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There is a single lacrimal canaliculus in each eyelid, a superior lacrimal canaliculus in the upper eyelid and an inferior lacrimal canaliculus in the lower eyelid.The canaliculi travel vertically and then turn medially to travel towards the lacrimal sac.
From that sac, the tears drain through the lacrimal duct into the nose. Anatomists divide the gland into two sections, a palpebral lobe, or portion, and an orbital lobe or portion. [3] The smaller palpebral lobe lies close to the eye, along the inner surface of the eyelid; if the upper eyelid is everted, the palpebral portion can be seen.
They produce meibum, an oily substance that prevents evaporation of the eye's tear film. Meibum prevents tears from spilling onto the cheek, traps them between the oiled edge and the eyeball, and makes the closed lids airtight. [1] There are about 25 such glands on the upper eyelid, and 20 on the lower eyelid.
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 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 lacrimal punctum (pl.: puncta) or lacrimal point is a minute opening on the summits of the lacrimal papillae, seen on the margins of the eyelids at the lateral extremity of the lacrimal lake. There are two lacrimal puncta in the medial (inside) portion of each eyelid. Normally, the puncta dip into the lacrimal lake.
In medical terms, the lacrimal papilla is a small conical elevation on the margin of each eyelid at the basal angles of the lacrimal lake. Its apex is pierced by a small orifice, the lacrimal punctum, the commencement of the lacrimal canaliculi. It is otherwise known commonly as simply the 'tear duct'.
Their ducts unite into a rather long sinus which open into the fornix conjunctiva. [2] There are approximately forty Krause glands in the region of the upper eyelid, and around 6 to 8 in the region of the lower lid. [2] The function of these glands are to produce tears which are secreted onto the surface of the conjunctiva.