| Popis: |
1. The dilatator pupillas of the human iris consists of a thin stratum of radially disposed, riband-shaped, plain muscle-cells: this stratum covers the posterior surface of the iris-stroma. 2. At the peripheral zone of the iris the dilatator is somewhat thickened, and its cells, in place of being in a single layer as is the case over the greater part of the iris, are two or three deep. 3. The dilatator is not separated from the uveal pigment by a basement membrane. 4. The uveal pigment which covers the back of the iris is composed of two strata not very closely adherent to one another. The more superficial or posterior stratum, which is formed of large columnar cells, is in thin sections relatively easily detached from the deeper or anterior stratum. This last is composed of cells which are spindle-shaped in radial sections; they are arranged over the greater part of the iris in a single layer, but here and there, especially near the periphery, may be two deep. The deeper stratum of the pigmented epithelium is intimately adherent to the adjacent layer which forms the dilatator muscle, but, at least in the adult, the cell-elements of the two layers are differentiated from one another and do not form a part of the same tissue. |
Plný text