Iris anatomy and physiology Flashcards
Pupil is located slightly ___
Inferior nasal
Iris root
Peripheral region of iris that is continuous with the ciliary body.
Pupillary margin
Free edge of the iris that rests of the lens.
Collarette
Circular, jagged ridge 1.5mm from the pupillary margin.
Attachment site for the fetal pupillary membrane (blood vessels) during embryonic development. Vessels disappear by 8.5 months of gestation.
Divides the iris into the pupillary and ciliary zone.
3 layers of the iris anterior to posterior
Stroma- contains the sphincter muscle and dilator extension.
Anterior pigmented epitheloum- single layer. Dilator muscle arises from basal layer.
Posterior pigmented epithelium.
Stroma layer of the iris is composed of
Loose connective tissue, pigmented cells, WBCs, the sphincter muscle, extensions of the dilator muscle.
Loose connective tissue contains collagen, fibroblasts, and ground substance.
Pigmented cells contain melanocytes and clump cells.
Sphincter muscle is composed of circularly arranged smooth muscle fibrils in the pupillary zone.
Dilator muscle extensions.
Loose connective tissue components in iris stroma.
Fibroblasts- meshwork over the collagen and ground substance.
Collagen- Fibrils are arranged in radial columns.
Anchors blood vessels arranged radially in place. Protects arteries from kinking and compressing during iris movement.
2 types of pigmented cells in the iris stroma
Melanocytes- concentrated in stroma under meshwork of fibroblasts.
Clump cells- scavengers of free pigment within the iris. Similar to macrophage. Concentrated under fibroblasts in the pupillary zone.
Anterior pigmented epithelium
Composed of a single layer of pigmented ___ cells.
Dilator muscle arises from the ___ surface. Forms 3-5 layers that extent into the stroma.
What type of junctions join adjacent cells?
Composed of a single layer of pigmented my-epithelial cells.
Dilator muscle arises from the basal surface. Forms 3-5 layers that extent into the stroma. Radially arranged smooth muscle fibrils in the iris root.
Tight junctions join adjacent cells? Regulates passage of aqueous humor from post chamber into iris.
Arrangement of basal surface and apex of the two layers of pigmented epithelium?
Apexes touch.
Basal surface of anterior pigmented epi touches stroma.
Basal surface of posterior pigmented epi touches posterior chamber.
What forms the pupillary ruff/frill?
the 2 layers of the pigmented epithelial cells curl around from the posterior iris to the anterior surface.
What blood supplies the iris? How do the capillaries contribute to the blood aqueous barrier?
Major and minor arterial circle of the iris.
Capillaries lack fenestrations and are joined by tight junctions.
Dilator muscle
Radiator, in ciliary zone.
sphincter muscle
circular, pupillary zone.
