The cardiovascular system

Inferior sagittal

-....7':::Tracheasinus Left internal

jugular vein....-Right internal jugular veinSuperior

sagillalsinus ----/-">1'./

_

Right subclavian

vein

Left subclavlan vein

Flight brachio-cephalic

vein

---{Straightsinus ---+-.t---'r--r

...,"-+-+----- Left brachlo- cephalic vein

Superior-----f' vena cava

transversesinus

Left internal jugular vein

Figure 5.39 The superior vena cava and the veins which form it

Venous sinuses of the brain viewed from the right

Figure 5.37

bone. Inferiorly it continues as the internal jugular vein.The internal jugular veins begin at the jugular foramina

in the middle cranial fossa and each is the continuation of a sigmoid sinus. They run downwards in the neck behind

Superior sagittal sinusf<F-----:;> ,:.....,~"..:.,~

the sternocleidomastoid muscles. Behind the claviclethey unite with the subclavian veins, carrying blood fromthe upper limbs, to form the brachiocephalic veins.

The brachiocephalic veins are situated one on each side in the root of the neck. Each is formed by the union of the internal jugular and the subclavian veins. The left brachiocephalic vein is longer than the right and passes obliquely behind the manubrium of the sternum, where it joins the right brachiocephalic vein to form the superior vena cava (Fig. 5.39).

The superior vena cava, which drains all the venousblood from the head, neck and upper limbs, is about 7 cm long. It passes downwards along the right border of the sternum and ends in the right atrium of the heart.

101

Left transverse

sinus

Internal jugular veins

Righi transverse sinus

Venous sinuses of the brain viewed from above.

Figure 5.38

the skull to the occipital region where it turns to the rightside and continues as the right transverse sinus.

The inferior sagittal sinus lies deep within the brain and passes backwards to form the straight sinus.

Circulation of blood to the upper limbArterial supply

The subclavian arteries. The right subclavian artery arises from the brachiocephalic artery; the left branches from the arch of the aorta. They are slightly arched and pass behind the clavicles and over the first ribs before entering the axillae, where they continue as the axillary arteries (Fig. 5.40).

Before entering the axilla each subclavian arterygives off two branches: the vertebral artery, which passes

The straight sinus runs backwards and downwardsbecome the left transverse sinus.

The transverse sinuses begin in the occipital region. They run forward and medially in a curved groove of the skull, to become continuous with the sigmoid sinuses.

The sigmoid sinuses are a continuation of the transversesinuses. Each curves downwards and medially and lies in a groove in the mastoid process of the temporal bone. Anteriorly only a thin plate of bone separates the sinus from the air cells in the mastoid process of the temporal

to

brain, and the internal thoracicthe breast and a number of cavity.

upwards to supply theartery, which supplies structures in the thoracic