Eardrum

The eardrum ( tympanic membrane, Myrinx ) is a thin membrane at the inner end of the ear canal (if one exists ) and seals it to the middle ear. An eardrum own all land vertebrates, with the exception of caecilians, salamanders, snakes, and amphisbaenians. In humans it is about 0.1 mm thick and has an area of ​​about 85 mm ², which can effectively absorb approximately 55 mm ² Sound. The longest (vertical ) diameter is 9 to 10 mm.

Anatomy

The main part of the tympanic membrane ( Pars tensa " strained portion") consists of three layers: the outer epithelium (stratum cutaneum ), a stable average fiber layer ( lamina propria ) and an inner lining layer (stratum mucosum ). By the pars tensa of the tympanic membrane intergrown with hammer handle, a part of the first ossicle, the hammer ( malleus ), can be seen. The pars tensa of the tympanic membrane is crimped with a fibrous ring ( annulus fibrocartilagineus ) in a channel of the surrounding bone ( tympanic sulcus ) of the ear canal. The eardrum is not strained, especially membrane but funnel-shaped inward drawn to the lowest point ( umbo, navel) at the top of the hammer handle in the center of the tympanic membrane.

In the direction of the external auditory canal, the pars tensa consists of a multi-layered flat epithelium, which normally reflects incident light. At the tympanic cavity, epitympanum himself is a single- squamous epithelium. Both rest on a basement membrane. Then follows the lying between two epithelia connective tissue fiber layer, lamina propria. This shows a composite structure, outside the connective tissue fibers run radially, stratum radiatum and inside they run circularly, stratum circulare. Both fiber systems unite the eardrum edge to the annulus fibrocartilagineus enables the connection to the bone, a tympanic sulcus.

At the top, the bony rim of the tympanic membrane on a notch tympanic notch. This notch is called by the small pars flaccida ( " floppy part " ) of the tympanic membrane, also Shrapnellsche membrane sealed. The pars flaccida has no lamina propria, the ectodermal stratum cutaneum is here mucosum from endodermal stratum only separated by a basement membrane. The lack of mesodermal intermediate layer is unique in the body.

The eardrum has a glossy finish and has a characteristic light reflex on. The color of the tympanic membrane is described as " pearly " as " dove gray " or.

By sound waves, or more precisely by the sound pressure p, the eardrum to vibrate, which are transmitted by the ossicles in the middle ear to the inner ear.

At the sensory nerve supply of the tympanic branches of several nerves are involved, in particular the auricular branch of the vagus nerve and the nerve auriculotemporal, a branch of the trigeminal nerve.

The inside of the tympanic membrane is supplied by small branches of the plexus of the middle ear mucosa ( tympanic plexus ). Touches the tympanic membrane are painful and can trigger in some cases discomfort, nausea, and even fainting.

The blood supply of the tympanic membrane via an external and internal network. The outer surface of the tympanic membrane is supplied mainly by radiating branches of the arteria profunda auricular, a branch of the maxillary artery, with a comparatively larger branch, the artery manubrialis externa in the stria malleolaris along the malleus handle pulls from the top to the middle ear drum. The internal network is supplied by small branches of the artery anterior tympanic.

The Kopfhörerstereofonie takes into account the distance between the two eardrums from each other, the one also called ear distance.

Embryology

The fabric layer which the tympanic membrane is lined on its inner side, so the middle ear endodermal origin. The fabric layer of the outside, so the external auditory canal produces the layer of connective tissue covered with their circular and radial fibers, is of ectodermal origin. The eardrum forms from the endoderm of the first pharyngeal arch and the ectoderm of the first branchial cleft. The first pharyngeal pouch is a lateral protuberance of the so-called primitive pharynx dar. This Schlundtaschenausstülpung is located between the first and second branchial arch. The exact term is pharyngotympanicus recess. It forms the tympanic cavity, cavum tympani. Starting from here the pharyngeal pouch forms a series of small cavities in the bone of the mastoid process of the temporal bone, mastoid process ossis temporalis, the common input is also called as antrum. Adjacent to the outer portion adjacent the first pharyngeal pouch to the invaginated from the outside ectoderm of the first branchial cleft The first branchial cleft later forms the external auditory meatus, external acoustic meatus. Here, then developed the eardrum, tympanic membrane.

Diseases

With hard objects can easily direct injury ( perforation ) through blow to the ear or an explosion indirect Trommelfellzerreißung ( rupture) arise. Also a middle ear infection, barotrauma, a skull fracture can cause an injury. If the eardrum is perforated, the hearing will be affected depending on the location of the perforation and pathogens through the perforation ( especially water ) enter the middle ear. Traumatic tympanic membrane show a good tendency to spontaneous healing. Will not such an one, the tympanic membrane defect can be surgically closed by a tympanoplasty.

A tympanic membrane inflammation is called myringitis.

Medical Diagnostics

For the diagnosis of diseases of the ear an ear speculum, an otoscope or an ear microscope will be used. It allows the doctor to measure changes in the tympanic membrane associated with diseases of the outer ear or middle ear.

With tympanometry, acoustic resistance ( acoustic impedance ) of the tympanic membrane is measured. A tympanogram is the result of this measurement. To a sealed probe is inserted into the ear canal, and the resulting change in the acoustic impedance of the tympanic membrane is measured and recorded by changing the air pressure in the ear canal. The tympanogram allows conclusions to the pressure in the middle ear or the contents of the middle ear and the ability to vibrate the eardrum - ossicular system.

Furthermore, the body temperature can be measured at the tympanic membrane. This is known as the measurement of Tympanaltemperatur.