Blood Supply to the Head and Neck

• Most arteries in the anterior cervical triangle arise from the common carotid artery or one of the branches of the external carotid artery.
• Most veins in the anterior cervical triangle are tributaries of the large internal jugular vein.

The Common Carotid Arteries

• The right common carotid artery begins at the bifurcation of the brachiocephalic trunk, posterior to the right sternoclavicular joint.
• The left common carotid artery begins arises from the arch of the aorta and ascends into the neck, posterior to the left sternoclavicular joint.

• Each common carotid artery ascends into the neck within the carotid sheath to the level of the superior border of the thyroid cartilage.
• Here it terminates by dividing into the internal and external carotid arteries. 

The Internal Carotid Artery

• This is the direct continuation of the common carotid artery and it has no branches in the neck.
• It supplies structures inside the skull.
• The internal carotid arteries are two of the four main arteries that supply blood to the brain.

• Each artery arises from the common carotid at the level of the superior border of the thyroid cartilage.
• It then passes superiorly, almost in a vertical plane, to enter the carotid canal in the petrous part of the temporal bone.

• A plexus of sympathetic fibres accompany it.

• During its course through the neck, the internal carotid artery lies on the longus capitis muscle and the sympathetic trunk.
• The vagus nerve (CN X) lies posterolateral to it.

• The internal carotid artery enters the middle cranial fossa beside the dorsum sellae of the sphenoid bone.
• Within the cranial cavity, the internal carotid artery and its branches supply the hypophysis cerebri (pituitary gland), the orbit, and most of the supratentorial part of the brain. 

The External Carotid Arteries 

• This vessel begins at the bifurcation of the common carotid, at the level of the superior border of the thyroid cartilage.
• It supplies structures external to the skull.

• The external carotid artery runs posterosuperiorly to the region between the neck of the mandible and the lobule of the auricle.
• It terminates by dividing into two branches, the maxillary and superficial temporal arteries.
• The stems of most of the six branches of the external carotid artery are in the carotid triangle. 

The Superior Thyroid Artery

• This is the most inferior of the 3 anterior branches of the external carotid.
• It arises close to the origin of the vessel, just inferior to the greater horn of the hyoid.
• The superior thyroid artery runs anteroinferiorly, deep to the infrahyoid muscles and gives off the superior laryngeal artery. This artery pierces the thyrohyoid membrane in company with the internal laryngeal nerve and supplies the larynx.

The Lingual Artery

• This arises from the external carotid artery as it lies on the middle constrictor muscle of the pharynx.
• It arches superoanteriorly, about 5 mm superior to the tip of the greater horn of the hyoid bone, and then passes deep to the hypoglossal nerve, the stylohyoid muscle, and the posterior belly of digastric muscle.

• It disappears deep to the hyoglossus muscle.
• At the anterior border of this muscle, it turns superiorly and ends by becoming the deep lingual artery.

The Facial Artery

• This arises from the carotid artery either, in common with the lingual artery, or immediately superior to it.
• In the neck the facial artery gives off its important tonsillar branch and branches to the palate and submandibular gland.
• The facial artery then passes superiorly under the cover of the digastric and stylohyoid muscles and the angle of the mandible.

• It loops anteriorly and enters a deep groove in the submandibular gland.

• The facial artery hooks around the inferior border of the mandible and enters the face. Here the pulsation of this artery can be felt (anterior to the masseter muscle).

The Ascending Pharyngeal Artery

• This is the 1^st or 2^nd branch of the external carotid artery.
• This small vessel ascends on the pharynx, deep to the internal carotid artery.
• It sends branches to the pharynx, prevertebral muscles, middle ear and meninges.

The Occipital Artery

• This arises from the posterior surface of the external carotid near the level of the facial artery.
• It passes posteriorly along the inferior border of the posterior belly of digastric.
• It ends in the posterior part of the scalp.
• During its course, it is superficial to the internal carotid artery and three cranial nerves (CN IX, CN X and CN XI).

The Posterior Auricular Artery

• This is a small posterior branch of the external carotid artery.
• It arises from it at the superior border of the posterior belly of the digastric muscle.
• It ascends posteriorly to the external acoustic meatus and supplies adjacent muscles, the parotid gland, the facial nerve, structures in the temporal bone, the auricle, and the scalp. 

The Internal Jugular Vein

• This is usually the largest vein in the neck.
• The internal jugular vein drains blood from the brain and superficial parts of the face and neck.
• Its course corresponds to a line drawn from a point immediately inferior to the external acoustic meatus to the medial end of the clavicle.

• This large vein commences at the jugular foramen in the posterior cranial fossa, as the direct continuation of the sigmoid sinus.

• The dilation at its origin is called the superior bulb of the internal jugular vein.
• From here it runs inferiorly through the neck in the carotid sheath.

• The internal jugular vein leaves the anterior triangle of the neck by passing deep to the SCM muscle.
• Posterior to the sternal end of the clavicle, it unites with the subclavian vein to form the brachiocephalic vein.
• Near its termination is the inferior bulb of the jugular vein contains a bicuspid valve similar to that of the subclavian vein.

• The deep cervical lymph nodes lie along the course of the internal jugular vein, mostly lateral and posterior.

Tributaries of the Internal Jugular Vein

• This large vein is joined at its origin by the: inferior petrosal sinus, the facial, lingual, pharyngeal, superior and middle thyroid veins, and often the occipital vein.

The Lateral Wall of the Orbit

• This wall is thick, particularly its posterior part, which separates the orbit from the middle cranial fossa.
• The lateral wall is formed by the frontal process of the zygomatic bone and the greater wing of the sphenoid bone.

• Anteriorly, the lateral wall lies between the orbit and the temporal fossa.

• The lateral wall is partially separated from the roof by the superior orbital fissure.

The Articular Capsule

• The capsule of this joint is loose.
• The thin fibrous capsule is attached to the margins of the articular area on the temporal bone and around the neck of the mandible.

Nerve Supply of the Muscles of the Orbit (pp. 715-6)

• Three cranial nerves supply the muscles of the eyeball; the oculomotor (CN III), trochlear (CN IV) and abducent (CN IV) nerves.
• All three enter the orbit via the superior orbital fissure.

• The trochlear nerve supplies the superior oblique muscle.
• The abducent nerve supplies the lateral rectus muscle.
• The oculomotor nerve supplies everything else.

• A mnemonic that is used is this formula for this strange sulfate: SO₄(LR₆)₃

Muscles of the Tongue

• The tongue is divided into halves by a medial fibrous lingual septum that lies deep to the medial groove.
• In each half of the tongue there are four extrinsic and four intrinsic muscles.

• The lingual muscles are all supplied by the hypoglossal nerve (CN XII).
• The only exception is palatoglossus, which is supplied by the pharyngeal branch of the vagus nerve, via the pharyngeal plexus.

Extrinsic Muscles of the Tongue

The Genioglossus Muscle

• This is a bulky, fan-shaped muscle that contributes to most of the bulk of the tongue.

• It arises from a short tendon from the genial tubercle (mental spine) of the mandible.
• It fans out as it enters the tongue inferiorly and its fibres attach to the entire dorsum of the tongue.
• Its most inferior fibres insert into the body of the hyoid bone.

• The genioglossus muscle depresses the tongue and its posterior part protrudes it.

The Hyoglossus Muscle

• This is a thin, quadrilateral muscle.

• It arises from the body and greater horn of the hyoid bone and passes superoanteriorly to insert into the side and inferior aspect of the tongue.

• It depresses the tongue, pulling its sides inferiorly; it also aids in retrusion of the tongue.

The Styloglossus Muscle

• This small, short muscle arises from the anterior border of the styloid process near its tip and from the stylohyoid ligament.
• It passes inferoanteriorly to insert into the side and inferior aspect of the tongue.

• The styloglossus retrudes the tongue and curls its sides to create a trough during swallowing. 

The Palatopharyngeus Muscle

• Superior attachment: hard palate and palatine aponeurosis.
• Inferior attachment: lateral wall of pharynx.
• Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.

• This thin, flat muscle is covered with mucous membrane to form the palatopharyngeal arch.
• It passes posteroinferiorly in this arch.

• This muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing. 

Intrinsic Muscles of the Tongue

The Superior Longitudinal Muscle of the Tongue

• The muscle forms a thin layer deep to the mucous membrane on the dorsum of the tongue, running from its tip to its root.
• It arises from the submucosal fibrous layer and the lingual septum and inserts mainly into the mucous membrane.

• This muscle curls the tip and sides of the tongue superiorly, making the dorsum of the tongue concave.

The Inferior Longitudinal Muscle of the Tongue

• This muscle consists of a narrow band close to the inferior surface of the tongue.
• It extends from the tip to the root of the tongue.
• Some of its fibres attach to the hyoid bone.

• This muscle curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.

The Transverse Muscle of the Tongue

• This muscle lies deep to the superior longitudinal muscle.
• It arises from the fibrous lingual septum and runs lateral to its right and left margins.
• Its fibres are inserted into the submucosal fibrous tissue.

• The transverse muscle narrows and increases the height of the tongue.

The Vertical Muscle of the Tongue

• This muscle runs inferolaterally from the dorsum of the tongue.
• It flattens and broadens the tongue.
• Acting with the transverse muscle, it increases the length of the tongue.

The Meatus of the Nose

Sphenopalatine Recess

• This space is posterosuperior to the superior concha.
• The sphenoidal sinus opens into this recess.

Superior Meatus

• This is a narrow passageway between the superior and middle nasal conchae.
• The posterior ethmoidal sinuses open into it by one or more orifices.

Middle Meatus

• This is longer and wider than the superior one.

• The anterosuperior part of this meatus lead into a funnel-shaped opening, called the infundibulum, through which the frontonasal duct leads to the frontal sinus.
• There is one duct for each frontal sinus and since there may be several, there may be several frontonasal ducts.

• When the middle concha is removed, rounded elevation called the ethmoidal bulla (L. bubble), is visible
• The middle ethmoidal air cells open on the surface of the ethmoidal bulla.

• Inferior to this bulla is a semicircular groove called the hiatus semilunaris.
• The frontal sinus opens into this hiatus anterosuperiorly.
• Near the hiatus are the openings of the anterior ethmoid air cells.
• The maxillary sinus also opens into the middle meatus.

Inferior Meatus

• This is a horizontal passage, inferolateral to the inferior nasal concha.
• The nasolacrimal duct opens into the anterior part of this meatus.
• Usually, the orifice of this duct is wide and circular.