Tympanic cavity
The tympanic cavity (cavitas tympanica) is the central space of the middle ear located within the petrous part of the temporal bone. It is completely lined from the inside with mucous membrane — tunica mucosa cavitatis tympani.
There are six walls distinguished in the tympanic cavity:
- Membranous wall (paries membranaceus);
- Labyrinthine wall (paries labyrinthicus);
- Jugular wall (paries jugularis);
- Carotid wall (paries caroticus);
- Mastoid wall (paries mastoideus);
- Roof of the tympanic cavity (tegmen tympani).
The cavity has important anatomical communications: anteriorly, it opens into the nasopharynx via the auditory tube, and posteriorly, it communicates with the mastoid antrum (antrum mastoideum).
Auditory ossicles
Inside the tympanic cavity are the auditory ossicles (ossicula auditus). They form a single movable chain, the main function of which is the transmission and amplification of sound vibrations.
The system consists of three elements:
- Malleus (malleus). Includes the head (caput mallei), neck (collum mallei), handle (manubrium mallei), and processes (anterior and lateral — processus anterior et lateralis). It is important to note that the handle of the malleus is tightly fused with the tympanic membrane.
- Incus (incus). Consists of the body (corpus incudis), as well as short and long limbs (crus breve, crus longum). The long limb articulates directly with the stapes.
- Stapes (stapes). Has a head (caput stapedis), base (basis stapedis), and two limbs — anterior and posterior (crura stapedis). The base of the stapes is securely fixed in the vestibular window (fenestra vestibuli).
The ossicles are connected to each other by two joints: the incudomalleolar joint (articulatio incudomallearis) and the incudostapedial joint (articulatio incudostapedia).
Middle ear muscles
The movement of the auditory ossicles chain and the tension of the membrane are regulated by two specialized muscles:
- Tensor tympani muscle (m. tensor tympani). As the name implies, it is responsible for tensioning the membrane. It is innervated by branches of the trigeminal nerve (n. trigeminus).
- Stapedius muscle (m. stapedius). Its function is to reduce excessive mobility of the stapes, which protects the inner ear from loud sounds. It is innervated by the facial nerve (n. facialis).
Auditory tube
The auditory tube (tuba auditiva) is a channel about 3.5–4 cm long that anatomically connects the tympanic cavity with the nasopharynx.
Its structure includes two parts:
- Bony part (pars ossea);
- Cartilaginous part (pars cartilaginea).
The main functions of the auditory tube are continuous ventilation of the middle ear and equalization of pressure in the tympanic cavity relative to the external atmospheric pressure.
Briefly: answers to topical questions
What openings does the auditory tube have?
The auditory tube has two openings that open into the nasopharynx and the tympanic cavity.
- Pharyngeal opening of the auditory tube (ostium pharyngeum tubae auditivae) is located on the lateral wall of the nasal part of the pharynx.
- Tympanic opening of the auditory tube (ostium tympanicum tubae auditivae) is located in the upper part of the anterior (carotid) wall of the tympanic cavity.
Which arteries supply blood to the tympanic cavity?
The blood supply to the walls and mucous membrane of the tympanic cavity is provided by the following arteries:
- Anterior tympanic artery (a. tympanica anterior), a branch of the maxillary artery (a. maxillaris).
- Caroticotympanic branch (r. caroticotympanicus), branching from the internal carotid artery.
- Superior tympanic artery (a. tympanica superior), a branch of the middle meningeal artery.
- Posterior tympanic artery (a. tympanica posterior), a branch of the stylomastoid artery (a. stylomastoidea).
- Inferior tympanic artery (a. tympanica inferior), a branch of the ascending pharyngeal artery (a. pharyngea ascendens).
Which nerves form the tympanic plexus?
The tympanic plexus (plexus tympanicus) is formed by branches of the glossopharyngeal nerve.
The main nerve forming this plexus is:
- Tympanic nerve (n. tympanicus), which arises from the inferior ganglion of the glossopharyngeal nerve, passes to the tympanic cavity, and forms the tympanic plexus (Jacobson's nerve).
Sources mention the presence of several nerves that have bony canals on the surface of the promontory, however, their exact names (other than the tympanic nerve) are not specified.
What anatomical structures are located on the labyrinthine wall of the tympanic cavity?
The labyrinthine (medial) wall of the tympanic cavity contains the following anatomical structures:
- Promontory (promontorium), a central prominence formed by the basal turn of the cochlea.
- The vestibular window (fenestra vestibuli) — an oval window superior and posterior to the promontory, closed by the base of the stapes.
- Fenestra cochleae (fenestra cochleae), the round window inferior to the promontory, closed by the secondary tympanic membrane.
- Pyramidal eminence, which contains the stapedius muscle (m. stapedius).
- Depression (fossula antefenestram), located near the anterior margin of the vestibular window.
- Bony aperture, which serves for the exit of the chorda tympani.
Which ligaments fix the auditory ossicles in the tympanic cavity?
The auditory ossicles are fixed within the tympanic cavity by a system of ligaments:
- Anterior ligament of the malleus, connecting the neck of the malleus to the spine of the sphenoid bone.
- Lateral ligament of the malleus, extending from the head and neck to the edges of the tympanic notch (its posterior bundles form the posterior ligament of the malleus).
- Superior ligament of the malleus, connecting the head to the roof of the tympanic cavity.
- Posterior ligament of incus — connects the posterior crus to the floor of the mastoid antrum entrance.
- Superior ligament of incus — suspends the body of the incus to the roof of the epitympanic recess.
- Annular ligament of stapes — attaches the base of the stapes to the margins of the vestibular window.
To remember the order of the auditory ossicles (from the tympanic membrane inward), use the mnemonic MIS: Malleus — Incus — Stapes.
Class and exam questions
Where is the tympanic cavity located?
The tympanic cavity is located within the pyramid of the temporal bone.
What is the handle of the malleus fused with?
The handle of the malleus (manubrium mallei) is anatomically fused with the tympanic membrane.
Where is the base of the stapes fixed?
The base of the stapes (basis stapedis) is fixed in the so-called vestibular window (fenestra vestibuli).
What are the functions of the pharyngotympanic tube?
The pharyngotympanic tube provides ventilation of the middle ear cavities and pressure equalization between the tympanic cavity and the nasopharynx.
What else to study on this topic
- Topography of the tympanic cavity walls and their relation to blood vessels
- Mechanism of the auditory ossicle joints
- Clinical anatomy of the communication between the tympanic cavity and the mastoid antrum
- Detailed structure of the tympanic cavity mucosa
- Features of the middle ear muscle innervation
Study the complete topic in the Anatomy course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on the "Middle Ear" and 1,363 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 295 video lessons by subject
Other topics in the "Sensory Organs" section
Free video lessons: AnatomyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.