What is an endolymphatic sac?
Listen to pronunciation. (EN-doh-lim-FA-tik sak) A balloon-shaped structure filled with fluid in the inner ear. The fluid in the endolymphatic sac surrounds and protects the structures in the inner ear that affect hearing and balance.
Where does endolymphatic duct open?
The ED leads from the utricular and saccular ducts within the vestibule through the vestibular aqueduct (VA) to the ES, which extends through the distal VA out the external aperture of the aqueduct (Fig 1) to terminate in the epidural space of the posterior cranial fossa.
What fluid runs through the endolymphatic duct?
The endolymphatic sac (ES) is a membranous structure in the inner ear located partly in the temporal bone and partly within the dura of the posterior fossa. It contains endolymph, which is similar in chemical makeup to intracellular fluid (high in K, low in Na).
Where does endolymph come from?
The endolymph is a secretion product of the dark cells in the vestibular part of the labyrinth and the stria vascularis in the cochlear part of the labyrinth.
Which part of ear has endolymph?
The inner ear has two parts: the bony labyrinth and the membranous labyrinth. The membranous labyrinth is contained within the bony labyrinth, and within the membranous labyrinth is a fluid called endolymph.
What is the main function of endolymph?
Endolymph is a fluid located deep in the inner ear that is essential to normal hearing, as well as balance and movement.
Is endolymph in the cochlear duct?
Endolymph is produced continuously by specialized epithelial cells calledstria vascularis in one wall of the cochlear duct and in several other locations in the membranous labyrinth, using an active pumping mechanism that results in a positive electrical potential inside the membranous labyrinth.
How do you approach an endolymphatic sac?
Once the endolymphatic sac is identified, the sac may be incised with a sharp sickle knife, and the lumen, characterized by its glistening and shiny appearance, is entered with an annulus elevator or blunt probe. The right endolymphatic sac is opened. Shunt may be placed inside the lumen of the sac.
What is endolymphatic duct blockage?
Thus, by blocking the endolymphatic duct, we decrease the volume of endolymph in the inner ear coming from the sac, which helps alleviate the symptoms of Meniere’s Disease; in absence of this result, all our patients operated by the EDB should develop a worsening of their symptoms, which is not the case.
What is the difference between the perilymph and the endolymph?
Endolymph is the fluid found inside the membranous labyrinth while perilymph is the fluid that surrounds the endolymph, located inside the bony labyrinth. The conversion of sound waves into the nerve impulses occurs inside the endolymph while the perilymph transforms the sound waves into the endolymph.
Which chamber contains endolymph?
The cochlea is filled with fluid (perilymph and endolymph) and is divided into three chambers called the scala vestibuli, scala media, and the scala tympani.
How does endolymph drain?
The endolymphatic duct and sac drain endolymph from the auditory and vestibular apparatus. Endolymph is produced continuously. It is drained and its fluid secretion is regulated via the endolymphatic sac. The sac has fenestrated blood vessels that are leaky and can allow fluid to pass between their membranes.
Is endolymph extracellular or intracellular?
The membranous labyrinth is filled with endolymph, which is unique among extracellular fluids of the body, including the perilymph, in that its potassium ion concentration is higher (about 140 milliequivalents per litre) than its sodium ion concentration (about 15 milliequivalents per litre).
What structure produces endolymph?
The stria vascularis, a complex epithelial structure composed of various cell types, produces endolymph and releases it into the cochlea.
Why is endolymph important?
The acceleration of endolymph within regions of the vestibular apparatus allows for our perception of balance and equilibrium. This occurs through head movement that causes endolymph to move specialized cells known as hair cells.
What is the function of the endolymphatic sac?
Studies suggest that the endolymphatic duct and endolymphatic sac perform both absorptive and secretory, as well as phagocytic and immunodefensive, functions. Neoplasms of the endolymphatic sac are very rare tumors.
Is the endolymphatic sac intraosseous or extramuscular?
Note that proximal to the external aperture, the endolymphatic sac is intraosseous, lying within the vestibular aqueduct, and that distal to the external aperture, the sac is extraosseous.
What are neoplasms of the endolymphatic sac?
Neoplasms of the endolymphatic sac are very rare tumors. This article incorporates text in the public domain from page 1052 of the 20th edition of Gray’s Anatomy (1918)
What happens if the endolymphatic sac is damaged?
Injury to the endolymphatic sac may, over time, severely compromise hearing. The endolymphatic sac is located in a duplication of the dura of the posterior aspect of the petrous pyramid and is, therefore, in the surgical field of many neurosurgical operations performed on the posterolateral cranial base.