Anatomy - Left carotid bifurcation eversion endarterectomy (EEA) in symptomatic carotid bifurcation stenosis

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Common carotid artery

Origin	Left: aortic arch Right: brachiocephalic trunk
Course	Ascends posteriad to the sternocleidomastoid muscle Within the carotid sheath
Division	Carotid bifurcation: divides into internal and external carotid artery
Distribution	1. Internal carotid artery Brain Eye Forehead Anterior nasal cavity 2. External carotid artery Extracranial structures of the head and neck

Internal carotid artery

Origin

Branch of the common carotid artery (carotid bifurcation)

Caudocephalad course

1. Cervical part

Segment between origin of common carotid artery and base of skull
Enters the skull via the carotid canal
Does not give rise to any branches

2. Petrous part

Courses in the petrous portion of the temporal bone
Minor branches to the tympanic cavity and pterygoid canal

3. Cerebral part

Courses in the subarachnoid space
Passes through the dura mater
Divides into anterior and middle cerebral artery
Anterior cerebral artery communicates via the anterior communicating artery with the contralateral anterior cerebral artery

The arterial vascular ring at the base of the brain supplying it with blood is known as the cerebral arterial circle (of Willis). From anterior to posterior, it comprises the following vessels:

Anterior communicating artery (unpaired)
Anterior cerebral artery (left and right)
Internal carotid artery (left and right) and its direct continuation, the middle cerebral artery
Posterior communicating artery (left and right)
Posterior cerebral artery (left and right, both arising from the basilar artery).

However, the circle of Willis has numerous variations both in branch caliber and anastomoses (hypoplasia of individual branches or even agenesis of subsegments). This is clinically relevant for collateral blood supply in stenosis.

External carotid artery

The areas supplied by the external carotid artery can be divided into four groups depending on their location: anterior, middle and posterior group and the terminal branches.

1. Anterior group

Branches (cranial -→ caudal)	Branches	Area supplied
Thyroid artery	Infrahyoid branch Cricothyreoid branch Sternocleidomastoid branch	Homonymous muscles
	Superior laryngeal artery	Inner larynx
	Glandular branches	Thyroid gland
Lingual artery	Suprahyoid branch	Hyoid bone
	Dorsal lingual branches	Dorsum of tongue
	Sublingual artery	Sublingual gland
	Deep lingual artery	Tip of tongue
Facial artery	Ascending palatine artery	Soft palate Tonsils Pharynx
	Submental artery	Submandibular gland Suprahyoid muscles
	Inferior labial artery	Lower lip
	Superior labial artery	Upper lip
	Angular artery	Medial canthus

2. Middle group

Branches (cranial -→ caudal)	Branches	Area supplied
Ascending pharyngeal artery	Pharyngeal branches	Pharynx
	Inferior tympanic artery	Tympanic cavity
	Posterior meningeal artery	Dura mater

3. Posterior group

Branches (cranial -→ caudal)	Branches	Area supplied
Occipital artery	Mastoid branch	Mastoid cells
	Occipital branches	Occipital region
	Meningeal branch	Dura mater
Posterior auricular artery	Auricular branch	External ear
	Occipital branch	Occipital region
	Stylomastoid artery	Facial nerve Tympanic cavity Mastoid cells
	Posterior tympanic arteries	Tympanic cavity Mastoid cells
	Pharyngeal branches	Pharynx
	Parotid branch	Parotid gland
Parotid branch	Parotid gland

4. Terminal branches

Branches (cranial -→ caudal)			Area supplied
Superficial temporal artery	Transverse facial artery		Face
	Zygomatico-orbital artery		Lateral canthus
	Middle temporal artery		Temporalis muscle
	Frontal branch		Scalp
Maxillary artery	Mandibular part	Deep auricular artery	Temporomandibular joint External acoustic meatus
		Anterior tympanic artery	Tympanic cavity
		Inferior alveolar artery	Teeth Mandibula Mylohyoid branch: floor of mouth Mental branch: chin
		Middle meningeal artery	Meninges
	Pterygoid part	Masseteric artery	Masseter muscle
		Pterygoid branches	Pterygoid muscles
		Deep temporal arteries	Temporalis muscle
		Buccal artery	Buccinator muscle
	Pterygopalatine part	Posterior superior alveolar artery	Teeth Maxilla
		Infraorbital artery	Maxilla
		Descending palatine artery	Tonsils Soft palate
		Sphenopalatine artery	Nasal cavity Nasal septum
		Artery of pterygoid canal	Pharynx Tympanic cavity

Venous systems

The superficial and deep venous systems join in the venous (Pirogoff) angulus to become the brachiocephalic vein, which drains into the superior vena cava

1. Superficial veins

External jugular vein

Courses in lateral neck and is roofed by the platysma
Passes through the superficial lamina of the cervical fascia
Unites with the internal jugular vein at the venous angle, possibly even before, which empties into the superior vena cava

Anterior jugular vein

Mostly runs anterior to the sternocleidomastoid muscle
The bilateral anterior jugular veins usually link up in the suprasternal space through the jugular venous arch
Empties into the venous angle or external jugular vein

2. Deep veins

Internal jugular vein

See below

Subclavian vein

Continuation of axillary vein
Courses anterior to anterior scalene muscle
Unites with the internal jugular vein at the venous angle to form the brachiocephalic vein → superior vena cava

Internal jugular vein

Origin	Arises extracranially from the confluence of the sigmoid sinus and inferior petrosal sinus Originates as superior bulb of jugular vein Leaves the base of the skull in the jugular foramen
Course	Parallels the common carotid artery within the carotid sheath Unites with the subclavian vein at the venous angle to form the brachiocephalic vein
Tributaries (cranial -→ caudal)	Superior ophthalmic vein Facial vein Retromandibular vein Pterygoid plexus Pharyngeal veins Lingual vein Superior and middle thyroid vein Sternocleidomastoid vein
Drainage	Entire brain Face Thyroid gland

Lymphatic vessels
The lymphatic vessels draining the head and neck empty into the paired jugular trunks.
Left jugular trunk
- Drainage: left side of head and neck
- Junction: thoracic duct
Right jugular trunk
- Drainage: right side of head and neck
- Junction: right lymphatic duct

Nervous system

1. Cervical plexus -predominantly motor innervation

Nerve	Segments	Course/Special aspects	Motor innervation	Sensory innervation
Ansa cervicalis	Superior root: C1, C2 Inferior root: C2, C3	Superior root parallel with hypoglossal nerve	Geniohyoid muscle Infrahyoid muscles	Ø
Phrenic nerve	C3 - C5	Courses on the anterior scalene muscle In the mediastinum between mediastinal pleura and pericardium to diaphragm	Diaphragm	Pericardiac branch: Pericardium Mediastinal pleura Diaphragmatic pleura Phrenicoabdominal branches: Peritoneum Inferior aspect of diaphragm Gallbladder
Sternocleidomastoid branch	C1 - C3	Forms plexus with branches of the acessory nerve (XII)	Sternocleidomastoid muscle (together with XII)	Ø
R. trapezius	C2 - C4		Trapezius muscle (together with XII)	Ø

2. Cervical plexus - strictly sensory innervation

Nerve	Segments	Course, Special aspects	Innervation
Lesser occipital nerve	C2, C3	Courses posteriorly to the sternocleidomastoid muscle	Lateral occiput
Great auricular nerve	C2, C3	Crosses anterior to the sternocleidomastoid muscle	Skin below auricle
Transverse cervical nerve	C2, C3	Crosses anterior to the sternocleidomastoid muscle Superior branch: anastomosis with cervical branch of facial nerve	Anterior cervical region
Supraclavicular nerves	C3, C4	Fanning out toward clavicle	Clavicle Upper chest Shoulder

3. Sympathetic nervous system

Sympathetic ganglion	Special aspects	Nerve branches, innervation
Superior cervical ganglion	Level C2/C3 Branches mostly parallel the arteries	Jugular nerve → glossopharyngeal nerve and vagus nerve Internal carotid nerve → deep petrosal nerve External carotid nerves → salivary glands Laryngopharyngeal branches → pharyngeal plexus Superior cervical cardiac nerve→ cardiac plexus Fibers to epiphysis
Middle cervical ganglion	Varied location, not always present	Middle cervical cardiac nerve→ cardiac plexus
Inferior cervical ganglion	often fused with 1st ganglion of thoracic trunk to form the cervicothoracic (stellate) ganglion	Inferior cervical cardiac nerve→ cardiac plexus Vertebral nerve → sympathetic fibers to cranial nerves Ansa subclavia → loop interconnecting inferior and middle cervical ganglion when fused to cervicothoracic ganglion → sympathetic fibers to sweat glands and skin vessels of upper limb

Anatomy - Left carotid bifurcation eversion endarterectomy (EEA) in symptomatic carotid bifurcation stenosis – Vascular Surgery