Dalley, 10th Edition

125

Muscles of Back

2

Rectus abdominis

Erector spinae Multifidus Semispinalis thoracis

Psoas major

Gluteus maximus

(A) Flexion (starting from extended position)

(B) Neutral

(C) Extension (starting from flexed position)

(A–C) Lateral views

Splenius *

Sternocleidomastoid *

Sternocleidomastoid

Rhomboids

Splenius

Serratus anterior

Transversospinalis

External oblique (anterior part)

Internal and external obliques (lateral part) Quadratus lumborum Gluteus medius * Gluteus maximus *

Iliocostalis and longissimus

External oblique

Internal oblique

Internal oblique (anterior part) Adductor longus *

*

Lower limb muscles involved in overall movement but do not produce movement at IV joints.

(D) Posterior view, lateral flexion

(E) Right posterolateral view, rotation

(Muscles shown contract to bend to opposite [left] side)

(Muscles shown contract to rotate to the left)

FIGURE 2.39. Principal muscles producing movements of thoracic and lumbar intervertebral joints. Copyright © 2027 Wolters Kluwer. Unauthorized reproduction of the article is prohibited.

TABLE 2.9. PRINCIPAL MUSCLES PRODUCING MOVEMENTS OF THORACIC AND LUMBAR INTERVERTEBRAL (IV) JOINTS Flexion Extension Lateral Bending Rotation

Bilateral action of

Bilateral action of Erector spinae Multi dus Semispinalis thoracis

Unilateral action of Iliocostalis thoracis and lumborum Longissimus thoracis Multi dus External and internal oblique Quadratus lumborum Rhomboids Serratus anterior

Unilateral action of Rotatores Multi dus Iliocostalis Longissimus External oblique acting synchronously with opposite internal oblique Splenius thoracis

Rectus abdominis Psoas major Gravity