Atlas of Human Anatomy by Netter

[Plate 181, Costovertebral Joints]

page 101

page 102

These muscles are arranged in three layers.
External intercostal muscles:
Have fibers that slope down and medially.
Extend from the posterior tubercle of the rib to the junction of the rib and its costal cartilage anteriorly.
Anteriorly, are replaced by external intercostal membranes that extend from the costochondral junctions to the sternum.
Internal intercostal muscles:
Lie internal to the external intercostal muscles
Their fibers lie at right angles to those of the external intercostal muscles and run inferiorly and laterally.
Anteriorly extend to the lateral border of the sternum.
Posteriorly extend only to the angles of the ribs; medial to the angles, are replaced by the internal intercostal membranes.
Innermost intercostal muscles
Lie deep to the internal intercostal muscles
Are separated from the internal intercostals by the intercostal vessels and nerves
Occupy the middle parts of the intercostal spaces
Connect inner surfaces of adjacent ribs
All intercostal muscles are supplied by intercostal nerves corresponding in number to their intercostal space.
Main action of the intercostals is to maintain the space between the ribs during inspiration and expiration.
Other muscles of the rib cage
Subcostal muscles-internal to the internal intercostals, cross from the angle of one rib to internal surface of the rib 1 to 2 spaces
below.
Transversus thoracis-4 to 5 slips of muscle that attach to the xiphoid process and inferior sternum and pass superiorly and laterally
to attach to the 2nd through 6th costal cartilages.

Muscle Superior

Attachment

(Origin)

Inferior

Attachment

(Insertion)

InnervationBlood Supply Main Actions

External

intercostal

Inferior border

of rib

Superior border

of rib below

Intercostal

nerve

Aorta, posterior intercostals and their collaterals,

costocervical trunk, anterior intercostals of internal

thoracic and musculophrenic arteries

Elevate ribs

Internal Inferior border Superior borderIntercostalAnterior intercostals, posterior intercostals, Elevate ribs (upper