L5, thoracolumbar fascia, iliac crest, ribs 9–12 → Insertion: Intertubercular groove of humerus

Teres Major – Major Action

Extension, adduction, and medial rotation of humerus

Supraspinatus – Major Action

Abduction of humerus (first 15°)

Infraspinatus – Major Action

Lateral rotation of humerus

Subscapularis – Major Action

Medial rotation of humerus

Rhomboideus Major – Major Action

Retraction and downward rotation of scapula

Erector Spinae – Major Action

Extension and lateral flexion of vertebral colum

Linea Alba

Midline fibrous structure from xiphoid process to pubic symphysis; attachment for abdominal muscles

Tendinous Intersections

Transverse fibrous bands dividing rectus abdominis into visible segments (“six-pack”)

Thoracolumbar Fascia

Dense connective tissue sheath over deep back muscles; attachment for latissimus dorsi, internal oblique, and transversus abdominis