a) Arteries

Common Carotid Artery

Right Common Carotid Artery

The right common carotid artery is one of the terminal divisions of the brachiocephalic artery. It begins behind the sternoclavicular joint and passes superiorly and laterally, on an oblique line from the sternoclavicular joint to the lateral aspect of the thyroid cartilage.

Left Common Carotid Artery

The left common carotid arises as the second branch of the arch of aorta. It ascends within the thorax and passes behind the sternoclavicular joint. It then follows a similar path to the right common carotid.

Relations of the Common Carotids

Within the neck, the carotid is enclosed in the carotid fascia with the internal jugular vein laterally and the vagus nerve posteriorly.
The trachea, oesophagus, recurrrent laryngeal nerve, thyroid gland, pharynx and larynx lie medial to the common carotid. The thyroid may pass a little anterior to the vessel. Below the cricoid cartilage, the carotid is deep to the skin, platysma, sternocleidomastoid and the strap muscles of the neck (sternothyroid etc). Above this level, it is only covered by the skin, platysma and strap muscles. Posteriorly, the artery is separated from the transverse processes of the cervical spine by the longus colli and longus capitis, with the sympathetic ganglia lying anterior to the muscles and posterior to the sheath.

Branches of the Common Carotids

The common carotid has no regular branches. It divides at the superior extent of the thyroid cartilage into the internal and external carotid arteries.

Vertebral Artery

The paired vertebral arteries arise from the subclavian vein. They initially pass posteriorly and superiorly, and then ascend through the foramina present in the cervical transverse processes from C6 to C1. After passing through the C1 transverse foramen, it travels posterior and medial to enter the posterior cranial fossa via the foramen magnum. Within the posterior cranial fossa, it lies anteriorly to the medulla and then unites with the contralateral artery to form the basilar artery at the level of the pons.

Relations of the vertebral artery

In its most inferior course, it lies posterior to the common carotid, thoracic duct/right lymphatic duct and the vertebral vein. The transverse process of C7 lies posteriorly.

Branches of the vertebral artery

The vertebral artery provides spinal branches for the spinal cord and meninges. It also contributes to the supply of the posterior neck muscles.

Thyrocervical trunk

The thyrocervical trunk is a short vessel that arises from the subclavian artery just before it passes behind scalenus anterior. It divides into three vessels, two of which supply the neck.

Inferior thyroid artery

The paired inferior thyroid arteries are important for the supply of the thyroid gland, larynx and inferior pharynx. It passes medially to enter the substance of the thyroid gland, usually posterior to the recurrent laryngeal nerve. It lies between the vertebral artery and the carotid sheath. Pharyngeal branches supply the laryngopharynx. The inferior laryngeal branch accompanies the recurrent laryngeal nerve to the inferior larynx. An ascending cervical branch passes superiorly in front of the transverse processes of the cervical spine, supplying the anterior spinal muscles.

Superficial cervical artery

The superficial cervical artery passes posteriorly across the posterior triangle to the anterior border of trapezius.

Costocervical trunk

The costocervical trunk gives rise to the deep cervical artery, which passes between the transverse processes of C7 and T1 before curving superiorly and passing between the deep muscles of the neck, which it supplies.

External Carotid Artery

Internal Carotid Artery