Muscles of the Upper Limb That Are Dissected with the Thorax
| Muscle | Origin | Insertion | Action | Innervation | Artery | Notes |
|---|---|---|---|---|---|---|
| pectoralis major | medial 1/2 of the clavicle, manubrium & body of sternum, costal cartilages of ribs 2-6, sometimes from the rectus sheath of the upper abdominal wall | crest of the greater tubercle of the humerus | flexes and adducts the arm, medially rotates the arm | medial and lateral pectoral nerves (C5-T1) | pectoral branch of the thoracoacromial trunk | the deep fascia on its anterior surface should not be fused to the fascia of the mammary gland - if it is, this is an important clinical sign indicating breast disease |
| pectoralis minor | ribs 3-5 | coracoid process of the scapula | draws the scapula forward, medialward, and downward | medial pectoral nerve (C8, T1) | pectoral branch of the thoracoacromial trunk | branches of medial pectoral nerve usually pierce pectoralis minor to reach the pectoralis major muscle |
Muscles of the Thoracic Region
| Muscle | Origin | Insertion | Action | Innervation | Artery | Notes |
|---|---|---|---|---|---|---|
| diaphragm | xiphoid process, costal margin, fascia over the quadratus lumborum and psoas major mm.(lateral & medial arcuate ligaments), vertebral bodies L1-L3 | central tendon of the diaphragm | pushes the abdominal viscera inferiorly, increasing the volume of the thoracic cavity (inspiration) | phrenic nerve (C3-C5) | musculophrenic a., superior phrenic a., inferior phrenic a. | left crus attaches to the L1-L2 vertebral bodies, the right crus attaches to the L1-L3 vertebral bodies |
| external intercostal | lower border of a rib within an intercostal space | upper border of the rib below, coursing, downward and medially | keeps the intercostal space from blowing out or sucking in during respiration | intercostal nerves (T1-T11) | intercostal a. | 11 in number; they extend from the tubercle of the rib to the costochondral junction; continuous with the external intercostal membrane anteriorly |
| innermost intercostal | upper borders of a rib | fibers course up and medially to insert on the inferior margin of the rib above | keeps the intercostal space from blowing out or sucking in during respiration | intercostal nerves (T1-T11) | intercostal a. | innermost intercostal mm. have the same fiber direction as the internal intercostal mm., the only difference being that they lie deep to the intercostal neurovascular bundle |
| internal intercostal | upper border of a rib | lower border of rib above, coursing up and medially | keeps the intercostal space from blowing out or sucking in during respiration | intercostal nerves (T1-T11) | intercostal a. | 11 in number; they extend from the margin of the sternum to the angle of the rib; continuous posteriorly with the internal intercostal membrane |
| levatores costarum | transverse processes C7-T11 | rib below its origin, medial to the angle | elevates the rib | dorsal primary rami of spinal nerves C7-T11 | deep cervical a., intercostal aa. | these are fairly small and insignificant muscles |
| subcostalis | angle of ribs | angle of a rib 2-3 ribs above origin | compresses the intercostal spaces | intercostal nerves | intercostal a. | subcostalis, transversus thoracis & innermost intercostal mm. make up the deepest intercostal muscle layer |
| transversus thoracis | posterior surface of the sternum | inner surfaces of costal cartilages 2-6 | compresses the thorax for forced expiration | intercostal nerves 2-6 | internal thoracic a. | transversus thoracis, subcostalis & innermost intercostal mm. make up the innermost intercostal muscle layer |