Digestive System and digestive problems

DIGESTIVE SYSTEM 

 DIGESTION

The process by which complex molecules of food are broken down into simpler ones and are used by the body for energy, growth and cell repair is called digestion. The process of digestion starts with food intake. It involves the following steps:

1. Breakdown of complex molecules into simpler ones.
2. Uptake of simple molecules into blood stream.
3. Utilization of these molecules for production of energy or synthesis of materials used by the body.
4. Removal of undigested food from the body.

The process of digestion in humans occurs in a systematic manner. The system involved in digestion is called the digestive system. Let's study the digestive system in humans.

HUMANDIGESTIVE SYSTEM

The digestive system in humans is made up of a long, coiled tube that starts from the mouth and ends at the anus. It is a 10m long tube called the alimentary canal or digestive duct. The organs that play their role in the digestive system are the mouth, stomach, small intestine and large intestine. Other organs that are associated with this system are the liver and pancreas. The digestion of food takes place at three sites in the digestive tract, i.e. mouth, stomach and small Intestine. Let's study how this system work.

MOUTH

The journey of food starts in the mouth. The food we eat is selected by senses of sight, smell and taste. If any unpleasant material like dust or stone is found in the food, it is rejected. After selection, the food is crushed and grinded by teeth to increase the surface area for enzymes in the alimentary canal.

The grinded food is then mixed with the saliva produced by salivary glands. Sliva is a slimy liquid that lubricates the grinded food and converts it into soft form that it can pass through the oesophagous efficiently. It also contains an enzyme called amylase which breaks down starch into a soluble sugar called maltose. The tongue also plays a very important role in  digestion. It pushes food around our mouth for better chewing. The partly digested food is rolled by the tongue into an oval lump called bolus. The bolus is then swalowed by upward and backward movement of the tongue. When the bolus enters the food pipe, backward movement of the tongue blocks the oral cavity, a soft palate blocks this cavity and a flexible flap called the epiglottis closes the windpipe so that food can move into the right pipe.

OESOPHAGOUS

The bolus then moves into a stretchy pipe that connects the mouth with the stomach. This pipe is the oesophagous. When the bolus enters the oesophagous, the muscles in the walls of oesophagous contract and relax. This wave-like contraction and relaxation pushes the bolus movement through which food is moved down into the stomach is called peristalsis.

Sometimes, food moves back from the stomach to the mouth which leads to vomiting. This is called antiperistalsis. Have you ever felt hunger pangs?  Hunger pangs are actually peristaltic contractions which are felt when you have not eaten for a long time.

STOMACH

When a peristaltic wave reaches the stomach, the mouth of the stomach opens for the bolus enters it. The stomach is a J-shaped muscular bag present under the diaphragm on the left of the body. It works like a blender. It churns and squashes the food.

Do you know how the stomach does so?

The walls of the stomach secrete gastric juice. The food in the stomach is mixed with gastric juice. Hydrochloric acid present in gastric juice kills the bacteria present in food. It also provides suitable conditions for working of the enzyme. This enzyme breaks down protein present in food into its simpler molecules, i.e. amino acids. The food in the stomach is then converted into a thick creamy semi-solid mass called chyme. The chyme is stored in the stomach for some time and then moved to the small intestine.

SMALL INTESTINE

The small intestine is a long tube consisting of three parts. i.e. duodenum, jejunum and ileum. The first part of the small intestine that receives the chyme is about 20-25cm long and is called duodenum. When the chyme enters the duodenum, it is mixed with secretions from the liver, pancreas and duodenum walls. The pancreas releases pancreatic juice through the pancreatic duct to the duodenum. This juice contains enzymes that digest all carbohydrates, fats and proteins in the chyme. The liver releases bile through the bile duct to the duodenum. It is stored in the gallbladder if need be. Bile breaks down fats present in the chyme into fatty acids and glycerol.

The next part of the small intestine after the duodenum is the jejunum. It is about 2.5m long. The remaining part of the intestine is called ileum. The food that remains undigested in the duodenum is completely digested in the jejunum and ileum.

After digestion, the food is absorbed by the small intestine and then it enters blood.

Almost all absorption takes place in the ileum. The small intestine has many folds. Many finger-like outgrowths called villi are present in the intestine. These villi have a thin layer of cells and a thick network of blood vessels. Villi increase the surface area of the intestine for absorption of food. Absorbed food is then passed to the blood.

The blood transports absorbed food to the liver. It is then used for different purposes. Food that remains undigested in the ileum is then moved to the large intestine.

LARGE INTESTINE

It is made of three parts, i.e. caecum, colon and rectum. The material that enters the large intestine contains a large amount of water, salts and undigested food. Water and salts are absorbed into blood while the undigested food is converted into solid form. It is then passed to the rectum. This undigested food is called faeces. It contains dead bacteria, fibers of plants, cholesterol and bile pigments. The rectum stores faeces temporarily and then removes them from the body through an opening called the anus. Our digestive system can work efficiently only if all parts of the digestive tract are healthy.

COMMON DIGESTIVE PROBLEMS

Some common digestive problems are given below. 

INDIGESTION

When food is not chewed properly and is swallowed too quickly, it remains undigested. This is called indigestion of food. 

ACIDITY (HEART BURN)

The stomach releases a large amount of gastric juice to digest it. Sometimes, the acid moves to the oesophagous and causes a burning sensation called heartburn.

Indigestion and acidity can be cured by neutralizing the effect of acid using medicine.

ULCERS

When a large amount of gastric juice is released in the stomach, the digestive enzymes start to break down walls of the stomach and intestine. This results in a sore which is called ulcer. It can be cured by avoiding spicy food, carbonated drinks, and tea and taking medicines.

DIARRHOEA

It is one of the most common diseases of the digestive system. It is caused by bacteria and viruses present in contaminated food or water. In this condition, water and salts are not absorbed by the large intestine due to infection. As a result, the body excretes watery faeces. This condition of diarrhoea can be prevented by keeping yourself and your surroundings clean, drinking boiled or filtered water and eating properly cooked food.

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CONSTIPATION

If absorption of water occurs excessively in the large intestine, it leads to hardening of faeces. This condition is called constipation. In this condition, passing faeces out of your body becomes difficult. It is caused by lack of intake of water or fibrous food. It can be prevented by taking large amounts of fluids, eating healthy and fibrous food and doing exercise daily. Food is broken down into smaller components during the process of digestion.

To know more about constipation, click here.

Constipation in children  (click here)