The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the

ossicle The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossicu ...

s, three small bones that transmit vibrations used in the detection of

sound In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...

Structure

On its lateral surface, it abuts the external auditory meatus (ear canal) from which it is separated by the tympanic membrane (eardrum).

Walls

The tympanic cavity is bounded by: * Facing the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

, the medial wall (or ''labyrinthic wall'', ''labyrinthine wall'') is vertical, and has the oval window and round window, the promontory, and the prominence of the facial canal. * Facing the outer ear, the lateral wall (or ''membranous wall''), is formed mainly by the tympanic membrane, partly by the ring of bone into which this membrane is inserted. This ring of bone is incomplete at its upper part, forming a notch (notch of Rivinus), close to which are three small apertures: the "iter chordæ posterius", the petrotympanic fissure, and the "iter chordæ anterius". The iter chordæ posterius (apertura tympanica canaliculi chordæ) is situated in the angle of junction between the mastoid and ''membranous wall of tympanic cavity'' immediately behind the tympanic membrane and on a level with the upper end of the

manubrium The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, human lung, lungs, and ma ...

of the malleus; it leads into a minute canal, which descends in front of the canal for 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 ta ...

, and ends in that canal near the stylo-mastoid foramen. Through it the chorda tympani nerve enters the tympanic cavity. The petrotympanic fissure opens just above and in front of the ring of bone into which the tympanic membrane is inserted; in this situation it is a mere slit about 2 mm. in length. It lodges the anterior process and anterior ligament of the malleus, and gives passage to the anterior tympanic branch of the internal maxillary artery. The iter chordæ anterius (canal of Huguier) is placed at the medial end of the petrotympanic fissure; through it the chorda tympani nerve leaves the tympanic cavity. * The roof of the cavity (also called the ''tegmental wall'', ''tegmental roof'' or ''tegmentum tympani'') is formed by a thin plate of bone, the tegmen tympani, which separates the cranial and tympanic cavities. It is situated on the

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

(frontal) surface of the petrous portion of the temporal bone close to its angle of junction with the squama temporalis; it is prolonged backward so as to roof in the tympanic antrum, and forward to cover in the semicanal for the tensor tympani muscle. Its lateral edge corresponds with the remains of the petrosquamous suture.Public domain edition of Gray's Anatomy The ''Atticus'' is the part of the tegmentum tympani where the stapes and

incus The ''incus'' (: incudes) or anvil in the ear is one of three small bones (ossicles) in the middle ear. The incus receives vibrations from the malleus, to which it is connected laterally, and transmits these to the stapes medially. The incus i ...

are attached. * The floor of the cavity (also called the ''jugular wall'') is narrow, and consists of a thin plate of bone (fundus tympani) which separates the tympanic cavity from the jugular fossa. It presents, near the labyrinthic wall, a small aperture for the passage of the tympanic branch of the glossopharyngeal nerve. * The posterior wall (or ''mastoid wall'') is wider above than below, and presents for examination the entrance to the tympanic antrum, the pyramidal eminence, and the fossa incudis. * The anterior wall (or ''carotid wall'') is wider above than below; it corresponds with the carotid canal, from which it is separated by a thin plate of bone perforated by the tympanic branch of the internal carotid artery, and by the deep petrosal nerve which connects the sympathetic plexus on the internal carotid artery with the tympanic plexus on the promontory. At the upper part of the anterior wall are the orifice of the semicanal for the Tensor tympani muscle and the tympanic orifice of the auditory tube, separated from each other by a thin horizontal plate of bone, the septum canalis musculotubarius. These canals run from the tympanic cavity forward and downward to the retiring angle between the squama and the petrous portion of the temporal bone.

Development

It is formed from the tubotympanic recess, an expansion of the first pharyngeal pouch.

Clinical significance

If damaged, the tympanic membrane can be repaired in a procedure called tympanoplasty. Should fluid accumulate within the middle ear as the result of infection or for some other reason, it can be drained by puncturing the tympanic membrane with a large bore needle ( tympanocentesis).

Additional images

File:Gray907.png, External and middle ear, opened from the front. Right side. File:Gray908.png, Horizontal section through left ear; upper half of section. File:Occipital bone dissection.jpg, Tympanic cavity. Facial canal. Internal carotid artery. File:Slide1ghe.JPG, Auditory ossicles. Tympanic cavity. Deep dissection.

References

External links

{{Authority control Ear Otorhinolaryngology Otology Human head and neck