7C - Muscles of the superficial back + pectoral region

External Intercostals

O: inferior border of rib above

In: superior border of rib below

A: contraction creates inhalation by elevating ribs; relaxation depresses the ribs resulting in exhalation

I: intercostal nerves

Internal Intercostals

O: superior border of rib below

In: inferior border of rib above

A: contraction draws adjacent ribs together during forced exhalation

I: intercostal nerves

External Oblique

O: inferior 8 ribs

In: iliac crest and linea alba

A: Together: compress abdomen and flex vertebral column; Singly: laterally flex vertebral column to the same side and rotate to the opposite side

I: intercostal nerves

Internal Oblique

O: iliac crest, inguinal ligament, and thoracolumbar fascia

In: cartilage of last four ribs and linea alba

A: Together: compress abdomen and flex vertebral column; Singly: laterally flex and rotate vertebral column to the same side

I: intercostal nerves

Transverse Abdominis

O: iliac crest, inguinal ligament, lumbar fascia, and cartilages of inferior six ribs

In: xiphoid process, linea alba, and pubis

A: compress abdomen

I: intercostal nerves

Rectus Abdominis

O: pubic crest and pubic symphysis

In: cartilage of 5th-7th ribs and xiphoid process

A: flexes trunk and compresses abdomen

I: intercostal nerves

Quadratus Lumborum

O: iliolumbar ligament and iliac crest

In: inferior border of 12th rib and transverse processes of L1-L4

A: Together: stabilize rib 12 during respiration; assist with lumbar extension; Singly: laterally flex vertebral column

I: T12 thoracic nerve and nerves of L1-L3

Diaphragm

O: xiphoid process, cartilage of the lower 6 ribs, and lumbar vertebrae

In: central tendon

A: 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)

I: phrenic nerve

Trapezius

O: superior nuchal line of occipital bone, ligamentum nuchae, and spines of C7 and T1-T12

In: Clavicle, acromion, and spine of scapula

A: Upper trap: elevate scapula, upwardly rotate the scapula and extend head; Middle trap: retract scapula; Lower trap: depress scapula and upwardly rotate the scapula

I: spinal accessory nerve

Latissimus Dorsi

O: spines of T7-T12 and L1-L5, sacrum and ilium, inferior 4 ribs

In: bicipital groove

A: extends, adducts, and internally rotates the arm at the shoulder joint; draws arm inferiorly and posteriorly

I: thoracodorsal nerve

Rhomboid Major

O: spines of T2-T5

In: medial border of scapula inferior to spine

A: elevation, retraction, and downward rotation of the scapula

I: dorsal scapular nerve

Rhomboid Minor

O: spines of C7-T1

In: medial border of scapula superior to spine

A: elevation, retraction, and downward rotation of the scapula

I: dorsal scapular nerve

Levator Scapulae

O: transverse processes of C1-C4

In: superior medial border of scapula

A: elevation and downward rotation of the inferior angle of scapula

I: dorsal scapular nerve

Pectoralis Major

O: clavicle, sternum, and costal cartilages of ribs 2-6

In: greater tuberosity and bicipital groove

A: shoulder adduction and internal rotation and assists with flexion

I: medial and lateral pectoral nerves

Pectoralis Minor

O: ribs 3-5

In: coracoid process

A: scapular protraction and downward rotation

I: medial pectoral nerve

Serratus Anterior

O: superior 9 ribs

In: anterior (costal) surface of the medial border of the scapula

A: protraction and upward rotation of the scapula

I: long thoracic nerve