Physiology of Gastro Intestinal Tract

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.

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