1 Iris. Frontally-located, round, variably colored disk about 10-12 mm in diameter, with a central aperture (pupil). The iris forms the posterior border of the anterior chamber of the eye. Its lateral margins become continuous with the ciliary body. A

2 Pupillary margin. Margo pupillaris. Medial (internal) margin of the iris bordering the pupil. A B

3 Ciliary margin. Margo ciliaris. Lateral (external) margin of iris attached to ciliary body at the ir-idocorneal angle. B

4 Anterior surface. Facies anterior. It faces the anterior chamber. B

5 Posterior surface. Facies posterior. Surface facing the posterior chamber. A B

6 Greater ring (circle) of iris. Anulus iridis major. Ciliary segment of the iris, and outer cirucular zone on the anterior surface of the iris. It is coarser and broader than the lesser ring. A

7 Lesser ring (circle) of iris. Anulus iridis minor. Pupillary segment of iris. Narrow, circular inner zone on the anterior surface of iris. Its structure is finer than that of the greater ring. A

8 Iridial folds. Plicae iridis. Folds passing around the pupillary margin on the anterior side of the iris. They make the pupillary margin appear slightly serrated. A

9 Pupil. Pupilla. Aperture in the iris surrounded by the pupillary margin of the iris. Its diameter varies depending upon the intensity of light and the focal distance of the observed object. A

10 M. sphincter pupillae. Network of spirally coursing muscle fibers the longitudinal axes of which run approximately parallel to the pupillary margin when the pupil is dilated. It is innervated by parasympathetic fibers from the oculomotor nerve. B

11 M. dilator pupillae. Thin layer of smooth muscle mainly comprised of radially oriented fibers. It is innervated by sympathetic fibers from the carotid plexus.

12 Stroma iridis. Vascular framework of the iris infiltrated by pigmented connective tissue cells. Its anterior and posterior portions are thicker than the rest and are divided by a fine fibrous network. A B

13 Pigmented (posterior) epithelium. Epithelium pigmentosum. Bilayered epithelium on the posterior surface of the iris. It is so heavily pig-mented that no nuclei are visible on the surface facing the posterior chamber. A

14 Spaces of iridocorneal angle [spaces of Fontana]. Spatia anguli iridocornealis. Interstices between the fibers of the trabecular meshwork. They form passageways that convey aqueous fluid to the sinus venosus sclerae. A

15 Greater arterial circle of iris. Circulus arterio-sus iridis major. Ringlike vascular system with radiating branches. It is formed by anastomoses between the long and short posterior ciliary arteries. A

16 Lesser arterial circle of iris. Circulus arteriosus iridis minor. Ringlike vascular system in the vicinity of the pupillary margin formed by anastomoses between the radial branches of the greater arterial circle. A

17 Pupillary membrane. [Membrana pupillaris]. Anterior part of embryonical vascular membrane around the lens that is situated behind the pupil. It is fused to the pupillary margin and receives blood vessels from there.

18 INTERNAL (SENSORY) TUNIC OF EYEBALL. Tunica interna bulbi. It comprises the retina with its pigment epithelium.

19 Retina. Inner lining of eyeball developed from the two layers of the optic cup. Most of it is light-sensitive (pars optica). B

20 Pars optica retinae. Retinal segment capable of transforming light stimuli into nerve impulses. It lines the posterior aspect of the eyeball and extends as far anteriorly as the ora serrata. B

21 Pigmented part. Pars pigmentosa. Pigment epithelium arising from the external layer of the optic cup. B

22 Nervous part. Pars nervosa. Retina proper consisting essentially of three nuclear layers lying internal to the pigment epithelium. B

23 Neuroepithelial (photosensitive) layer. Stratum neuroepitheliale (photosensorium). Outer layer of the cerebral stratum. It consists of rods and cones, the outer segments of which affect the transformation of light stimuli into nerve impulses. Cell bodies of rods and cones form the outermost layer of the retinal nuclei (external nuclear layer). D

24 Internal nuclear layer. [[Stratum ganglionare retinae]]. Middle layer of cell nuclei mainly consisting of the cell bodies of bipolar and amacrine cells. D

25 Ganglion cell layer. [[Stratum ganglionare n. op-tici]]. Internal layer of nuclei consisting of multipolar cell bodies of initially non-myelinated ganglion cells the axons of which form the optic nerve. D

26 Ora serrata. Serrated margin between the light-sensitive and light-insensitive parts ofthe neural retina. B C

27 Pars ciliaris retinae. Light-insensitive retinal segment consisting of a bilayered cuboidal epithelium (ciliary epithelium) forming the posterior surface of the ciliary body. Its outer layer of epithelium is continuous with the pigment epithelium of the retina and is pigmented, whereas the innermost epithelium is continuous with the pars nervosa of the retina and is devoid of pigment. B

28 Pars iridica retinae. Light-insensitive retinal segment on the posterior surface of the iris. It is continuous with the pars ciliaris retinae and forms the bilayered posterior epithelium of the iris. Both layers are heavily pigmented. B

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