Mastoid process

Mastoid process
Side view of skull. Mastoid process shown in red.
Mastoid process
Details
Identifiers
Latin	processus mastoideus ossis temporalis
TA	A02.1.06.004
FMA	52872
Anatomical terms of bone [edit on Wikidata]

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.

Structure

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.

Development

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

Function

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.

History

Etymology

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

See also

• mastoiditis
• mastoidectomy

Additional Images

• 
  Animation.
• 
  Animation. Left temporal bone.
• 
  Base of skull. Mastoid process labeled at middle left.
• 
  Close up of the right side of the skull. Mastoid process at left.
• 
  Mastoid process labeled at bottom.
• 
  Mastoid process labeled bottom right.
• 
  Base of skull. Muscle attachments are shown in red lines.
• 
  Side view of head, showing surface relations of bones. (Mastoid process labeled near center.)

References

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

External links

• lesson5 at The Anatomy Lesson by Wesley Norman (Georgetown University)
• Diagram - #5 (source here)
• Anatomy diagram: 34257.000-1 at Roche Lexicon - illustrated navigator, Elsevier