Human Anatomy Vol 1

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INTRODUCTION

The thorax is covered by muscles of pectoral region of

upper limb. In addition, the intercostal muscles and

membranes fill up the gaps between adjacent ribs and

cartilages. These muscles provide integrity to the

thoracic wall. A right and left pair of thoracic nerves

fulfil the exact definition of the dermatome.

The posterior intercostal vein, posterior intercostal

artery and intercostal nerve (VAN) lie from above

downwards in the costal groove of the ribs.

Sympathetic part of autonomic nervous system starts

from the lateral horns of thoracic 1 to thoracic 12

segments of the spinal cord. It continues up to lumbar

2 segment.

Coveilngs of the lhorocic !l

The thoracic wall is covered from outside to inside by

the following structures-skin, superficial fascia, deep

fascia, and extrinsic muscles. The extrinsic muscles

covering the thorax are as follows.

1 Pectoralis major

2 Trapezius

3 Serratus anterior

4 Pectoralis minor

5 Latissimus dorsi

6 Levator scapulae

7 Rhomboid major

8 Rhomboid minor

9 Serratus posterior superior

10 Serratus posterior inferior

Muscles of the Ab men

1 Rectus abdominis.

2 External oblique.

Mus s of lhe Bock

Erector spinae (sacrospinalis).

In addition to the muscles listed above, a number of

other muscles of the abdomen and of the head and neck

are attached to the margins of the two apertures of the

thorax.

DISSECTION

Detach the serratus anterior and the pectoralis major

muscles from the upper ribs. Note the external

intercostal muscle in the second and third intercostal

spaces. lts fibres run anteroinferiorly. Follow it fonruards

to the external intercostal membrane which replaces it

between the costal cartilages.

Cut the external intercostal membrane and muscle

along the lower border of two spaces. Reflect them

upwards to expose the internal intercostal muscle. The

direction of its fibres is posteroinferior, at right angle to

that of external oblique.

Follow the lateral cutaneous branch of one intercostal

nerve to its trunk deep to internal intercostal muscle.

Trace the nerve and accompanying vessels round the

thoracic wall. Note their collateral branches lying along

the upper margin of the rib below. Trace the muscular

branches of the trunk of intercostal nerve and its

collateral branch. Trace the anterior cutaneous nerve

as well (Fig. 1a.3).

ldentify the deepest muscle in the intercostal space,

the innermost intercostal muscle (Table 14.1). This

muscle is deficient in the anterior and posterior ends of

the intercostal spaces, where the neurovascular bundle

rests directly on the parietal pleura.

Expose the internal thoracic artery 1 cm from the

lateral margin of sternum by carefully removing the