Muscles of the Thorax and Abdomen
Muscles Of The Posterior Abdominal Wall
Muscle: Psoas major
Origin: Sides of T12-L5 vertebra and disk; transverse processes
Insertion: Lesser trochanter of femur
Nerve: Anterior rami of L1, L2, and L3
Action: Flexes and rotates thigh laterally at hip; flexes lumbar vertebrae anteriorly and laterally
Muscle: Psoas minor
Origin: Sides of T12-L1 vertebra and intervertebral disk
Insertion: Pectineal line, iliopectineal eminence via iliopectineal arch
Nerve: Anterior rami of L1, L2
Action: Works conjointly with psoas major to flex thigh at hip; stabilizes joint
Muscle: Quadratus lumborum
Origin: Medial half of inferior border of 12th rib and tips of lumbar transverse processes
Insertion: Iliolumbar ligament and internal tip of iliac crest
Nerve: Ventral branches of T12, L1-L4
Action: Extends, laterally flexes vertebral column; flexes 12th rib during inspiration
Superficial Muscles Of The Back
Muscle: Erector spinae
Origin: Arises by a broad tendon from posterior part of iliac crest, posterior surface of sacrum, sacral and inferior lumbar spinous processes and supraspinous ligament
Insertion: Iliocostal - lumborum, thoracis and cervicis; Longissimus - thoracis, cervicis and capitis; spinalis: thoracis, cervicis and capitis
Nerve: Posterior rami of spinal nerves
Action: Extend vertebral column and head
Muscle: Interspinales
Origin: Superior surface of spinous processes of cervical and lumbar vertebrae
Insertion: Inferior surface of spinous process of vertebrae superior to vertebrae of origin
Nerve: Posterior rami of spinal nerves
Action: Assist in extension and rotation of vertebral column
Muscle: Intertransversarii
Origin: Transverse process of cervical and lumbar vertebrae
Insertion: Transverse process of adjacent vertebrae
Nerve: Posterior and anterior rami of spinal nerves
Action: Assists in lateral bending of vertebral column; stabilizes vertebral column
Muscle: Latissimus dorsi
Origin: Spines of T5-T12
Insertion: Floor of bicipital groove
Nerve: Thoracodorsal
Action: Adducts, extends, and rotates arm medially
Muscle: Levator scapulae
Origin: Transverse process of C1-C4
Insertion: Superior part of medial border of scapula
Nerve: Dorsal scapular C5; cervical C3-C4
Action: Elevates scapula
Muscle: Rhomboid major
Origin: Spines of T2-T5
Insertion: Medial border of scapula
Nerve: Dorsal scapular, C4, C5
Action: Adducts scapula
Muscle: Rhomboid minor
Origin: Spines of C7-T1
Insertion: Root of spine of scapula
Nerve: Dorsal scapular, C4, C5
Action: Adducts scapula
Muscle: Serratus anterior
Origin: External surface of lateral parts of 1-8 ribs
Insertion: Anterior surface of medial border of scapula
Nerve: Long thoracic nerve, C5, C6, C7
Action: Protracts and rotates scapula
Muscle: Serratus posterior inferior
Origin: Spinal processes of T11 to L2 vertebrae
Insertion: Inferior border of 8th-12th ribs near their angles
Nerve: Anterior thoracic spinal 9-12
Action: Depresses ribs
Muscle: Serratus posterior superior
Origin: Ligamentus nuchae, supraspinal ligament and spines of C7-T3
Insertion: Superior borders of 2nd-4th ribs
Nerve: Intercostal, 2-5
Action: Elevates ribs
Muscle: Transversospinal
Origin: Transverse process of C4-T12 vertebrae; multifidus arises from sacrum, ilium, transverse process of T1-T3 and articular process of C4-C7
Insertion: Thoracis, cervicis, and capitis
Nerve: Spinal, posterior rami
Action: Extends and rotates vertebral column; stabilizes vertebrae during movement
Muscle: Trapezius
Origin: External occipital protuberance, superior nuchal line, ligamentum nuchae, spines of C7-T12
Insertion: Lateral third of clavicle, acromion, and spine of scapula
Nerve: Spinal accessory, C3-C4
Action: Adducts, rotates, elevates, and depresses scapula
Prevertebral Muscles: Lateral Vertebral
Muscle: Anterior scalene
Origin: Transverse process of C4-C6 vertebrae
Insertion: First rib
Nerve: Cervical, C4, C5, C6
Action: Elevates first rib; laterally flexes and rotates neck
Muscle: Middle scalene
Origin: Posterior tubercles of transverse processes of C4-C5 vertebrae
Insertion: Superior surface of first rib, posterior groove for subclavian artery
Nerve: Cervical spine, anterior rami
Action: Elevates first rib during forced inspiration; flexes neck laterally
Muscle: Posterior scalene
Origin: Posterior tubercles of transverse processes of C4-C5 vertebrae
Insertion: External border of second rib
Nerve: Anterior rami of cervical spine, C7, C8
Action: Elevates second rib during forced inspiration; flexes neck laterally
Prevertebral Muscles: Anterior Vertebral
Muscle: Longus capitis
Origin: Anterior tubercles of C3-C6
Insertion: Basilar part of occipital bone
Nerve: Spinal, anterior rami, C1-C3
Action: Flexes or twists neck anteriorly
Muscle: Longus colli
Origin: Anterior tubercle of C2 vertebra; bodies of C1-C3 and transverse processes of C3-C6 vertebrae
Insertion: Bodies of C5-T3 vertebrae, transverse processes of C3-C5 vertebrae
Nerve: Spinal, anterior rami, C2-C6
Action: Flexes and rotates head to opposite side
Muscle: Rectus capitis anterior
Origin: Anterior surface of lateral mass of atlas, C1
Insertion: Base of skull, anterior to occipital condyle
Nerve: C1 and C2
Action: Flexes head
Muscle: Rectus capitis lateralis
Origin: Transverse processes of C1
Insertion: Jugular process of occipital bone
Nerve: C1 and C2
Action: Flexes head; helps stabilize head
Muscle: Rectus capitis posterior
Origin: Spinous processes of C2 vertebra
Insertion: Middle of inferior nuchal line of occipital bone
Nerve: Suboccipital
Action: Extends head
Muscle: Splenius capitis
Origin: Inferior half of ligamentum nuchae, spinous processes of C7-T3 of T4 vertebrae
Insertion: Splenius capitis - superolaterally to mastoid process of temporal bone, lateral third of superior nuchal line of occipital bone; Splenius cervicis - posterior tubercles of transverse C1-C3 or C4 vertebrae
Nerve: Dorsal primary rami, C2-C6
Action: Rotates head and extends neck