Emissary veins

Emissary veins are veins that connect the intracranial and extracranial venous systems. They are valveless and can carry blood in either direction. This unique characteristic allows them to play a crucial role in the body's thermoregulation, but also makes them potential pathways for the spread of infection.

Anatomy

Emissary veins are found throughout the body, but are most commonly associated with the cranium. They pass through small channels in the skull known as emissary foramina. The most significant of these are the mastoid emissary vein, which drains into the sigmoid sinus, and the condylar emissary vein, which drains into the transverse sinus.

Function

The primary function of emissary veins is to aid in the body's thermoregulation. They do this by allowing blood to flow from the outside of the skull to the inside, or vice versa, depending on the body's needs. In hot conditions, blood can be diverted to the surface of the skull where it can be cooled by the surrounding air. In cold conditions, blood can be kept inside the skull to conserve heat.

Clinical significance

Because emissary veins are valveless and can carry blood in either direction, they can potentially serve as pathways for the spread of infection. This is particularly true for infections of the scalp, which can spread to the meninges and brain via the emissary veins. This can lead to serious conditions such as meningitis and brain abscess.

See also

• Vein
• Cranium
• Thermoregulation
• Meningitis
• Brain abscess