Mastoid antrumThe ear mastoid antrum relations be split into three parts; externalmiddle and inner. We shall look mastoid antrum relations its structural anatomy, vasculature, innervation, and the clinical conditions that can occur. The middle ear lies within the temporal bone, and extends from the tympanic membrane to the lateral wall of the internal ear. The main function of the middle ear is to transmit vibrations from the tympanic membrane to the inner ear — mastoid antrum relations does this via the three bones of the ear. The middle ear can be split into two; the tympanic cavity and epitympanic recess. The tympanic cavity eq 300mg ml medially to the tympanic membrane.
Mastoid Process : Definition, Location, Function and Pain
Show related SlideShares at end. Full Name Comment goes here. Are you sure you want to Yes No. Embeds 0 No embeds. No notes for slide. Anatomy of External Ear and Middle Ear 1. Its outer one-third 8 mm is cartilaginous and its inner two-third 16 mm is bony. The hydrophobic, slightly acidic pH 6. Approximately 6 mm lateral to tympanic membrane, bony EAC has a narrowing called the isthmus.
Foreign body impacted medial to bony isthmus of EAC are difficult to remove. In children and occasionally in adults, anteroinferior bony EAC may have a deficiency that is called foramen of Huschke.
It permits spread of infections to and from EAC and parotid. It is a branch of mandibular division of trigeminal nerve and supplies antero-superior wall of EAC. It innervates the skin of the mastoid and posterior of EAC. The hypoesthesia of posterior meatal wall occurs due to the pressure on facial nerve sensory fibers are affected early in patients with acoustic neuroma. While cleaning the EAC, patient may develop coughing, bradycardia, syncope and even cardiac arrest.
Because of vagal innervation, instilling spirit in EAC before meal can stimulate appetite. Vesicles of herpes zoster oticus occur on mastoid and posterior meatal wall which indicate that this part of external ear has facial nerve innervation.
It is positioned obliquely. Its posterosuperior part is more lateral than its anteroinferior part. It is continuous with the EAC skin.
Keratinised, stratified squamous type. It encloses the handle of malleus and consists of three types of fibers: In comparison to pars tensa, this layer is very thin in pars flaccida consists of loose conn.
It is continuous with the middle ear mucosa. Single layer of flat cells. Cilliated collumnar cells are absent over medial aspect of TM. Tympanic membrane consists of two parts: TM is thickened in the periphery and forms a fibrocartilaginous ring called the annulus tympanicus that fits in the tympanic sulcus.
The central part of TM near the tip of malleus is tended inwards and is called the umbo. A bright cone of light radiating from the tip of malleus to the periphery in the anteroinferior quadrant is usually seen during otoscopy. It is situated above the lateral process of malleus between the notch of Rivinus and the anterior and posterior malleal folds.
It is not as tense as pars tensa and may appear little pinkish. It is a branch of mandibular division of trigeminal nerve and supplies anterior half of lateral surface of TM. Tegmen plate separates it from middle cranial fossa and its contents like meninges and temporal lobe of cerebrum.
Posteromedial to mastoid air cells is situated cerebellum in the posterior cranial fossa This is the portion of middle ear that lies at the level of pars tensa. This is the portion of middle ear that lies below the level of pars tensa. The portion of middle ear around the eustachian tube opening is termed as protympanum. Presence of more goblet cells near the orifice of E. It is formed by tegmen tympani a thin plate of bone , which extends posteriorly to form the roof of the aditus and antrum tegmen antri.
Tegmen tympani separates middle ear from the middle cranial fossa. The floor, a thin plate of bone, separates tympanic cavity from the jugular bulb. In such cases, jugular bulb projects into the middle ear and is at greater risk of injury during surgery because it is only covered by middle ear mucosa. The anterior wall, a thin plate of bone, which separates the middle ear cavity from internal carotid artery, has following features: It connects the middle ear with nasopharynx.
It aerates and drains the middle ear. Malfunctioning of eustachian tube is common cause of ear infections especially in children. It is situated in the roof of eustachian tube. Carotid Plexus to tympanic plexus Caroticotympanic Nr It lies close to the mastoid air cells and presents following structures: It is a bony projection through the summit of which appears the tendon of the stapedius muscle that is inserted to the neck of stapes.
It is an opening through which mastoid antrum opens into the attic. It lies above the pyramid. Its relations are following: Bony prominence of the horizontal semicircular canal. Fossa incudis, to which is attached the short process of incus.
Fallopian canal for facial nerve. The vertical mastoid part of the fallopian canal for facial nerve runs in the posterior wall just behind the pyramid.
This recess is a depression in the posterior wall lateral to the pyramid. Its boundaries are following: Chorda tympani branch of 7th CN and tympanic annulus. Fossa incudis, in which lies short process of incus.
This deep recess lies medial to the pyramid. It is bounded by the subiculum below and the ponticulus above. It is formed by the lateral wall of labyrinth. It presents following structures: It is a bony bulge which is due to the basal coil of cochlea. Tympanic plexus present over it. Situated above and behind promontory. The footplate of stapes is placed over this window guarded by anular ligament.
It is covered by the secondary tympanic membrane, having 3 layers: External — tymp mucosa Intermediate — fibrous layer Internal — cochlear lining membrane. It lies above the oval window. It lies above the fallopian canal, facial nerve.
It is a hook-like projection, which lies anterior to the oval window. The tendon of tensor tympani takes a turn on this process and then is inserted on the neck of malleus. Lateral wall is formed mainly by the tympanic membrane. Some structures of the middle ear such as long process of incus, incudostapedial joint, round window and eustachian tube can be seen through the normal semitransparent tympanic membrane. An upper part of epitympanum is formed by outer bony attic wall called scutum.
There are three middle ear ossicles. It consists of a head, neck, handle manubrium , a lateral and an anterior process. It is the largest ossicle and measures 8 mm in length. They lie in the attic. It is embedded in the fibrous layer of the tympanic membrane. It appears as a knob-like projection on the outer surface of the tympanic membrane and provides attachments to the anterior and posterior malleal folds. It consists of following parts: Is connected to fossa incudis by lig.
It runs above the eustachian tube in a bony tunnel.