THE DIGESTIVE SYSTEM

The Digestive System consists of the alimentary canal and the accessory organs of digestion. It is responsible for receiving food, breaking it down into smaller units, absorbing the nutrients into the blood stream and eliminating the undigested food from the body. The study, diagnosis and treatment of diseases of the stomach and intestines is called as Gastro-enterology.

PROGRESS OF FOOD ALONG THE ALIMENTARY CANAL

The above picture shows the time taken for an average meal to travel from the mouth to the large intestine.  Leafy vegetables like palak (spinach), methi, dhania(coriander leaves), pudina(mint) etc will take a slightly longer time. 

During its progress along the canal, food is subjected to mechanical as well as chemical changes – to render it suitable for absorption and assimilation.

Functions of Digestive System :-

Digestion :- The breaking down of larger food particles into smaller particles suitable for use by the body is known as digestion.  Digestion involves six different processes.

1.                 Ingestion :- Taking in food by the mouth into the alimentary tract.

2.                 Secretion : - A total of about 9 litres of water, acid, buffers and enzymes is secreted daily in various parts of the GIT.

3.                 Mixing and propulsion :- These movements are present all along the alimentary tract.

4.                 Mechanical and chemical digestion :

(a)              Mechanical digestion includes break down of food by teeth, in the mouth, as well as the movement of the GIT that aid digestion.

(b)              Chemical digestion is a series of chemical reactions by enzymes in mouth, stomach, duodenum & jejunum.  These break down large molecules of carbohydrates, proteins and fats into smaller molecules that can enter the blood stream and can be used by body cells for various purposes.

5.                 Absorption :- Passage of these smaller particles into blood and lymph is known as absorption. It takes place partly in the jejunum and maximum in the ileum. Structures known as villi in the small intestine help digestion and absorption by increasing the surface area of the intestinal wall.

6.                 Defecation or elimination takes place in the Large intestine, Rectum & Anus.

ALIMENTARY TRACT OR  CANAL

The alimentary canal or GIT (gastro-intestinal tract) is one continuous coiled, muscular tube which has different diameters and shapes at different locations. It extends from the mouth to the anus. It is 6-9 meters long when fully extended.

The different parts of the alimentary canal are:

mouth, esophagus, cardiac sphincter, stomach, pyloric sphincter, duodenum, jejunum, ileum, ileo-cecal valve, ascending colon, transverse colon, descending colon, sigmoid colon, rectum & anus. The entire pathway from mouth to anus is lined with a mucous membrane which secretes mucus, whose main purpose is to provide lubrication for the smooth passage of food through the GIT.

The different organs of digestion are held in place by the peritonium (p’]r`{n}ym), which is the largest serous membrane of the body.  It lines the wall of the abdominal cavity. It helps to bind the intestines to different areas of the abdominal wall and holds them loosely in place, while allowing great amount of movement for mixing the food properly. It also carries blood and lymphatic vessels to the intestines.

In Neurotherapy, we stimulate the peritoneum by Raman treatment and the alimentary canal by (10) Medulla.  This activates the Vagus nerve, which stimulates the digestive system from mouth to the transverse colon only; the descending colon is stimulated by sacral nerves.

MOUTH

The mouth is an oval cavity at the beginning of the alimentary tract. In the mouth, the food is masticated and mixed with saliva. Swallowing moves food from the mouth through the pharynx into the esophagus and then to the stomach. The most important component of saliva is Ptyalin, which starts the chemical digestion of carbohydrates. It helps the pancreas by partial digestion of Carbohydrates in the mouth. The mass of chewed, moistened food is called as Bolus. It is pushed into the pharynx by the voluntary action of the tongue and swallowing movements.

ESOPHAGUS 

It is a muscular tube ( length : 25cm.) in-between the pharynx & cardiac sphincter of the stomach. In the esophagus, the bolus is pushed into the stomach by waves of involuntary muscular contractions known as peristalsis.

STOMACH 

The stomach is a ‘J’ shaped dilatable portion of the alimentary tract   (Volume :- 1500 ml). It consists of three parts :- Fundus,        Body            &       Pylorus.

There are two sphincters at either end of the stomach. The sphincter at the end of the esophagus is called as cardiac sphincter.  The sphincter at the other end of the stomach is known as pyloric sphincter.  Here the stomach narrows down to form a C-shaped structure known as duodenum, the first part of the small intestine.

Functions of stomach

1. Acts as reservoir of food.
2. It secretes gastric juice ( which means a mixture of ALL stomach fluids). Pepsin in the gastric juices starts the partial digestion of proteins.
3. The movements of stomach help in the proper mixing of gastric juices and make chyme.
4. The stomach wall is impermeable to most substances. Among the substances absorbed are water, certain ions, drugs and alcohol.                      

Composition and Functions of Gastric Juice -

Gastric juice is the general term for a mixture of the following :

HCl, Mucus, pepsin, intrinsic factor, water, salts and minerals.

HCl :- (Hydrochloric acid) has two functions.  It helps to maintain pH below 3 for the proper action of Pepsin so that partial digestion of proteins takes place.  HCl will be formed in the stomach only when Gastrin, Acetylcholine & Histamine – are present. Its second function is to destroy all bacteria and viruses present in the food.  For both these functions to be done well, it is necessary that the stomach acid should be quite concentrated.  So we should not drink water during food

Mucus :- It acts as a lubricant. It protects the stomach wall from the acid present in gastric juice.

Pepsin :- It starts initial digestion of proteins in the food and converts them into peptides and peptones.

Intrinsic factor – It is known as a glyco-protein. Its job is to protect vitamin B₁₂ from the action of acid and other digestive enzymes in the jejunum and ileum, until Vitamin B₁₂ is absorbed in the villi of the ileum.

Gastric lipase – it is found in small quantities and helps in digesting butter-fat.

Water, Salts and minerals are also necessary for the digestive processes.

In addition, some earlier books mention the following :

Rennin :- An enzyme which converts casinogen to casein. It is present in the gastric juice of ruminants (eg. Cow), but not in the human stomach. (Taber’s 17^th  edn. p. 1696). Nowadays its preferred name is chymosin, so as not to confuse it with renin secreted by the kidney. (Taber’s 18^th edn.p 386).

The mixture of food and gastric juice is called as chyme (k;em).   

Phases of Secretion of gastric juice

To properly digest the food, secretion of gastric juice is governed in three phases:-

[1] Cephalic phase             [2] Gastric phase     [3] Intestinal phase.

[1] Cephalic phase :- Some flow of juice occurs even before food reaches the stomach.  Even the mere sight, smell or taste of food is enough to stimulate flow of gastric juice. This is due to reflex stimulation by the vagus nerve. This phase of gastric secretion stops when the vagus nerve is cut ( this is called vagotomy). 

[2] Gastric phase :- After food reaches the lower portion of the stomach, the endocrine cells in the pyloric antrum and duodenum secrete gastrin. Gastrin is a hormone, which circulates in the blood, and when it reaches the stomach wall, it stimulates the gastric glands to produce HCl. The pH of the food from the mouth is approx. 6.5.  By action of HCl this goes on decreasing. Gastrin secretion is suppressed when the pH in the pyloric antrum falls to about 1.5.  This helps prevent undue formation of stomach ulcers.

In Neurotherapy we stimulate production of Gastrin through UDF & HCl treatments in the following ways:

(10) Medulla stimulates Vagus Nerve              

‘Gas Only’ stimulates the different secretions of the stomach, including HCl and intrinsic factor.

(1 pt) Gal stimulates the pyloric end of the stomach where cells releasing Gastrin are located.    
If  Intrinsic Factor is not produced properly, vitamin B₁₂  will not reach the Ileum.  So the person who does not have intrinsic factor will soon suffer from B₁₂ deficiency.

[3] Intestinal phase :- When the partially digested contents of the stomach reach the duodenum, two hormones (Secretin & Cholecystokinin) are produced by the endocrine cells in the intestinal mucosa, which slows down the secretion of gastric juice and reduces gastric motility. Without these hormones digestion of food will not take place.

In Neurotherapy we use CCK, Secretin and Chole treatments to stimulate the action of these hormones.

SMALL INTESTINE

The small intestine consists of 3 parts : Duodenum, Jejunum and Ileum

Duodenum :-  It is the first part of small intestine. It is shaped like a ‘C’ ; length – 25 cm. It starts with the pyloric sphincter of the stomach and extends to jejunum.

Functions of Duodenum

1) Produces two hormones- Secretin & Cholecystokinin, when the chyme enters the duodenum. Secretin sends message to the Pancreas to release sodium bicarbonate; Cholecystokinin  sends the message to the Gall Bladder to release Bile and to pancreas to release digestive juices.

2) Digestion of Proteins, fats & carbohydrates takes place here with the action of pancreatic juice, aided by bile from the liver.

Jejunum :-  It is the middle part of small intestine. (length about 2 m).

Functions of Jejunum   

1)     Completes the digestion of carbohydrates, fats & proteins.

2)     Some nutrients and water are absorbed in this region

Ileum :-  It is approx. 300 cm. (3m.) long and ends at the ileocaecal valve, where it meets the ascending colon of the large intestine.

Functions of Ileum

1.     In the ileum the end products of digestion are absorbed by the villi.  They then reach the blood either directly or through lymphatics.  (See picture)

End product of Carbohydrates are – monosaccharides eg. Glucose, maltose, fructose etc.

End product of Proteins are – amino acids.

End product of fats are free fatty acid and glycerol.

(Monosaccharides reach the blood directly. Fatty acids and large proteins are first absorbed into the lymphatic channel. Then they are broken down into smaller particles and then sent into the blood.  )

1. Water, Vitamin B₁₂  & drugs are also absorbed in the ileum.

In LMNT, we stimulate the small intestine by GAS-I treatment.

LARGE INTESTINE

 This is about 150 cm. long; beginning at the cecum and ending at the rectum. The parts of Large intestine are – cecum, ascending colon, transverse colon, descending colon, and sigmoid colon

Functions of large intestine

(a)  Synthesis of Vitamin K & Folic acid in the ascending colon.

(b)  Absorption of water, minerals & salts (through out the colon)

(c)   Mass movement :- By this movement waste products of digestion are thrown into the descending colon.

(d)  Elimination & Defecation through the rectum and anus.

RECTUM & ANUS

The rectum is 13 cm. long. It is a reservoir of stool.

The anus is 8cm. long. Defecation occurs by the action of autonomic nervous system.  The chart below gives an average volumes of fluid ingested, secreted, absorbed and eliminated from the GIT (gastrointestinal tract) daily

                                      ACCESSORY ORGANS OF DIGESTION

These organs lie outside digestive tract & their secretion is poured into the Alimentary canal by ducts. These are – salivary glands, pancreas, liver and gall bladdder. Teeth and tongue are other accessory structures which also help in the process of digestion.

SALIVARY GLANDS

There are 3 Pairs of Salivary Glands. Their secretion is called Saliva.

(1) Parotid glands   (2) Sublingual glands      (3) Submaxillary glands

The optimum pH of Saliva is 6.8

Main Components of saliva :-      

(i) Ptyalin               (ii) Water                         (iii)  Salts               (iv) Mucus

ptyalin = (enzyme responsible for partial digestion of proteins)

Functions: - Saliva helps in the following :

Lubrication             Antiseptic / Germicidal               

Taste                      Mastication & deglutition              Temperature maintenance

Digestion of Carbohydrates by Ptyalin can happen only in pH 6.8 to 4.5.         
(When pH of food goes below 4.5 in the stomach, then the action of Ptyalin will be stopped).Salivation is controlled by the nervous system – Cranial nerves VII, IX and X.  Lack of saliva makes it difficult to enjoy and swallow the food.  So the person drinks water in between meals, which hampers the digestive process. In such cases, we stimulate the salivary glands by (7) Medulla, (9) Medulla and (10) Medulla – which stimulates these cranial nerves.

PANCREAS  The pancreas is a pale grey gland weighing about 60 gms.; ( length – 12 to 15 cm).  It is situated in the curve of the duodenum, just behind the stomach. It consists of broad head, a body (which lies behind the stomach ) and the tail lies in front of the left kidney, just touching the spleen. It is both an exocrine and endocrine gland.  

Exocrine Functions of Pancreas :- 

The Acini cells of pancreas secrete Pancreatic juice.  This is carried by Pancreatic duct and poured into the duodenum (after joining the bile duct) through the ampulla of VATER, (controlled by sphincter of ODDI).

The pancreatic juice consists of  electrolytes PLUS digestive enzymes.

The digestive enzymes are:        

Trypsin & Chymotrypsin in their inactive forms (Trypsinogen & Chymotrypsinogen) – these digest proteins and convert them into amino acids

Pancreatic amylase  - these digest carbohydrates into mono and di saccharides

Pancreatic lipase      - these digest fats into triglycerides, free fatty and glycerol.  

Electrolytes are       - Sodium Bicarbonate  (NaHCO₃) – this neutralizes stomach acid.

Endocrine Functions of Pancreas :-

There are groups of specialised call called Islets of Langerhans, which are distributed throughout the outer surface of the pancreas. These have three major types of cells which secrete different hormones.      These are –

(a) Insulin              (b) Glucagon                    &                 (c) Somatostatin.

Insulin and glucagon regulate the amount of sugar present in the blood.  As soon as food is eaten, sugar level in the blood will rise.  At that time, insulin lowers blood sugar level, by giving message to liver, muscles and other body cells to use up the available sugar or store it for future use. Thus insulin helps to bring blood sugar to normal value. Later, if muscles require energy for doing manual work, then glucagon will give message to various organs, to release the stored sugar, which in turn will increase blood sugar.  In a normal person, both these functions go on automatically, under the control of PSNS (para symoathetic nervous system).

In Neurotherapy, we stimulate the Pancreas in various counts, for the following functions:

·        (8) Pan - To produce the 3 digestive enzymes to digest Carbohydrates, proteins and fats and to produce electrolytes (Sodium Bicarbonate) to reduce the acidity of chyme.