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Table 5-2. Actions of muscles which may restrict movement of the thoracic spine and ribs

MUSCLE	ACTION
Abdominals; external & internal obliąue	Move upper body with respect to pelvis and vice versa; tense abdominal wali; compress abdominal viscera.

iliocostalis thoracis    )

longissimus thoracis    ) Dorsal flex, laterally flex, rotate, and stabilize the    spine

spinalis thoracis    )

semispinalis thoracis    )

intertransversarii	Laterally flex and rotate spine to the same side.
interspinales	Dorsal flex spine.
rotatores	Dorsal flex and rotate spine to opposite side.
multifidi	Dorsal flex and rotate spine to opposite side.
diaphragma	Principal muscle of respiration; increases thoracic cavity volume.
scalenus anterior. medius	Raise lst rib; ventral flex and laterally flex to same side, rotate neck to opposite side.
scalenus posterior	Raises2nd rib; laterally flexes neck to same side.
subclavius	Depresses and stabilizes clavicle during movements of shoulder; lifts lst rib.
intercostales interni	Draw ribs together.
intercostales externi	Draw ribs together; elevate rib cage; increase thoracic cavity size.
sternocleidomastoideus	Ventral flexes, laterally flexes to same side, rotates cervical spine to opposite side, elevates chin.
levatores costarum	Raise ribs to increase thoracic capacity.
serratus posterior superior	Raises ribs in inspiration.
serratus posterior interior	Lowers ribs in expiration.
transversus abdominis	Supports and compresses abdominal viscera.
rectus abdominis	Flexes thoracic and lumbar spine; supports abdominal wali.
ąuadratus lumborum	Laterally flexes to the same side, aids forced expiration.
latissimus dorsi	Extends, adducts and medially rotates at shoulder; depresses shoulder girdle.
longus colli	Yentral flexes, laterally flexes and rotates to the same side.

96