Human Anatomy Vol 1

THORAX

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1 Each nerve passes below the neck of the rib of the
same number and enters the costal groove.

2 In the costal groove, the nerve lies below the poste-
rior intercostalvessels. The relationship of structures
in the costal groove from above downwards is
posterior intercostal vein, posterior intercostal artery
and intercostal nerve (VAN) (Fig. ru..
In the posterior part of the costal groove, the nerve
lies between the pleura, with the endothoracic fascia
and the internal intercostal membrane.
In the greater part of the space, the nerve lies between
the intercostalis intimi and the internal intercostal
muscle (Fig. la.a).

3 Near the sternum the nerve crosses in front of the
internal thoracic vessels and the sternocostalis
muscle. It then pierces the internal intercostal muscle,
the external intercostal membrane and the pectoralis
major muscle to terminate as the anterior cutaneous
nerve of the thorax.

Bronches

1. Numerous muscular branches supply the intercostal
   muscles, the transversus thoracis and the serratus
   posterior superior.

2 A collateral branch arises near the angle of the

rib and runs in the lower part of the space in the

same neurovascular plane. It supplies muscles of the

sPace.

3 The main branch and the collateral branch also

supply parietal pleura, periosteum of the ribs. The

lower nerves in addition supply the parietal

peritoneum.

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1 The lateral cutaneous branch arises near the angle

of the rib and accompanies the main trunk up to the

lateral thoracic wall where it pierces the intercostal

muscles and other muscles of the body wall along

the midaxillary line. It is distributed to the skin after

dividing into anterior and posterior branches.

2 The anterior cutaneous branch emerges on the side

of the sternum to supply the overlying skin after

dividing into medial and lateral branches.

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1 Each nerve is connected to a thoracic sympathetic

ganglionby a distally placed white and a proximally

placed grey ramus communicans (Fig. 14.3).

2 The lateral cutaneous branch of the second intercostal

nerve is known as the intercostobrachial neroe. II

supplies the skin of the floor of the axilla and of the

upper part of the medial side of the arm.

Dorsal primary ramus

Posterior division

Lateral cutaneous

branch

Anterior division

Sternocostalis

lntercostal nerve

External intercostal

lnternal intercostal

membrane

lnnermost intercostal

or intercostalis intimi

lnternal intercostal

lnternal thoracic vessels

Fig. 14.4: The course and branches of a typical intercostal nerve