UAMS Department of Neurobiology and Developmental Sciences - Muscles of the Thorax

Gross Anatomy


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 - Listed Alphabetically

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


Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

The content of these tables has been edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2009, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.
Unauthorized use is prohibited.




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