Chemical composition<unk>  are made up of three layers: lipid, aqueous, and mucous.<unk>  are composed of water, salts, antibodies, and lysozymes (antibacterial enzymes), though composition varies among different<unk> types. The composition of<unk>  caused by emotion differs from that of<unk>  as a reaction to irritants, such as onion fumes, dust, or allergy. Emotional<unk>  contain higher concentrations of stress hormones such as adrenocorticotropic hormone and leucine enkephalin (a natural pain killer), which suggests that emotional<unk>  play a biological role in balancing stress hormone levels. Name Contents Secretors Functions Lipid layer Oils Meibomian glands (or<unk> al glands) Coats the aqueous layer, provides a hydrophobic barrier that envelops<unk>  and prevents their spilling onto the cheek. These glands are located among the<unk> al plates, and thus deposit the<unk> fluid between the eye proper and the oil barriers of the lids. Aqueous layer Electrolytes, 60 metabolites—Amino Acids (1-Methylhistidine/3-Methylhistidine, Arginine, Asymmetric, Asymmetric dimethylarginine/Symmetric dimethylarginine, Citrulline, Creatine, Glutamine, Homoarginine, Hydroxyproline, Phenylalanine, Proline, Pyroglutamic acid, Serine, Taurine, Theonine, Tryptophan, Tyrosine, Urocanic acid, Valme), Amino Alcohols (Panthenol), Amino Ketones (Allantoin, Creatine), Aromatic Acids (Cinnamic acid, o-Coumaric acid/m-Coumaric acid/p-Coumaric acid), Carbohydrates (N-Acetylneuraminic acid), Carnitines (Acetylcarnitine, Carnitine, hexanoylcarnitine, Palmitoylcarnitine), Cyclic Amines (Niacinamide), Dicarboxylic Acids (Fumaric acid/ Maleic acid), Nucleosides (1-Methyladenosine, Adenosine, Cytidine, Guanosine, Inosine, S-Adenosyl-homocysteine, S-Adenosylmethionine, Uridine, and Xanthosine), Nucleotides (ADP, AMO, CMP, Cytidine diphosphate choline, GMP, IMP, UDP, UMP, UDP-N-acetylgalactosamine/UDP-N-acetylglucosamine), Peptides (Oxidized glutathione), Phospholipids (1-Palmitoyl-lysophosphatidylcholine), Purines and derivatives (Hypoxanthine, Theobromine, Uric acid, Xanthine), Purines and derivatives (4-Pyridoxic acid), Quaternary Amines (Acetylcholine, Glycerophosphocholine, Phosphocholine), and Tricarboxylic Acids (Citric acid), and other substances such as proteins (e.g., antibodies, lipocalin, lactoferrin, lysozyme, and lacritin) Lacrimal gland Promotes spreading of the<unk> film, the control of infectious agents, and osmotic regulation. Mucous layer Mucins Conjunctival goblet cells Coats the cornea, provides a hydrophilic layer and allows for even distribution of the<unk> film. Drainage of<unk> film The lacrimal glands secrete lacrimal fluid, which flows through the main excretory ducts into the space between the eyeball and the lids. When the eyes blink, the lacrimal fluid is spread across the surface of the eye. Lacrimal fluid gathers in the lacrimal lake which is found in the medial part of the eye. The lacrimal papilla is an elevation in the inner side of the eyelid, at the edge of the lacrimal lake. The lacrimal canaliculi open into the papilla. The opening of each canaliculus is the lacrimal punctum. From the punctum,<unk>  will enter the lacrimal sac, then on to the nasolacrimal duct, and finally into the nasal cavity. An excess of<unk> , as caused by strong emotion, can cause the nose to run. Quality of vision is affected by the stability of the<unk> film. Types There are three basic types of<unk> : basal, reflex and emotional. Category Description Basal<unk>  In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal<unk> . They lubricate the eye and help keep it clear of dust.<unk> fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid (such as lysozyme) fight against bacterial infection as a part of the immune system. Lysozyme does this by dissolving a layer in the outer coating, called peptidoglycan, of certain bacteria. It is a typical body fluid with salt content similar to blood plasma. Usually, in a 24-hour period, 0.75 to 1.1 grams (0.03–0.04-ounce avoirdupois) of<unk>  are secreted; this rate slows with age. Reflex<unk>  The second type of<unk>  results from irritation of the eye by foreign particles, or from the presence of irritant substances such as onion vapors, perfumes and other fragrances,<unk> gas, or pepper spray in the eye's environment, including the cornea, conjunctiva, or nasal mucosa, which trigger TRP channels in the ophthalmic nerve. It can also occur with bright light and hot or peppery stimuli to the tongue and mouth. It is also linked with vomiting, coughing, and yawning. These reflex<unk>  attempt to wash out irritants that may have come into contact with the eye. Emotional<unk>  (psychic<unk>  The third category, in general, referred to as crying or weeping, is increased<unk> ng due to strong emotional stress, pleasure, anger, suffering, mourning, or physical pain. This practice is not restricted to negative emotions; many people cry when extremely happy, such as times of intense humor and laughter. In humans, emotional<unk>  can be accompanied by reddening of the face and sobbing — cough-like, convulsive breathing, sometimes involving spasms of the whole upper body.<unk>  brought about by emotions have a different chemical makeup than those for lubrication; emotional<unk>  contain more of the protein-based hormones prolactin, adrenocorticotropic hormone, and Leu-enkephalin (a natural painkiller) than basal or reflex<unk> . The limbic system is involved in the production of basic emotional drives, such as anger, fear, etc. The limbic system, or, more specifically the hypothalamus, also has a degree of control over the autonomic system. The parasympathetic branch of the autonomic nervous system controls the lacrimal glands via the neurotransmitter acetylcholine through both the nicotinic and muscarinic receptors. When these receptors are activated, the lacrimal gland is stimulated to produce<unk> . 150px Neurology The trigeminal V1 (fifth cranial) nerve<unk>  the sensory pathway of the<unk> reflexes. When the trigeminal nerve is cut,<unk>  from reflexes will stop, while emotional<unk>  will not. The great (superficial) petrosal nerve from cranial nerve VII provides autonomic innervation to the lacrimal gland. It is responsible for the production of much of the aqueous portion of the<unk> film.
Tears
Whitlow
Drustbed
Squawk 
Elscint
Wart
Doula
Caul