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M. Lorber; The Distribution of Elastic Fibers Within the Rat Eyelid . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4950.
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That elastic fibers exist in the human eyelid skin has long been known (Maximow and Bloom, A Textbook of Histology, 4th ed., 1942, p. 633). Additionally, one sentence mentioned their association with meibomian glands (Seifert & Spiznas, Graefe’s Arch Clin Exp Ophthalmol 234:648, 1996). To see whether these findings occur in rodents the rat eyelid has been studied.
Three male and three female adult rats were anesthetized with pentobarbital and their lids excised. Following formalin fixation and routine histological methodology the 12 specimens were sectioned through the lid thickness. Sections were stained by the Verhoeff’s – Van Gieson method.
Numerous elastic fibers exist in specific lid areas; in all having an orthogonal relationship among themselves. The three axes being: 1) parallel to the lid's free border; the fibers' lengths are evident in their naso–temporal orientation. 2) fibers extending in an antero–posterior plane within the lid are transected and seen only as dots. 3) parallel to the lid thickness, the fibers in the connective tissue are seen penetrating the lid substance vertically in a supero–inferior plane between the skin of the outer eyelid and the palpebral conjunctiva of its inner surface. Long fibers are more numerous and prominent nearer the epidermis, its cilia and glands of Zeis than those in the lamina propria of the conjunctiva. This is true irrespective of the presence of goblet cells. Numerous fibers lie closely about the row of meibomian glands with small numbers of fine ones interlobularly and between adjacent meibomian glands. In the endo– and perimysial connective tissue of the striated muscle fibers that course mediolaterally in the center of the lid many elastic fibers extend toward the skin, crossing some muscle fibers as they do so. Bordering one or both sides of the muscle fiber aggregate are long bands of connective tissue having an outer grouping of many transected elastic fibers and an inner zone of many long ones.
Elastic fibers in the rat eyelid are particularly numerous about its glands and muscle fibers, suggesting they may influence the functions of these tissues. For example, their ability to recoil would increase periglandular tension, exerting a compressive force which might enhance secretory flow. Their association with the striated muscle fibers suggests the elastic fibers’ ability to extend and recoil assists the muscles during eye closure and opening respectively. Their abundance under the epidermis might aid furrowing of the eyelid skin during eye opening. The subconjunctival fibers may adapt the inner region of the lid as it slides along the anterior globe whose diameter peaks at the level of lid closure.
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