Human Anatomy Vol 1

Below thefirst costal cartilage the artery runs vertically
downwards up to its termination in the 6th intercostal
space. Its relations are as follows.

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1 Pectoralis major.
2 Upper six costal cartilages.
3 External intercostal membranes.
4 Internal intercostal muscles.
5 The first six intercostal nerves.

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The endothoracic fascia and pleura up to the second or
third costal cartilage. Below this level the stemocostalis
muscle separates the artery from the pleura (Fig.1.a.l2).

Bronches
1 The pericardiacophrenic artery arises in the root of the
neck and accompanies the phrenic nerve to reach the
diaphragm. It supplies the pericardium and the
pleura.
2 The mediastinal arteries are small irregular branches
that supply the thymus, in front of the pericardium,
and the fat in the mediastinum.
3 Two anterior intercostal arteries are given to each of
the upper six intercostal spaces.
4 The perforating branches accompany the anterior
cutaneous nerves. In the female, the perforating
branches in the second, third and fourth spaces are
large and supply the breast.
5 The superior epigastric arteryruns downwardsbehind
the seventh costal cartilage and enters the rectus
sheath by passing between the stemal and costal slips
of the diaphragm.
5 The musculophrenic artery runs downwards and
laterallybehind the seventh, eighth, and ninth costal
cartilages. It gives two anterior intercostal branches
to each of these three spaces. It perforates the
diaphragm near the 9th costal cartilage and termi-
nates by anastomosing with other arteries on the
undersurface of the diaphragm.

WALL OF THORAX

Note that through its various branches the internal

thoracic artery supplies the anterior thoracic and

abdominal walls from the clavicle to the umbilicus.

AZYGOS VEIN

The azygos vein drains the thoracic wall and the upper

lumbar region (Figs 14.10 and 20.5b and c). It forms an

important channel connecting the superior and inferior

venae cavae. The term 'azygos'means unpaired. The

vein occupies the upper part of the posterior abdominal

wall and the posterior mediastinum. It also connects

portal venous system and caval venous system.

Formolion

The azygos vein is formed by union of the lumbar

azygos, right subcostal and right ascending lumbar

veins.

1 The lumbar azygos vein may be regarded as the

abdominal part of the azygos vein. It lies to the right

of the lumbar vertebrae. Its lower end communicates

with the inferior vena cava.

2 The right subcostal vein accompanies the corres-

ponding artery.

3 The ascending lumbar vein is formed by vertical

anastomoses that connect the lumbar veins. The

azygos vein is formed by union of the right subcostal

and ascending lumbar veins..

Course

1 The azygos vein enters the thorax by passing

through the aortic opening of the diaphragm.

2 The azy1os vein then ascends up to fourth thoracic

vertebra where it arches forwards over the root of

the right lung and ends by joining the posterior

aspect of the superior vena cava just before the latter

pierces the pericardium (see Fig. 15.1).

Relotions

Anteriorly : Oesophagus.

Posteriorly:

L Lower eight thoracic vertebrae.

2 Right posterior intercostal arteries.

Sternocostalis

Fig. 14.12: Transverse section through the anterior thoracic wall to show the relations of the internal thoracic vessels. ln the lower

part of their course, the vessels are separated from the pleura by the sternocostalis muscle

Pleura