Anterior Trunk and Neck

Muscle	Origin	Insertion	Action
Scalenus anterior	Transverse process of C3-C6	Suuperior surface of first rib	Unilateral: flexes and rotates cervical spine to opposite side; Bilateral: flexes neck; raises first rib
Scalenus medius	Transverse process of C2-C7	Superior surface of first rib behind subclavian groove	Unilatera: Lateral flexion; rotates cervical spine in opposite direction; Bilateral: flexes neck; raises first rib
Scalenus posterior	Transverse process of C4-c6	Outer surface of second rib	unilateral: lateral flexion; rotates cervical in opposite direction; Bilateral: flexes neck; raises second rib
Sternocleidomastoid	Sternal head:anterior part of manubrium; Clavicular head: medial 1/3 of clavicle	lateral surface of mastoid process; lateral half of occipital bone	Unilateral: head towards shoulder (lateral flexion?); Bilateral: flexes head
Rectus Abdominis	pubic crest and symphysis pubis	Costal cartilage of fifth and seventh rib; side of xiphoid process	Flexion and lateral flexion of trunk: supports organs anteriorly; anterior support for lumbar spine; prevents anterior tilting of pelvis with aid of glutes and hamstrings decreasing lordosis
external abdominal oblique	External surfaces and inferior borders of 5-12th ribs	Linea alba; anterior half of iliac crest	Unilateral: rotates trunk to opposite side, lateral flexion; Bilateral: flexes trunk; anterior support to spine; anterior stabilization of pelvis decreasing lordosis; forces expiration
Internal abdominal oblique (anterior)	anterior 1/3 of medial iliac crest	Crest of pubis; linea alba	Unilateral: rotates trunk to same side, lateral flexion of trunk; Bilateral: flexes vertebrae; supports and compresses abdominals; forced expiration
Internal abdominal oblique (lateral)	Medial 1/3 of iliac crest	Inferior borders of 10-12th ribs	Unilateral: moves thorax and pelvis laterall, rotation of trunk on fixed pelvis towards side of contraction; Bilateral: flexes trunk on pelvis