الفهرس 
Introduction
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Abstract
The eyeball:
• The domesticated turkey has an ellipsoidal eyeball with a fronto-lateral position within the head.
• The fibrous tunic of the eyeball consists of an anterior transparent non-vascular cornea and a posterior pigmented sclera.
• The sclera consists of thick outer fibrous layer and thin inner cartilaginous layer.
• The sclera forms a continuous surrounding layer for the eyeball except at its ventrolateral quadrant for the exit of the optic nerve.
• Along the internal aspect of the cartilaginous layer of the sclera near the optic disc and around the exit of optic nerve, there are collagenous fibers that extend to surround the optic disc.
• Turkey has a linear optic disc.
• The sclortic ring of both male and female turkey consists of 14 concave trapezoidal bony plates or scales and located just behind the corneoscleral junction. These plates are enclosed and fixed in its position by a dense connective tissue of the sclera.
• The sclortic ring in turkey is asymmetrical in shape as the ossicles at the nasal side are narrower and shorter than those at the temporal side. Also the space between the neighboring ossicles in the nasal side is narrower than that present at the temporal side.
• In male turkey the sclortic ring shows some degree of overlapping between bases of 2 adjacent ossicles.
• At the external surface of corneoscleral junction, the sclera is covered by the bulbar conjunctiva. The outer stratified squamous epithelium of the conjunctiva forms the direct continuation of the stratified squamous epithelium of the cornea. The conjunctiva covers the scleral fibers, which consist of collagenous fibers containing some pigment cells.
• At the internal surface of the corneoscleral junction, the endothelium of the cornea continues as a dense connective tissue to form the pectinate ligament. Between the tissues of the pectinate ligament there are wide spaces lined by flat endothelial cells which represent the Fontana spaces for the drainage of the aqueous humor.
• At limbus within the scleral fibers there are sinuses lined by endothelial cells which represent canals of Schlemm.
• The ciliary muscles take an origin from the fibers of the scleral sheet at limbus and inserted at the scleral plate and ciliary body.
• The extraocular muscles in turkey are represented by 6 muscles, 4 recti and 2 oblique. There is no retractor bulbi muscle, however a quadratus and pyramidalis muscles are present for the nictitating membrane.
• The two oblique muscles originate from the rostrodorsal part of the interorbital septum, the m.obliqus dorsalis is inserted on the dorsal part of the sclera by a thin flat tendon and the m. obliqus ventralis is inserted on the ventral part of the sclera by a similar flat thin.
• The four straight ocular muscles arise from the caudal part of the orbit taking their origin from the wall around the optic foramen in a way of ensheathing the optic nerve. Each muscle crosses the equator of the eyeball and become inserted by a flat (transparent) tendon into the corresponding quadrant of the sclera.
The pecten oculi:
• The pecten oculi of the domesticated turkey (Meleagris gallopava) is thin, folded and black heavily pigmented intraocular structure situated over a linear optic disc and the adjacent nerve fibers which extends from the nerve fiber layer of the retina that form the optic disc. It projects freely into the vitreous body from the posterior ventral wall of the eyeball.
• The covering surface of the retina (inner limiting membrane) is continuous with the adjacent covering pectineal membrane which can be referred as retino-pectineal membrane which covers the entire surface of the pectineal folds.
• Under the steriomicroscope the pecten oculi in the domesticated turkey is of a pleated type consists of 22-23 folds and 24 folds by SEM arranged in a form of inverted van.
• The pectineal folds are connected with each other apically by highly pigmented bridge which runs transversely like a balustrade along the vitreous margin of the pecten. Its transverse position tends to keep the apical parts of the pectineal plates to fix together.
• The number of the pectineal folds is equal in the examined male and female samples.
• It was observed that in the examined samples the folds at the middle of the pecten are longer than the ones at the sides.
• It was noticed that there is a division of one pectineal fold in one sample from the examined samples.
• The pecten oculi is fixed in position within the vitreous body on the optic disc. There are heavy thick strands of the vitreous body matrix are anchored within the pores that present on the bridge and surfaces of the pecten and this provides a tight fixation for the pecten and keeps it in an erectile fixed position within the vitreous body.
• At the apex of the pectineal plates, there are large number of processes of the melanocytes present distal to the bridge ascends in a huge number to share in the formation of the bridge and to insure the complete fixation of the proximal part of the pecten to the vitreous body.
• SEM of the pectineal fold surface shows that at the base there are numerous longitudinal blood vessels appear as several concentric cord-like prominences and less prominent melanocytes. At the middle thirds of the pectineal surface there are clusters of melanocytes in a form that allows the exposure most of the capillaries, in contrast, the capillaries at the apical end of the pleats are completely hidden under a thick blanket of melanocytes.
• Along the surface of the pecten, some oval and rounded hyalocytes with numerous cell processes covering the pores in which the vitreous body is anchored.
• SEM on cut surface of the pectineal fold wall shows few elliptical, oval and even circular blood vessels, numerous circular small capillaries containing elliptical erythrocytes and melanocytes are extravasculary embedded in the wall of the pectineal fold.
• Histological sections show that the pecten consists of connective tissue, complex vascular network numerous capillaries and small and large blood vessels, extravascular polymorphic pigmented cells, hyalocytes attached to the outer surface of the pecten and a superficial covering membrane.
• Transmission electron microscopy and Histological sections at the base of each fold show that the pectineal tissue extends as a wedge shape between the fasiculi of the underlying optic disc that aid in fixation of the pecten to the optic disc.
• Transmission electron microscopy shows that turkey bird has specialized pectineal capillaries as they are lined by endothelial cells displaying a number of microprojections on their luminal and abluminal borders that represent extensions from its cell membrane on its both luminal and abluminal borders.
• Luminal microfolds appear longer and slender than those at the abluminal borders which are shorter and tortuous.
• Nuclear region of the endothelial cell is always the widest potion of the cell body and the luminal microfolds at this region are numerically reduced while the endothelial cell lining the blood vessel show few microfolds along its entire luminal surface.
• The thickened basal lamina of the pectineal capillaries consists of several concentric layers of fine fibrillar material, each separated by amorphous ground substance.
• Pericytes are found underlying the endothelial cells and often enclosed within this thickened basal lamina of pectineal capillaries and vessels. They have no microvilli or microfolds in any surface and its nucleus tend to be more dense, flattened and ovoid in appearance.
• The melanocytes are large pleomorphic cells with long processes present extravasculary within and along the outer surface of the pecten. These extravascular melanocytes are involved in the protection of pectineal capillaries against the UV rays.
• By transmission electron microscopy hyalocytes appear as large cells with different shapes (rounded, oval to elliptical). They are located within ambush along the outer surface of the retino-pectineal membrane with numerous cytoplasmic vacuoles and large oval nucleus located near the internal part of the cell. There are many cytoplasmic processes which join each other as a network or a rete enclosing several vesicles or parts of foreign materials along the external surface of the cell. While along the internal surface of some cells there are numerous filopodia extend and occupy the depressions on the outer surface of the retino-pectineal membrane. The presence of the cytoplasmic processes along the external surface of the cell, numerous cytoplasmic vesicles or ingested foreign materials, localization of the nucleus toward the internal part of the cell and the appearance of filopodia in a moving condition along the internal surface of the cell insure that hyalocytes are considered highly active phagocytic cells.