inner ear anatomy

inner ear anatomy

All vertebrates have the inner ear although their structure are different. Their inner ear has eight cranial nerves which are inverted. The inner most part of a human ear is known as inner ear, internal ear or auris interna (Bohne, 2019). The main function of the inner is to perceive ad detect sound and maintain balance in human. The inner ear cavity contains many parts, main being bony labyrinth which is the hollow cavity in the ear. This hollow cavity has two main parts which serve different function. Cochlea serves the purpose of hearing. It ads in converting sound patterns from the outer ear and passes the information to the brain via the nerves where the information is interpreted and processed. The second part is the vestibular system which ensures that a person stays in balance (Landgren, 2019).

Development of the ear occurs very early, during embryo development. The development of the inner ear occurs from the auditory palacode from the fourth week of embryonic development. As the auditory palacode further develops and extend to ear the embryonic mesoderm, there is formation of vesicle. Latter on the utricular and saccular parts of the labirnth will develop from the otocyst (Landgren, 2019). They contain hair like structures which detects the gravitational balance and helps to maintain balance in human beings. The scala vestibule is separated from chochlea by the vestibular wall. The wall is normally formed from spiral ligaments which produce endophyl. Then the hair like strictures grows laterally on the walls of the vestibular and they all together form an organ of Corti.

Cochlea has aspiral canal (Rosenthal’s canal) section in the inner ear and at the centre of the cochlea there is the spiral gongloin, the inner ear also has specialized cells which aid in sound waves reception. These cells makes it easy four sound perceived to be contained or ‘captured’ where it is in turn transferred to the to the brain vial the necessary fiber cords. Example of these cells is haie cell, pillar cells, Boettcher’s cells, Claudius cells, spiral ganglion neuron and Deiters’ cells (Landgren, 2019).

The primary auditory receptors are the hair cells, which are also known as sensory cells, acoustic hair cells, auditory cells or cells of Corti. When the outer ear captures the sound waves from the external environment, it is first conveyed through the outer ear and receipted by the hair cells. The inner membrane has two sets of hair cells. First is lined with a single row of inner hair cells and three rows of outer hair cells. The hair cells are aligned with actin based stereocilia. When this two cells are disrupted, it leads to balance defects and hearing impairment.

Corti then supports the inner and the outer pillar cells. Outer cells have a unique character from the inner cells (Bohne, 2019). They stand on their own and only contact the adjacent cells which are at the base of the inner wall. The hair has also thousands of cross linked micro tubles which further aid in sound reception. The micro tubules increases the surface area of the hair therefore increases the surface on which the sound waves lands on. They also provide a connection between the basement membrane and the mechanoreceptors of the hair cells.

On the lower turn of the cochlea, we find the Boettcher’s cells, named after German Pathologist Arthur Bottcher (Bohne, 2019). They are organized in rows on the basilar membrane beneath Claudis cells. The cells have integrated with each other which and has micro-vili projected into the inter-cellular space. They are mainly functioned with supporting the auditory air cells.

Just above the Boettcher’s cells, we have the Claudiu’s cells, which were named after a German anatomist Friedrich Matthaias Claudius (Bohne, 2019). They are mainly functioned with supporting the auditory hair cells in the organ of Corti. Due o the presence of aquaporin water hannel on them, they tend to be transporting ions (Bohne, 2019). They also provide a sealing of the endolymphatic space.

Delter’s cells named after German pathologist Otto Delters describes them as and neurological cells which are found in the organ corti. They are arranged in one row of inner phalangeal cells and three rows of outer phalangel cells. Adjecentto Delters’ cells, is the Hensen’s cell that appear in column (Wageih, 2017). There isalso the tectorial cells that occur that occur above the inner air cells, known as Hensen’s stripe.

Blood supply in the inner ear is done in different complex channels. Blood is supplied by three main arteries namely maxillary artery, meningleal artery from the middle and auricular artery from the posterior (Wageih, 2017). Survival and effectiveness of these cells is determined by availability of enough oxygen supply which is aided by sufficient blood supply. After the blood circulate the inner ear cells, is then emptied through abyrinthine vein (Wageih, 2017).

The neurons in the inner ear are functioned with responding to simple tones which I in turn communicated to the brain where they are processed (Wageih, 2017). An adult can detect sounds which ranges from 20 and 20,000 HZ, as the human age, their ability to detect sound detororiates. The main function of the ear is to detect sound.

Interference with or infection of sound receptors can lead to auditory disorders. When the labyrinth are affected it can led to an ailment known as labyrinthisis. Its symptoms include, dizziness, nausea, disorientation and vertigo. It can be caused by physical blockage of the inner ear, viral infection or bacterial infection. Outoimmune inner ear condition disease (AIED) is another condition it is characterized by idiopathic, rapidly progressive, bilateral sensorineural hearing loss. It is a rare disorder and is not easily detectable (Wageih, 2017).

References

Wageih, G. (2017). Ear Anatomy Presentation. Otolaryngology, 07(01). doi: 10.4172/2161-119x.1000290

Bohne, B. (2019). Ultrastructural Atlas of the Inner Ear. Ear And Hearing, 6(4), 219-220. doi: 10.1097/00003446-198507000-00015

Landgren, K. (2019). Ear Acupuncture Saintt Louis: Elsevier Health Sciences UK.