Venous Drainage of the Head and Neck
The veins of the head and neck collect deoxygenated blood and return it to the heart. Anatomically, the venous drainage can be divided into three parts:
- Venous drainage of the brain and meninges: Supplied by the dural venous sinuses.
- Venous drainage of the scalp and face: Drained by veins synonymous with the arteries of the face and scalp. These empty into the internal and external jugular veins.
- Venous drainage of the neck: Carried out by the anterior jugular veins.
In this article, we shall look at the veins mentioned above, their anatomical course, and any clinical correlations.
There are three main jugular veins – external, internal and anterior. They are ultimately responsible for the venous drainage of the whole head and neck.
External Jugular Vein
The external jugular vein and its tributaries supply the majority of the external face. It is formed by the union of two veins:
- Posterior auricular vein – drains the area of scalp superior and posterior to the outer ear.
- Retromandibular vein (posterior branch) – itself formed by the maxillary and superficial temporal veins, which drain the face.
These two veins combine immediately posterior to the angle of mandible, and inferior to the outer ear, forming the external jugular vein.
After formation, the external jugular vein descends down the neck within the superficial fascia. It runs anteriorly to the sternocleidomastoid muscle, crossing it in an oblique, posterior and inferior direction.
In the root of the neck, the vein passes underneath the clavicle, and terminates by draining into the subclavian vein. Along its route down the neck, the EJV receives tributary veins – posterior external jugular, transverse cervical and suprascapular veins.
Clinical Relevance: Severance of the External Jugular Vein
The external jugular vein has a relatively superficial course down the neck, leaving it vulnerable to damage.
If it is severed, in an injury such as a knife slash, its lumen is held open – this is due to the thick layer of investing fascia (for more information see Fascial Layers of the Neck). Air will be drawn into the vein, producing cyanosis, and can stop blood flow through the right atrium. This is a medical emergency, managed by the application of pressure to the wound – stopping the bleeding, and the entry of air.
Anterior Jugular Veins
The anterior jugular veins vary from person to person. They are paired veins, which drain the anterior aspect of the neck. Often they will communicate via a jugular venous arch. The anterior jugular veins descend down the midline of the neck, emptying into the subclavian vein.
Internal Jugular Vein
The internal jugular vein (IJV) begins in the cranial cavity, as a continuation of the sigmoid sinus (see dural venous sinuses below). The initial part of the IJV is dilated, and is known as the superior bulb. The vein exits the skull via the jugular foramen.
In the neck, the internal jugular vein descends within the carotid sheath, deep to the sternocleidomastoid, and lateral to the common carotid artery. At the bottom of the neck, posteriorly to the sternal end of the clavicle, the IVJ combines with the subclavian vein to form the brachiocephalic vein. Immediately before its termination, the inferior end of internal jugular vein dilates, to form the inferior bulb of the IJV. It has a valve that stops back-flow of blood.
During its descent down the neck, the internal jugular vein receives blood from the facial, lingual, occipital, superior and middle thyroid veins. These veins drain blood from the anterior face, trachea, thyroid, oesophagus, larynx, and muscles of the neck.
Clinical Relevance: Jugular Venous Pressure
In clinical practice, the internal jugular vein can be observed for pulsations – the nature of which provide an estimation of right atrial pressure.
When the heart contracts, a pressure wave passes upwards, which can be observed. There are no valves in the brachiocephalic or subclavian veins – so the pulsations are a fairly accurate indication of right atrial pressure
Dural Venous Sinuses
The dural venous sinuses are spaces between the periosteal and meningeal layers of dura mater, which are lined by endothelial cells. They collect venous blood from the veins that drain the brain and bony skull, and ultimately drain into the internal jugular vein.
Clinical Relevance: Cavernous Sinus
The cavernous sinuses are a clinically important pair of dural sinuses. They are located next to the lateral aspect of the body of the sphenoid bone. This sinus receives blood from the superior and inferior ophthalmic veins, the middle superficial cerebral veins, and from another dural venous sinus; the sphenoparietal sinus.
Located within the cavernous sinus is the internal carotid artery, which crosses the sinus. This allows for cooling of the arterial blood before it reaches the brain. Along with the internal carotid artery, the abducens (VI) nerve crosses the sinus. Several nerves are located within the lateral wall of each sinus; oculomotor (III), trochlear (IV), ophthalmic (V1) and maxillary (V2) nerves.
If the cavernous sinus becomes infected, these nerves are at risk of damage. The facial vein is connected to cavernous sinus via the superior ophthalmic vein. The facial vein is valveless – blood can reverse direction and flow from the facial vein to the cavernous sinus. This provides a potential pathway by which infection of the face can spread to the venous sinuses.