WORKSHOP IN HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 5. SPECIAL HISTOLOGY

Nervous system and sense organs.

Slide 71. Meridional section of the anterior segment of the eye ("iridocorneal angle").

Staining: hematoxylin and eosin.

Magnification: x56.

Under low magnification, identify the dome-shaped cornea (1), followed by the anterior chamber of the eye (2), the iris (3), the lens (4), the posterior chamber of the eye, and the vitreous body (5).

Externally, the cornea is covered by stratified squamous non-keratinized epithelium, which transitions into the conjunctival epithelium, while internally it is lined by a simple squamous epithelium that continues into the epithelium of the iris. The structural details of the cornea are described in slide 72.

Posteriorly, the cornea transitions into the sclera (6). At the junction, a system of spaces is located — the venous sinus of the sclera, or canal of Schlemm. The vascular tunic (choroid) (7) adheres to the inner surface of the sclera and is easily identified by the dark brown/black melanin pigment it contains. Approximately at the level of the canal of Schlemm, the vascular tunic forms a wedge-shaped thickening — the ciliary body (8). Ciliary processes extend from the broad Base of the ciliary body, and fine fibers stretch from these processes to the lens, collectively forming the suspensory ligament (zonule of Zinn).

Under high magnification, the base of the ciliary body is seen to be formed by smooth myocytes (the ciliary Muscle) as well as Connective Tissue rich in pigment Cells.

The posterior surface of the ciliary body, iris, and ciliary processes is covered by the ciliary (blind) part of the retina, which is a direct continuation of the pigmented layer of the optic part of the retina. The boundary between the optic and ciliary PARTS OF THE retina forms the ora serrata.

High magnification reveals that the lens is composed of lens fibers and is enclosed externally by a capsule. A simple squamous epithelium is located underneath the capsule on the anterior surface.

In the angle between the cornea and the iris (where the latter meets the inner surface of the sclera), elements of the pectinate ligament (9) can be observed. This region is referred to as the "iridocorneal angle" (angle of the eye), which, together with the canal of Schlemm, ensures the outflow of aqueous humor from the anterior chamber of the eye.

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Slide 71. Meridional section of the anterior segment of the eye ("iridocorneal angle").