Physiology in Ayurveda

Physiology in Ayurveda


‘Śarīra Vicaya’ is the Ayurvedic term that represents bothAnatomy and Physiology. ‘Vicaya’
means the special or detailed knowledge. As per Caraka, thedetailed knowledge of normal
human body is helpful to understand the factors influencinghealth and therefore such
knowledge is widely appreciated by experts. (Ca.Śā. 6/3).


Theory of ‘Tridoṣa’:A Physiological Perspective
This theory forms the basis of Ayurvedic physiology,pathology and pharmacology.Though, the term ‘Doṣa’means ‘the disturbing factor’, it has got definite physiological importance innormal state. Basically three ‘Doshas’- ‘Vāta’, ‘Pitta’ and ‘Kapha’- areresponsible for maintenance of homeostasis in the body, and health is nothingbut a state of equilibrium of these ‘Tridoshas’.Disease is manifested as a result of disturbance in the state of equilibriumamong these ‘Doshas’.
The concept of ‘Tridosha’ isbasically a theory and any single substance or structure inthe body cannot represent a ‘Dosha’. Terms like ‘Pittavarga’ and‘Kaphavarga’ have been used in some textbooks and such usage indicatesthat these (‘Vāta’-‘Pitta’-‘Kapha’) were perceived to be three groups of physiologicallysimilar substances.
‘Vāta’ is responsible for all movements and it is theinitiating and controlling factor.‘Pitta’ performs the activities likedigestion, metabolism, production of heat and that is why it is called ‘Agni’meaning ‘Fire’. ‘Kapha’ performs the functions like protection,strength,stability and resistance.As Ayurveda is based on functionalunderstanding of body, the different entities representing ‘Tridoshas’ at each level of organizationcan be assumed by analyzing these functions. In generalized terms, the nervous,endocrine and immune mechanisms can be equated to ‘Vāta’, ‘Pitta’ and ‘Kapha’respectively.


Homeostasis: Imbalance in the state of bodily-tissuesis known as ‘Disease’ and equilibrium is called ‘Health’. (Ca.Sū. 9/3, Ca. Śā.6/18). Aim of this entire stream of science (Ayurveda) is to re-establish thestate of equilibrium among different tissues (Ca. Sū. 1/53).
‘Dhātusāmya’ is the term given for homeostasis in Ayurveda.In Suśruta’s view, the life on this universe is maintained because of threeopposing factors known as Sun, Moon and the Air. The Sun exerts a drying effecton earth whereas the moon is coolant and strengthening in nature. Air bringsabout all types of movements. In exactly similar manner, the body is sustainedby three opposing factors called ‘Vāta’, ‘Pitta’ and ‘Kapha’ (Su. Sū. 21/.


Concept of a Cell: Caraka has explained that the bodyparts can be divided and re-divided into innumerable individual componentscalled ‘Paramānhus’. These are innumerable because oftheir huge number, highly minute structure and limited perceptive ability ofsense organs (Ca. Śā. 7/17).
This statement indicates that there existed a concept ofminute and numerous individual living units in the body. Today we call suchmicroscopic units by the name ‘Cell’. ‘Anhu Srotas’is another such very similar term, probably indicative of a cell. Some scholarseven held the view that the living body is nothing but the resultant ofaggregation of such innumerable ‘Srotāmhsi’. (Ca.Vi. 5/4).‘Srotāmhsi’ is the plural form of ‘Srotas’. The term ‘Srotas’ means an individual‘Cell’ - ‘An u Srotas’ and also an individual ‘OrganSystem’ - ‘Sthūula Srotas’. A tissue is a group of structurally andfunctionally similar cells. ‘Srotāmhsi’ arestructurally similar to their corresponding tissues. Also, each ‘Srotas’ isfunctionally (Metabolically) related to its corresponding tissue.


Basic Tissues: Plasma and lymph (‘Rasa’), blood cells(‘Rakta’), muscular and general connectivetissues (‘Māmhsa’), body-lipids including adiposetissue (‘Meda’), tissues resisting easy degradation - like bones(‘Asthi’), bone marrow and nervous tissue (‘Majjā’) and tissues responsible forreproductive functions (‘Śukra’) are the basic tissues from which the body is formed.(A.H. Sū.1/13).
Tissues producing breast-milk (Stanya), female reproductivetissues (Ārtava),‘Kanhdharā’ (tendons), Sirā (blood vessels),‘Vasā’ (muscle fat), six layers of skin and ‘Snāyus’(sinews) are the‘Upadhātus’ subsidiary tissues). Tissues producing breast-milk and female reproductivetissues are Upadhātus of ‘Rasa’. ‘Kanhdarā’ and ‘Sirā’are Upadhātus of ‘Rakta’.
‘Vasā’ and skin are Upadhātus of ‘Māmhsa’.‘Snāyu’ is the Upadhātu of ‘Medas’. (Ca. Ci.15/17).
Classification of tissues described in Ayurveda is based onsome rational observations. For example, ‘Rasa Dhātu’ includes both plasma andlymph (Intravascular fluid). ‘Rakta Dhātu’ mainly stands for RBCs. ‘Māmhsa Dhātu’ stands for muscular tissue in general but alsoincludes general connective tissue and parenchymal and stromal tissues of differentviscera. As ‘coating’ or ‘covering’ is the function of ‘Māmhsa Dhātu’, even epithelial tissue is included under the same.‘Medo Dhātu’ includes adipose tissue and circulating lipids of blood because itis of two types: ‘Baddha’ (bound) and ‘Abaddha’ (free). ‘Asthi Dhātu’ includesall those structures of the body, which resist easy degradation. So, teeth andnails also are included under this ‘Dhātu’. ‘Majjā Dhātu’ stands for everythingthat fills bony cavities. So, apart from bone marrow, it also stands for Brainsubstance because this fills up a cavity formed by the union of several cranialbones. ‘Śukra Dhātu’ mainly stands for all hormones ofhypothalamo-pituitary-gonadal axis.
Supplying the nourishment (Prīn ana),delivery of life-principle (Jīvana), providing covering or coating(Lepa), providing lubrication (Sneha), giving mechanical support (Dhāran a), filling-in the (bony) cavities(Pūran a) and reproduction(Garbhotpāda) - are the most important functions of these seven ‘Dhātus’respectively. (A.H. Sū. 11/4).

Physiology of Nervous System
All movements are due to ‘Vāta’ and that is why it is calledthe ‘Prānha’ of all living beings. (Ca. Sū.18/118). So, ‘Prānhavaha Srotas’ stands for the systemconcerned with the activities of ‘Vāta’. Prānhavaha Srotas’stands for the system that transports a specific type of ‘Vāta’ called‘Prānha Vāta’. This is a special Srotas meant for aspecial type of ‘Vāta’ (Cakrapānhi on Ca.Vi. 5/.

Brain and Brainstem: ‘Śiras’ (Head) is the regionwhere all ‘Prān as’ (most vital entities) are situatedand all sensory and motor activities are controlled from. That is why ‘Head’ iscalled the ‘Most important organ’ among all parts of the body (Ca. Sū. 17/12).It is described that all sensory and motor organs along with their ‘Prāanhavaha Srotāmhsi’, are connected to the brain in a fashion thatis similar to the connections between the sunrays and the Sun. (Ca. Si. 9/4).
Bhela has explained that the mind is situated in between thehead and palate. The efficiency of mind is beyond any other sensory or motororgan (Bh.Ci. 8/2-3).
Reflexes: Caraka has opined that one should notsuppress the natural urges related to micturition, defecation, ejaculation,flatus, vomiting, sneezing, eructation, yawning, hunger, thirst, tears, sleepand also dyspnoea developed after exertion (Ca. Sū. 7/3-4). It should be notedthat one or the other reflex is involved in all these activities. So, the term‘Vega’ stands almost equivalent to reflex.
Concept of ‘Vāta’: All functions of nervous system inhuman body are represented through ‘Vāta’ in Ayurveda. In general, thefunctions ascribed to ‘Vāta’ are: Control and coordination of different partsof the body, initiation of all movements, regulation of psychologicalprocesses, initiation of all activities of sense organs, transmission ofdifferent sensations, production of speech, secreto- motor functions in thegut, expulsion of wastes from the body and control of respiration (Ca.Sū.12/.‘
Vāta’ is divided into five sub types –
‘Prānha’, ‘Udāna’, ‘Vyāna’, ‘Samāna’ and ‘Apāna’.


‘Prānha Vāta’: This is situated in head and is responsible for the control overintellectual functions, cardiovascular functions, sense organs,psychological activities, respiration, and reflex activities like sneezing,belching and deglutition (A.H.Sū. 12/5). Based on this subtype of ‘Vāta’, ‘Prānhavaha Srotas’ has derived its name.

‘Udāna Vāta’: Its active site is chest region. It isbasically responsible for production of speech. The effort and strengthrequired for speech are also the functions of ‘Udāna’. It also helps in recallof vocabulary required for well-articulated speech (A.H.Sū. 12/5).

‘Vyāna Vāta’: The active site of ‘Vyāna Vāta’ isHeart. It makes the circulation of blood possible by controlling the heart.Vyana makes ‘Rasa’ (the intravascular fluid including plasma and lymph) to getforcefully ejected out of the heart and makes it circulate throughout the body(Ca. Ci. 15/36). So, sympathetic and parasympathetic control of heart isindicated by ‘Vyāna Vāta’. Some authors have ascribed the functions of somaticnervous system also to ‘Vyāna Vāta’ as movements like flexion, extension,opening and closure of eyelids have been said to be under its control (Ca. Ci.28/9).

‘Samāna Vāta’: Active site of ‘Samāna’ is adjacent togastro intestinal tract. It performs the functions like reception of food, itsdigestion through the activation of ‘Agni’, its division into useful and wasteparts and its onward propulsion (A.H. Sū. 12/. All these functions are eitherthose of parasympathetic nerves supplying the gut or those of enteric nervoussystem.

‘Apāna Vāta’: This is active in pelvic region.‘Apāna’ governs physiological processes like micturition, defecation,ejaculation, menstruation and parturition (A.H.Sū.12/9). Autonomic nervoussystem has got a definite role in most of these activities.

Physiology of Gastro Intestinal Tract
‘Annavaha Srotas’ has got its roots situated in stomach,especially on its left side. ‘Purīshavaha Srotas’has got its roots in large intestine, especially at rectum (Ca.Vi. 5/.‘Annavaha Srotas’ and ‘Purīshavaha Srotas’together form the complete gastrointestinal tract. ‘Annavaha Srotas’includes upper and middle part of the gut whereas ‘Purīshavaha Srotas’is lower GIT.
Deglutition, Mucous secretion and Secretion of Enzymes: Thefood is brought towards the gut through ‘Prānha Vāta’.There, various fluids making its bonds loosen, act on it. Also, the foodis softened here. Then the ‘Samāna Vāta’ stimulates ‘Jathharāgni’.This ‘Agni’ finally digests the food (Ca.Ci.15/6, 7). After the foodreaches stomach, several digestive juices act on it. Gastric juice, pancreaticjuice, and enterocytes in the intestines - all contain important digestiveenzymes and act on food. Secretion of these enzymes is mostly under the controlof parasympathetic nerves and intrinsic enteric nervous system. This is how‘Samāna Vāta’ stimulates ‘Agni’.

Digestion in Upper GIT:
First stage of digestion is called ‘Madhura Avasthāpāka’.This takes place in the stomach. During this stage, there occurs the release offroth-like ‘Kapha’ (Ca. Ci.15/9). Salivary juice and mucous secreted in thestomach serve many protective functions but do not directly participate in theactual process of digestion. These are therefore indicative of froth-like‘Kapha’, which is ‘Malarūpī’ in nature.

Digestion in Small Intestine: ‘Pitta’ that is presentin between stomach and large intestine is called ‘Pācaka Pitta’. Though made upof five basic elements, it is dominant in fire principle. So, it is devoid ofliquidity and is called ‘Anala’ (‘Agni’). This digests the food and splits it intoessential nutrient part called ‘Sāra’ and waste part called ‘Kiththa’ (A.H. Sū. 12/10-12).

The ‘Pācaka Pitta’ is directly responsible for digestion ofthe food and therefore stands for all amylolytic, proteolytic, lipolytic andnucleic acid splitting enzymes. Gastrointestinal hormones like gastrin,secretin, cholecystokinin etc. also must be regarded as the representatives of‘Pācaka Pitta’. ‘Sāra’ (Nutrient) portion separated at this stage gets absorbedand thereafter it is called ‘Rasa Dhātu’.

Release of Bile Juice:
In the small intestine, ‘Accha Pitta’ (Bile) is released(Ca. Ci. 15/10) during the second stage of digestion. This stage is called‘Amla’ ‘Avasthāpāka’ and during this phase, the bile juice and pancreaticjuices are secreted into the duodenum. The bile is liquid and it is called the‘Accha Pitta’. ‘Accha’ means ‘liquid in form’. This is the ‘Mala’ of ‘Rakta’.Bilirubin is a derivative of hemoglobin metabolism and represents this ‘AcchaPitta’.


Factors influencing Digestion:
Digestion of food depends on following important factors:
optimum temperature, ‘Vāyu’, fluid medium, lubricatingsubstances, time and appropriate administration.‘Vāyu’ helps in movement of food in the gut. Fluids make the food particles easilybreakable. Lubricating substances make the food softer. Time factor makes surethat the food is completely and properly digested. Along with all thesefactors, if the administration also is proper, the resultant digested materialwill be capable of maintaining ‘Dhātusāmya’(Ca. Śā. 6/14,15).

Absorption and distribution of Digested Material: After thecompletion of the digestive process, the digested material reaches all parts ofthe body through the vessels called ‘Dhamanīs’ (Ca.Vi. 2/18).

Large Intestine:
After the nutrientsare absorbed from the small intestine, the remaining undigested portion of foodreaches the large intestine. Here, it experiences the drying effect of ‘Agni’and there is formation of solid fecal matter along with the release of ‘Vāta’of ‘Kathu’ (pungent) nature. This stage is the thirdstage of digestion and is called ‘Kathu Avasthāpāka’(Ca. Ci. 15/9-11). In the large intestine, except for absorption of water and some electrolytes, no digestive activitytakes place. But this absorption of water makes the remaining undigestedmaterial hard and this material is called feces. Due to the activity of bacterialflora, some pungent gases like methane and ammonia are also produced here.These represent ‘Kathu’ nature of ‘Vāta’ released during thisstage.

Physiology of Respiratory System
Functions in General: ‘Prānha Vāta’situated at ‘Nābhi’, comes out through the throat to consume anectar-like substance called ‘Vishnhupadāmrhta’ fromthe atmosphere. After consuming this nectar of atmosphere, it re-entersthe body speedily and nourishes the ‘Jīva’ (Śā. Pū. 5/51). Though the site of‘Prānha Vāta’ is described to be ‘head’ in all earliertextbooks, Śārnńgadhara has described it to be ‘Nābhi’ in thisreference. ‘Nābhi’, in Samhskrhta language,just means ‘a center’. So, this is indicative of a particular center in thehead.
‘Raktamh jīva itisthitihh’ is the opinion of Suśruta and this means that the terms ‘Jīva’ and ‘Rakta’are synonyms. So, when translated with this background, the above verse givesthe following meaning: “Because of theactivity of ‘Prānha Vāta’ that is situated inbrain, a nectarlike substance is consumed through the act of respiration. Thissubstance in turn, nourishes the ‘Jīva’ (Blood).” This nectar-like substancemust be oxygen. Nervous control of respiration and transportation of oxygenthrough blood also can be inferred from this reference.
Lung – Phupphusa:
On the left inferior aspect of the heart, ‘Plīhā’ (spleen)is situated and on its left side there is ‘Phupphusa’ (Left lung). On rightside, the corresponding organs situated are ‘Yakrht’ (Liver)and ‘Kloma’ (Right lung) respectively (Su. Śā. 4/31). Suśruta has usedtwo different terms to mean left and right lungs- ‘Phupphusa’ for left lung and‘Kloma’ for right lung. This conclusion is drawn because of the fact that theterm ‘Phupphusa’ has not been used in its plural form.

Physiology of Cardiovascular System
Cardiovascular system (‘Rasavaha Srotas’) originates atheart and ten great vessels attached to it(Ca. Vi. 5/7). Ten vessels may beindicating two venae cavae (superior and inferior), one aorta, four pulmonaryveins, one pulmonary trunk and two coronary arteries- as all these are directlyconnected to heart.

Contents of Cardiovascular Compartment: The term ‘Rasa’stands for all circulating fluids in the body including the fluid portion ofblood (Cakrapānhi on Ca.Ci. 15/36). ‘Rasa’ is alsothe minutest and essential fraction of properly digested food. Heart is thesite for this ‘Rasa’ (Su. Sū. 14/3). This ‘Rasa’ circulates in the body alongwith ‘Rakta’ (Ātañkadarpan a on Mā.Ni. 33/4). Ten great blood vessels connected to heart carry the ‘RasātmakaOjas’, on which the whole life processis dependent (A.H. Śā. 3/18). From the above references it is clear that threemajor substances circulate in the cardiovascular compartment- the first one is ‘Rasa’-the liquid nutrient portion of blood (Plasma); the second substance is ‘Rakta’,the oxygen- carrying red material(RBCs); and the third one is ‘Ojas’- the white substance that is responsiblefor immunity (WBCs).

Autonomic Control of Heart: ‘
Vyāna Vāta’ is responsible for the forceful ejection of‘Rasa Dhātu’ from the heart that later circulates all over the body to performits function of providing nutrition (Ca. Ci. 15/36 and Su. Ni. 1/17).

Cardio Vascular System is a Closed Circuit:
‘Rasa’ is ejected out of the heart. It is then carried toall parts of the body. The blood vessels called ‘Sirās’ bring it back to theheart (Bh.Sū. 21).

Structure and Functioning of Heart:
Appearance of heartis similar to that of an inverted bud of lotus. When the individual is ‘awake’,this lotus blossoms forth and when he is ‘asleep’, it closes up (Su. Śā. 4/32).The narrow apex of the heart is directed downwards and broader base is directedupwards when the individual is standing. This observation is reflected in thisexplanation saying that the heart looks like an inverted bud of lotus. To indicate‘life’ and ‘death’, the terms ‘awake’ and ‘asleep’ are often used in Sanskritliterature. So, eaning of this statementis that functioning of heart continues till the death of an individual.

Mean Flow Velocity of Blood:
The manner, in which ‘Rasa’ moves all over the body, is exactlysimilar to the manner in which sound, fire and water move (Su.Sū. 4/16). As perthe view of different commentators, velocity with which sound moves is greaterthan that of fire and the velocity of fire is greater than that of water.Therefore, it can be said that this is the explanation of the mean flow velocity of blood which is maximum in theaorta and minimum in the capillaries. This is because the smallestcross-sectional area, which receives the entire output of the blood from heart,is aorta and accordingly, the mean flow velocity is highest in that vessel.

Theories for Microcirculation

‘Kedārī – Kulyā Nyāya’: This theory describesdifferent tissues as different fields, which receive water through differentchannels, which in turn, are connected to a big reservoir of water. Nutrientfluid in this case is ‘Rasa’, which nourishes all tissues through specific channels.This theory explains the importance of pressure-gradient, which determines the flowof fluid into the tissue-spaces as this is similar to the movement of water inthe direction of gravitational force in the above example (Cakrapānhi on Ca.Ci. 15/16-17).

‘Khale- Kapota Nyāya’: This theory explains theauto-regulation of blood flow by tissuefactors.Blood flow to each tissue isregulated depending on the metabolic needs of the particular tissue. Theexample given to explain this theory is that of different pigeons, picking upthe grains from the same field and then returning to their original places.Here, the choice regarding the amount of grains purely depends on the need ofthe individual pigeon (Cakrapānhi on Ca.Ci.15/16-17).

Physiology of Hemopoietic System
The roots of Hemopoietic system are explained to be Liverand Spleen (Ca.Vi. 5/. Role of liver and spleen in the functioning ofhemopoietic system is very important. RBC synthesis occurs in liver and spleenin between 3rd and 5th month of intrauterine life. Liver
stores some important hemopoietic factors like Vitamin B-12,folic acid and iron. It produces many clotting factors also. Cells ofmonocyte-macrophage system destroy RBCs in the spleen after they complete theirlife span.

Role of Bone Marrow:
In the cavities of larger bones ‘Majjā’ is present whereasin the smaller ones it is ‘Sarakta Meda’(Su. Śā. 4/10). This ‘Sarakta Meda’ isindicative of Red bone marrow.

Formation of Bilirubin:
Byproduct ofmetabolism of ‘Rakta’ is ‘Pitta’.(Ca. Ci. 15/18). This ‘Pitta’ is Bilirubin,the product of hemoglobin metabolism. This is formed in the monocytemacrophage system,mainly in the spleen.

Hyperbilirubinemia:
When the ‘Pitta’exceeds its normal levels, there is manifestation of symptoms like yellowishdiscoloration of feces, urine, eyes and skin (A.H. Sū. 11/7). When the totalserum bilirubin level exceeds 2mg/dl, usually there is manifestation ofclinical jaundice.

Endocrinology and Metabolism
Normal vision, normal appetite, normal thirst, normal bodytemperature, normal softness of body parts, normal complexion, normalnourishment and normal intellectual functions- are all the functions of normal‘Pitta’ (Ca.Sū. 18/50). These parameters are good indicators of many ofmetabolic activities. For example, impaired Vitamin A metabolism leads toproblems in vision. In hyperthyroidism there is excessive hunger and increasedbody temperature. In diabetes mellitus there is polydypsia and polyphagia. Inhypothyroidism, normal softness of the skin and subcutaneous tissue is lost. InAddison’s disease the excessive pigmentation leads to alteration in thecomplexion. In Cretinism, the mental growth is retarded.

Intermediary Metabolism:
The five ‘Agnis’ viz., ‘Bhaumāgni’, ‘Āpyāgni’, ‘Āgneyāgni’, ‘Vāyavyāgni’and ‘Nābhasāgni’ are the causative factors for the metabolism of five groups ofrespective ingredients of the food. Normally, the specific tissues arenourished from those ingredients of food which are similar to the respectivetissues in their composition (Ca. Ci. 15/ 13-14). The function of ‘Bhūtāgnis’is to metabolize the ingredients of food and to ‘sort them out’ into fivegroups depending on the predominance of particular ‘Mahābhūta’. These functionsof ‘Bhūtāgnis’ can be explained through the functions of liver. Basically,whatever is digested and absorbed has to reach liver first and metabolicinterconversion of the substances occurs there. For example, plant-derived aminoacids can be used to synthesize human proteins, glucose can be converted intoglycogen or in to fat, amino acids can be converted into glucose – and so on.‘Sorting out’ of different substances occurs in liver and that is the functionof ‘Bhūtāgnis’ too. After the digestion in gastro intestinal tract is over, theingredients of food (‘Rasas’) undergo metabolism once again. This metabolicend- product is called ‘Vipāka’(A.H. Sū. 9/20). This indicates that ‘Vipāka’ isthe end product of the action of ‘Bhūtāgnis’. In other words to say,‘Bhūtāgnipāka’ itself produces ‘Vipāka’ and therefore, ‘Vipāka’ in general,stands for intermediary metabolism.

Metabolism at the Tissue-Level:
Each tissue derivesits nutrition through the activity of so called ‘Dhātvagni’. Metabolism attissue level is dependent on these ‘Dhātvagnis’. Some part of the tissuebecomes supportive whereas some part becomes waste after the metabolism at thislevel (Ca. Ci. 15/15).

Different Metabolic Pathways at Cellular level- ‘Kshīra- Dadhi Nyāya’:
This theory speaks oftransformation of one substance into another in a particular order through the activityof respective ‘Dhātvagnis’. The example given to state this theory is that of transformationof milk into curd, curd into butter and butter into ghee in the particularorder (Cakrapānhi on Ca. Ci. 15/16-17). All metabolicpathways like Glycolytic pathway, Kreb’c TCA cyce, β- oxidation pathway,Urea cycle, Gluconeogenesis etc. could be the examples for this type oftransformations with the involvement of their specific enzymes.

Metabolic State of a Tissue: ‘Jathharāgni’, though is situated in its own site, has its fractions situatedat the tissues. If these fractions become over active, there will be ‘Kshaya’ (Catabolism) of‘Dhātu’ and if they become depressed, there will be abnormal ‘Vrhddhi’ of ‘Dhātu’ (A. H. Sū. 11/34)
In fact, severalclassical hemocrine hormones determine the metabolic state of a tissue. Forexample, many amino acids circulating in the blood stream are taken up by musclesand they are utilized to synthesize muscle proteins under the influence of thyroxin, growth hormone, insulin andtestosterone. So, these hormones can be grouped under ‘Māmhsa Dhātvagni’. If thyroid hormone levels increase in the blood, thereis muscle wasting and loss of weight due to ‘MāmhsaKshaya’. Similarly, Calcitonin, parathormone and Vitamin D3 can beincluded under ‘Asthidhātvagni’. In hyper parathyroidism, osteoporosis or ‘Asthikshaya’ is evident.


Physiological Effects of Normal Metabolism:
At the end of ‘Bhūtāgnipāka’, three groups of etabolites areformed: ‘Madhura’, ‘Amla’ and ‘Kathu’. ‘Guru’ (Heavy)is another name for ‘Madhura’ whereas ‘Laghu’ (Light) includes remainingtwo i.e., ‘Amla’ and ‘Kathu’. These groups are called‘Vipākas’. ‘Madhura Vipāka’ promotes the synthesis of reproductive factor andpromotes the excretion of feces and urine. ‘Amla Vipāka’ opposes the formationof reproductive factor and promotes theexcretion of urine and feces. ‘Kathu Vipāka’, on the otherhand, opposes the synthesis of reproductive factor and causes retention ofurine and feces. Effects of ‘Vipāka’ on the formation of ‘Doshas’ are as follows: ‘Madhura Vipāka’ promotes ‘Kapha’, ‘AmlaVipāka’ promotes ‘Pitta’ and ‘Kathu Vipāka’ promotesthe formation of ‘Vāta’(Ca. Sū. 26/61,62). Effects of this stage ofmetabolism may be of manifold. Some products may be used for tissue synthesiswhereas the others may be used for the purpose of energy. Anabolic effects maybe called ‘Guru’ and catabolic ones, ‘Laghu’. Again, ‘Doshas’ synthesized here are of ‘Dhāturūpi’ type (‘Malarūpi Doshas’ areformed during ‘Avasthāpāka’).

Importance of Normal Metabolism:
‘Agni’ itself ispresent in the body in the form of Pitta. When it is normal, it performs thefunctions like maintenance of normal digestion, normal vision, normal bodytemperature, normal complexion, valor, happiness and nutrition. When it isabnormal, all these functions also will be abnormal (Ca.Sū. 12/11). Otherfunctions of endocrine system are described under the functions of ‘Pitta’.

Concept of ‘Pitta’:
‘Pitta’ includes allthose factors responsible for digestion and metabolism. For all practicalpurposes, ‘Agni’ & ‘Pitta’ are to be considered as identical entities (Su.Su. 21/9, Ca.Sū. 12/11).

‘Pācaka Pitta’:
‘Pācaka Pitta’ isequivalent to ‘Jathharāgni’ (A.H. Sū. 12/11). As itsfunctions suggest, all enzymes responsible for digestion along with allgastrointestinal hormones and all local hormones of G.I.T. are to be includedin it.

‘Rañjaka Pitta’: It is responsible for synthesis of‘Rakta’. It is situated in stomach (‘Amāśaya’) according to Vāgbhatha and the sites are liver and spleen according to Suśruta. Gastric intrinsic factor is the bestcandidate to represent Vāgbhatha’ s view, as itis required for the absorption of Vitamin B12, which in turn is neededfor DNA synthesis of RBC precursors in bone marrow.

‘Bhrājaka Pitta’: As is known, pigmentation of skinis under the control of some hormones like ACTH & MSH from anteriorpituitary. Some enzymes in the skin responsible for the metabolism of certaindrugs applied topically also can be considered under ‘Bhrājaka Pitta’ alongwith the hormones controlling pigmentation.

‘Sādhaka Pitta’: All functions ascribed to this‘Pitta’are of cerebrum, limbic system, hypothalamus and other CNS structures.For motivation and other psychosocial behaviors Norepinephrine is a veryessential neurotransmitter in the brain. Incidentally, it also acts on heart asa cardiac stimulant. During emergency situations it is released from adrenalmedulla and it helps for “fight or flight phenomenon”.

‘Alocaka Pitta’: This is said to be responsible fornormal vision. Photosensitive chemicals in the eye, called Photo-pigments andthe whole process involved in photochemistry of vision can be represented by‘Alocaka pitta’. Also, neurotransmitters involved in the visual pathway can beincluded under this.

Immune System
General Functions: When the Śleshma (Kapha) is in normal state, it is called ‘Bala’ as well as‘Ojas’; but when it attains an abnormal state, it is then called ‘Mala’ (Waste)and ‘Pāpmā’ (Disease) (Ca.Sū. 27/117). From the above statement it is clearthat ‘Bala’, ‘Ojas’ and ‘Kapha’ are identical entities, at least when ‘Kapha’is in normal state. When ‘Kapha’ is in its normal state, it providescompactness, stability, virility, immunity and resistance (Ca.Sū. 18/51).
Importance: The most essential fraction of all bodilytissues is called ‘Ojas’. Eventhough it resides in the heart, itcirculates all over the body to maintain the normal healthy status of the body.It is ‘Snigdha’ (unctuous) and ‘Somātmaka’ (mild and cool) in nature. Though predominantlywhite in colour, it has got some yellowish and reddish tinge. If this is lost,life also is lost and if this remains intact, life continues (A. H. Sū.11/37-38).
‘Ojas’ has been described to exist in different forms in thebody. The fraction of ‘Ojas’ that circulates all over the body through thecardiovascular system, moves along with ‘Rasa Dhātu’. This is called ‘RasātmakaOjas’. Another form of ‘Ojas’, is present in all tissues and is called‘Dhātutejorūpi’. This indicates the immune mechanisms present at tissue-level.A third form of ‘Ojas’ is ‘Śukra mala rūpi’. This enters the fetus to provide protectionto the fetus during intrauterine life. Another form of ‘Ojas’ is described as ‘Jivaśonhita rūpi’ (Hemādri on A.H. Sū 11/37-38).
Classification of Immunity:
Immunity isclassified in to three types: Innate (Sahaja),Acquired (Kālaja) and Artificial(Yukti kr ta) (Ca.Sū. 11/36).
Factors Influencing Immunity: The following factorsinfluence the promotion of immunity:
place of birth, time of birth, favorable weather, excellenceof genetic qualities, excellence of properties of food being consumed,excellence of physique, good ability to tolerate various factors, excellence ofmental status, favorable factors related to nature, youthfulness, exercise andcheerful attitude (Ca. Śā. 6/13).

Antigen-Exposure and Host Response:
Substances, which have opposite qualities to those of bodilytissues, (when gain entry into the body) encounter the opposition by the bodilytissues (Ca. Sū. 26/91). Etiological factors, ‘Doshas’, and‘Dhātus’ determine the bodily immunity or susceptibility for thedisease. When all the three factors do not support each other or when they areweek due to passage of time, either the disease does not manifest at all or ittakes some time in manifestation or the disease is very mild or all its signsand symptoms are not fully manifested. If the situation is opposite to that ismentioned above, the corresponding results also will be otherwise (Ca. Ni.4/4). This means that susceptibility of a particular tissue to any antigenicattack plays an important role in the manifestation or non manifestation of adisease. At the same time, the potency of the causative agent also is important.Virulent strains of infectious agents produce severe symptoms. Along with thesetwo factors, homeostatic mechanisms also are important. If immune system isnormally functioning, injurious agents will be tackled effectively.

Concept of Active and Passive Immunity:
Treatment of thediseases manifested due to the presence of opposing agents in the body, shouldbe planned either by administering the substances having opposite qualities tothem or by prior sensitization of thebody by administering the similar substances as those of offending agent (Ca.Sū. 26/104). This forms the basis of active and passive immunity. Priorsensitization of the body with specific antigen makes one develop activeimmunity. On the other hand, antibodies can be procured out of an animal inwhich active immunity has been already produced, and can be administered to theindividual suffering from the same disease. Other functions of immune systemare described under the functions of ‘Kapha’

Concept of ‘Kapha’:
Functions of immune system and all such other protective mechanismsin the body have been grouped under ‘Kapha’ in Ayurveda. ‘Ojas’ is also closelyrelated with ‘Kapha’.

‘Avalamhbaka Kapha’: Situated in the thorax, ‘Avalamhbaka Kapha’ protects the‘Trika’ and other vital structures like heart, through what is called ‘Amhbukarma’. Other anatomical sites where other types of ‘Kapha’are situated also are dependent on this (A.H. Sū. 12/15-16).
‘Trika’ region indicates the meeting point of three bones.As this is present in thorax, it must be indicating the junction between thesternum and clavicles, behind which, the thymus gland is situated. ‘Amhbu’ means liquid or water. So, ‘Amhbukarma’ must be referring tolymphatic drainage.

‘Kledaka Kapha’: This is present in stomach and it moistensthe ingested food (A.H. Sū. 12/16-17). Mucous secreted in stomach playsimportant role in offering protection to mucous membrane of the stomach alongwith providing liquid medium for digestive process. Also, Gut AssosiatedLymphoid Tissue helps in providing protection by preventing the entry of any microbesthrough gut. HCl secreted in stomach also provides innate immunity to someextent. All these mechanisms can be explained through ‘Kledaka Kapha’.

‘Bodhaka Kapha’: This is said to be present in oral cavityand helps in the perception of taste. Salivary juice secreted in the oralcavity not only helps in the process of taste perception but also performs someprotective functions. Root of the tongue is the site of ‘Bodhaka Kapha’.Tonsils are the important lymphoid tissue-containing structures present there.

‘Tarpaka Kapha’: This sub-type of ‘Kapha’ is present insidethe head and is responsible for the protection and nourishment of sense organs.Microglia and other similar Glial cells of brain tissue are some of theimportant entities, which may represent ‘Tarpaka Kapha’.

‘Śleshaka Kapha’: This Kapha is present in thebony joints and is responsible for lubrication and easy movements.Movements are most obvious in synovial variety of joints and synovial fluidreduces the friction between two articular bony surfaces. But ‘Slesaka Kapha’is not only synovial fluid. For several reasons known and unknown, these jointsare the sites of prominent inflammation in most of the systemic autoimmunediseases like Systemic Sclerosis, Systemic Lupus Erythematosus and Rheumatoidarthritis. Such involvement must be, therefore, ascribed to the problems of‘Śleshaka Kapha’.
Physiology of Male Reproductive System
The roots of ‘Śukravaha Srotas’ are the testicles and penis(Ca. Vi. 5/10). Testicles synthesize the hormone testosterone and also they arethe sites of spermatogenesis. Penis is the male copulatory organ through whichthe seminal fluid is deposited in the female reproductive tract. The factor,which is responsible for the formation of ‘Garbha’ (embryo), is known as‘Śukra’ (Ca.Śā. 2/4). ‘Śukra’ is distributed all over the body in the samemanner in which the fat in the milk and juice in the sugar cane plant aredistributed (Ca.Ci. 2/46). Also, this is present in males and females. Allhormones of hypothalamo-pituitary-gonadal axis can thus be included under theterm ‘Śukra’. In some references, ‘Śukra’ stands for only semen. Fatty portionof ‘Majjā’ forms ‘Śukra’. This ‘Śukra’ comes out of bones through the porescreated by ‘Vāyu’ and ‘Ākāśa Mahābhūtas’. As if the water oozing out of new mudpot,
‘Śukra’ also oozes out of these pores and then circulatesall over the body through ‘Śukravaha Srotāmhsi’(Ca.Ci. 15/32-33). ‘Majjā’ stands for even brain substance. ‘Mastakamajjā’ isthe term given to indicate brain by Dalhanha, thecommentator of Suśruta Samhhitā, while commenting on Su.Śā.10/42.Hypothalamus secretes GnRH and Hypothalamohypophysial portal system carriesthis to the anterior pituitary. Anterior pituitary, in response to GnRH,secretes FSH and LH into the blood stream. These hormones then circulate allover the body and stimulate ovaries and testicles to secrete their own hormones.

Ejaculation:
When the person gets excited because of the sexual urge,determination and romantic mental attitude, ‘Śukra’ comes out through theurethra (with which the bladder is connected)as if the melted ghee. This occurs because of the heat produced by the physicalexertion during copulation. The simile given to describe this process is theflow of water from a place of lower altitude to a place of higher altitude(Ca.Ci. 15/34-35). Generalized sympathetic stimulation is an essential featureof sexual activity. Erection requires parasympathetic stimulation whereasejaculation is dependent on sympathetic one. Also, ejaculation is brought aboutby ‘Apāna Vāta’, which represents the sympathetic activity in this case.

Physical properties of Semen: The semen is ‘Snigdha’(unctuous), dense, slimy, sweet, nonirritating (mild), and white just like apiece of alum crystal (Ca.Ci. 30/145-146).
Physiology of Female Reproductive System
Menstrual blood (‘Raja’) also is a derivative of ‘Rasa’only. Menstruation occurs in females once in every month and lasts for aboutthree days. This process of menstrual cycle begins at the age of twelve yearsand stops at about fifty years of age (Su.Sū. 14/6). During the act of copulation,production of ‘Śukra’ occurs in females also; and it should not be thought thatit is of no use in the process of production of embryo i.e., it is also ofdefinite use (A.S. Śā.1/72). Features of ‘Rakta’ and ‘Ārtava’ are similar.‘Ārtava’ is responsible for the productionof embryo (Su. Sū. 15/5). ‘Rakta’ and ‘Ārtava’ are similar functionally. Thisis because the function of ‘Rakta’ is to ‘Give life’ (‘Jivana’) and thefunction of ‘Ārtava’ also is to give life to a new individual (embryo). So,‘Ārtava’ means ovum in this context. This ‘Ārtava’, after getting nourishedover the period of a month, enters (the uterus and then)
vagina through the specialized structures called ‘Dhamanis’meant for the transportation of the same. ‘Vāta’ is responsible for thismovement of ‘Ārtava’(Su.Śā. 3/10). This is the explanation regarding theprocess of ovum entering the uterus through the Fallopian tube. If notfertilized, it is shed off through menstrual fluid.
Physiology of Lactation:
Breast-milk is formed out of ‘Rasa Dhātu’ (Ca. Ci. 15/17).The essential nutrient fraction of ‘Rasa Dhātu’, enters the breasts from theentire body and it is known as ‘Stanya’ (Su. Ni. 10/18).
Development of Breasts:
Ducts in the breasttissue of non-pregnant women are narrow and are constricted. During pregnancyand after delivery they get dilated as a natural phenomenon (Su. Ni. 10/16-17).
Various Stimuli for Milk Letdown:
Breast-milk isoriginally formed from the essential fraction of food. It is ejected out ofbreasts because of touch, sight and even because of mere remembrance of thebaby. Uninterrupted love of mother towards her baby is the cause of its flow(Su. Ni. 10/12-13). Emotions, touch or even sight of the baby cause thehypothalamus of mother to release oxytocin stored in the posterior pituitary.This causes the myo-epithelial cells surrounding the glandular apparatus tocontract and exert a squeezing effect, thus allowing the milk to flow.
Urinary System
The abode of urine called ‘Mūtrāśaya’ supports the wastes ofthe body and is one of the very important vital structures in the body. Minute‘Nād īs’ (specialized structures meant fortransportation) arising from the large intestine, carry the urine continuouslyand contribute in the urine formation. This process is just similar to themanner in which many small tributaries and rivers contribute their water to theocean. Openings of these ‘Nād īs’ cannot be tracedout because of their minuteness and huge number. Because of this urine, carriedby these ‘Nād īs’ from the proximity of stomach,‘Basti’ (urinary bladder) gets filled up continuously throughout the dayand night through the process of filtration. This process is similar to thefashion in which a new earthen pot kept immersed in the water up to its neck getsfilled up (by the water) after some time through its sides (Su. Ni. 3/20-24).‘Mūtrāśaya’ in the above reference has been told to be very vital, andtherefore, definitely is indicative of kidneys, from a functional point ofview. Suśruta probably knew the role of kidneys in the formation of urine. Heprobably also had observed that there exists some relationship between waterintake and urine formation. The fact that increased water intake results in increasedurinary output must have been the reason for this observation. Also, decreasein the urinary output observed in the persons suffering from diarrhea orvomiting might have been another reason. So, he proposed the existence ofinvisible minute channels connecting GIT and urinary tract. This prediction isnot totally wrong because cardiovascular system definitely connects both thesesystems. Water is absorbed from the gut into the venous circulation and this iscarried to the kidneys through the arterial system. Also, the capillaries atGut and glomerulus are definitely microscopic. The example of mud pot in theabove explanation indicates the role of filtration played by the kidneys in theformation of urine. Thousands of ‘Nād īs’ taking part inthe process of filtration may stand for nephrons from a functional point of view.