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The plica semilunaris is a small fold of bulbar conjunctiva on the medial canthus of the eye.It functions during movement of the eye, to help maintain tear drainage via the lacrimal lake, and to permit greater rotation of the globe, for without the plica the conjunctiva would attach directly to the eyeball, restricting movement. [1]
The lacrimal apparatus is the physiological system containing the orbital structures for tear production and drainage. [1] It consists of: The lacrimal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the eye; it is a j-shaped serous gland located in lacrimal fossa.
The lacrimal gland is a compound tubuloacinar gland, it is made up of many lobules separated by connective tissue, each lobule contains many acini.The acini composed of large serous cells which, produce a watery serous secretion, serous cells are filled with lightly stained secretory granules and surrounded by well-developed myoepithelial cells and a sparse, vascular stroma.
Dacryoscintigraphy (DSG), also known as lacrimal scintigraphy, is a nuclear medicine technique for imaging the lacrimal apparatus. It is used to identify obstructions, for example in the lacrimal duct , nasal cavity or nasolacrimal duct .
The lacrimal canaliculi (sg.: canaliculus) are the small channels in each eyelid that drain lacrimal fluid, from the lacrimal puncta to the lacrimal sac. This forms part of the lacrimal apparatus that drains lacrimal fluid from the surface of the eye to the nasal cavity.
The lacrimal sac or lachrymal sac [1] is the upper dilated end of the nasolacrimal duct, [2] and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla. It connects the lacrimal canaliculi , which drain tears from the eye's surface, and the nasolacrimal duct , which conveys this fluid into the nasal cavity. [ 3 ]
The acini are surrounded, sometimes incompletely, by a row of myoepithelial cells. Animal studies suggest that the ducts of Wolfring glands have a tortuous course and open onto the palpebral conjunctiva. Like the main lacrimal gland, the accessory lacrimal glands are also densely innervated, but they lack parasympathetic innervation.
Involutional stenosis is probably the most common cause of nasolacrimal duct obstruction in older people. It affects women twice as frequently as men. Although the inciting event in this process is unknown, clinicopathologic study suggests that compression of the lumen of the nasolacrimal duct is caused by inflammatory infiltrates and edema.