Physiology of Gastro Intestinal Tract

General description

‘Annavaha Srotas’ has got its roots situated in stomach, especially on its left side. ‘Purīsavaha Srotas’ has got its roots in large intestine, especially at rectum (Ca.Vi. 5/8). ‘Annavaha Srotas’ and ‘Purīsavaha Srotas’ together form the complete gastrointestinal tract. ‘Annavaha Srotas’ includes upper and middle part of the gut whereas ‘Purīsavaha Srotas’ is lower GIT.

Deglutition, Mucous secretion and Secretion of Enzymes

The food is brought towards the gut through ‘Prāna Vāta’. There, various fluids making its bonds loosen, act on it. Also, the food is softened here. Then the ‘Samāna Vāta’ stimulates ‘Jatharāgni’. This ‘Agni’ finally digests the food (Ca.Ci.15/6, 7). After the food reaches stomach, several digestive juices act on it. Gastric juice, pancreatic juice, and enterocytes in the intestines - all contain important digestive enzymes and act on food. Secretion of these enzymes is mostly under the control of 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 of froth-like ‘Kapha’ (Ca. Ci.15/9). Salivary juice and mucous secreted in the stomach serve many protective functions but do not directly participate in the actual process of digestion. These are therefore indicative of froth-like ‘Kapha’, which is ‘Malarūpī’ in nature.

Digestion in Small Intestine

‘Pitta’ that is present in between stomach and large intestine is called ‘Pācaka Pitta’. Though made up of five basic elements, it is dominant in fire principle. So, it is devoid of liquidity and is called ‘Anala’ (‘Agni’). This digests the food and splits it into essential nutrient part called ‘Sāra’ and waste part called ‘Kitta’ (A.H. Sū. 12/10-12). The ‘Pācaka Pitta’ is directly responsible for digestion of the food and therefore stands for all amylolytic, proteolytic, lipolytic and nucleic 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 absorbed and 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 pancreatic juices 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 ‘Accha Pitta’.

Factors influencing Digestion

Digestion of food depends on following important factors: optimum temperature, ‘Vāyu’, fluid medium, lubricating substances, time and appropriate administration. ‘Vāyu’ helps in movement of food in the gut. Fluids make the food particles easily breakable. Lubricating substances make the food softer. Time factor makes sure that the food is completely and properly digested. Along with all these factors, if the administration also is proper, the resultant digested material will be capable of maintaining ‘Dhātusāmya’(Ca. Śā. 6/14,15).

Absorption and distribution of Digested Material

After the completion of the digestive process, the digested material reaches all parts of the body through the vessels called ‘Dhamanīs’ (Ca.Vi. 2/18).

Large Intestine

After the nutrients are absorbed from the small intestine, the remaining undigested portion of food reaches 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 ‘Katu’ (pungent) nature. This stage is the third stage of digestion and is called ‘Katu Avasthāpāka’ (Ca. Ci. 15/9-11). In the large intestine, except for absorption of water and some electrolytes, no digestive activity takes place. But this absorption of water makes the remaining undigested material hard and this material is called feces. Due to the activity of bacterial flora, some pungent gases like methane and ammonia are also produced here. These represent ‘Katu’ nature of ‘Vāta’ released during this stage.