A light and electron microscopic study of the pecten of the pigeon eye

Abstract

Abstract The pecten in the pigeon is a pleated lamina that consists of blood vessels and interstitial pigment cells. Arterioles with thin, unspecialized endothelium give origin to an exceedingly dense capillary network. The endothelial cells of the capillaries are provided on both the luminal and basal surfaces with thin lamellar processes, constricted at their origins from the cell body. Luminal lamellae are long, erect and have a prevailing longitudinal orientation. Basal lamellae are shorter, more irregularly oriented and more closely compressed. Besides the usual complement of cytoplasmic organelles, a moderate number of coated vesicles and of coated and uncoated inpocketings of the plasmalemma is present in the endothelial cells. A labyrinthine system of interstices surrounds the stalks of the basal lamellae and contains a material that resembles the substance of the basement lamina in density and texture. A similar material is found on the outer surface of the basal lamellae and imperceptibly merges with the ground substance of an unusually thick adventitial layer that is permeated by numerous unit fibrils of collagen. The capillary network is drained by venules, whose wall resembles the capillary wall. The pigment cells contain melanin granules, large mitochondria and many bundles of filaments. They are sandwiched between two basement laminae and separate the blood vessels from the vitreous body. The bridge of the pecten consists of pigment cells with a few interspersed capillaries.