The Gastrointestinal tract a.k.a Gut
Imagine you have just ordered your favourite pizza and are waiting for the delivery guy to arrive. Does your stomach start churning and your mouth start watering just by thinking about it? Digestion process starts way before we actually take our first bite.
The bell rings and you rush towards the door to collect your order. You thank the delivery guy and make arrangements to start eating it before it gets cold. And then you take your much awaited first bite, and second bite and third bite. What happens next?
The mechanical action of chewing the food combined with the chemical action of saliva helps break down food. Saliva helps form bolus (ball like mixture), which makes it easy to swallow. Once you swallow the food, The food then travels through the oesophagus and reaches your stomach. Here it mixes with enzymes and stomach acids to form a semi-liquid called chyme.
So, what exactly is the digestive system? The gut, or the gastrointestinal tract or the GI tract along with the liver, pancreas and gall bladder form the digestive system.
Liver is responsible for production of bile and releasing it from the gallbladder when needed. Bile breaks down fats into fatty acids to be absorbed by the body. It is also responsible for eliminating waste from the body. Pancreas makes pancreatic juices called enzymes which are also responsible for breaking down fats, sugar and starch.
The food from the stomach goes to the small intestine where the bile and pancreatic juices work together to further digest the food. Muscles in the small intestine contract to mix up the food and push it forward. The small intestine is covered with a tiny one cell thick villi which increases the surface area of absorption. They absorb the nutrients from the food and transfer them into the bloodstream.
The fluid then travels to the large intestine where the body absorbs water and salt from whatever has not yet been digested. It also gets rid of the waste products and forms stool. The stool is finally moved out of the body. And we are done, what a relief! We all know that heavenly feeling. :D