The mastoid part of the temporal bone is the posterior (back) part 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. ...
, one of the
bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
s 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, th ...
. Its rough surface gives attachment to various
muscles (via
tendon
A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
s) and it has
openings for
blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s. From its borders, the mastoid part
articulates with two other bones.
Etymology
The word "mastoid" is derived from the Greek word for "
breast
The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues.
In females, it serves as the mammary gland, which produces and sec ...
", a reference to the shape of this bone.
Surfaces
Outer surface
Its outer surface is rough and gives attachment to the
occipitalis and
posterior auricular muscle
The posterior auricular muscle is a muscle behind the auricle of the outer ear. It arises from the mastoid part of the temporal bone, and inserts into the lower part of the cranial surface of the auricle of the outer ear. It draws the auricle ...
s. It is perforated by numerous
(holes); for example, the
mastoid foramen
The mastoid foramen is a hole in the posterior border of the temporal bone. It transmits an emissary vein between the sigmoid sinus and the suboccipital venous plexus, and a small branch of the occipital artery, the posterior meningeal artery to ...
is situated near the posterior border and transmits a vein to the
transverse sinus and a small branch of the
occipital artery 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. ...
. The position and size of this foramen are very variable; it is not always present; sometimes it is situated in the occipital bone, or in the suture between the temporal and the occipital.
Mastoid process
The mastoid process is located posterior and inferior to the
ear canal, lateral to the
styloid process, and appears as a conical or pyramidal projection. It forms a bony prominence behind and below the ear. It has variable size and form (e.g. it is larger in the
male
Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization.
A male organism cannot reproduce sexually without access to ...
than in the
female
Female ( symbol: ♀) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction.
A female has larger gametes than a male. Females ...
). It is also filled with
sinuses, or
mastoid cells
The mastoid cells (also called air cells of Lenoir or mastoid cells of Lenoir) are air-filled cavities within the mastoid process of the temporal bone of the cranium. The mastoid cells are a form of skeletal pneumaticity. Infection in these cells ...
. The mastoid process serves for the attachment of the
sternocleidomastoid, the posterior belly of the
digastric muscle,
splenius capitis
The splenius capitis () () is a broad, straplike muscle in the back of the neck. It pulls on the base of the skull from the vertebrae in the neck and upper thorax. It is involved in movements such as shaking the head.
Structure
It arises from th ...
, and
longissimus capitis
The longissimus ( la, the longest one) is the muscle lateral to the semispinalis muscles. It is the longest subdivision of the erector spinae muscles that extends forward into the transverse processes of the posterior cervical vertebrae.
Structu ...
. On the medial side of the 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
The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, t ...
, which lodges the
occipital artery. The
facial nerve
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste ...
passes close to the mastoid process.
Inner surface
The inner surface of the mastoid portion presents a deep, curved groove, the
sigmoid sulcus
Sigmoid means resembling the lower-case Greek letter sigma (uppercase Σ, lowercase σ, lowercase in word-final position ς) or the Latin letter S. Specific uses include:
* Sigmoid function, a mathematical function
* Sigmoid colon, part of the l ...
, which lodges part of the
transverse sinus; in it may be seen in the opening of the
mastoid foramen
The mastoid foramen is a hole in the posterior border of the temporal bone. It transmits an emissary vein between the sigmoid sinus and the suboccipital venous plexus, and a small branch of the occipital artery, the posterior meningeal artery to ...
.
The groove for the transverse sinus is separated from the innermost of the mastoid cells by a very thin lamina of bone, and even this may be partly deficient.
Borders
The ''superior border'' of the mastoid part is broad and serrated, for articulation with the mastoid angle of the parietal.
The ''posterior border'', also serrated, articulates with the inferior border of the occipital between the lateral angle and
jugular process
The jugular process is a quadrilateral or triangular bony plate projecting lateralward from the posterior half of the occipital condyle; it is a part of the lateral part of the occipital bone.
The jugular process is excavated in front by the jugu ...
.
Anteriorly, the mastoid portion is fused with the descending process of the
squama above; below, it enters into the formation of the
ear canal and the
tympanic cavity.
Spaces
A section of the mastoid process shows it to be hollowed out into a number of spaces, the
mastoid cells
The mastoid cells (also called air cells of Lenoir or mastoid cells of Lenoir) are air-filled cavities within the mastoid process of the temporal bone of the cranium. The mastoid cells are a form of skeletal pneumaticity. Infection in these cells ...
, which exhibit the greatest possible variety as to their size and number. At the upper and front part of the process, they are large and irregular and contain air, but toward the lower part, they diminish in size, while those at the apex of the process are frequently quite small and contain marrow; occasionally, they are entirely absent, and the mastoid is then solid throughout.
In addition to these a large irregular cavity is situated at the upper and front part of the bone. It is called the
tympanic antrum
The mastoid antrum (tympanic antrum, antrum mastoideum, Valsalva's antrum) is an air space in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear vi ...
and must be distinguished from the mastoid cells, though it communicates with them. Like the mastoid cells, it is filled with air and lined by a prolongation of the mucous membrane of the tympanic cavity, with which it communicates. The tympanic antrum is bounded above by a thin plate of bone, the
tegmen tympani
The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound.
Structure
On its lateral surface, it abuts the external auditor ...
, which separates it from the middle fossa of the
base of the skull
The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.
Structure
Structures found at the base of the skull are for ...
, below by the mastoid process, laterally by the squama just below the
temporal line
The parietal bones () are two bones in the skull which, when joined at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named ...
, and medially by the
lateral semicircular canal of the
internal ear
Internal may refer to:
*Internality as a concept in behavioural economics
*Neijia, internal styles of Chinese martial arts
*Neigong or "internal skills", a type of exercise in meditation associated with Daoism
*''Internal (album)'' by Safia, 2016
...
, which projects into its cavity. It opens in front into that portion of the tympanic cavity which is known as the attic or
epitympanic recess. The tympanic antrum is a cavity of some considerable size at the time of birth; the mastoid air cells may be regarded as diverticula from the antrum and begin to appear at or before birth. By the fifth year, they are well-marked, but their development is not completed until toward
puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a bo ...
.
Development
The mastoid process is absent or rudimentary in the neonatal skull. It forms postnatally (starts to develop after 1 year old), as the sternocleidomastoid muscle develops and pulls on the bone. It usually finishes structural development by 2 years old.
Clinical significance
Mastoid process
Because of the late
postnatal development of the mastoid process, antenatal injuries to the region often recover spontaneously.
The largest size is found in
South Africans
The population of South Africa is about 58.8 million people of diverse origins, cultures, languages, and religions. The South African National Census of 2022 was the most recent census held; the next will be in 2032.
In 2011, Statistics South ...
and least found in North American Indians.
Rarely, lesions can develop on the mastoid process.
See also
*
mastoiditis
Mastoiditis is the result of an infection that extends to the air cells of the skull behind the ear. Specifically, it is an inflammation of the mucosal lining of the mastoid antrum and mastoid air cell system inside the mastoid process. The ma ...
*
mastoidectomy
A mastoidectomy is a procedure performed to remove the mastoid air cells, air bubbles in the skull, near the inner ears. This can be done as part of treatment for mastoiditis, chronic suppurative otitis media or cholesteatoma. In addition, it is ...
References
External links
*
*
*
Diagram - #5(sourc
here
*
{{Authority control
Bones of the head and neck