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

temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. Th ...

. 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 human skull, skull, into t ...

between the

sigmoid sinus The sigmoid sinuses (sigma- or s-shaped hollow curve), also known as the , are venous sinuses within the skull that receive blood from posterior dural venous sinus veins. Structure The sigmoid sinus is a dural venous sinus situated within the du ...

and the

suboccipital venous plexus The suboccipital venous plexus drains deoxygenated blood from the back of the head. It communicates with the external vertebral venous plexuses. The external vertebral venous plexuses travel inferiorly from this suboccipital region to drain into ...

, and a small branch of the

occipital artery The occipital artery arises from the external carotid artery opposite the facial artery. Its path is below the posterior belly of digastric to the occipital region. This artery supplies blood to the back of the scalp and sternocleidomastoid muscles ...

, the

posterior meningeal artery The posterior meningeal artery is the largest vessel supplying the dura region of the posterior fossa. It typically arises from the ascending pharyngeal artery although other origins have been seen, such as the occipital artery. The artery or its b ...

to the

dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...

Structure

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

of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

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

asterion In Greek mythology, Asterion ( Greek: , gen.: , literally "starry") or Asterius () may refer to the following figures: * Asterion, one of the Potamoi. * Asterius, one of the Giants. * Asterion, an attendant of the starry-god Astraeus. * As ...

, 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 pinna 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 overlies the occipital lobe ...

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

Function

The mastoid foramen transmits: * an

between the

and the

or the posterior auricular vein. * a small branch of the

, the

, to the

References

External links

* *
Akram Abood Jaffar: Personal website, Anatomical variations
{{Authority control Foramina of the skull