As you eat food, it goes through various organs in your body to give you the nourishment. Your organs play a vital role in converting the food you eat into the energy your body gets out of it. In this article, we’ll understand the various organs involved in the human digestive system and how they do what they do.
An interesting fact to remember- Your digestive system is nothing but one long tube which begins from your mouth and reaches the anus. This tube is known as the alimentary canal.
So, let’s proceed with learning the parts of the human digestive system. And what better way to learn than a diagram. Have a look at the schematic of the digestive system here and make a note of all the organs in your head. It shall come in handy as we move ahead in the article.
We also have a list of some really cool facts about the digestive system at the end of this article.
Diagram of the Human Digestive System:
Now, that you have seen a clean diagram of the digestive system, let’s jump on to learning the various parts of it and how they function together to create the energy from the food you eat. Let’s also learn how the food you eat is broken down so as to derive nutrients and energy from it. Here’s how the digestive system works.
Mouth
As you saw above, it’s your mouth which is the starting point of digestion of food in your body. And what does it do?
Well, you have teeth in your mouth, and they grind the food you eat. But this is not it. The salivary glands produce saliva, which has a special enzyme called salivary amylase. This enzyme breaks down the starch in the food into simple sugars. The saliva has another function as well. It is to add moisture to the food so it can pass through the canal easily, since the canal has a soft lining. And this moist lump of food is called the Bolus.
Once the food is moist enough, it is pushed further into the system by the tongue. Next up is the oesophagus- or food pipe- as you may call it.
Oesophagus
It’s a thin muscular tube which connects your throat (pharynx) to the stomach. It acts a passage between the mouth and the stomach. The job of oesophagus is to contract as the food moves down the line into the stomach.
A key feature of the oesophagus is the presence of a valve called the Lower Oesophageal Sphincter. This valve is located right at the beginning of the stomach and it lets the food pass into the stomach. Besides letting the food pass into the stomach, it also prevents the back flow of food into oesophagus.
Stomach
The next stop for the food is your stomach. A large organ in essence, it expands as the food enters it. Here, the digestive juices, hydrochloric acid and other enzymes break down the food and convert it into liquid. Anatomically, it is on the left side of the abdominal cavity, right beneath the diaphragm.
Here in the stomach, the digestion happens with the help of the glands in the wall of stomach. These glands produce and release mucus, pepsin (digestive enzyme) and hydrochloric acid. While the acid is required to kill the bacteria which enters the system along with food, mucus provides protection to the stomach lining from the acid itself. HCL also creates an acidic medium in order to facilitate the action of pepsin.
The walls of the stomach pound the bolus thus breaking it into a number of chunks. The acid and digestive enzymes then begins to dissolve the food and breaks down the protein in it. The hormones in the inner lining of the stomach also alert the organs like liver, pancreas and gall bladder to release and transfer the digestive juices.
After having spent a considerable time inside the stomach, the bolus transforms into a frothy liquid called chyme. And it is now ready to make it to the next organ- small intestine.
Small Intestine
The longest part of the digestive system, it is anywhere between ten-twenty feet in length. The small intestine is also known as the power house of the human digestive system.
As the chyme makes its way to the small intestine, the liver sends bile juice to the gall bladder, which in turn secretes it into the first portion of the small intestine- duodenum. A key point to remember is that the food coming from the stomach is acidic in nature. But it should be alkaline for the pancreatic secretions to work. This is where the bile juice helps.
The walls of the small intestine contain glands which are responsible for the secretion of intestinal juice. This juice further contains enzymes which convert the fats into fatty acids and glycerol, carbohydrates into glucose and proteins into amino acids. This happens in the lower regions of the intestine, which are- jejunum and ileum.
Next is the structure of the inner lining of the small intestine. It has small finger like projections which increase the surface area for absorption. These projections are known as villi, which have a large number of blood vessels in them.
Large Intestine
Once all this is over, the unabsorbed food now enters the large intestine, also known as bowel, where its walls absorb the water from the leftover. And whatever remains is the faeces, which is then stored in the rectum.
Rectum
The waste products from the large intestine enter the rectum after complete absorption of water. There, it sits until the brain sends a signal for its excretion from the body.
Anus
It is the final destination of the food you eat in the digestive system. It has two sphincters- internal and external- both of which work together to control when the stool should be excreted. They do so by detecting the nature of rectal contents; whether they are solid, liquid, or gas.
Accessory Organs of the Human Digestive System
While these were all the organs which are a part of the digestive system, there are accessory organs which only participate in the process. They are not a part of the gastrointestinal tract. All they do is release the enzymes and juices necessary for the digestion to take place. These are:
Liver
Liver is an essential organ in the human body as it has a number of functions. When it comes to digestion, it produces bile juice, which aids in the digestion of fat in small intestine. Another main function of the liver in the digestion process is to purify the blood.
Gall Bladder
Located right beneath the liver, the gall bladder is the storage area for the bile juice which the liver produces. The bile is stored in the gall bladder when it isn’t urgently needed in the small intestine.
Pancreas
It connects with the small intestine at one end and the gall bladder at the other end. Right behind the stomach is this large gland that helps in digestion by releasing digestive enzymes and secreting them into the duodenum- the first part of the small intestine. Besides digestive enzymes, it also produces insulin, which helps in the regulation of blood sugar levels.
