The Human Digestive System

5th Grade Science

Parts of the Human Digestive System

We are going to learn about the parts of the human digestive system, how they work and why they are important.

The mouth

The digestive system starts with the mouth. Have a variety of foods to chew and ask what is happening as they chew and swallow. Suggestions:
  • Something soft like yogurt, ice cream, cottage cheese
  • Something cruncy like crackers, popcorn, nuts, pretzels
  • Something with stringy fiber like celery or carrots that take lots of chewing
Soft Foods - Notice the function of the tongue in moving food to the back to be swallowed.

Crunchy Foods - Note the effect of saliva in keeping food particles together. It is not like grinding a cracker with a rock.

Fiber Foods - Notice the use of the teeth in grinding the food. Also notice that no matter how long you chew fiber, it stays somewhat "stringy". This fiber is important for digestion.


The esophagus is the tube that takes food from the mouth to the stomach.

We usually are not aware of our esophagus. However, when swallowing warm or cold foods you may be aware of it moving down "your throat." That is one of the reasons soup and other foods "taste so good."

Any other experiences with your esophagus? Ask what it is like to get a potato chip "stuck in your throat."


Now is the time to make certain you can differentiate the stomach from the abdomen (or belly.) The stomach is an actual internal organ.

The stomach is a muscular bag the can get larger and smaller - like a balloon. It contains digestive acids which break solid food into smaller and softer particles. Ask what sensations can be felt by the stomach:
  • Hunger - stomach "growling". The digestive juices have nothing to work on.
  • Full - the stomach has expanded as far as it can with the food that has been eaten.
  • Water logged - so much water has been consumed you can feel it sloshing in the stomach.
  • Vomiting - The contents of the stomach are expelled up the esophagus and out the mouth. Yuck!
Okay, now that we are on the yucky topic of vomiting, we might as well learn something from it. When a person vomits, they can see what the stomach has done to the food. It is mushy and in small pieces. Often the food is partially digested and can be recognized. This is what the digestive acids have done to the food.

Ever notice a yucky taste after vomiting? That's the effect of the digestive acids. It is sure a whole lot nicer to keep all that stuff inside your stomach.

Small Intestine

Food leaves the stomach and enters the small intestine. You can compare it to a long, long garden hose that is all wound up into a small space in the middle of the abdomen.

Inside the small intestine, digestive acids keep working to liquify food particles.

You can put some food into a blender and compare the action of the small intestines to the blender. The intestines don't have any sharp blades. But they do have a movement called peristalsis which mixes things up.

If you have ever squeezed a bag to mix the ingredients, you can compare that to peristalsis. You can also hear it with a stethescope on your own belly.

More than just blending is going on, however. The small intestines break large molecules of food into small molecules. Then the small molecules of nutrition are absorbed through the intestinal wall into the blood stream. That blood will go to the liver which will get those nutrients ready for the rest of the body.

However, most of the food product is not absorbed into the blood stream. It continues into the large intestines.

Large Intestine

Most of the food that was swallowed will continue into the large intestine. It would not be recognized now. Because of the work of the small intestines, it would be a very watery, mushy mess when it first enters the large intestine.

The large intestine starts in the lower right part of the abdomen. The appendix is located close to the place where the small intestines joins the large intestine. Severe pain in this area can sometimes mean a problem.

The large intestine moves food upward on the right hand side, across the abdomen at the top, and downward on the left side.

While the waste is in the large intestine, water is being absorbed from it.

When people have diarrhea, the waste moves so fast through the large intestine the water is not absorbed and instead is very liquid like. Diarrhea is also associated with cramping. The cramping is caused by very strong peristalsis waves.

Rectum and Anus

The digestive system ends with the rectum, which is a storage place for feces until a person is ready to elimate the stool. The anus is the opening the feces pass through. The anus has a very strong muscular closing (sphincter) which holds the feces in until the right time.

Three more importatnt organs in the Digestive system...


When the food is blended into a liquid mixture in the small intestines, particles of nutrition are absorbed through the wall of the intestine and into the blood stream. That blood goes a short distance to the liver.

The liver has several important functions necessary for life.

First, it cleans the blood coming from the intestines of toxins and poisons. Cirrhosis of the liver is a disease that alcholics may get when the liver fails from the affect of the alcohol.

The liver also changes glucose, fats, and protein into forms of nutrition needed by the cells of the body. It can convert glucose into protein or fat. It can also change it back, depending on what the body needs.

The liver also produces a substance called bile. Bile is a green digestive juice that helps the small intestine break down fat.

In summary, the liver produces bile that goes into the small intestine and helps it break up fat particles. The nutrients in the small intestine go from the blood stream to the liver for it to change the nutrients into the chemical form needed by the cells of the body.

Gall Bladder

The gall bladder is a small pouch hidden under the curved lobe of the liver. It is a storage container for the bile produced in the liver. After a meal is eaten and food is moving into the small intestine, the gall bladder will secrete the bile into the intestines to help it digest the food.

Bile is green and gives the green color associated with diarrhea. Sometimes people call it "vile bile."


The pancrease is another organ of the digestive system that produces a number of important digestive enzymes.

Insulin is a hormone produced by the pancrease that helps glucose move across a cell membrane from the blood stream into the cells of the body. Diabetics have a decrease in insulin so that the amount of glucose in their blood stays high.

Read the article on the following webpage to find out how the digestive system breaks down the food we eat!

Watch the following video to learn more about the digestive system

The Digestive System- A Digital Story for 5th Grade Science

If you want to learn more or to find out some cool and little known facts about the digestive system, follow the following link!