Lecture Note: “Principles of Physiology in Ayurveda” (Part -2- Digestion)

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“Principles of Physiology in Ayurveda”
(Part-2 Digestion)

This is a transcript prepared by Dr. Varsha More,
based on the lecture available at Ayurvedic Principles of Human Physiology

Digestive tract

The digestive tract should include two important Srotamsi. The first one is Annavah Srotas and the second one is Purishvah Srotas taken together to form the digestive tract not only simply Annavah Srotas. Many times scholars commit the mistake of equating Annavah Srotas to the digestive tract. But Annavah Srotas and Purishvah Srotas should be taken together to understand the digestive tract.

अन्नवह स्रोतस

]न्नवहानां स्रोतसामामाशयो मूलं वामं च पार्श्वं …..(Ch.Vi5/8)

पुरिषवह स्रोतस

पुरीषवहानां स्रोतसां पक्वाशयो मूलं स्थूलगुदं….. |(Ch.Vi5/8)

‘Annavah Srotas’ has got its root in the stomach, especially on its left side. The term ‘Mool’ does not only indicate anatomical relationship rather it may stand for functional significance. Most of the time it is a functional significance and indirect relationships are often taken into consideration.  e.g Amashaya, the upper portion of the gut is responsible for receiving food and food is still in Apakva/Aam ( partially digested)stage. Therefore such a portion of the gut is considered as Amashay. The stomach along with the upper part of the gastrointestinal tract should be considered as Amashaya. The left side (Vama Parshav) has been given special importance. One of the explanations given by many authors is that the left side of the stomach has a greater curvature and is also a site for maximum secretions.

 ‘Purishvah Srotas’ has got its root in the large intestine, especially at rectum. Sthula Guda stands for the distal part of the rectum. Pakvashaya means is the site where Pakva Mala is present and not the Pakva Ahara. Many times students often get confused with the terms Amashaya and Pakvashaya. Amashaya is the site where undigested food is present while Pakvashaya is the site where Pakva Mala is present and not the Pakva Ahara. Because after the Ahar gets digested completely Pakva Ahar gets absorbed, it does not go into the large intestine. Tough Pakvashaya stands mainly for large intestine it doesn’t mean it contains the Pakva Ahar rather it contains Pakva mala (matured faecal) matter. Therefore it is called Pakvashaya.

Deglutition, Mucus Secretion, and Neural Control:

अन्नमादानकर्मा तु प्राणः कोष्ठं प्रकर्षति|
तद्द्रवैर्भिन्नसङ्घातं स्नेहेन मृदुतां गतम्||
समानेनावधूतोऽग्निरुदर्यः पवनोद्वहः|
काले भुक्तं समं सम्यक् पचत्यायुर्विवृद्धये||Ch.Chi. 15/6, 7

Pranvayu carries the food towards the Koshtha. ‘Adankarma’ is an adjective for Pranvayu. It means to cause the movement of something. The Pran Vata whose function is to cause movement propels the food towards the lower portion of the gut (Koshtha) forcefully. There are several liquids consumed along with food that helps in dividing the foodstuffs.  The term ‘Sanghat’ means something that is bound together. If something gets divided and binding can be loosened then this process is called ‘Bhinnasanghat’.  Lack of compactness eventually led to the division of food. Sneha causes softening of the food that one consumes. Sneha stands for the fatty substance consumed along with food. It could be oil or ghee or any other fat-containing substances.

Role of Saman Vata:

Jatharagni gets stimulated by the activity of Saman Vata. ‘Avdhootargni’(अवधूतोऽग्नि)  means Agni is being stimulated or activated by the action of Saman Vayu. Because Saman Vayu is residing near the Koshstha and causes the stimulation of the Jathargni. Here’ Pavanodhvaha’ is the adjective used for Agni because it indicates the one that gets intensified because of Vayu. If the food is consumed in optimal quality, quantity, and in proper time, then digestion of such food leads to the sustenance of the lifespan.

Factors Influencing Digestion (Ahar Parinamkar Bhava):

आहारपरिणामकरास्त्विमे भावा भवन्ति|
तद्यथा- ऊष्मा, वायुः, क्लेदः, स्नेहः, कालः, समयोगश्चेति |तत्र तु खल्वेषामूष्मादीनामाहारपरिणामकराणां भावानामिमे कर्मविशेषा भवन्ति| तद्यथा- ऊष्मा पचति, वायुरपकर्षति, क्लेदः शैथिल्यमापादयति, स्नेहो मार्दवं जनयति, कालः पर्याप्तिमभिनिर्वर्तयति, समयोगस्त्वेषां परिणामधातुसाम्यकरः सम्पद्यते|| (Ch. Sha 6/14, 15)

The factors that are responsible for the Parinam of Ahara i.e transformation of Ahara are as follows.

Ushma: It means optimal temperature; sometimes it refers to Agni also but most of the time it is for optimum heat.

Vayu: It is responsible for movement, stimulation, or activation.

Kelda: Fluid substances may be produced in the body or sometimes the fluids consumed. Most of the time it stands for the fluids that are formed within the body.

Sneha: This includes fatty substances.

Kaal: It means time factor.

Samyog: Optimal combination of all these factors.

Important functions of each factor are as follows.

Ushma: It is the heat that leads to digestion. Food being cooked outside the body leads to proper cooking of food. Similarly inside the body after food is consumed that also being cooked or digested. Optimal temperature is required for the digestion of food.

Vayu: It causes movement of foodstuff. Apkarshan means taking away from some point, especially in the human body it is a direction that is from the mouth towards the anus i.e. aboral direction.

Kelda: The fluids that may be secreted during the process of digestion or sometimes ingested during consumption cause loosening of the bonds within the foodstuffs. Loosening of compactness of food thus causes division of food particles. In modern physiology digestion of food has been explained in two phases one is physical digestion and the second one is chemical digestion.

In physical digestion, the particle size becomes smaller whereas in chemical digestion the actual enzymatic digestion of foodstuff takes place.

Sneha: It causes softening.

Kaal: Appropriate time is required for the completion of digestion.

Samyoga: Effect of optimal combination all of these factors would lead to Dhatusamya or the status of health.

The digestion as such has been further explained in Charak Samhita in three phases. These three phases are called Avasthapak. It is dependent on the location of Ahar when it is undergoing the process of digestion. There are three phases namely Madhur Avasthapak, Amla Avasthapak and Katu Avasthapak. The Madhur, Amla and Katu stand for sweet, sour and pungent literally but possibly these three phases have been used to indicate phases of digestion and these tastes are actually not the actual tastes that food attains rather it is indicative of the effects of food.  Because each Rasa has its own functional effects or physiological effects. Thus Rasa in this case indicates physiological effects and that is why this nomenclature has been used.

Digestion in upper GIT:

अन्नस्य भुक्तमात्रस्य षड्रसस्य प्रपाकतः|
मधुराद्यात् कफो भावात् फेनभूत उदीर्यते|| (Ch.Chi 15/9)

As soon as the food is consumed; it undergoes the first stage of digestion.  Food which is of six tastes when gets consumed immediately starts undergoing the process of digestion. The first stage is called Madhur and this leads to a release of froth like Kapha (Phenbhut Kapha). The Kapha here does not stands for actual functional   Kapha Dosha rather this is possibly indicative of Malarupi Kapha. Because the term Phenbhoot have been used which is indicative of the physical appearance and being functional significant entity Vaat, Pitta and Kapha do not have any physical appearance as such. Physical appearance cannot be explained because the Tridosha stands for a different entity for different contexts. Here froth like Kapha is released during the first stage of digestion and in modern physiology, it is clearly understood that the stomach contains several glands that secret mucus. Two types of mucus viscid mucus and another one is soluble mucus. The viscid layer forms a very thick layer of mucus in the stomach and this is physiologically very important. It prevents the acid pepsin mixture from digesting the gastric mucosa. Gastric mucosa does not get digested by acid pepsin mixture because there is a thick layer of mucus. This is a protective layer. Possibly this is being indicated by the term ‘Phenbhoot Kapha’.

Digestion in Small Intestine:

परं तु पच्यमानस्य विदग्धस्याम्लभावतः|
आशयाच्च्यवमानस्य पित्तमच्छमुदीर्यते|| (Ch.Chi 15/9 )

The second stage of digestion occurs in the small intestine which is called ‘Pachymanashya’.It is the location or organ where the process of digestion is still going on. After the first stage, the Ahar which is undergoing digestion or partially digested attains Amlabhav. The food is getting propelled further From the Ashay and during this process, there is a release of Accha Pitta. The term Accha Pitta does not stand for Pitta Dosha as such but it stands for Malarupi Pitta. Because Accha is indicative of the physical property and in Chakrapani tika it has been mentioned that Accham is Aghan means liquid. A liquid substance that gets released during the process of digestion when the chyme is present in the small intestine, it is actually the bile. Possibly this is indicative of the release of bile in the small intestine or duodenum and also the site where the actual digestion takes place.

——————-तत्र पक्वामाशयमध्यगम्|
पञ्चभूतात्मकत्वेऽपि यत्तैजसगुणोदयात्||
त्यक्तद्रवत्वं पाकादिकर्मणाऽनलशब्दितम्|
पचत्यन्नं विभजते सारकिट्टौ पृथक् तथा||
तत्रस्थमेव पित्तानां शेषाणामप्यनुग्रहम्|
करोति बलदानेन पाचकं नाम तत्स्मृतम्||(A.H .Su 12/10, 11, 12)

It is important to note that Pachak Pitta is also known as Jathargni. The Pitta which is located between Pakvashaya and Amashay is predominant in Tejas guna, though it is made up of Panchamahabhoot. Because of this it loses its liquidity and becomes devoid of fluidity and performs functions such as digestion. Therefore it is known as Anal or Agni. It causes digestion, divides the food into Saara and Kitta. Saar is an absorbable portion that is nutritive in nature and nourishes the body while Kitta is the waste portion. Though Pachak Pitta is situated at its own site, it also supports all other types of Pitta by extending its support. Therefore it is known as Pachak Pitta. The Saar portion gets absorbed and the Kitta portion does not get absorbed and enters into the large intestine.

Physiology of absorption:

आमाशयगतः पाकमाहारः प्राप्य केवलम्|
पक्वः सर्वाशयं पश्चाद्धमनीभिः प्रपद्यते||(Ch.Vi 2/18)

During digestion, there is the role of Pachak Pitta and Saman Vayu. After the digestion is over there is the absorption of absorbable portion and only the portion that is not absorbable reaches the large intestine. So before reaching the large intestine the absorbable portion gets absorbed. After the completion of digestion in Amashay is over, this Pakva(digested) portion gets carried through different Dhamanis (blood vessels) to all parts of the body. It is important to note that Pakva Ahar gets absorbed and reaches all parts of the body. The remaining Kitta portion that is not able to be absorbed reaches the large intestine. Therefore the large intestine contains the Mala.

Large Intestinal Functioning:

पक्वाशयं तु प्राप्तस्य शोष्यमाणस्य वह्निना|
परिपिण्डितपक्वस्य वायुः स्यात् कटुभावतः||(Ch.Chi 15/10)

The remaining portion reaches Pakvashaya, afterwards action of Agni exerts a drying effect. Therefore the water gets absorbed and the remaining portion gets solidified and causes a release of Malarupi Vayu.  The pungent gases like hydrogen sulphide etc get released.

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