Head and Neck Anatomy: Arteries of Carotid Triangle

Common Carotid Artery

The right common carotid artery is a branch of the brachiocephalic artery.
It begins in the neck behind the right sternoclavicular joint.
It begins in the neck behind the right sternoclavicular joint.
The left common carotid artery is branch of the arch of the aorta.
It begins in the thorax in front of the trachea opposite a point a little to the left of the centre of the manubrium.
It ascends to the back of left sternoclavicular joint and enters the neck.

In the neck, both arteries have a similar course. Each artery runs upwards within the carotid sheath, under cover of the anterior border of the sternocleidomastoid.
It lies in front of the lower four cervical transverse processes.
At the level of the upper border of the thyroid cartilage, the artery ends by dividing into the external and internal carotid arteries
It lies in front of the lower four cervical transverse processes.
At the level of the upper border of the thyroid cartilage, the artery ends by dividing into the external and internal carotid arteries

Carotid Sinus

The termination of the common carotid artery, or the beginning of the internal carotid artery shows a slight dilatation, known as the carotid sinus.
In this region, the tunica media is thin,
but the adventitia is relatively thick and receives a rich innervation from the glossopharyngeal and sympathetic nerves.
The carotid sinus acts as a baroreceptor of pressure receptor and regulates blood pressure

Carotid Body

Carotid body is a small, oval reddish brown structure
situated behind the bifurcation of the common carotid artery.
It receives a rich nerve supply mainly from the glossopharyngeal nerve, but also from the vagus and sympathetic nerves.
It acts as a chemoreceptor and responds to changes in the oxygen, carbon dioxide and pH content of the blood.
Other allied chemoreceptors are found near the arch of the aorta, the ductus arteriosus, and the right subclavian artery. These are supplied by the vagus nerve.

Clinical Anatomy

The carotid sinus is richly supplied by nerves.
In some persons, the sinus may be hypersensitive. In such persons, sudden rotation of the head may cause slowing of heart. This condition is called as "carotid sinus syndrome".
The supraventricular tachycardia may be controlled by carotid sinus massage/ due to inhibitory effects of vagus nerve on the heart.
The necktie should not be tied tightly, as it may compress both the internal carotid arteries, supplying the brain.
The supraventricular tachycardia may be controlled by carotid sinus massage/ due to inhibitory effects of vagus nerve on the heart.
The necktie should not be tied tightly, as it may compress both the internal carotid arteries, supplying the brain.

External Carotid Artery

Course & Relations

The external carotid artery begins in the carotid triangle at the level of the upper border of the thyroid cartilage opposite the disc between the third and fourth cervical vertebrae.
It runs upwards and slightly backwards and laterally, and terminates behind the neck of the mandible by dividing into the maxillary and superficial temporal arteries.
The external carotid artery has a slightly curved course, so that it is anteromedial to the internal carotid artery in its lower part, and anterolateral to the internal carotid artery in its upper part.
ln the carotid triangle, the external carotid artery is comparatively superficial, and lies under cover of the anterior border of the sternocleidomastoid.
The artery is crossed superficially by the cervical branch of the facial nerve, the hypoglossal nerve, and the facial, lingual and superior thyroid veins.
The artery is crossed superficially by the cervical branch of the facial nerve, the hypoglossal nerve, and the facial, lingual and superior thyroid veins.

Deep to the artery, there are:
a. The wall of the pharynx.
b. The superior laryngeal nerve which divides into the external and internal laryngeal nerves.
c. The ascending pharyngeal artery

Above the carotid triangle, the external carotid artery lies deep in the substance of the parotid gland. Within the gland, it is related superficially to the retromandibular vein and the facial nerve

Deep to the external carotid artery, there are:
a. The internal carotid artery.
b. Structures passing between the external and internal carotid arteries; these being styloglossus, stylopharyngeus, IX nerve, pharyngeal branch of X, and styloid process.
c. Two structures deep to the internal carotid artery, namely the superior laryngeal nerve and the superior cervical sympathetic ganglion

Branches

The external carotid artery gives off eight branches which may be grouped as follows.
Anterior

1. Superior thyroid

2. Lingual
3. Facial
Posterior
1. Occipital
2. Posterior auricular.

Medial

1. Ascending pharyngeal

Terminal

1. Maxillary
2. Superficial temporal

Superior Thyroid Artery

arises from the external carotid artery just below the level of the greater cornua of the hyoid bone. runs downwards and forwards parallel and just superficial to the external laryngeal nerve.

passes deep to the three long infrahyoid muscles to

reach the upper pole of the lateral lobe of the thyroid gland.
relationship to the external laryngeal nerve, which supplies the cricothyroid muscle is important to the surgeon during thyroid surgery.
The artery and nerve are close to each other higher up, but diverge slightly near the gland.
To avoid injury to the nerve, the superior thyroid artery is ligated as near the gland as possible
Apart from its terminal branches to the thyroid gland, it gives one important branch, the superior laryngeal artery which pierces the thyrohyoid membrane in company with the internal laryngeal nerve
The superior thyroid artery also gives a sternocleidomastoid branch to that muscle and a cricothyroid branch that anastomoses with the artery of the opposite side in front of the cricovocal membrane.

Lingual Artery

arises from the external carotid artery opposite the tip of the greater cornua of the hyoid bone.
It is tortuous in its course.
Its course is divided into three parts by the hyoglossusmuscle.
The first part lies in the carotid triangle.
It forms a characteristic upward loop which is crossed by the hypoglossal nerve.

The lingual loop permits free movements of the hyoid bone.
The second part lies deep to the hyoglossus along the upper border of hyoid bone.
It is superficial to the middle constrictor of the pharynx.
The third part is called the arteria profunda linguae, or the deep lingual artery.
It runs upwards along the anterior border of the hyoglossus, and then hoizontally forwards on the undersurface of the tongue as the fourth part.
In its vertical course, it lies between the genioglossus medially and the inferior longitudinal muscle of the tongue laterally.
The horizontal part of the artery is accompanied by the lingual nerve.
During surgical removal of the tongue, the first part of the artery is ligated before it gives any branch to the tongue or to the tonsil.

Facial Artery:

arises from the external carotid just above the tip of the greater cornua of the hyoid bone.
It runs upwards first in the neck as cervical part and then on the face as facial part. The course of the artery in both places is tortuous.
The tortuosity in the neck allows free movements of the pharynx during deglutition. On the face, it allows free movements of the mandible, the lips and the cheek during mastication and during various facial expressions.
The artery escapes traction and pressure during these movements.
The tortuosity in the neck allows free movements of the pharynx during deglutition. On the face, it allows free movements of the mandible, the lips and the cheek during mastication and during various facial expressions.
The artery escapes traction and pressure during these movements.
The cervical part of the facial artery runs upwards on the superior constrictor of pharynx deep to the posterior belly of the digastric, with the stylohyoid and to the ramus of the mandible.
It grooves the posterior border of the submandibular salivary gland.
Next the artery makes an S-bend (two loops) first winding down over the submandibular gland, and then up over the base of the mandible
The facial part of the facial artery enters the face at anteroinferior angle of masseter muscle, runs upwards close to angle of mouth, side of nose till medial angle of eye.

The cervical part of the facial artery gives off

1. ascending palatine,
2. tonsillar,
3. submental, and

4. glandular branches for the submandibular salivary gland and lymph nodes.

The ascending palatine artery arises near the origin of the facial artery. It passes upwards between the styloglossus and the stylopharyngeus, crosses over the upper border of the superior constrictor and supplies the tonsil and the root of the tongue.
The submental branch is a large artery which accompanies the mylohyoid nerve, and supplies the submental triangle and the sublingual salivary gland

The facial part

It enters the face by winding around the base of the mandible, and by piercing the deep cervical fascia, at the anteroinferior angle of the masseter muscle.
It can be palpated here and is called ‘anaesthetist's artery'.
First it runs upwards and forwards to a point 1.25 cm lateral to the angle of the mouth.
Then it ascends by the side of the nose up to the medial angle of the eye, where it terminates by supplying the lacrimal sac; and by anastomosing with the dorsal nasal branch of the ophthalmic artery.
The facial artery is very tortuous.
The tortuosity of the artery prevents its walls from being unduly stretched during movements of the mandible, the lips and the cheeks.
It lies between the superficial and deep muscles of the face.

Branches

The anterior branches on the face are large and named.
They are:

1. lnferior labial, to the lower lip.
2. Superior labial, to the upper lip and the anteroinferior part of the nasal septum.
3. Lateral nasal, to the ala and dorsum of the nose.

The posterior branches are small and unnamed.

Anastomoses
1. The large anterior branches anastomose with similar branches of the opposite side and with the mental artery. In the lips, anastomoses are large, so that cut arteries spurt from both ends
2. Small posterior branches anastomose with the transverse facial and infraorbital arteries.
3. At the medial angle of the eye, terminal branches of the facial artery anastomose with branches of the ophthalmic artery. This is, therefore, a site for anastomoses between the branches of the external and internal carotid arteries

Occipital Artery

The occipital artery arises from the posterior aspect of the external carotid artery, opposite the origin of the facial artery
It is crossed at its origin by the hypoglossal nerve.
In the carotid triangle, the artery gives two sternocleidomastoid branches.
The upper branch accompanies the accessorynerve, and the lower branch arises near the origin of the occipital artery

Posterior Auricular Artery

The posterior auricular artery arises from the posterior aspect of the external carotid just above the posterior belly of the digastric.
It runs upwards and backwards deep to the parotid gland, but superficial to the styloid process.
It crosses the base of the mastoid process, and ascends behind the auricle.
It supplies the back of the auricle, the skin over the mastoid process, and over the back of the scalp.
It is cut in incisions for mastoid operations.
Its stylomastoid branch enters the stylomastoid foramen, and supplies the middle ear, the mastoid antrum and air cells, the semicircular canals, and the facial nerve.

Ascending Pharyngeal Artery

This is a small branch that arises from the medial side of the external carotid artery.
It arises very close to the lower end of external carotid artery.
It runs vertically upwards between the side wall of the pharynx, and the tonsil, medial wall of the middle ear and, the auditory tube.
It sends meningeal branches into the cranial cavity through the foramen lacerum, the jugular foramen and the hypoglossal canal

Maxillary Artery

This is the larger terminal branch of the external carotid artery.
It begins behind the neck of the mandible under cover of the parotid gland.
It runs forwards deep to the neck of the mandible below the auriculotemporal nerve, and enters the infratemporal fossa

Superficial Temporal Artery

1. It is the smaller terminal branch of the extemal carotid artery.
It begins, behind the neck of the mandible under cover of the parotid gland.

2. It runs vertically upwards, crossing the root of the zygoma or preauricular point, where its pulsations can be easily felt.
About 5 cm above the zygoma, it divides into anterior and posterior branches which supply the temple and scalp.

The anterior branch anastomoses with the supraorbital and supratrochlear branches of the ophthalmic artery.
3. In addition to the branches which supply the temple, the scalp, the parotid gland, the auricle and the facial muscles,

the superficial temporal artery gives off a transverse facial artery, and a middle temporal artery which runs on the temporal fossa deep to the temporalis muscle