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==Physiology of sweat==
==Physiology of sweat==
Sweat is a clear, watery and salty liquid produced by the sweat glands present in the skin. Sweat is mainly produced in noticeable amounts under the arm, feet and palms. When it comes in contact with the bacteria on skin, it can cause a smell. Regular bathing and use of antiperspirants or deodorant can help to control odor. In extreme conditions or during heavy exercise, large quantities of sweat is produced. It proves to be a great method of thermoregulation as long as humidity in surrounding atmosphere is relatively low. Stimulation of anterior hypothalamus-preoptic area is responsible for the action of sweating. The impulses from this area are transmitted in the autonomic pathways to the cord and then through the sympathetic outflow to the skin and elsewhere in the body. The volume of sweat produced and expelled every day is generally about 100ml/day and may vary from person to person. The water loss through sweat may increase upto 1-2 L/hour in case of exercise or extremely hot weather.<ref>Baker LB. Physiology of sweat gland function: The roles of sweating and sweat composition in human health. Temperature (Austin). 2019 Jul 17;6(3):211–59.</ref>
Sweat is a clear, watery and salty liquid produced by the sweat glands present in the skin. Sweat is mainly produced in noticeable amounts under the arm, feet and palms. When it comes in contact with the bacteria on skin, it can cause a smell. Regular bathing and use of antiperspirants or deodorant can help to control odor. In extreme conditions or during heavy exercise, large quantities of sweat is produced. It proves to be a great method of thermoregulation as long as humidity in surrounding atmosphere is relatively low.<ref>Baker LB. Physiology of sweat gland function: The roles of sweating and sweat composition in human health. Temperature (Austin). 2019 Jul 17;6(3):211–59.</ref> Stimulation of anterior hypothalamus-preoptic area is responsible for the action of sweating. The impulses from this area are transmitted in the autonomic pathways to the cord and then through the sympathetic outflow to the skin and elsewhere in the body.[Text book of physiology.p.298]<ref name=Guyton>Guyton A, Hall J, Textbook of Physiology, ninth edition, Prism Books, USA, 1996</ref> The volume of sweat produced and expelled every day is generally about 100ml/day and may vary from person to person. The water loss through sweat may increase upto 1-2 L/hour in case of exercise or extremely hot weather.[Text book of physiology.p.915-16]<ref name=Guyton/>
'''Sweat glands:'''
Sweat glands are of two types:
#Eccrine glands
#Apocrine glands
'''Eccrine glands:''' These are the common sweat glands distributed all over the body, especially over the thick skin. The eccrine sweat gland is basically of tubular structure which at beginning is in the deeper part of dermis and is highly coiled. The rest of the gland courses through the dermis- epidermis- open to the exterior. Sweat forms by coiled portion. These are functional throughout the life. These are present largely over the back and chest regions. [Hutchinson’s Clinical Methods.p.512]<ref name=Hutch>Swash M, Glynn M, Hutchinson’s Clinical Methods, 22nd Edition, Saunders Elsevier, USA.</ref>
When synthesized the sweat is isotonic, but while moving towards the exterior, some sodium ions are reabsorbed. In case of severe sweating, this reabsorption is more intense due to the action of aldosterone. The thermoregulation via sweating occurs through the eccrine glands innervated by sympathetic cholinergic fibres. The eccrine sweat is basically made up of water and sodium chloride (NACl). It may also contain mixture of many other chemicals from the interstitial fluid as well. The amount of sodium and cholride in the eccrine sweat is considered to be less, 60mmol/L and 70 mmol/L respectively.<ref name=Guyton/>
'''Apocrine glands:''' These glands are located deep in subcutaneous layer in limited areas like axilla (armpit), pubic region, around the nipple of breast, scalp. The activity of apocrine glands increases with the onset of puberty and declines at old age. This process shows that these glands have got some relationship with reproductive physiology. The secretion from apocrine glands is odorless but bacterial decomposition makes it odorous, secretion show cyclic changes in females with menstrual cycle. These glands are structurally similar to eccrine glands, but are larger. Their coiled region lies within the subcutaneous tissue rather than the dermis.<ref>Pocock G et.al. Human Physiology, Oxford Printing Press, Sweat glands, regulation of internal environment, part nine, Fifth Edition, 2018, Page No.655-657</ref> In contrast to the eccrine glands, apocrine glands produce vicious, lipid rich sweat comprising of proteins, sugars and ammonia.
The third type of glands i.e. apoeccrine glands have been described by Sato et. al in 1987. These are intermediate in size and develop from both eccrine and apocrine glands. These are mainly located in the axillary part and don’t play a significant role in thermoregulation.
'''Mechanism of secretion of sweat:'''
Though the eccrine glands are supplied by symphathetic fibres, yet adrenaline (epinephrine) has got little or no action on them. The apocrine however responds to both adrenergic and cholinergic stimuli. Pilocarpine, which stimulates the parasympathetic fibers, increases the flow of sweat and atropine which paralyses the parasympathetic endings, abolishes sweating.
'''Different types of sweating:'''
#Insensible sweating: which occurs even in cold climate amounts to 600 – 800 ml daily.
#Thermal sweating: This occurs in hot environmental temperature, the threshold being 28°C for men and 31˚C for women. As the environmental temperature rises sweating increases. It is to be emphasized that when the ambient temperature is higher than body temperature sweating is the only method of keeping the body temperature normal.
#Psychic sweating:-
Emotional sweating: In emotional condition, sweating occurs chiefly in the palms, soles, and axilla and upto some extent it is also present at head, neck and elsewhere in the body.
In muscular exercise: The sweating i.e. both thermal and mental is reduced by cold, which at the same time also reduces, cutaneous circulation. It is also reduced by dehydration which be the result of deprivation of fluids intake or due to the process of sweating itself.
Hot & spicy food intake: Eating of spicy food stimulates sweating (gustatory sweating), because pain in nerve endings in the mouth are stimulated. Hence reflect sweating in forehead neck and face.
'''Composition of sweat:'''
Sweat mainly consists of secretions of the eccrine glands. It is the most dilute amongst all the animal fluids. When freshly collected, it contains epithelial cells and some sebum. When filtered, it forms a clear colorless fluid. The human sweat has specific gravity of about 1.001-1.006 and a pH of 3.8 to 6.5.
Each 100 ml of sweat contains:-
- ………………………..
Solids- ………………………….1.174- 1.587g
Ash - …………………………...0.144- 0.566g
Creatinine-……………………….0.1-1.3mg
Urea- ……………………………12-57 mg
Lactic acid- ……………………….285-336 mg
Carbolic acid- ………………………2.8 mg
Sugar (as glucose)-…………………1-3 mg
Uric acid- ……………………………0.07-0.25 mg
Ascorbic acid- ………………………70.5µg
(as a dehydroascorbic acid)
Total nitrogen- ……………………… 33.2mg
Non protein nitrogen-………………...27-64 mg
Amino acid N – ……………………1.1- 10.2mg
Ammonia N - ………………………...5.9 mg
Urea N ………………………………5-36 mg
Calcium -……………………………..1-8 mg
Iodine- ………………………………...0.5-1.2 ug
Iron- …………………………… ……0.022-0.045
Chloride-…………………………………36-468 mg
Na+ - …………………………………. 24-312mg
K+ - ……………………………………21-126mg
Sulphur- …………………………………...0.7-7.4 mg
Cooper - ……………………………………0.006mg
Amino acids- ……………………………… 43.62 mg
{| class="wikitable"
|+ Table 1: Composition of sweat
|-
! Each 100 ml of sweat contains !!
|-
| | Water || 99.22- 99.74g
|-
| | Solids||1.174- 1.587g
|-
| |Ash ||0.144- 0.566g
|-
| | Creatinine||0.1-1.3mg
|-
| | Urea||12-57 mg
|-
| | Lactic acid||285-336 mg
|-
| | Carbolic acid||2.8 mg
|-
| | Sugar (as glucose)||1-3 mg
|-
| | Uric acid||0.07-0.25 mg
|-
| |Ascorbic acid(as a dehydroascorbic acid) ||70.5µg
|-
| | Total nitrogen||33.2mg
|-
| |Non protein nitrogen ||27-64 mg
|-
| | Amino acid N ||1.1- 10.2mg
|-
| |Ammonia N ||5.9 mg
|-
| |Urea N ||5-36 mg
|-
| | Calcium||1-8 mg
|-
| |Iodine ||0.5-1.2 ug
|-
| |Iron ||0.022-0.045
|-
| |Chloride ||36-468 mg
|-
| | Na+||24-312mg
|-
| | K+||21-126mg
|-
| | Sulphur||0.7-7.4 mg
|-
| |Cooper ||0.006mg
|-
| |Amino acids ||43.62 mg
|-
|}
==Role of Swedana as therapy==
In [[Ayurveda]], the treatment “Swedanakarma”, is a therapy by which person is made to sweat. [[Swedana]] (sweating or fomentation) is used for all [[vata]] and [[kapha]] dominant diseases. [Cha.Sa.[[Sutra Sthana]] 14/3] If administered after oleation, fomentation controls [[vata]] and thereby facilitates the elimination of feces, urine and semen. [Cha.Sa.[[Sutra Sthana]] 14/4]
Even dry pieces of wood can be bent by means of oleation and fomentation, when duly applied. This simile shows immense benefit of [[swedana]].
'''Types of swedana:'''
A. Agni sweda: It is [[swedana]] or fomentation involving the application of direct heat. They are of 13 types where the heat is produced from fire.
B. Anagni sweda: This [[swedana]] or fomentation is done without the application of direct heat. The ten methods which in a way serve the purpose or fomentation without involving the direct application of heat, are exercise, residing in a warm chamber, wearing of heavy clothing, hunger, excessive drinking, fear, anger application of poultice, wrestling and exposure to sunshine. Perspiration is indicative of the exercise being performed correctly.
'''Indications:'''
Fomentation is useful for coryza (pratisyaya), cough, hiccup, dyspnea, heaviness of the body, pan in the ear, neck and head, hoarseness of voice, spasmodic obstruction in the throat, paralysis of the face, one limb, whole body or half of the body, in flexures of the body, distension of the abdomen, constipation and suppression of urine, pandiculation (vijrmbhaka), stiffness of sides of back etc.
'''Contraindications:'''
The physician should not administer fomentation therapy to those who have taken too much astringents and alcohol, the pregnant woman, those suffering from bleeding disorders ([[raktapitta]]), diarrhoea, paittika type of obstinate urinary disorder specially diabetes mellitus, inflammation and prolapse of the rectum (vidagdha- bhrashta-bradhna), toxic conditions, alcoholism. Those having [[pitta]] dominant constitution and dry skin, fatigue, unconscious, fatty, thirsty, hungry, in a fit of anger and anxiety, those suffering from jaundice, abdominal disease, gouty arthritis (vatarakta), loss of vision (timira), those who are weak and dried up and who’s [[ojas]] has been reduced.
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