Vascular Layer DR MAHN L9

Ciliary Body

A thickened ring of tissue that encircles the lens. It consists of ciliary muscles.

Irises (Rainbow)

Come in diff. colors, but they contain only brown pigment.

Sympathetic fibers

Control pupillary dilation

Parasympathetic fibers

Control restriction.

Ciliary zonule (suspensory ligament)

Extends from the ciliary processes to the lens. This halo of fine fibers encircles and helps hold the lens in its upright position.

A lot of pigment

Eyes are brown or black

Vascular Layer

Forms the middle coat of the eyeball. Also called the uvea, this pigmented layer has three regions: choroid, ciliary body, and iris.

Ciliary muscles

Interlacing smooth muscle bundles that act to control lens shape

Structure of the Iris

Made up of two smooth muscle layers with bunches of sticky elastic fibers that congeal into a random pattern before birth. Its muscle fibers allow it to act as a reflexively activated diaphragm to vary pupil size.

Changes in pupil size

May also reflect our interests and emotional reactions.

The Choroid's Brown Pigement

Produced by melanocytes, helps absorb light, preventing it from scattering and reflecting within the eye.

Ciliary processes

Radiating folds that secrete the fluid that fills the cavity of the anterior segment of the eyeball.

Most newborn babies' eyes

Slate gray or blue because their iris pigment is not yet developed.

In distant vision and dim light:

The Dilatory pupillae (radial muscles) contract and the pupil dilates, allowing more light to enter.

In close vision and bright light:

The Sphincter pupillae (circular muscles) contract and the pupil constricts.

Pupil

The opening through which light enters the eye

Pupils dilate when...

The subject matter is appealing, in response to fear, and during problem solving. Ex. Computing your taxes should make your pupils get bigger. Ex. Boredom or repulsive matter causes pupils to constrict.

Small amount of pigment or restricted to the posterior surface of the iris

The unpigmented parts simply scatter the shorter wavelengths of light and the eyes appear blue, green, or gray.

Iris

The visible colored part of the eye, is the most anterior portion of the vascular layer. Shaped like a flattened donut, it lies between the cornea and the lens.

Choroid

Vascular middle layer of the eye. Its blood vessels nourish all eye layers.