Stroma of iris

Stroma of iris
The upper half of a sagittal section through the front of the eyeball. ("Stroma of iris" labeled at bottom right.)
Details
Identifiers
Latin	stroma iridis
TA	A15.2.03.031
FMA	58526
*Anatomical terminology* [edit on Wikidata]

The stroma of the iris is a fibrovascular layer of tissue. It is the upper layer of two in the iris.

Structure

The stroma is a delicate interlacement of fibres. Some circle the circumference of the iris and the majority radiate toward the pupil. Blood vessels and nerves intersperse this mesh.

In dark eyes, the stroma often contains pigment granules. Blue eyes and the eyes of albinos, however, lack pigment.

The stroma connects to a sphincter muscle (sphincter pupillae), which contracts the pupil in a circular motion, and a set of dilator muscles (dilator pupillae) which pull the iris radially to enlarge the pupil, pulling it in folds. The back surface is covered by a commonly, heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the muscles dilate.

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

External links

UIUC Histology Subject 156

Anatomy of the globe of the eye

Fibrous tunic (outer)

Sclera	Episcleral layer Schlemm's canal Trabecular meshwork

Cornea	Limbus layers Epithelium Bowman's Stroma Dua's layer Descemet's Endothelium

1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:Schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea 27:sclera 28:choroid 29:superior rectus muscle 30:retina

Uvea/vascular tunic (middle)

Choroid	Capillary lamina of choroid Bruch's membrane Sattler's layer

Ciliary body	Ciliary processes Ciliary muscle Pars plicata Pars plana

Iris	Stroma Pupil Iris dilator muscle Iris sphincter muscle

Retina (inner)

Layers	Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium

Cells	Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Retina ganglion cell (Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell) → Diencephalon: P cell, M cell, K cell, Muller glia

Other	Macula Foveola Fovea centralis Parafovea Perifovea Optic disc Optic cup Ora serrata

Anatomical regions of the eye

Anterior segment	Adnexa Fibrous tunic Anterior chamber Aqueous humor Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn

Posterior segment	Vitreous chamber Vitreous humor Retina Choroid

Other

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