Aqueous Humor, Endolymph, and Perilymph

By: Christian Kroll

What is Aqueous Humor?

• 99.9 % Water

• .1 % Proteins, Glucose, and Electrolytes

• Cellular Debris

Functions of Aqueous Humor• Bringing Oxygen to cells

• Clear medium

• Maintains IOP

• Helps to fight infection

Formation of Aqueous Humor

• Diffusion

• Ultrafiltration

• Active Secretion

Pars Plicata

Ciliary Body

Lens

Posterior Chamber

Suspensory Ligaments

Aqueous Humor Flow

Trabecular outflow 90%

Uveoscleral outflow 10%Anterior Chamber Angle

Outflows

Trabecular Outflow

Guyton R, Hall Textbook of Medical Physiology

Trabecular Meshwork

Anterior Chamber

Anterior Chamber AngleSchlemm’s

Canal

Ciliary body

Posterior Chamber

Episcleral v.

Uveoscleral outflow- 2 sub flows

Uveoscleral Uveovortex

Passage through

• Root of Iris• Interstitial Spaces• Suprachoroidal

Space

Passage through

• Iris• Ciliary Muscle• To Vortex Veins

Used earlier in life

Pressure Independent

Image taken from Rohit Rao’s Presentaion “Physiology of Aqueous Humor

Clinical ApplicationGlaucoma

Primary • Open Angle Glaucoma• Angle Closure Glaucoma

Symptoms• Enlarged Eye Ball• High IOP• Vision Loss• Redness

Treatment• Beta Blockers• Steroid Eye Drops• Surgery?

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health

Endolymph

Source: ControversialCreated from perilymph

Flow: Controversial

Known Location: Membranous Labyrinth

High K+

Perilymph

Source: cochlea?

Derived from CSF?

Known Location:Bony Labyrinth

High Na+

Image from Gilroy et. al Atlas of Anatomy 2 ed.

Endolymphatic Sac

Oval Window

Ampulla

Endolymphatic Duct

Image from Gilroy et. al Atlas of Anatomy 2 ed.

Image from Gilroy et. al Atlas of Anatomy 2 ed.

Scala Vestibuli

Scala Media

Scala Tympani

Reissner’s Membrane

Image from Gilroy et. al Atlas of Anatomy 2 ed.

Organ of Corti is bathed in endolymph

Perilymph different

Why endolymph?Regulates potassium flow without using ATP

Clinical ApplicationMeniere’s Disease

Symptoms: • Vertigo• Hearing loss• Ringing in ears• Pressure in ear

Causes:Abnormal volume of inner ear?

Treatment:Medications such as motion sicknessFluid Retention Reduction

ReferencesLeonard LA, Nilsson SFE, Hoeve JV, Wu S, Kaufman PL, Alm A. 2011. Adler's Physiology of the Eye, 11 th ed, Saunders Elsevier, Philadelphia.

Harris JP and Nguyen QT. 2010. Volume 43, Issue 5. Otolaryngologic Clinics of North America. Saunders, Philadelphia.

Llobet A , Gasull X , Gual A. 2003. Vol. 18. No. 5. Understanding Trabecular Meshwork Physiology: A Key to the Control of Intraocular Pressure American Physiological Society., APS, Bethesda.

Ghanem TA, Breneman KD, Rabbitt RD, Brown HM. 2008. Ionic composition of endolymph and perilymph in the inner ear of the oyster toadfish, Opsanus tau. US National Library of Medicine National Institutes of Health. 214(1):83-90.

Nin F, Hibino H, Murakami S, Suzuki T, Hisa Y, and Kurachia Y. 2011. Computational model of a circulation current that controls electrochemical properties in the mammalian cochlea. Proceedings of the National Academy of Sciences of the United States of America, 10.1073/pnas.1120067109.

Villamarina A, Roya S, Hasballaa R, Vardoulisa R, Reymonda P, Stergiopulosa N. 2012. 3D simulation of the aqueous flow in the human eye. Medical Engineering and Physics Vol 34. Issue 10.

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