Blood Vessels of the Neck

• Is a branch of the brachiocephalic trunk on the right but arises directly from the arch of the aorta on the left.
• Is divided into three parts by the anterior scalene muscle: the first part passes from the origin of the vessel to the medial margin of the anterior scalene; the second part lies behind this muscle; and the third part passes from the lateral margin of the muscle to the outer border of the first rib.
• Its branches include the following:

1) Vertebral artery

• Arises from the first part of the subclavian artery and ascends between the anterior scalene and longus colli muscles.
• Ascends through the transverse foramina of vertebrae C1 to C6, winds around the superior articular process of the atlas, and passes through the foramen magnum into the cranial cavity.

2) Thyrocervical trunk

• Is a short trunk from the first part of the subclavian artery that divides into the following arteries:

Inferior thyroid artery

• Ascends in front of the anterior scalene muscle, turns medially behind the carotid sheath but in front of the vertebral vessels, and then arches downward to the lower pole of the thyroid gland.
• Gives rise to an ascending cervical artery, which ascends on the anterior scalene muscle medial to the phrenic nerve.

Transverse cervical artery

• Runs laterally across the anterior scalene muscle, phrenic nerve, and trunks of the brachial plexus, passing deep to the trapezius.
• Divides into a superficial branch and a deep branch, which takes the place of the dorsal (descending) scapular artery. In the absence of the deep branch, the superficial branch is known as the superficial cervical artery.

Suprascapular artery

• Passes in front of the anterior scalene muscle and the brachial plexus parallel to but below the transverse cervical artery.
• Passes superior to the superior transverse scapular ligament, whereas the suprascapular nerve passes inferior to this ligament.

3) Internal thoracic artery

• Arises from the first part of the subclavian artery, descends through the thorax behind the upper six costal cartilages, and ends at the sixth intercostal space by dividing into the superior epigastric and musculophrenic arteries.

4) Costocervical trunk

• Arises from the posterior aspect of the second part of the subclavian artery behind the anterior scalene muscle and divides into the following arteries:

Deep cervical artery

• Passes between the transverse process of vertebra C7 and the neck of the first rib, ascends between the semispinalis capitis and semispinalis cervicis muscles, and anastomoses with the deep branch of the descending branch of the occipital artery.

Superior intercostal artery

• Descends behind the cervical pleura anterior to the necks of the first two ribs and gives rise to the first two posterior intercostal arteries.

5) Dorsal (descending) scapular artery

• Arises from the third part of the subclavian artery or arises as the deep (descending) branch of the transverse cervical artery.

• Have different origins on the right and left sides: the right common carotid artery , which begins at the bifurcation of the brachiocephalic artery, and the left common carotid artery , which arises from the aortic arch.
• Ascend within the carotid sheath and divide at the level of the upper border of the thyroid cartilage into the external and internal carotid arteries.

1) Receptors

Carotid body

• Lies at the bifurcation of the common carotid artery as an ovoid body.
• Is a chemoreceptor that is stimulated by chemical changes (e.g., lack of oxygen, excess of carbon dioxide, and increased hydrogen ion concentration) in the circulating blood that help control respiration.
• Is innervated by the nerve to the carotid body , which arises from the pharyngeal branch of the vagus nerve, and by the carotid sinus branch of the glossopharyngeal nerve.

Carotid sinus

• Is a spindle-shaped dilatation located at the origin of the internal carotid artery which functions as a pressoreceptor (baroreceptor) , that is stimulated by changes in blood pressure. When stimulated, it causes a slowing of the heart rate, vasodilation, and a decrease in blood pressure.
• Is innervated primarily by the carotid sinus branch of the glossopharyngeal nerve but is also innervated by the nerve to the carotid body of the vagus nerve.

2) Internal carotid artery

• Has no branches in the neck, ascends within the carotid sheath in company with the vagus nerve and the internal jugular vein, and enters the cranium through the carotid canal in the petrous part of the temporal bone.
• In the middle cranial fossa, gives rise to the ophthalmic artery and the anterior and middle cerebral arteries and participates in the formation of the circulus arteriosus (circle of Willis), which is an important polygonal anastomosis between four arteries: the two vetebrals and the two carotids. It is formed by the posterior cerebral, posterior communicating, internal carotid, anterior cerebral, and anterior communicating arteries.

3) External carotid artery

• Extends from the level of the upper border of the thyroid cartilage to the neck of the mandible, where it ends in the parotid gland by dividing into the maxillary and superficial temporal arteries.

Has eight named branches:

Superior thyroid artery

• Arises below the level of the greater horn of the hyoid bone.
• Descends obliquely forward in the carotid triangle and passes deep to the infrahyoid muscles to reach the superior pole of the thyroid gland.
• Gives rise to an infrahyoid, sternocleidomastoid, superior laryngeal, cricothyroid, and several glandular branches.

Lingual artery

• Arises at the level of the tip of the greater horn of the hyoid bone and passes deep to the hyoglossus to reach the tongue.
• Gives rise to suprahyoid, dorsal lingual, sublingual, and deep lingual branches.

Facial artery

• Arises just above the lingual artery and ascends forward, deep to the posterior belly of the digastric and stylohyoid muscles.
• Hooks around the lower border of the mandible at the anterior margin of the masseter to enter the face.

Ascending pharyngeal artery

• Arises from the deep surface of the external carotid artery in the carotid triangle and ascends between the internal carotid artery and the wall of the pharynx.
• Gives rise to pharyngeal, palatine, inferior tympanic, and meningeal branches.

Occipital artery

• Arises from the posterior surface of the external carotid artery, just above the level of the hyoid bone.
• Passes deep to the digastric posterior belly, occupies the groove on the mastoid process, and appears on the skin above the occipital triangle.
• Gives rise to the following:

1) Sternocleidomastoid branch

• Descends inferiorly and posteriorly over the hypoglossal nerve and enters the substance of the muscle.
• Anastomoses with the sternocleidomastoid branch of the superior thyroid artery.

2) Descending branch

• Its superficial branch anastomoses with the superficial branch of the transverse cervical artery.
• Its deep branch anastomoses with the deep cervical artery of the costocervical trunk.

Posterior auricular artery

• Arises from the posterior surface of the external carotid artery just above the digastric posterior belly.
• Ascends superficial to the styloid process and deep to the parotid gland and ends between the mastoid process and the external acoustic meatus.
• Gives rise to stylomastoid, auricular, and occipital branches.

Maxillary artery

• Arises behind the neck of the mandible as the larger terminal branch of the external carotid artery.
• Runs deep to the neck of the mandible and enters the infratemporal fossa.

Superficial temporal artery

• Arises behind the neck of the mandible as the smaller terminal branch of the external carotid artery.
• Gives rise to the transverse facial artery , which runs between the zygomatic arch above and the parotid duct below.
• Ascends in front of the external acoustic meatus into the scalp, accompanying the auriculotemporal nerve and the superficial temporal vein.