The human digestive system biology lesson for kids: 1st, 2nd, 3rd, 4th, 5th, 6th and 7th grades biology lesson.
When you eat, your food passes through a long, complex tube that breaks down and absorbs what you eat so your body can use it. This tube is called the digestive system, and has lots of different parts that process your food both physically and chemically to make the whole process easier. Let’s start at the beginning!
First, your food passes your lips (of course) and enter your mouth. Your teeth grind and tear the food, making it easier to digest. Even your tongue is involved in the process, believe it or not, placing the food in the right place to be chewed up. Your saliva (spit) starts the chemical process of digestion right there in your mouth; it has an enzyme called amylase, which breaks down starch into simpler sugary forms.
When you swallow, your food heads down to the stomach. It gets there easily because the muscles in your esophagus (the tube from the mouth to the stomach) has muscles that push it along. This process is called peristalsis, and is very important for the digestive system. The stomach has a strong acid, which helps you to digest proteins while the stomach walls churn the food with peristalsis, mixing digestive enzymes into it.
When all this is done, peristaltic action pushes the digesting food into another section of the tube: the small intestine. It is long and windy and it’s where the body absorbs water, fats, and proteins, and a lot of other stuff, too. The walls of the intestine have lots of tiny blood vessels so that the blood can come as close to the digesting food as possible to absorb the nutrients it needs.
Not everything in the food you eat can be digested, but that’s a good thing. Fiber, which is in stuff like fruits and vegetables, don’t get broken down in the digestion process, and give the intestine something to hold on to as it squeezes, and allows the digesting food to be pushed along more easily.
A lot of interesting things happen along the way. The stuff the stomach squeezes into the small intestine is too acidic for the digestive process that need to happen there, so one organ galled the gall bladder releases chemicals that make it less acidic. There is also an organ called the spleen dumps the remains of old blood cells into the intestine to be released with the food you ate. Another organ called the pancreas provides the intestine with a lot of the enzymes it needs to break down starch, carbohydrates, and fats. The digesting stuff moves along, until it gets to the large intestine.
The large intestine slows down the peristalsis, allowing fermentation to happen. This means that whatever stuff is left that to be digested is broken down by good bacteria in our intestines, and absorbed by the body. Then, when you’re ready to go to the bathroom, everything goes down through the rectum and out of the anus.
It’s a long, complicated process, but an important one for our survival!