Human Anatomy Vol 1

lnternal intercostal

muscle

Collateral branch of

intercostal nerve

External intercostal

muscle

Fig. 14.2: Section through intercostal space showing neuro-
vascular bundle and their collateral branches

2 The fibres of the internal intercostal run downwards,
backwards and laterall/, i.e. at right angle to those
of the external intercostal.

3 The fibres of the transversus thoracis run in the same
direction as those of the intemal intercostal:

f\le Sapply

All intercostal muscles are supplied by the intercostal
nerves of the spaces in which they lie.

WALL OF THORAX

Actions of lhe lnlercoslal fuluscfes

The main action of the intercostal museles is to

prevent intercostal spaces being drawn in during

inspiration and bulging outwards during expiration.

The external intercostals, interchondral portions of

the internal intercostals, and the levator costae may

elevate the ribs during inspiration.

The intemal intercostals except for the interehondral

portions and the transversus thoraeis may depress

the ribs or cartilages during expiration.

lnlercostol Nerves

The intercostal nerves are the anterior primary rami of

thoracic one to thoracic eleven (Fig. 143) spinal nerves

after the dorsal primary ramus has been given off. The

anterior primary ramus of the twelfth thoracie nerve

forms the strbcostal nerve. In adclition to supplying the

intercostal spaces, the upper two intercostal nerves also

supply the upper limb. The lower five intercostal

nerves, seventh to eleventh thoracic nerves also supplv

abdominal wall. These are, therefore, said tobe thoraco-

abdominnl nerues. The remaining nerves; third to sixth

supply only the thoracic wall; they are called typical

intercostal neraes.

The subcostnl nerae is distributed to the abdominal

wall and to the skin of the buttock.

U

Intercostal nerve runs in the costal groove and encls

near the sternum.

Costal pleura

Rib

Posterior

intereostal vessels

lntercostal nerve

lntercostalis intimi

Collateral branches of

posterior intercostal vessels

Dorsal root ganglion

Lateral branch

Dorsal ramus

Pleural branch

Lateral cutaneous branch

Muscular branch

Periosteal branch

Medial branch

Transverse section of

spinal cord

Trunk

Ventral ramus (intercostal nerve)

Grey ramus communicans

Sympathetic ganglion

Fig. 14.3: Typical thoracic spinal nerve

Anterior cutaneous braneh