| Perilymph | |
|---|---|
 Cross-section ofcochlea. Perilymph is located in thescala vestibuli andscala tympani - the aqua regions at the top and bottom of the diagram. | |
 Cross-section of semi-circular canal and duct showing perilymphatic space | |
| Details | |
| Identifiers | |
| Latin | perilympha |
| MeSH | D010498 |
| TA98 | A15.3.03.056 |
| TA2 | 6938 |
| FMA | 60908 |
| Anatomical terminology | |
Perilymph is anextracellular fluid located within theinner ear. It is found within thescala tympani andscala vestibuli of thecochlea. The ionic composition of perilymph is comparable to that ofplasma andcerebrospinal fluid. The majorcation in perilymph issodium, with the values ofsodium andpotassium concentration in the perilymph being 138 mM and 6.9 mM, respectively.[1] It is also named Cotunnius' liquid and liquor cotunnii forDomenico Cotugno.
Theinner ear has two major parts, the cochlea and the vestibular organ. They are connected in a series of canals in the temporal bone referred to as thebony labyrinth. The bone canals are separated by the membranes in parallel spaces referred to as themembranous labyrinth. The membranous labyrinth containsendolymph, and is surrounded by perilymph.[2] The perilymph in the bony labyrinth serves as connection to thecerebrospinal fluid of thesubarachnoid space via theperilymphatic duct.[3]
Perilymph andendolymph have unique ionic compositions suited to their functions in regulatingelectrochemical impulses ofhair cells necessary for hearing. Theelectric potential of endolymph is ~80-90 mV more positive than perilymph due to a higher concentration of potassium cations (K+) in endolymph and higher sodium (Na+) in perilymph.[4] This is referred to as theendocochlear potential.[5]
Perilymph is the fluid contained within the bony labyrinth, surrounding and protecting the membranous labyrinth; perilymph resembles extracellular fluid in composition (sodium salts are the predominant positive electrolyte) and, via the cochlear aqueduct (sometimes referred to as the "perilymphatic duct"), is in continuity withcerebrospinal fluid.
Endolymph is the fluid contained within the scala media of the membranous labyrinth of the inner ear and within the semicircular canals of the vestibular apparatus; endolymph resemblesintracellular fluid in composition (potassium is the main cation).
Apart from the importance in the electric cochlear potential, the perilymph also contains a large number of proteins, e.g. extracellular enzymes and immunoglobulins. These proteins are important for the immune response and metabolism among others physiological functions.[6]
It has also been suggested that perilymph and endolymph participate in a unidirectional flow that is interrupted inMénière's disease.
