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Human tears. Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals. [1] Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes. [2] The different types of tears—basal, reflex, and emotional—vary significantly in composition. [2]
Persons with dry eye conditions can be fitted with punctal plugs that seal the ducts to limit the amount of fluid drainage and retain moisture. During an ear infection, excess mucus may drain through the nasolacrimal duct in the opposite way tears drain. [citation needed] In humans, the tear ducts in males tend to be larger than the ones in ...
The lacrimal gland produces tears which are secreted by the lacrimal ducts, and flow over the ocular surface, and then into canals that connect to 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 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.
Nasolacrimal duct obstruction is the obstruction of the nasolacrimal ducts (better known as the tear ducts) and may be either congenital or acquired. Obstruction of the nasolacrimal ducts leads to the excess overflow of tears called epiphora .
Dry eye syndrome can lead to blurred vision, instability of the tear film, increased risk of damage to the ocular surface such as scarring of the cornea, and changes in the eye including the neurosensory system. [2] [6] Dry eye occurs when either the eye does not produce enough tears or when the tears evaporate too quickly. [2]
Onions, in particular, produce a sulfur product that acts as a lacrimator, or a substance that causes tearing: “This volatile chemical escapes from the damaged onion into the air, and lands in ...
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]