FACTOID # 29: 73.3% of America's gross operating surplus in motion picture and sound recording industries comes from California.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Aqueous humour
Schematic diagram of the human eye.
Schematic diagram of the human eye.

The aqueous humour is a thick watery substance that fills the space between the lens and the retina. Image File history File links Schematic_diagram_of_the_human_eye_en. ... Image File history File links Schematic_diagram_of_the_human_eye_en. ...

Contents

Locations

The anterior segment is the front third of the eye that includes the structures in front of the vitreous humour: the cornea, iris, ciliary body, and lens.[1][2] Within the anterior segment are two fluid-filled spaces divided by the iris plane: anterior segment ... Vitreous humour is the clear aqueous solution that fills the space between the lens and the retina of the vertebrate eyeball. ... In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... Schematic diagram of the human eye The ciliary body is the part of the eye containing the ciliary muscle and ciliary processes. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...

Aqueous humour fills these spaces within the anterior segment to provide nutrients to the lens and corneal endothelium, and its pressure maintains the convex shape of the cornea.[3][4] The anterior chamber if the fluid-filled space inside the eye between the iris and the corneas innermost surface, the endothelium . ... Corneal endothelium is the inner most layer of the cornea, the corneal endothelium is actually a monolayer of squamate epithelial cells lining the anterior chamber of the eye. ... The posterior chamber is a narrow chink behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes. ... Corneal endothelium is the inner most layer of the cornea, the corneal endothelium is actually a monolayer of squamate epithelial cells lining the anterior chamber of the eye. ...


In a healthy eye, the aqueous humour does not mix with the firm, gel-like vitreous humour because of the lens and its Zonule of Zinn between the two. Vitreous humour is the clear aqueous solution that fills the space between the lens and the retina of the vertebrate eyeball. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. ...


Functions

  • Maintains the intraocular pressure and inflates the globe of the eye.
  • Provides nutrition for the avascular ocular tissues; posterior cornea, trabecular meshwork, lens, and anterior vitreous.
  • Carries away waste products from metabolism of the above avascular ocular tissues.
  • May serve to transport ascorbate in the anterior segment to act as an anti-oxidant agent.
  • Presence of immunoglobulins indicate a role in immune response to defend against pathogens.

Its main function is to provide diopteric power to the cornea. Intraocular pressure (IOP) is the fluid pressure inside the eye. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... This is an area of tissue located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humour from the eye via the anterior chamber (the chamber on the front of the eye covered by the cornea). ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... Ascorbic acid is an organic acid with antioxidant properties. ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... A dioptre (also diopter) is a unit of curvature equal to one per metre; that is, inverse metres, or 1/(metres). ...


Composition

  • Water: 99%[5]
  • Ions: HCO3-, buffers metabolic acids; Cl-, preserves electric neutrality; Na+; K+; Ca2+; PO42-.
  • Proteins: albumin, β-globulins. Very low density due to filtration.
  • Ascorbate: anti-oxidative, protects against UV.
  • Glucose
  • Lactate: produced by metabolism of anaerobic structures of the eye.
  • Amino acids: transported by cilary epithelial cells.

Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... This article is about the electrically charged particle. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Albumin can refer to ovalbumin, the principal protein in egg white albumins, a group of proteins including serum albumin and together constituting roughly 60% of the protein in blood plasma. ... Schematic representation of a protein electrophoresis gel Beta globulins are a group of globular proteins in plasma that are more mobile in alkaline or electricaly charged solutions than gamma globulins, but less mobile than alpha globulins. ... Ascorbic acid is an organic acid with antioxidant properties. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Lactic acid is a chemical compound that plays a role in several biochemical processes. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...

Production and drainage

Aqueous humour is secreted into the posterior chamber by the ciliary body, specifically the non-pigmented epithelium of the ciliary body. It flows through the narrow cleft between the front of the lens and the back of the iris, to escape through the pupil into the anterior chamber, and then to drain out of the eye via the trabecular meshwork. From here, it drains into Schlemm's canal by one of two ways: directly, via aqueous vein to the episcleral vein, or indirectly, via collector channels to the episcleral vein by intrascleral plexus and eventually into the veins of the orbit. Schematic diagram of the human eye The ciliary body is the part of the eye containing the ciliary muscle and ciliary processes. ... This is an area of tissue located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humour from the eye via the anterior chamber (the chamber on the front of the eye covered by the cornea). ... Schlemms canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream. ... The episclera is the outermost layer of the sclera[1]. It is composed of loose, fibrous, elastic tissue and attaches to Tenons capsule[1]. In episcleritis, the episclera and Tenons capsule are infiltrated with inflammatory cells [2]. References ^ a b Cassin, B. and Solomon, S. Dictionary of Eye... In the circulatory system, a vein is a blood vessel that carries blood toward the heart. ... In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. ...


Production

  • Filtration: As blood flows in the cilary body's capillaries, it is coarsely filtered by the capillaries' endothelial cells. The resulting plasma is then refiltered by the pigmented and nonpigmented cilary epithelial cells and poured into the posterior chamber of the eye as aqueous humor.
  • Diamond-Bossert model: Active transport occurring in the nonpigmented cilary epithelial cells induces small osmotic pressure gradients in between the cells. A higher concentration of solutes in the proximal part of the intercellular space generates a flow of water. The concentration diminishes from the proximal part to the distal part, releasing the liquid into the posterior chamber.

This article or section does not adequately cite its references or sources. ...

Drainage

Aqueous humour is continually produced by the ciliary processes - to maintain a constant intraocular pressure, the production of aqueous humour must be balanced by an equal rate of aqueous humour drainage. Small variations in the changes in production or outflow of aqueous humour will have a large influence on the intraocular pressure. Intraocular pressure (IOP) is the fluid pressure inside the eye. ...


The primary route for aqueous humour flow is first through the posterior chamber, then the narrow space between the posterior iris and the anterior lens (contributes to small resistance), through the pupil to enter the anterior chamber. From there, the aqueous humour exits the eye through the trabecular meshwork into Schlemm's canal, it flows through 25 - 30 collector canals into the episcleral veins. The greatest resistance to aqueous flow is provided by the trabecular meshwork, and this is where most of the aqueous outflow occurs. The posterior chamber is a narrow chink behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes. ... The anterior chamber if the fluid-filled space inside the eye between the iris and the corneas innermost surface, the endothelium . ... This is an area of tissue located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humour from the eye via the anterior chamber (the chamber on the front of the eye covered by the cornea). ... Schlemms canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream. ...


The secondary route is the uveoscleral drainage, and is independent of the intraocular pressure, the aqueous flows through here, but to a lesser extent than through the trabecular meshwork.


Diseases and disorders

Main article: Glaucoma

Glaucoma is a condition characterised by increased intraocular pressure (pressure within the eye) either through increased production or decreased outflow of aqueous humor.[6] Increased resistance to outflow of aqueous humour may occur due to an abnormal trabecular meshwork or to obliteration of the meshwork due to injury or disease of the iris. Uncontrolled glaucoma typically leads to visual field loss and ultimately blindness. Intraocular pressure (IOP) is the fluid pressure inside the eye. ... This article is about the visual condition. ...


References

  1. ^ Cite error 8; No text given.
  2. ^ "Departments. Anterior segment." Cantabrian Institute of Ophthalmology.
  3. ^ Miguel Coca-Prados, Ph.D.
  4. ^ Uzzle T. "The Eye, the Ear, and the Brain."
  5. ^ Pipe & Rapley, "Ocular Anatomy and Histology" 1999
  6. ^ http://www.emedicinehealth.com/understanding_glaucoma_medications/article_em.htm

External links


  Results from FactBites:
 
aqueous humour - definition of aqueous humour in Encyclopedia (257 words)
The aqueous humour is the clear, watery fluid that fills the complex space in the front of the eye which is bounded at the front by the cornea and at the rear by the front surface or face of the vitreous humour.
The face of the vitreous humour spans the eye transversely behind the lens, and the aqueous-filled space in front of this is divided by the iris plane into the anterior chamber and the posterior chamber (which, despite its name, is still an anterior structure).
The aqueous humour allows nutrients to circulate to the corneal endothelium and its pressure maintains the convex shape of the cornea.
Vitreous humour - Wikipedia, the free encyclopedia (255 words)
Vitreous humour is the clear aqueous solution that fills the space between the lens and the retina of the vertebrate eyeball.
The phagocytic cells are present to remove unwanted debris in the visual field.
The primary purpose of the vitreous humour is to provide a cushioned support for the rest of the eye, as well as a clear unobstructed path for light to travel to the retina.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m