The mastoid foramen is a hole in the posterior border of the

temporal bone The temporal bone is a paired bone situated at the sides and base of the skull, lateral to the temporal lobe of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples where four of the cranial bone ...

. It transmits an

emissary vein The emissary veins connect the extracranial venous system with the intracranial venous sinuses. They connect the veins outside the cranium to the venous sinuses inside the cranium. They drain from the scalp, through the skull, into the larger men ...

between the sigmoid sinus and the suboccipital venous plexus, and a small branch of the

occipital artery The occipital artery is a branch of the external carotid artery that provides arterial supply to the back of the scalp, sternocleidomastoid muscles, and deep muscles of the back and neck. Structure Origin The occipital artery arises from (the ...

, the posterior meningeal artery to the dura mater.

Structure

The mastoid foramen is a hole in the posterior border of the

of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

. The opening of the mastoid foramen is an average of 18 mm from the

asterion In Greek mythology, Asterion (Ancient Greek, Greek: , gen.: , literally "starry") or Asterius () may refer to the following figures: * Asterion (god), Asterion, one of the River gods (Greek mythology), river gods. * Asterius (giant), Asterius ...

, and around 34 mm from the

external auditory meatus The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. Str ...

. It is typically very narrow. This may be around 2 mm.

Variation

The position and size of this foramen are very variable. It is not always present. Sometimes, it is duplicated on one side or both sides. Sometimes, it is situated in the

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...

, or in the suture between the temporal bone and the occipital bone.

Function

The mastoid foramen transmits: * an

between the sigmoid sinus and the suboccipital venous plexus or the

posterior auricular vein The posterior auricular vein is a vein of the head. It begins from a plexus with the occipital vein and the superficial temporal vein, descends behind the auricle, and drains into the external jugular vein. Structure The posterior auricula ...

. * a small branch of the

, the posterior meningeal artery, to the dura mater.

References

External links

* *
Akram Abood Jaffar: Personal website, Anatomical variations
{{Authority control Foramina of the skull Otorhinolaryngology Human head and neck Skull