The pecten oculi was located over the optic disc and was projected out into the vitreous body. The parameters were analyzed with one-way ANOVA (SPPSS 9.0 SPSS Inc. The diameter of the capillaries and thickness of capillary basement membrane of pecten oculi were measured with IM-50 image analysis program. Īll specimens were examined under light microscope (Leica DM-2500 model with DFC-320 camera attachment giving digital images). The serial sections from the apex to the base of pecten were cut in 6 μm thick, and the sections were stained using Crossman’s triple technique and periodic-acid Schiff (PAS) reaction for basement membrane composed of glycoconjugates. After the fixation, the samples dehydrated in increasing concentrations of ethanol, cleared with xylene, and embedded in paraffin. The pecten oculi and its underlying retinal tissue were painstakingly dissected out, then they were fixed in 10% buffered formalin for histologic examination. The number of pleats of duck, pigeon, turkey, and starling pecten oculi was counted in stereomicroscope images. The eyeballs were cut at the equator, and the posterior half which contained the pecten oculi was photographed using digital camera attached stereomicroscope (Nikon SMZ- 2T, Nikon Corp., Tokyo, Japan). The animals were anaesthetized and decapitated and the eye rapidly enucleated. Six animals from each species were used in this study. The eyeballs were obtained from adult ostrich, duck, pigeon, turkey, and starling. In the present study we studied the anatomical and histological details of the pecten oculi in the ostrich ( Struthioniformes), duck (Anseriformes), pigeon (Columbiformes), turkey (Galliformes), and starling (Passeriformes) which belong to different orders of the avian species. Significant variations in the pecten oculi such as type and number of pleats exist within the avian species due to the behavior of birds in relation to their general activity and visual pattern. Also two barrier-specific proteins, that is, the HT7-antigen and the glucose transporter isoform GluT-1, are expressed by the endothelial cells. The endothelia of the pectinal capillaries are continuous, possessing elaborate tight junctions. One of functions of pecten is the formation of a blood-retina barrier. Therefore it has been suggested that the main function of pecten oculi is to supply nutrition to the avascular avian retina. Birds have thicker retinas compared to mammals but have not retinal blood vessels. Histologic studies have shown that the pecten oculi consists of blood vessels, extravascular pigmented cells, and superficial covering membrane. The size of the pecten depends on the visual requirements of the bird, so that daily active bird species have a relatively large and highly complex pecten oculi with many folds while night active bird species will have a relatively small and simple pecten oculi. The conical type is only reported in the brown kiwi ( Apteryx mantelli) the vaned type is present in ostriches ( Struthio camelus) and rheas ( Rhea americana) and pleated form is widely reported in most birds (neognathae) such as quail, black kite, galah, common buzzard, mallard, pigeon, and jungle crow. Three morphological types of pecten oculi are recognized as conical, vaned, and pleated types. It is situated over the optic nerve head and projects from the retina into the vitreous body. The pecten oculi is a highly vascular and pigmented structure peculiar to the avian eye. The capillaries are surrounded by thick basal membrane, and pigmented cells were observed around the capillaries. Capillaries were 20.23, 14.34, 11.78, 12.58, and 12.78 μm in diameter in ostrich, duck, pigeon, turkey, and starling, respectively. Light microscopic investigation demonstrated that pecten oculi is basically composed of numerous capillaries, large blood vessels, and pigment cells in all investigating avian species. The numbers of pleats of the pectens were 12, 13-14, 21-22, and 17 in duck, pigeon, turkey, and starling, respectively. However, duck, pigeon, turkey and starling had a pleated-type pecten oculi which displayed folded structure. The pecten oculi of the ostrich was vaned type and made up primary, secondary, and few tertiary lamellae. In this study was investigated the structure of pecten oculi in the ostrich, duck, pigeon, turkey, and starling.
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