Mastoid cells
Encyclopedia
A section of the mastoid process
of the temporal bone of the cranium shows it to be hollowed out into a number of spaces, the mastoid 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 (a form of skeletal pneumaticity
), 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.
can easily spread into the mastoid area via the aditus ad antrum and mastoid antrum
.
Mastoid process
The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process...
of the temporal bone of the cranium shows it to be hollowed out into a number of spaces, the mastoid 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 (a form of skeletal pneumaticity
Skeletal pneumaticity
Skeletal pneumaticity is the presence of air spaces within bones. Skeletal pneumaticity exists only in synapsids and archosaurs. It is generally produced during development by excavation of bone by pneumatic diverticula from an air-filled space such as the lungs or nasal cavity...
), but toward the lower part they diminish in size, while those at the apex of the process are frequently quite small and contain marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
; occasionally they are entirely absent, and the mastoid is then solid throughout.
Clinical significance
Infections in the middle earOtitis media
Otitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
can easily spread into the mastoid area via the aditus ad antrum and mastoid antrum
Mastoid antrum
The mastoid antrum is a cavity in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear via the aditus to mastoid antrum .-External links: - "Illustration of the continuity of the...
.