Dental Anatomy Quiz

Blood Supply to the Head and Neck - Venous Drainage

• The venous drainage of the head and neck is an intricate system, starting at the final drainage point (superior vena cava) and working backward.
• Unlike the arterial system, which starts from the aorta and travels upward, venous drainage originates from the head and neck, moving downward.

GDC Learning Outcomes

• Describe relevant dental, oral, craniofacial and general anatomy and explain their application to patient management.

Intended Learning Outcomes

• Name the major veins in the head and neck.
• Explain the areas these main veins drain.
• Describe the relationships of the jugular vein.
• Describe the significance of the pterygoid plexus.

Why do I need to know this?

• The head and neck area is complex, often involving procedures with sharp instruments.
• Understanding the blood supply is crucial to avoid damaging important vessels.
• Knowing the normal blood supply is important to identify deviations from the norm.

How is best to learn this?

• Engage with the material and use available resources to prevent it from becoming tedious.
• Memorize the key anatomical structures.
• Learn relevant mnemonics for recall
• Use available resources

Let's start with the basics...

• The superior vena cava is the end point for head and neck blood drainage, entering the right atrium of the heart, and then moves to the lungs for oxygenation.
• The main tributaries draining into the superior vena cava are the right and left brachiocephalic veins.
• These veins mirror the arterial supply (brachiocephalic artery) on the right side.

Let's start with the basics... (cont.)

• Tributaries to the right and left brachiocephalic veins include the right and left subclavian, and internal jugular veins.
• These drain similarly on both sides.

Let's start with the basics... (cont.)

• The external and internal carotid arteries have matching veins; both sides have vertebral veins.

What next?

• The external jugular vein has multiple branches that drain the face and neck area (green vessel on the diagram).
• The posterior external jugular vein is formed by the joining of the posterior retromandibular and posterior auricular veins, along with cervical, suprascapular, and anterior jugular veins.
• The external jugular vein passes into the subclavian vein.

What next? (cont.)

• Mnemonic "PAST" can help with recalling the sub-branches of the external jugular vein.
  • P = Posterior External Jugular
  • A = Anterior Jugular
  • S = Suprascapular
  • T = Transverse Cervical

What next? (cont.)

• The posterior retromandibular vein forms from the superficial temporal and maxillary veins.
• The superficial temporal vein drains the scalp.
• The maxillary vein forms from the pterygoid venous plexus and drains the palate, nasal cavity, sinuses and nasopharynx.

What next? (cont.)

• The posterior auricular vein drains the skin behind the ear.
• The cervical and suprascapular veins drain neck muscles.
• The anterior jugular vein forms from the confluence of submandibular veins and drains the anterior neck.

What about the internal jugular?

• Now, consider the internal jugular vein, another major vessel, which also has multiple branches draining the face and neck, illustrated as the green vessel on the diagram.
• Structures such as the superior/inferior petrosal sinuses, pharyngeal/meningeal veins, lingual, and the common facial veins are critical branches connecting to the internal jugular vein.

What about the internal jugular?(cont.)

• The internal jugular vein connects to subclavian veins.
• Mnemonic "MSLC-PI" is a helpful tool for remembering important branches:
  • M = Middle Thyroid
  • S = Superior Thyroid
  • L = Lingual
  • C = Common Facial
  • P = Pharyngeal
  • I = Inferior Petrosal Sinus

What about the internal jugular? (cont.)

• The inferior petrosal sinus drains parts of the brain, inner ear, and meningeal veins.

What about the internal jugular? (cont.)

• The common facial vein merges from the facial and anterior retromandibular veins.
• This is an important vessel draining from the forehead, eyelids, the nose, lips, surrounding regions, masseter, parotid gland and the soft palate.

What about the internal jugular? (cont.)

• For further understanding, the different veins (e.g., labial, lingual, and external palatine) that form the facial vein are worth noting.

And finally...

• The pterygoid venous plexus is a network of small veins surrounding the pterygoid muscles in the infratemporal fossa and is closely related to the maxillary vein.
• This plexus drains the palate, nasal cavity, sinuses, and nasopharynx.
• Its significance arises from its vulnerability during dental treatments, particularly nerve blocks. Incorrect administration can lead to vessel damage, hematoma formation, and potentially life-threatening complications.

And finally...(cont.)

• The pterygoid venous plexus acts as a venous pump, especially during mouth opening and yawning, assisting in blood return to the heart.

Summary

• The venous supply to the head and neck is complex.
• Understanding the internal/external jugular veins, other associated veins, and the pterygoid plexus is imperative.
• Knowledge of these structures is critical in local anesthetic injections and for preventing complications.
• Be aware of potential infection spread from the head and neck region into the cranial cavity.