The human digestive system is a uniquely designed system consisting of organs mainly involved in converting the food molecules into energy and other basic nutrients which are essential for the body.
Have you ever wondered, what happens to the food inside our body? or
Why do our stomach gets upset when we eat too much of junk food? The food we take in is digested and utilized by our body and the unused parts of the food are
In general, the food we eat get digested and is utilized by our body and the unused parts of the food are defeated.
Therefore, when we include too much of junk food in our diet, most of these food particles remain unused by the body and need to be defeated, This is the reason behind our stomach upset.
The process of digestion begins from the mouth and is completed in the small intestine. When we consume food, it travels from our mouth and reaches our stomach through a long tube called as an alimentary canal or the gastrointestinal tract.
This alimentary canal or gastrointestinal tract begins from the mouth cavity and continues into the pharynx, stomach, large intestines, and finally stops at the anus. During the movement of food particles from mouth to the stomach and to the small intestine, it gets digested gradually as they travel through various compartments of the gastrointestinal tract. The process of digestion begins from the mouth cavity and ends in the anus.
Let’s learn more about the human digestive system and the process of digestion.
The process of digestion has six steps, which are as follows:
- Ingestion – the process of taking food in.
- Secretion – the salivary glands, inner walls of the stomach, small intestine, liver, and pancreas functions by secreting juices to aid the process of digestion.
- Mixing and movement – the process of swallowing, moving the food through the food pipe and segmenting it in the small intestine.
- Digestion – the process of converting complex food particles into simpler substances in the presence of enzymes and acids secreted by different digestive organs.
- Absorption – this begins in the stomach after the food has been broken down into simple molecules.
- Excretion – the process of removing indigestible substances from the body by the process of defecation so that there is no accumulate inside the gut.
Let’s get a little more idea about the human digestive system.
Human Digestive System
Mouth & Buccal Cavity
Food begins its journey through the digestive system present in the mouth which is also known as the buccal cavity or the oral cavity. The mouth has many accessory organs which include teeth, salivary glands, and tongue that help in the digestion of food. Teeth function by chopping the food molecules into small pieces. Salivary glands secrete saliva, used to moisten the food and the tongue along with the help of other muscles pushes the chopped food into the pharynx.
Next part of the digestive system is the pharynx which is also called as the throat. It is a part of both the digestive and respiratory systems. It is triangular or a tube-shaped chamber covered by mucous membrane and connected to the mouth. During the digestion process, pharynx functions by moving the chewed food into the esophagus and in the respiration process it plays an important role in allowing air to the larynx. Pharynx comprises a flap of tissue known as the epiglottis that acts as a switch in transporting food molecules to the esophagus and air to the larynx during digestion and respiration respectively.
Oesophagus (or) Esophagus
The esophagus, also known as the food pipe. It is the part of the alimentary canal connecting the pharynx to the stomach. It functions by carrying the swallowed portions of chewed food along its length and gradually pushes it down into the stomach for further process. At the lower end of the esophagus lies a muscular ring called the lower oesophageal sphincter which closes the end of the food pipe to trap food in the stomach.
The stomach is the internal, thick-walled muscular organ present to the left side of the abdominal cavity. It plays a major role in the digestion and the largest part of the alimentary canal. Stomach functions by storing the food particles received from the pharynx until the complete digestion process is completed. It receives food from the food pipe at one end and opens into the small intestine at the other end. The interior walls of the stomach secrete digestive enzymes, mucus, and hydrochloric acid, which helps in continuing the process of digestion.
- Mucous: It is an aqueous secretion produced by the mucous membranes. It functions by protecting the stomach lining and gastric pits from the acid which is produced by the glands to destroys the bacteria entered along with the food particles.
- Digestive enzymes: They are the group of enzymes which functions by breaking down polymeric macromolecules like biopolymers into their smaller and simpler substances.
- Hydrochloric acid: It is the digestive fluid formed by the stomach during the process of digestion.It functions by destroying harmful microorganisms present in the food particles.
The small intestine is a highly coiled long, thin tube of about 7.5 meters. It receives secretions from the liver and the pancreas. The interior walls of the small intestine also secrete juices for digesting food. The complete small intestine is twisted or rolled like a hose with its inside surface being full of ridges and folds. The folds are used to increase the digestion of food and absorption of nutrients.
The liver is a roughly triangular, reddish brown accessory organ of the digestive system located to the right of the stomach. It produces bile, which plays an important role in the digestion of fat, into the small intestine. The bile is stored and recycled in the gallbladder. It is a small, pear-shaped organ which is located just next to the liver.
The pancreas is a large gland located just below the stomach. It secretes digestive enzymes into the small intestine to complete the chemical digestion of foods. The liquid secreted by the pancreas gland is referred as pancreatic juice which acts on proteins, carbohydrates, and fats to convert them into simpler substances.
Once the food is broken down in the small particles, it is ready to be absorbed by the body. The inner walls of the small intestine have numerous finger-like outgrowths called villi, which increase the surface area for the absorption of digested food. Each villus (singular for villi) has a network of thin blood vessels. When villi absorb the digested food, it is transported to different parts of the body through the blood vessels, where they are again used to build complex substances like proteins required by the body. This process of building complex substances from simpler forms is called assimilation.
The last part of the digestive system is the large intestine. It is a long, thick tube, about 1.5 meters long. It is located just below the stomach and coils around the external border of the small intestine. The large intestine absorbs a very little amount of both nutrients and water from the undigested food molecules with the help of several symbiotic bacteria residing within it. The unused wastes particles move into the rectum, where it stored as semi-solid feces which later exits from the body through the anal canal through the process of excretion.
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