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The common carotid artery
foramen spinosum. Inside the skull it passes laterally and then
Arises from the brachiocephalic artery on the right and from the arch of
ascends on the squamous temporal bone in a deep groove, which it
the aorta on the left (Chapter 4). Each common carotid passes up the
shares with the corresponding vein. The anterior branch passes
neck in the carotid sheath (Fig. 61.1), along with the internal jugular • The middle meningeal arteryaruns upwards to pass through the
vein and the vagus nerve. At the level of the upper border of the thyroid upwards and backwards towards the vertex and the posterior branch
cartilage it divides into internal and external carotid arteries. There are passes backwards. It supplies the dura mater and the bones of the
no branches. cranium. After head injuries it may bleed to produce a subdural
haemorrhage, the symptoms of which may be delayed for some time
The external carotid artery (Fig. 59.1) after the injury.
Ascends in the neck a little in front of the internal carotid to divide into • Branches which accompany the branches of the maxillary nerve in
its two terminal branches, the maxillary and superficial temporal arter- the pterygopalatine fossa and have the same names.
ies, in the substance of the parotid gland.
Branches: The internal carotid artery (Figs 59.2 and 59.3)
• The superior thyroid artery: runs downwards on the side of the At its origin from the common carotid artery it is enlarged to form the
pharynx before passing forwards to the upper pole of the thyroid gland carotid sinus, a slight dilatation which has baroreceptors supplied by
where it divides into two branches. The upper branch follows the upper the glossopharyngeal nerve in its wall. Associated with this is the
border of the gland towards the isthmus and the lower passes down the carotid body, a chemoreceptor supplied by the same nerve. The inter-
posterior border to anastomose with the inferior thyroid artery. There nal carotid has no branches in the neck. It enters the cranial cavity via
are a number of branches to the larynx. the carotid canal in the petrous temporal bone, accompanied by a sym-
• The lingual artery: arises at the level of the tip of the greater horn of pathetic plexus. Within the skull it passes forwards in the cavernous
the hyoid and loops upwards for a short distance before running for- sinus and then turns backwards behind the anterior clinoid process to
ward deep to hyoglossus to enter and supply the tongue. It gives a num- break up into its three terminal branches.
ber of dorsal lingual arteries. The upward loop of the lingual is crossed Branches:
by the hypoglossal nerve. • The ophthalmic artery: enters the orbit through the superior orbital
• The facial artery: travels forwards, deep to the mandible where it is fissure and follows the nasociliary nerve. It gives the important central
embedded in the back of the submandibular gland. It then curls round retinal artery which enters the optic nerve and supplies the retina. This
the lower border of the mandible to reach the face. Here it follows a tor- is an end-artery so that occlusion causes immediate blindness. Other
tuous course at the side of the mouth and lateral to the nose to reach the branches are described on p. 155.
medial angle of the eye where it anastomoses with branches of the oph- • The anterior cerebral artery: winds round the genu of the corpus
thalmic artery. It gives off a tonsillar branch in the neck, superior and callosum and supplies the front and medial surfaces of the cerebral
inferior labial branches and nasal branches. The facial arteries anasto- hemisphere. It anastomoses with its fellow of the opposite side.
mose very freely across the midline and with other arteries on the face. • The middle cerebral artery: traverses the lateral sulcus on the lat-
• The occipital artery: passes backwards, medial to the mastoid pro- eral surface of the hemisphere and supplies the hemisphere (including
cess, and supplies the back of the scalp. the main motor and sensory areas) as well as giving the striate arteries
• The superficial temporal artery: emerges from the parotid gland which supply deep structures including the internal capsule.
and runs up in front of the ear where its pulsations may be felt. It is dis- • The posterior communicating artery: a small artery which passes
tributed to the side of the scalp and the forehead. backwards to join the posterior cerebral artery, a terminal branch of
• The maxillary artery: emerges from the parotid gland and passes the vertebral artery.
deep to the neck of the mandible. It ends by entering the pterygopala- These arteries and the communications between them form the
tine fossa through the pterygomaxillary fissure. Its principal branches Circle of Willis so that there is (usually) free communication between
are to the local muscles including the deep temporal arteries to tem- the branches of the two internal carotid arteries across the midline.
poralis and: There is, however, considerable variation in the arrangement of the
• The inferior alveolar arteryaenters the mandibular canal to supply circle.
the teeth.

The arteries I 133