Analysis:
What's in a glass of sweat?
98 ~ 99% of the composition is mainly water, with a specific gravity of about 1.002 ~ 1.003 and a pH value of 4.2 ~ 7.5. NaCl is about 300mg/ 100ml.
1 ~ 2% is a small amount of urea, lactic acid and fatty acid.
Sweat is the liquid secreted by sweat glands. Thermal sweating caused by the increase of external temperature or internal heat production is called perceptual sweating. At this time, the sweating area is widely distributed, and the skin in all parts of the body, especially the forehead, neck, trunk, waist, back of hand and forearm, is the most; Followed by the neck, trunk side and most limbs; Once again, the inner thigh and armpit; At least the palms and feet. Mental stress can also lead to sweating, and sweating centers are distributed in all parts of the central nervous system. Normal people unconsciously evaporate about 600 ~ 700 ml of water within 24 hours.
Composition of tears
Normal eyes have a thin tear film covering the cornea and conjunctiva. This membrane can be divided into three layers: the outermost fat layer, the middle water-liquid layer and the innermost mucin layer. As long as there is a layer of tears that is insufficiently secreted or unevenly distributed, it will produce dry eye symptoms.
The "fat layer" is secreted by the meibomian gland of the eyelid. Its function is to inhibit the evaporation of tears and keep them moist.
The "water layer" is secreted by the main lacrimal gland and the auxiliary lacrimal gland. When the eyes are sad or emotional, the lacrimal gland will "reflexively" secrete a large number of water layers, which will be a phenomenon of "tears like rain". Contains a variety of minerals, nutrients and bactericidal substances, and has the functions of cleaning, protecting and moistening the eyeball surface.
Mucin layer is secreted by conjunctival goblet cells. It is hydrophilic and covers hydrophilic epithelial cells so that the epithelial cells can be wetted by water.
In addition to the complete and full tear components, the eyeball surface also needs some factors to maintain health: 1. Normal blinking: evenly bring mucus to conjunctiva and corneal epidermis. 2. The joint of eyelid, cornea and conjunctiva surface should be attached together. 3. There are normal epidermal cells in eyelid, cornea and conjunctiva.