Perilymph is an
extracellular fluid located within the
inner ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
. It is found within the
scala tympani and
scala vestibuli of the
cochlea. The ionic composition of perilymph is comparable to that of
plasma
Plasma or plasm may refer to:
Science
* Plasma (physics), one of the four fundamental states of matter
* Plasma (mineral), a green translucent silica mineral
* Quark–gluon plasma, a state of matter in quantum chromodynamics
Biology
* Blood pla ...
and
cerebrospinal fluid. The major
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
in perilymph is
sodium, with the values of
sodium and
potassium concentration in the perilymph being 138
mM and 6.9
mM, respectively. It is also named Cotunnius' liquid and liquor cotunnii for
Domenico Cotugno.
Structure
The
inner ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
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 the
bony labyrinth. The bone canals are separated by the membranes in parallel spaces referred to as the
membranous labyrinth. The membranous labyrinth contains
endolymph, and is surrounded by perilymph. The perilymph in the bony labyrinth serves as connection to the
cerebrospinal fluid of the
subarachnoid space
In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in th ...
via the
perilymphatic duct.
Composition
Perilymph and
endolymph have unique ionic compositions suited to their functions in regulating
electrochemical impulses of
hair cells necessary for hearing. The
electric 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. This is referred to as the
endocochlear potential.
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 with
cerebrospinal 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 resembles
intracellular 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.
Clinical significance
It has also been suggested that perilymph and endolymph participate in a unidirectional flow that is interrupted in
Ménière's disease.
References
External links
{{Authority control
Ear
Body fluids