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AQUEOUS

AQUEOUS. AQUEOUS HUMOR LECTURE. Reading Assignment: Chapter 8, Adler's Physiology of the Eye. I. DEFINITION AND FUNCTION.

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AQUEOUS

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  1. AQUEOUS

  2. AQUEOUS HUMOR LECTURE • Reading Assignment: Chapter 8, Adler's Physiology of the Eye.

  3. I. DEFINITION AND FUNCTION • A. Transparent, colorless liquid in the anterior and posterior chambers of the eye. Provides nutrition for ocular tissues, allows for waste product removal, and maintains eye pressure.

  4. II. PRODUCTION • A. Ciliary Body • 1. extends from the iris to the ora serrata. • 2. Principally unstriated muscle • a. longitudinal, radial and circular • 3. Two divisions • a. pars plicata - anterior third consisting of ciliary processes • b. pars plana - posterior 2/3rds

  5. II. PRODUCTION • 4. Ciliary processes - approximately 70 ridges projecting inward from the pars plicata

  6. II. PRODUCTION • 5. Firmly attached at the scleral spur • 6. Blood supply consist of the anterior and long posterior ciliary arteries • a. each ciliary process receives an arteriole and is drained by a venule which connects with the vortex system

  7. II. PRODUCTION • 7. Nervous supply - long posterior and short ciliary nerves, parasympathetic and sympathetic innervation

  8. II. PRODUCTION • B. Anatomy • 1. Stromal core surrounded by a layer of pigmented epithelium (cuboidal) and nonpigmented epithelium (columnar) • 2. Two layers of epithelium face apex to apex. • a. Bruchs membrane forms the basement membrane for the pigmented layer. • b. Basement membrane for the nonpigmented layer is the internal limiting membrane.

  9. II. PRODUCTION • 3. Many connections between the two layers • a. desmosomes, gap junctions, tight junctions • b. tight junctions - at apex of nonpigmented cells, form a tight barrier • c. tight junctions and blood vessels with small fenestrations result in a blood-aqueous barrier • i. clinical consequences

  10. II. PRODUCTION • C. Mechanism of Aqueous Formation • 1. Three possible • diffusion • ultrafiltration • active transport

  11. II. PRODUCTION • 2. Active transport • a. produces the bulk of the aqueous, requires energy • b. Na/K ATPase located along lateral cellular interdigitations of NPE • c. aqueous production decreases when use ouabain

  12. II. PRODUCTION • d. Na+ transported out with Cl-, HCO3- and H2O following • e. positive charge in aqueous near NPE wall • f. solute concentrated at region near the tight junction and decreases as you approach the posterior chamber

  13. II. PRODUCTION • 3. Ultrafiltration • a. a substance is forced across a membrane with the help of a hydrostatic driving force • b. produces a small amount of aqueous • c. hydrostatic pressure probably greater in opposite direction (out of eye)

  14. II. PRODUCTION • 4. Diffusion • a. movement of a substance down its concentration gradient • b. small amount of aqueous made this way

  15. III. AQUEOUS HUMOR COMPOSITION • A. Initially compared concentration with that of plasma • B. Substances in the aqueous are used by all the surrounding tissues and the aqueous contains all their waste products (cornea, lens, vitreous and iris)

  16. III. AQUEOUS HUMOR COMPOSITION • 1. Osmolarity • a. slightly hyperosmotic to plasma • 2. Electrolytes • a. Na+ and K+ concentrations similar to plasma • b. Cl- higher and HCO3- lower than plasma level • c. Oxygen diffuses into aqueous from blood so lower concentration in aqueous • d. Glucose lower and lactate higher than plasma concentrations

  17. III. AQUEOUS HUMOR COMPOSITION • e. Ascorbate - high concentration in aqueous (about 20 X that of plasma) rises with increasing concentration in the blood until a ceiling of about 50 mg/100 ml is reached in the aqueous • i. thus, secreted actively by a specific carrier mechanism that can be saturated • f. Amino acids • i. most amino acids in higher concentrations in the aqueous than the plasma which indicates active transport • ii. different amino acids have different concentrations

  18. III. AQUEOUS HUMOR COMPOSITION • g. Proteins are limited in the aqueous by the blood aqueous barrier (1/90) • i. low molecular weight proteins can get into the aqueous (albumin in high conc) • h. Immunoglobulins • i. IgG concentration of 3 mg/100 ml of aqueous • ii. IgD, IgA and IgM not normally found • iii. small quantities of complement can be found

  19. III. AQUEOUS HUMOR COMPOSITION • i. Other compounds found include hyaluronic acid, corticosteroids, lipids, vitamin B12 and lens proteins.

  20. III. AQUEOUS HUMOR COMPOSITION • Clinical Significance • may aid in Dx • diabetes mellitus • glaucoma

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