Question

Explain the process of digestion with diagram

Answer 1

The Human Digestive System:

1. Human Digestive System and Nutrition involve the intake of food by an organism and its utilisation for energy.
2. The food which we eat undergoes much processing before the nutrients present in them are utilised to generate energy. This processing is known as digestion.​
3. The digestive system of the human body comprises a group of organs working together to convert food into energy for the body.
4. Anatomically, the digestive system is made up of the gastrointestinal tract, along with accessory organs such as the liver, pancreas and gallbladder.
5. The hollow organs that make up the gastrointestinal tract (GI tract) include the mouth, stomach, oesophagus, small intestine and large intestine that contains the rectum and anus.

Parts of the Human Digestive System:

Mouth:

1. The intake of the food is called ingestion, which occurs through mouth.
2. There are many other organs that contribute to the digestion process, including teeth, salivary glands, and tongue.
3. Teeth are designed for grinding food particles into small pieces and are moistened with saliva.
4. Saliva also has salivary amylase which begins the digestion of the starch in mouth.

Pharynx:

1. A fibromuscular y-shaped tube attached to the terminal end of the mouth.
2. It is mainly involved in the passage of chewed/crushed food from the mouth through the oesophagus.​

Oesophagus:

1. This is a muscular tube that connects the pharynx, which is a part of an upper section of the gastrointestinal tract.
2. It supplies swallowed food along with its length.​

Stomach:

1. It serves as a muscular bag which is situated towards the left side of the abdominal cavity, beneath the diaphragm.
2. This vital organ acts as a storage for the food and provides enough time to digest meals.​
3. It churns the food and mixes it with mucus.
4. It secretes propepsin and hydrochloric acid.
5. Hydrochloric acid converts propepsin into pepsin which helps in digesting proteins.

Small intestine:

1. The small intestine is a thin, long tube of about 10 feet long and a part of the lower gastrointestinal tract.
2. It is present just behind the stomach and acquires a maximum area of the abdominal cavity​.
3. The small intestine has three parts: the duodenum, jejunum, and ileum.
4. Duodenum receives enzymatic secretions of pancreas and bile of liver and gall bladder.
5. The pancreas releases digestive enzymes to complete the process of chemical digestion.
6. The pancreas secretes digestive enzymes such as amylase, proteases and lipase into the duodenum. These enzymes help in digesting sugar, proteins and fat respectively.
7. The liver is a roughly triangular, reddish-brown accessory organ of the digestive system located to the right of the stomach.
8. It produces bile, which helps in the digestion of fat in the small intestine by emulsifying the fats.
9. The bile is stored and recycled in the gallbladder.
10. Therefore, complete digestion of food occur in small intestine.
11. The digested food is then absorbed.
12. This process begins in the small intestine where most of the nutrients and minerals are absorbed.

Large intestine:

1. ​This is a thick, long tube measuring around 5 feet in length.
2. It is present just beneath the stomach and wraps over the superior and lateral edges of the small intestine.
3. It absorbs water and consists of bacteria (symbiotic) that support the breakdown of wastes to fetch small nutrients.
4. It has three parts- cecum, colon and rectum.
5. Absorption of water occur at colon.
6. The remaining undigested waste material, also known as feces, are stored temporarily in rectum.
7. It is then removed outside the body from anus, a process known as egestion.

Steps involved in digestion:

1. Ingestion- the intake of food through mouth.
2. Mixing and movement- the food when passes through the gastrointestinal tract is mixed with digestive juices.
3. Secretion- the secretion of digestive juices from the digestive glands like pancreas and salivary glands.
4. Digestion- it is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma.
5. Absorption- the digested food is then absorbed by the villi and microvilli of small intestine.
6. Egestion- the removal of undigested waste from the anus.

Diagram:

Diagram: Human digestive system.