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
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Anatomy of the Muscles of the Thoracic Region
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