Blood Supply - Venous Drainage of Head and Neck

Venous Drainage of the Head and Neck

• Venous drainage starts from the head and neck and moves down, unlike the arterial supply.
• Focus will be on drainage point moving backwards.

Superior Vena Cava

• The endpoint where all the head and neck blood drains.
• Blood flows into the right atrium, then the right ventricle, and subsequently to the lungs for oxygenation.

Tributaries of Superior Vena Cava

• There are main tributaries which drain into the superior vena cava
• Right and left brachiocephalic veins drain into the superior vena cava, similar to the arterial supply and brachiocephalic artery.
• The right and left brachiocephalic veins drain into the subclavian and internal jugular veins, and this is symmetrical.
• Like the arterial supply, there is an external counterpart to the internal jugular vein, and both sides have vertebral veins.
• Vertebral veins drain blood from the spinal cord and vertebral muscles, similar to the arterial supply.
• Internal and external jugular veins drain blood from the brain, skull, oral cavity, and superficial face and neck structures.

External Jugular Vein

• Branches drain areas in the face and neck.
• The posterior external jugular vein is formed from the joining of the posterior retromandibular vein and posterior auricular vein.
• Then joined by the cervical, suprascapular, and anterior jugular veins.
• It forms the external jugular vein before joining the subclavian vein.
• Mnemonic PAST helps remember the branches: Posterior External Jugular, Anterior Jugular, Suprascapular, Transverse Cervical.

Posterior Retromandibular Vein

• Formed from the superficial temporal vein and the maxillary vein.

Superficial Temporal Vein

• This drains the scalp.

Maxillary Vein

• Formed from the pterygoid venous plexus
• It drains the palate, nasal cavity, sinuses, and nasopharynx.

Posterior Auricular Vein

• This drains skin from behind the ear.

Cervical and Suprascapular Veins

• They drain muscles of the neck.

Anterior Jugular Vein

• Formed by multiple superficial submandibular veins joining
• It drains blood from the anterior aspect of the neck.

Internal Jugular Vein

• After considering the external jugular vein, the internal jugular vein has multiple branches, and drains areas in both the face and neck.
• The internal jugular vein has a lot of tributaries prior to the joining subclavian vein.
• The main elements can be remembered with the mnemonic: Middle Thyroid, Superior Thyroid, Lingual, Common facial, Pharyngeal, Inferior Petrosal Sinus.

Inferior Petrosal Sinus

• Drains large parts of the brain and inner ear.
• Runs alongside the vein of the cochlear duct and the meningeal veins

Common Facial Vein

• Formed by the facial vein and anterior retromandibular vein joining together.
• Drains the forehead, eyelids, outer surface of the nose, lips, submental region, masseter, parotid gland, and soft palate, among other areas.

Facial Vein

• Veins that form the facial vein are labial, lingual, external palatine, submandibular from the anterior part of the neck.

Pterygoid Venous Plexus

• Collection of small veins around the pterygoid muscle in the infratemporal fossa.
• Forms the maxillary vein, which drains the palate, nasal cavity, sinuses, and nasopharynx.
• Acts as a venous pump, pumping blood back to the heart when the mouth opens and the muscle contracts, and gets increased when yawning.
• If an infection is present, it can quickly spread through this area, potentially extending into the skull with life-threatening consequences.
• Close to the area when administering inferior dental nerve blocks, there is a chance of damage to vessels and forming a haematoma if administered incorrectly.

Summary

• Knowledge of pterygoid plexus is essential for local anaesthetic administration to avoid spread of dental infections.