S.C.C.O. 5/17/20151 AQUEOUS S.C.C.O. 5/17/20152 AQUEOUS HUMOR LECTURE Reading Assignment: Chapter 8, Adler's Physiology of the Eye

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AQUEOUSAQUEOUS

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AQUEOUS HUMOR AQUEOUS HUMOR LECTURELECTURE

Reading Assignment: Chapter 8, Adler's Reading Assignment: Chapter 8, Adler's Physiology of the Eye.Physiology of the Eye.

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I. DEFINITION AND I. DEFINITION AND FUNCTIONFUNCTION A. Transparent, colorless liquid in the A. Transparent, colorless liquid in the

anterior and posterior chambers of the anterior and posterior chambers of the eye. Provides nutrition for ocular eye. Provides nutrition for ocular tissues, allows for waste product tissues, allows for waste product removal, and maintains eye pressure.removal, and maintains eye pressure.

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II. PRODUCTIONII. PRODUCTION

A. Ciliary BodyA. Ciliary Body– 1. extends from the iris to the ora serrata.1. extends from the iris to the ora serrata.– 2. Principally unstriated muscle2. Principally unstriated muscle

• a. longitudinal, radial and circulara. longitudinal, radial and circular

– 3. Two divisions3. Two divisions• a. pars plicata - anterior third consisting of a. pars plicata - anterior third consisting of

ciliary processesciliary processes• b. pars plana - posterior 2/3rdsb. pars plana - posterior 2/3rds

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– 4. Ciliary processes - 4. Ciliary processes - approximately 70 approximately 70 ridges projecting ridges projecting inward from the pars inward from the pars plicataplicata

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– 5. Firmly attached at the scleral spur5. Firmly attached at the scleral spur– 6. Blood supply consist of the anterior and 6. Blood supply consist of the anterior and

long posterior ciliary arterieslong posterior ciliary arteries• a. each ciliary process receives an arteriole and a. each ciliary process receives an arteriole and

is drained by a venule which connects with the is drained by a venule which connects with the vortex systemvortex system

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– 7. Nervous supply - long posterior and 7. Nervous supply - long posterior and short ciliary nerves, parasympathetic and short ciliary nerves, parasympathetic and sympathetic innervationsympathetic innervation

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B. AnatomyB. Anatomy– 1. Stromal core surrounded by a layer of 1. Stromal core surrounded by a layer of

pigmented epithelium (cuboidal) and pigmented epithelium (cuboidal) and nonpigmented epithelium (columnar)nonpigmented epithelium (columnar)

– 2. Two layers of epithelium face apex to apex.2. Two layers of epithelium face apex to apex.• a. Bruchs membrane forms the basement a. Bruchs membrane forms the basement

membrane for the pigmented layer.membrane for the pigmented layer.• b. Basement membrane for the nonpigmented b. Basement membrane for the nonpigmented

layer is the internal limiting membrane.layer is the internal limiting membrane.

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– 3. Many connections between the two 3. Many connections between the two layerslayers• a. desmosomes, gap junctions, tight junctionsa. desmosomes, gap junctions, tight junctions• b. tight junctions - at apex of nonpigmented b. tight junctions - at apex of nonpigmented

cells, form a tight barriercells, form a tight barrier• c. tight junctions and blood vessels with small c. tight junctions and blood vessels with small

fenestrations result in a blood-aqueous barrierfenestrations result in a blood-aqueous barrier– i. clinical consequencesi. clinical consequences

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C. Mechanism of Aqueous FormationC. Mechanism of Aqueous Formation– 1. Three possible1. Three possible

• diffusiondiffusion• ultrafiltrationultrafiltration• active transportactive transport

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– 2. Active transport2. Active transport• a. produces the bulk of the aqueous, requires a. produces the bulk of the aqueous, requires

energyenergy• b. Na/K ATPase located along lateral cellular b. Na/K ATPase located along lateral cellular

interdigitations of NPEinterdigitations of NPE• c. aqueous production decreases when use c. aqueous production decreases when use

ouabainouabain

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• d. Na+ transported out with Cl-, HCO3- and d. Na+ transported out with Cl-, HCO3- and H2O followingH2O following

• e. positive charge in aqueous near NPE walle. positive charge in aqueous near NPE wall• f. solute concentrated at region near the tight f. solute concentrated at region near the tight

junction and decreases as you approach the junction and decreases as you approach the posterior chamberposterior chamber

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– 3. Ultrafiltration3. Ultrafiltration• a. a substance is forced across a membrane a. a substance is forced across a membrane

with the help of a hydrostatic driving forcewith the help of a hydrostatic driving force• b. produces a small amount of aqueousb. produces a small amount of aqueous• c. hydrostatic pressure probably greater in c. hydrostatic pressure probably greater in

opposite direction (out of eye)opposite direction (out of eye)

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– 4. Diffusion4. Diffusion• a. movement of a substance down its a. movement of a substance down its

concentration gradientconcentration gradient• b. small amount of aqueous made this wayb. small amount of aqueous made this way

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III. AQUEOUS HUMOR III. AQUEOUS HUMOR COMPOSITIONCOMPOSITION A. Initially compared concentration with A. Initially compared concentration with

that of plasmathat of plasma B. Substances in the aqueous are used B. Substances in the aqueous are used

by all the surrounding tissues and the by all the surrounding tissues and the aqueous contains all their waste aqueous contains all their waste products (cornea, lens, vitreous and iris)products (cornea, lens, vitreous and iris)

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III. AQUEOUS HUMOR III. AQUEOUS HUMOR COMPOSITIONCOMPOSITION

– 1. Osmolarity1. Osmolarity• a. slightly hyperosmotic to plasmaa. slightly hyperosmotic to plasma

– 2. Electrolytes2. Electrolytes• a. Na+ and K+ concentrations similar to plasmaa. Na+ and K+ concentrations similar to plasma• b. Cl- higher and HCO3- lower than plasma levelb. Cl- higher and HCO3- lower than plasma level• c. Oxygen diffuses into aqueous from blood so c. Oxygen diffuses into aqueous from blood so

lower concentration in aqueouslower concentration in aqueous• d. Glucose lower and lactate higher than plasma d. Glucose lower and lactate higher than plasma

concentrationsconcentrations

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• e. Ascorbate - high concentration in aqueous e. Ascorbate - high concentration in aqueous (about 20 X that of plasma) rises with increasing (about 20 X that of plasma) rises with increasing concentration in the blood until a ceiling of about concentration in the blood until a ceiling of about 50 mg/100 ml is reached in the aqueous50 mg/100 ml is reached in the aqueous

– i. thus, secreted actively by a specific carrier i. thus, secreted actively by a specific carrier mechanism that can be saturatedmechanism that can be saturated

• f. Amino acidsf. Amino acids– i. most amino acids in higher concentrations in the i. most amino acids in higher concentrations in the

aqueous than the plasma which indicates active aqueous than the plasma which indicates active transporttransport

– ii. different amino acids have different concentrationsii. different amino acids have different concentrations

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• g. Proteins are limited in the aqueous by the g. Proteins are limited in the aqueous by the blood aqueous barrier (1/90)blood aqueous barrier (1/90)

– i. low molecular weight proteins can get into the i. low molecular weight proteins can get into the aqueous (albumin in high conc)aqueous (albumin in high conc)

• h. Immunoglobulinsh. Immunoglobulins– i. IgG concentration of 3 mg/100 ml of aqueousi. IgG concentration of 3 mg/100 ml of aqueous– ii. IgD, IgA and IgM not normally foundii. IgD, IgA and IgM not normally found– iii. small quantities of complement can be foundiii. small quantities of complement can be found

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• i. Other compounds found include hyaluronic i. Other compounds found include hyaluronic acid, corticosteroids, lipids, vitamin B12 and acid, corticosteroids, lipids, vitamin B12 and lens proteins.lens proteins.

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Clinical SignificanceClinical Significance– may aid in Dx may aid in Dx

• diabetes mellitusdiabetes mellitus• glaucomaglaucoma

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S.C.C.O. 5/17/20151 AQUEOUS S.C.C.O. 5/17/20152 AQUEOUS HUMOR LECTURE Reading Assignment: Chapter 8, Adler's Physiology of the Eye