Mastoid cells

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Mastoid cells
Gray139.png
Coronal section of right temporal bone. (Mastoid cells labeled at bottom left.)
Brain MRI 0106 17.jpg
MRI showing fluid in mastoid air cells
Details
Artery stylomastoid artery
Identifiers
Latin cellulae mastoideae
TA98 A15.3.02.029
TA2 646
FMA 72001
Anatomical terminology

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 is called mastoiditis.

Contents

The term cells here refers to enclosed spaces, not cells as living, biological units.

Anatomy

Mastoid cells Mastoid cells of Lenoir.jpg
Mastoid cells

The mastoid air cells vary greatly in number, shape, and size; they may be extensive or minimal or even absent. [1] :746

The cells are typically interconnected and their walls lined by mucosa that is continuous with that of the mastoid antrum and tympanic cavity. [1] :746

Extent

They may excavate the mastoid process to its tip, and be separated from the posterior cranial fossa and sigmoid sinus by a mere slip of bone or not at all. They may extend into the squamous part of temporal bone, petrous part of the temporal bone zygomatic process of temporal bone, and - rarely - the jugular process of occipital bone; they may thus come to adjoin many important structures (including the bony labyrinth, tympanic cavity, external acoustic meatus, pharyngotympanic tube, superior jugular bulb, posterior cranial fossa, middle cranial fossa, carotid canal, abducens nerve, sigmoid sinus) to which they may disseminate infection in case of infective mastoiditis. [1] :746

Innervation

The cells receive innervation[ clarify ] from the posterior branch of the meningeal branch of the mandibular nerve (nervus spinosus), [1] :400.e2 [2] :364 and branches of the tympanic plexus. [1] :749 [2] :366

Vasculature

The cells receive arterial supply from the stylomastoid branch of the occipital artery or posterior auricular artery, and (sometimes) a mastoid branch of the occipital artery. [1] :749

The superior petrosal sinus receives venous drainage from the mastoid air cells (mastoid infection may thus lead to a cerebellar abscess). [2] :443

Development

At birth, the mastoid is not pneumatized, but becomes aerated before age six. [3] At birth, the mastoid antrum is well developed but the air cells are represented only by small diverticula from the antrum. The air cells then gradually extend into the bone of the mastoid during the first years of life. Their most significant enlargements takes place during puberty. [1] :746

Function

The air cells are hypothesised to protect the temporal bone and the inner and middle ear against trauma and to regulate air pressure. [4]

Clinical significance

Infections in the middle ear easily spread into the mastoid air cells through the aditus ad antrum, resulting in mastoiditis, a potentially dangerous and life-threatening condition. Infection may then further spread into the middle cranial fossa or posterior cranial fossa, causing meningitis or abscess of adjacent brain tissue. Infection may also spread to muscles of the neck, causing pain and torticollis. [1] :746

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<span class="mw-page-title-main">Glossopharyngeal nerve</span> Cranial nerve IX, for the tongue and pharynx

The glossopharyngeal nerve, also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest.

<span class="mw-page-title-main">Temporal bone</span> Sides and base of skull, connecting to the jaw and occipital bone

The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex.

<span class="mw-page-title-main">Mastoid antrum</span>

The mastoid 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 via the aditus to mastoid antrum. These air spaces function as sound receptors, provide voice resonance, act as acoustic insulation and dissipation, provide protection from physical damage and reduce the mass of the cranium. The roof is formed by the tegmen antri which is a continuation of the tegmen tympani and separates it from the middle cranial fossa. The lateral wall of the antrum is formed by a plate of bone which is an average of 1.5 cm in adults. The mastoid air cell system is a major contributor to middle ear inflammatory diseases.

<span class="mw-page-title-main">Posterior cranial fossa</span> Area of the cranium containing the brainstem and cerebellum

The posterior cranial fossa is the part of the cranial cavity located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and occipital bone. It lodges the cerebellum, and parts of the brainstem.

<span class="mw-page-title-main">Tympanic cavity</span> Small cavity surrounding the bones of the middle ear

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.

<span class="mw-page-title-main">Occipital artery</span>

The occipital artery is a branch of the external carotid artery that provides arterial supply to the back of the scalp, sternocleidomastoid muscles, and deep muscles of the back and neck.

<span class="mw-page-title-main">Jugular fossa</span>

The jugular fossa is a deep depression in the inferior part of the temporal bone at the base of the skull. It lodges the bulb of the internal jugular vein.

<span class="mw-page-title-main">Jugular foramen</span> Opening in the base of the skull allowing many structures to pass

A jugular foramen is one of the two large foramina (openings) in the base of the skull, located behind the carotid canal. It is formed by the temporal bone and the occipital bone. It allows many structures to pass, including the inferior petrosal sinus, three cranial nerves, the sigmoid sinus, and meningeal arteries.

<span class="mw-page-title-main">Transverse sinuses</span>

The transverse sinuses, within the human head, are two areas beneath the brain which allow blood to drain from the back of the head. They run laterally in a groove along the interior surface of the occipital bone. They drain from the confluence of sinuses to the sigmoid sinuses, which ultimately connect to the internal jugular vein. See diagram : labeled under the brain as "SIN. TRANS.".

<span class="mw-page-title-main">Posterior auricular artery</span> Small artery

The posterior auricular artery is a small artery that arises from the external carotid artery. It ascends along the side of the head. It supplies several muscles of the neck and several structures of the head.

<span class="mw-page-title-main">Occipital vein</span> Vein of the scalp

The occipital vein is a vein of the scalp. It originates from a plexus around the external occipital protuberance and superior nuchal line to the back part of the vertex of the skull. It usually drains into the internal jugular vein, but may also drain into the posterior auricular vein. It drains part of the scalp.

<span class="mw-page-title-main">Squamous part of temporal bone</span> Front and upper part of the sides of the skull base

The squamous part of temporal bone, or temporal squama, forms the front and upper part of the temporal bone, and is scale-like, thin, and translucent.

<span class="mw-page-title-main">Mastoid part of the temporal bone</span> Back part of the sides of the skull base

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 and it has openings for blood vessels. From its borders, the mastoid part articulates with two other bones.

<span class="mw-page-title-main">Petrous part of the temporal bone</span> Feature at the base of the human skull

The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three angles, and houses in its interior, the components of the inner ear. The petrous portion is among the most basal elements of the skull and forms part of the endocranium. Petrous comes from the Latin word petrosus, meaning "stone-like, hard". It is one of the densest bones in the body. In other mammals, it is a separate bone, the petrosal bone.

<span class="mw-page-title-main">Tympanic nerve</span>

The tympanic nerve is a branch of the glossopharyngeal nerve found near the ear. It gives sensation to the middle ear, the Eustachian tube, the parotid gland, and mastoid air cells. It gives parasympathetic to supply to the parotid gland via the otic ganglion and the auriculotemporal nerve.

<span class="mw-page-title-main">Base of skull</span> Inferior area of the skull, composed of the endocranium and lower parts of the skull roof

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.

<span class="mw-page-title-main">Epitympanic recess</span> Hollow located on the superior/roof aspect of the middle ear

The epitympanic recess is the portion of the tympanic cavity situated superior to the tympanic membrane. The recess lodges the head of malleus, and the body of incus.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

References

  1. 1 2 3 4 5 6 7 8 Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42th ed.). New York. ISBN   978-0-7020-7707-4. OCLC   1201341621.{{cite book}}: CS1 maint: location missing publisher (link)
  2. 1 2 3 Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). Elsevier Australia. ISBN   978-0-7295-3752-0.
  3. Raphael Schillinger (July 1939) [1 July 1939]. "Pneumatization of the Mastoid: A Roentgen Study". Radiology. Radiological Society of North America. 33 (1): 54–67. doi:10.1148/33.1.54 . Retrieved 4 January 2021.
  4. "Ear Infections and Mastoiditis".