Deep Back & Anterior Thorax

External Intercostals Origin

Inferior border of rib above

External Intercostals Insertion

Superior border of rib below

External Intercostals Action

Contraction creates inhalation by elevating ribs; relaxation depresses the ribs resulting in exhalation

External Intercostals Innervation

Intercostal nerves

Internal Intercostals Origin

Superior border of rib below

Internal Intercostals Insertion

Inferior border of rib above

Internal Intercostals Action

Contraction draws adjacent ribs together during forced exhalation

Internal Intercostals Innervation

Intercostal nerves

External Oblique Origin

Inferior 8 ribs

External Oblique Insertion

Iliac crest and linea alba

External Oblique Action

Together: Compress abdomen and flex vertebral column

Singly: Laterally flex and rotate vertebral column to the opposite side

External Oblique Innervation

Intercostal Nerves

Internal Oblique Origin

Iliac crest, inguinal ligament, and thoracolumbar fascia

Internal Oblique Insertion

Cartilage of last four ribs and linea alba

Internal Oblique Action

Together: Compress abdomen and flex vertebral column

Singly: Laterally flex and rotate vertebral column to the same side

Internal Oblique Innervation

Intercostal Nerves

Transverse Abdominus Origin

Iliac crest, inguinal ligament, lumbar fascia, and cartilages of inferior six ribs

Transverse Abdominus Insertion

Xiphoid process, linea alba, and pubis

Transverse Abdominus Action

Compress abdomen

Transverse Abdominus Innervation

Intercostal Nerves

Rectus Abdominus Origin

Pubic crest and pubic symphysis

Rectus Abdominus Insertion

Cartilage of 5th-7th ribs and xiphoid process

Rectus Abdominus Action

Flexes trunk and compresses abdomen

Rectus Abdominus Innervation

Intercostal Nerves

Quadratus Lumborum Origin

Iliolumbar ligament and iliac crest

Quadratus Lumborum Insertion

Inferior border of 12th rib and transverse processes of L1-L4

Quadratus Lumborum Action

Together: Pull the ribs inferior during forces exhalation, Extend vertebral column

Singly: Laterally flex vertebral column

Quadratus Lumborum Innervation

T12 thoracic nerve and nerves of L1-L3

Diaphragm Origin

Xiphoid process, cartilage of the lower 6 ribs, and lumbar vertebrae

Diaphragm Insertion

Central tendon

Diaphragm Action

Contraction causes it to flatten and increase vertical dimension of thoracic cavity (inhalation); Relaxation causes it to move superiorly and decrease the vertical dimension of thoracic cavity (exhalation)

Diaphragm Innervation

Phrenic Nerve

Trapezius Origin

Superior nuchal line of occipital bone, ligamentum nuchae, and spines of C7 and T1–T12

Trapezius Insertion

Clavicle, acromion, and spine of scapula

Trapezius Action

Upper trap: Elevate scapula, upwardly rotate the scapula and extend head

Middle trap: Retract scapula

Lower trap: Depress scapula and upwardly rotate the scapula

Trapezius Innervation

Spinal accessory nerve

Latissimus Dorsi Origin

Spines of T7–T12 and L1–L5, sacrum and ilium, inferior 4 ribs

Latissimus Dorsi Insertion

Bicipital groove

Latissimus Dorsi Action

Extends, adducts, and internally rotates the arm at the shoulder joint; draws arm inferiorly and posteriorly

Latissimus Dorsi Innervation

Thoracodorsal nerve

Rhomboid Major Origin

Spines of T2–T5

Rhomboid Major Insertion

Medial border of scapula inferior to spine

Rhomboid Major Action

Elevation, retraction and downward rotation of the scapula

Rhomboid Major Innervation

Dorsal scapular nerve

Rhomboid Minor Origin

Spines of C7–T1

Rhomboid Minor Insertion

Medial border of scapula superior to spine

Rhomboid Minor Action

Elevation, retraction and downward rotation of the scapula

Rhomboid Minor Innervation

Dorsal scapular nerve

Levator Scapulae Origin

Transverse processes of C1–C4

Levator Scapulae Insertion

Superior medial border of scapula

Levator Scapulae Action

Elevation and downward rotation of the inferior angle of scapula

Levator Scapulae Innervation

Dorsal scapular nerve

Pectoralis Major Origin

Clavicle, sternum, and costal cartilages of ribs 2–6

Pectoralis Major Insertion

Greater tuberosity and bicipital groove

Pectoralis Major Action

Shoulder adduction and internal rotation and assists with flexion

Pectoralis Major Innervation

Medial and lateral pectoral nerves

Pectoralis Minor Origin

Ribs 2-5

Pectoralis Minor Insertion

Coracoid process

Pectoralis Minor Action

Scapular protraction and downward rotation

Pectoralis Minor Innervation

Medial pectoral nerve

Serratus Anterior Origin

Superior 9 ribs

Serratus Anterior Insertion

Medial border of scapula

Serratus Anterior Action

Protraction and upward rotation of the scapula

Serratus Anterior Innervation

Long thoracic nerve