How does food get from your mouth into all of your body cells? Watch this video to learn about the human digestive system.
Lesson B9: Human Systems: Digestion
Figure B.3.9.1 – Teeth are rooted in the gums.
Figure B.3.9.2 – Keeping your teeth clean prevents painful infections.
Figure B.3.9.3 – Teeth help break food into smaller pieces.
Reading and Materials for This Lesson
Science in Action 8
Reading: Pages 126–131
Materials:
2 hard-boiled eggs, 2 glasses, spoon, 1 can dark-coloured soda pop (such as Cokeâ„¢), water, 1 slice of bread, vinegar, scissors, potato masher, shallow glass pan, measuring cup, large spoon, medium-sized sealing plastic bag (such as Ziplocâ„¢), nylon
tights, large bowl, paper towels.
Teeth
Teeth are an important organ located at the start of the digestive system. Teeth contain hard minerals, but they are not bones. Unlike bones, teeth do not contain bone marrow and they do not grow back together if they break. Children grow twenty baby
teeth, and lose them between ages five to twelve. New teeth grow to form a set of thirty-two adult teeth.
Enamel is the hard mineral outer surface that covers teeth. Tooth pulp is located under enamel. Tooth pulp contains blood vessels and nerve fibers. Most of a tooth is hidden from sight in the gums and jaw. We only see the enamel-covered crowns of
teeth.
Sometimes a hole forms in tooth enamel. This is called a cavity. A cavity forms when bacteria in the mouth produce acids that eat away at a tooth. A cavity exposes tooth pulp and nerves, which is why it hurts. Dentists fill cavity holes with metal
or plastic. Brushing your teeth and flossing regularly prevents cavities.
Watch More
Taking Care of Your Chompers
This animated video explains more about the structure of teeth.
Watch these videos to learn more about how bacteria cause cavities.
Bacteria in the mouth also cause bad breath. Watch this video to learn more.
Try It!
Cavities
Try this simple experiment to learn how cavities form in teeth. An eggshell is made of minerals, just like teeth.
Materials:
2 hard-boiled eggs (Click here for instructions on hard boiling eggs)
2 glasses
Spoon
1 can dark-coloured soda pop (such as Pepsiâ„¢ or Cokeâ„¢)
Water
Safety Warning
Never leave a hot stove unattended. Take care with hot fluids.
Instructions:
Put one hard-boiled egg in each glass.
Add enough water to one glass to completely cover the egg.
Add enough dark-coloured soda pop to the other glass to completely cover the egg.
Let the eggs sit for 24 hours.
Remove both eggs from the glasses. What do you observe?
Watch this video to see this experiment and its results:
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
In this experiment, acid in the pop created holes in the mineral eggshell. Bacteria in the mouth produce acids, which create holes in mineral tooth enamel.
Try It!
Digestion Simulation
Try this experiment to simulate the different steps of digestion in the human body. You will need to work with another person near the end of this experiment.
Materials:
1 slice of bread
Water
Vinegar
Scissors
Potato masher
Shallow glass pan
Measuring cup
Large spoon
Medium-sized sealing plastic bag (such as Ziplocâ„¢)
Nylon tights
Large bowl
Paper towels
Instructions:
Use the scissors to cut the bread into smaller pieces.
Place the bread in the shallow glass pan.
Add ½ cup of water to the bread in the pan.
Use the potato masher to mash the bread and water together.
Use the large spoon to transfer the mashed bread and water into the plastic bag.
Add ½ cup vinegar to the bread and water mixture. Close the bag.
Use your hands to squeeze the outside of the bag, mixing the bread and liquids in the bag. Squeeze the bag until there are no large pieces of bread left.
Cut one leg off the nylon tights.
One person should open the nylon leg and suspend it over the large bowl. The other person should open the plastic bag and pour the bread mixture into the nylon leg. Some liquid will drip through the nylon leg into the bowl.
Once the mixture has stopped dripping, take the nylon leg out of the bowl and wrap it in several paper towels. Roll the nylon leg for the paper towels to absorb any remaining water.
Cut a hole in the other end of the nylon leg. Squeeze the remaining bread mixture into the large bowl.
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Steps 1 to 4 represented chewing in the mouth. The scissors were like front teeth that rip food into smaller pieces. The masher was like back teeth that grind food into small pieces. The water was like saliva that helps break down food.
Steps 8 and 9 represented the absorption of nutrients in the small intestine. Nutrients and water left the nylon leg, which is similar to how nutrients and water diffuse out of the small intestine into the body.
The remaining bread mixture in step 11 represented feces, which are the remains of any food not absorbed into the body.
Figure B.3.9.4 – People with diabetes need to give themselves insulin injections.
Figure B.3.9.5 – The pancreas produces insulin.
Figure B.3.9.6 – Type 2 diabetes is usually triggered by an unhealthy diet and a lack of exercise.
Diabetes
The pancreas is an organ that helps the digestive system absorb nutrients. The pancreas makes digestion juices for the small intestine. Insulin is a very important substance made by the pancreas. Insulin is a hormone that signals the body to take
sugar out of the blood and move it into cells.
Diabetes is a condition that occurs when the pancreas does not produce enough insulin. Type 1 diabetes occurs when the immune system attacks and destroys insulin-producing cells in the pancreas. Type 1 diabetes usually shows up in children. Type
2 diabetes occurs when the body doesn’t use insulin properly, which gets worse over time. Type 2 diabetes is also known as adult onset diabetes. Some pregnant women get temporary gestational diabetes. This occurs when the pancreas can’t make enough
insulin for both the mother and developing fetus.
Diabetic people have very high blood sugar after they eat, because their bodies don’t have the insulin signal to move sugar from blood into cells. High blood sugar can cause a number of life-threatening conditions, and diabetics used to die. In
1921, Canadian researchers Frederick Banting and Charles Best discovered that insulin injections treat diabetes.
Diabetics need to frequently check their blood sugar levels and give themselves insulin injections. Diabetics also need to monitor their diet carefully. They usually can’t eat sweet foods because it raises their blood sugar levels too quickly.
Watch More
Type 1 and Type 2 Diabetes
Watch this video to learn more about the role of the pancreas in the digestive system.
How did scientists discover that diabetes was caused by a lack of insulin in the body? Watch this video to find out more.
Figure B.3.9.7 – The liver is the largest solid organ in the human body.
Figure B.3.9.8 – The liver is a very important organ in the digestive system.
Figure B.3.9.9 – Jaundice is a symptom indicating liver problems.
The Liver Helps Manage the Digestive Process
After nutrients are absorbed into the bloodstream from the small intestine, they travel to the liver before being sent out to the entire body. The liver is an organ with a number of important functions. The liver converts nutrients from food into
simpler forms that cells can use. It also stores some nutrients for later. The liver cleans toxins out of the body by mixing them in a liquid called bile, which is released in the small intestine.
One symptom of a dysfunctional liver is jaundice. The liver breaks down dead red blood cells. If the liver isn’t working fast enough, dead red blood cells build up in the body. Dead red blood cells produce a substance that turns skin and eyes a
yellow colour. Newborn infants sometimes have jaundice for a few days because their livers are still growing. Jaundice in adults is usually a symptom of a liver disease, like hepatitis.
Hepatitis is an inflammation of the liver. Hepatitis is caused by viruses, but it can also be caused by overloading the liver for many years with toxins like alcohol and drugs.
Watch More
The Liver: Guardian of the Digestive System
Watch this video to learn more about the functions of the liver.
The liver removes alcohol from the body, but it doesn’t happen immediately. Watch this video to learn more.
Unlike many other organs, the human body is capable of regrowing its liver. Watch this video to learn more.
Indigestion
Sometimes people feel pain after eating, such as an upset stomach or a burning sensation in their chest. This is known as indigestion. Indigestion is just one of many conditions that can negatively affect the digestive system.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit B Lesson 9 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum,
or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Villi are structures on the small intestine’s walls where nutrients are absorbed into the body. A person with damaged villi cannot obtain enough nutrients. As a result, they would likely have low energy and lose weight.
In the esophagus, muscle tissue contracts to push food into the stomach by peristalsis. The stomach is surrounded by muscles that move and churn food into small pieces. In the small and large intestines, muscle tissue contracts to move food
along by peristalsis.
Mechanical digestion physically makes particles of food smaller. This helps food fit through the tubes of the digestive system. Physically breaking down food also creates more surface area for chemical digestion to happen.
Chemical digestion changes food particles into different smaller particles that are able to diffuse into the body and be used as nutrients in cells.
Reading and Materials for This Lesson
