Mastoid process

Mastoid process

Side view of skull. Mastoid process shown in red.

Mastoid process
Latin processus mastoideus ossis temporalis
TA A02.1.06.004
FMA 52872

Anatomical terms of bone

The mastoid process is a conical prominence projecting from the undersurface of the mastoid part of the temporal bone. It is located just behind the ear canal, and lateral to the styloid process.


Left temporal bone, muscle attachments shown in red lines

The mastoid process projects from the temporal bone in the skull and is roughly pyramidal or conical in shape. It is also filled with sinuses, or mastoid cells. On the medial side of the mastoid process is a deep groove, the mastoid notch, for the attachment of the digastric muscle. Medial to this is a shallow furrow, the occipital groove, which lodges the occipital artery.

Variation in humans

Its size and form vary somewhat; it is larger in the male than in the female.


The mastoid process is absent or rudimentary in the neonatal skull. It forms postnatally, as the sternocleidomastoid muscle develops and pulls on the bone.


One important role for this bone is as a point of attachment for several muscles - the splenius capitis, longissimus capitis, digastric posterior belly, and sternocleidomastoid. These muscles are one reason the mastoid process tends to be larger in men, because men have bigger muscles as a rule and thus require larger points of attachment.



The term “mastoid” is derived from the Greek word for “breast,” a reference to the shape of this bone.

See also

This article uses anatomical terminology; for an overview, see Anatomical terminology.

Additional Images


This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

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