Lesson Digestive System

Learning Objectives

After this lesson, students should be able to:

• List the major components of the digestive system.
• Draw a basic diagram of the digestive system.
• Explain how engineers work to resolve the challenges of eating in outer space.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Introduction/Motivation

Have you ever wondered how astronauts manage to eat in outer space? Can you imagine trying to eat your breakfast while it is floating away from you? Today we are going to talk about the difference between eating on Earth and eating in outer space. The bodily system that enables us to eat and digest our food is called the digestive system, and today we are going to learn how it works. We are also going to learn how astronauts are able to eat in outer space.

Many things are different when you travel into outer space, and eating is one of them. Since there are special challenges associated with eating in microgravity (meaning, there is almost no gravity in space), as illustrated in Figure 2, engineers and scientists working for NASA must solve this problem by figuring out what the astronauts can eat while in space. They design special devices to help them eat during their space travel, making their lives a little easier. Students can practice being engineers by designing their own devices to help astronauts eat meals in space with the associated activity Design Devices to Help Astronauts Eat: Lunch in Outer Space!

When astronauts first began traveling in space, the food they ate did not taste very good. Many of their meals were packed in aluminum tubes, which they squeezed to get the food out, similar to a toothpaste tube. Over time, scientists and engineers have developed tastier and healthier foods for the astronauts to eat, and they now have more variety for their meals.

Before they go up in outer space, the astronauts meet with nutritionists to sample different kinds of foods to see which ones they like best. Then, the astronauts put together their own menus, which are then checked by the nutritionists to make sure their selections are healthy and that the astronauts get enough vitamins while in outer space. Obviously, neither the NASA engineers nor the nutritionists want the astronauts to get sick while in space.

Once the nutritionists confirm that the menus are acceptable, the food is packaged and stowed in special refrigerated food lockers, designed by engineering, to keep it fresh until launch. The food does not actually get loaded onto the space shuttle until two to three days before launch. Since each astronaut has their own set of meals, each food package is marked with a colored dot indicating its owner (consumer). (Note: A bit of interesting trivia: the commander of the space vessel always is issued the red dot.) On the space shuttle, the food stays in special locker trays, with a net restraint to keep it from floating away.

Did you know that engineers help design the packages of food that astronauts eat while traveling in space? There are several types of food that the astronauts can choose from, such as rehydratable, thermostabilized, irradiated, and natural form foods. Rehydratable foods have had the water taken out of them. To eat this type of food, astronauts just add water. Thermostabilized foods have been heat processed to destroy microorganisms. They are ready to go; they just need to be warmed up before eating. Irradiated meat items are also ready to go and just need to be warmed up. Natural form foods are foods that can be eaten the same way we eat them on Earth, without any special processing. Natural form foods include nuts, cookies and granola bars. Since the astronauts' food does not need to be refrigerated, there is not a refrigerator on the space shuttle, but there is a special oven that engineers have added. One food you probably will not find on the space shuttles is bread. Can you guess why this is? Bread is crumbly, and the crumbs can float away and get stuck in equipment. So, instead of eating bread, astronauts eat flour tortillas, which are less likely to crumble.

Engineers are also responsible for designing the way astronauts eat their meals in space. When the astronauts want to eat a meal, they select their food package combination and then prepare it. Some food needs to be heated, and other food needs to have water added. The food packages are tightly sealed, so they have to be opened with scissors. A meal tray holds the food containers (see Figure 3), and the tray is then attached to the wall or the astronaut's lap with Velcro® strips. Once the meal is over, the astronauts put the food packaging in the trash and clean their silverware and meal trays with sanitizing towelettes. And that is how engineers have created solutions to eat in outer space!

Now that we understand how astronauts eat in outer space, let's learn about our amazing digestive system. The digestive system is the way that our bodies get energy from the food we eat. It works to break down food into smaller molecules that can pass into the circulatory or lymphatic systems and provide us with energy, help our bodies grow, and help our bodies heal themselves.

(Note: On the chalk/white board, write down each organ of the body as you mention it.) Food travels through the digestive system by entering your mouth and is then broken down by your teeth and tongue. Next, the food travels through your esophagus to your stomach. Food is broken down even further in your stomach. (Go over the components and functions of the digestive system with the class.) Digested food travels through your small intestine, large intestine and rectum. What happens to food that your body does not need? Well, your body gets rid of it as waste. Whatever food has not been taken up by your body during these different stages of digestion leaves your body through the anus. Other parts of the digestive system include your liver, pancreas and gall bladder. These organs make and store chemicals that help us break down or digest our food. (Note: Making an overhead of the attached Digestive System Map is a great way to help students visualize the different organs and how they connect together.)

Engineers need to understand how food is digested in the human body. They learn about all of the different organs involved in the digestive system to make sure they engineer food that astronauts can easily digest in space. They need to know which foods are harmful to the digestive system and which foods are good for the digestive system in order to design the equipment for re-hydrating or warming up food on the space shuttle. Clearly, engineers help astronauts stay healthy in space.

(For more information on how astronauts eat in outer space, check out NASA's Fact Sheet on Space Food at https://www.nasa.gov/wp-content/uploads/2015/05/167750main_fs_spacefood508c.pdf).

Lesson Background and Concepts for Teachers

The digestive tract (also called the gastrointestinal tract) is roughly nine meters long and begins at the mouth and ends at the anus. It has six primary functions: ingestion, mechanical digestion, chemical digestion, movements, absorption and elimination.

The two main components of the digestive system are the alimentary tract and the accessory organs. The alimentary tract consists of the mouth, pharynx and esophagus, stomach, small and large intestines, rectum and anus. The accessory organs are the salivary glands, liver, gall bladder and pancreas. The tongue and teeth are accessory structures, and assist in ingestion and mechanical digestion.

Now, let's learn what each part of the digestive system does:

Mouth – The mouth is where the process of digestion begins. In the mouth, the teeth work to break down food into smaller parts. Saliva helps break food down chemically and also helps clean your teeth!

Tongue – Your tongue helps move food around in your mouth, and it is also covered with taste buds that help you taste your food. Eating would not be much fun without the taste buds that you have on your tongue!

Teeth – Your teeth help chop up food and break it into smaller pieces so that you can swallow it more easily. Kids have 20 teeth, but by the time they are fully grown, they should have 32 teeth (some people do have less!). There are different kinds of teeth that have different jobs: some are for cutting and biting, others are for tearing, others are for crushing, and still others are for grinding.

Pharynx – The pharynx connects both your mouth and your nasal passageway to your esophagus. A small flap of cartilage called the epiglottis falls down and covers your windpipe to prevent food from going down it instead of your esophagus.

Esophagus – Your esophagus connects your pharynx to your stomach and is a long tube about nine inches long. Food moves down the esophagus through peristalsis, which is a wave-like series of squeezing movements along the esophagus. These successive squeezing movements move the food along the esophagus and into the stomach. Peristalsis helps food move along your intestines, too.

Liver – Your liver has many different jobs to do. One of its most important jobs is detoxification. This means that your liver can remove harmful chemicals from your blood so that they don't hurt your body. The liver also secretes bile, which is a yellowish-greenish fluid that helps the digestion process, especially fat absorption and digestion

Stomach – Your stomach is shaped like a J, and it has three main functions: to store food, to mix up food, and to pass the food into the small intestine. The partially digested food that leaves your stomach is part fluid and part solid, and it has a special name: chyme.

Pancreas – The pancreas secretes hormones (such as insulin) into your blood and also secretes enzymes into tiny ducts so they can travel throughout your body to help break down fats, proteins and carbohydrates.

Gallbladder – The gallbladder is a muscular membranous sac. It is shaped like a pear, and its main job is to store the bile that the liver secretes. This is a great example of how all the parts of the body work together to accomplish what they were designed to do.

Small Intestine – The small intestine is another long tube that carries your food onwards. The cells in the small intestine secrete chemicals that further break down the food and finish the digestion process.

Large Intestine – The large intestine is wider and shorter than the small intestine. It does not secrete chemicals, so its job is different than the small intestine's. The large intestine works to absorb water, as well as form and get rid of feces.

Rectum – The rectum is the last part of the large intestine, and it connects to the anus.

Anus – The anus is the exit point of the digestive system. Just think about all the amazing transformations that have occurred along the route of the digestive tract! Food enters your mouth, travels down your pharynx, esophagus, stomach, small intestine, large intestine, rectum, and finally leaves through the anus. Along the way, your body breaks down the food into small compounds that it can use to help you grow, stay healthy and give you energy. It's an incredible journey in an incredible system!

Associated Activities

• Design Devices to Help Astronauts Eat: Lunch in Outer Space! - In this activity, students learn about the challenges of eating in outer space. They get the opportunity to design their own devices to help astronauts eat meals in space.

  Watch this activity on YouTube

Lesson Closure

Today we learned more about our amazing bodies and how they digest the food that we eat. We also learned about how astronauts eat in outer space and how engineers play an important role in keeping astronauts eating healthy (and easily) while traveling in space. Can you name one way in which engineers help astronauts? (Examples include: design the packages and storage for food, create the systems for heating or hydrating food, design the routine that astronaut use to eat meals.)

Let's go around the room and have each person share one thing they learned today about digestion that they did not know before. (Note: Have each student share one piece of information that they learned.) Thank you all for sharing!

Vocabulary/Definitions

anus: The exit point of the digestive system.

bile: Yellowish-greenish fluid secreted by the liver that assists in the digestion and absorption of fats.

chyme: The partially-digested food that leaves your stomach.

digestion: The process of breaking down food into simpler chemical components that the body can use.

digestive system: The system of organs that helps our bodies digest food.

digestive tract: The series of hollow organs running from the mouth to the anus.

epiglottis: A thin flap of cartilage that covers your windpipe when you swallow.

esophagus: The part of the digestive tract that runs from the pharynx to the stomach.

gallbladder: A muscular, membranous sac that stores bile.

large intestine: The intestine that runs between the small intestine and the rectum; wider and shorter than the small intestine; absorbs water and forms feces.

liver: A large organ that secrets bile and removes toxins from the body.

mouth: The opening where we put food; where the digestive process begins.

pancreas: A digestive system gland that secretes enzymes and hormones.

peristalsis: Waves of contractions along the esophagus or intestines that propel food forward.

pharynx: The part of the digestive tract between the back of the mouth and the esophagus.

rectum: The last part of the large intestine; connects to the anus.

small intestine: The intestine that runs between the stomach and the large intestine; secretes enzymes, and absorbs nutrients.

stomach: Part of the digestive system responsible for storing, mixing, and passing on food.

tongue: A muscle in our mouths that helps us speak, taste, and move food around.

Assessment

Pre-Lesson Assessment

Drawing the Digestive System: Give each student a pencil and a blank piece of paper, and ask them to draw how they think their entire digestive system is laid out. Ask students to label each organ in their drawing, and clearly show how each part of the system connects to the next. After students finish, use the overhead Digestive System Map from the lesson introduction, explaining what each part of the system does and how the parts are connected.

Post-Introduction Assessment

Voting: Ask the students true/false questions about the lesson and have them vote whether they think the answer is true or false. Discuss student answers as needed.

• The system of the human body associated with eating is the digestive system? (Answer: True)
• Digestion begins in your stomach. (Answer: False, it begins in your mouth.)
• Eating in space is hard because gravity pulls the food down. (Answer: False, eating in space is hard because there is little gravity to hold food in place; it will float unless tethered down.)
• Astronauts do not get to choose their meals to have while in space. (Answer: False, before they go up in outer space, the astronauts meet with nutritionists and engineers to try out different kinds of foods to see which ones they like best.)
• Engineers help design the packages of food that astronauts eat while traveling in space. (Answer: True)
• Engineers are responsible for designing the way astronauts eat their meals in space. (Answer: True)
• The digestive system works to break down food into smaller molecules to provide us with energy, help our bodies grow and help our bodies heal themselves. (Answer: True)
• Your liver, pancreas and gall bladder are not parts of your digestive system. (Answer: False, these organs are part of your digestive system; these organs make and store chemicals that help us break down or digest our food.)
• Engineers help astronauts stay healthy in space. (Answer: True)
• Your liver's job is to quiver. (Answer: False, the liver's job is to remove harmful wastes and toxins from the body, although it might quiver from time to time.)

Lesson Summary Assessment

Human Diagram: On nine pieces of paper, write down the following organs of the digestive system: mouth, teeth, tongue, esophagus, stomach, small intestine, large intestine, rectum and anus. Ask for nine volunteers from the class to come up to the front of the room, and give each person one of the pieces of paper in a random order. One at a time, have each volunteer read what is written on their paper. Have the remainder of the class put the organs in order of the digestive system by voting. To complete the visual have the students pass a piece of paper through the digestive system, with each student tearing off a piece of the paper as they pass it to the next "organ." You can have one extra student be the "body" and collect the pieces of paper as they are torn off by the organs.

Drawing the Digestive System – Part Two: Turn off the overhead, and write the following parts on the board:

• Mouth
• Tongue
• Pharynx
• Esophagus
• Stomach
• Liver
• Gallbladder
• Pancreas
• Large intestine
• Small intestine
• Rectum
• Anus

Again, give each student a pencil and blank piece of paper, and ask them to re-draw the digestive system, being sure to include (and label) all of the parts listed on the board. Once they are finished, display the Digestive System Map again and have them correct their own drawings as needed.

Lesson Extension Activities

Have students taste "astronaut ice cream," which is freeze-dried ice cream. (Find this product online by conducting a browser search using keywords: astronaut ice cream.)

Try the University of Rochester Medical Center at https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=40&contentid=DigestionFoodDigestiQuiz.

Additional Multimedia Support

For more about astronaut food, see these NASA websites:

• Space Food Systems, https://www.nasa.gov/content/space-food-systems
• Space Food History, https://www.cnn.com/2019/07/19/world/apollo-space-food-history-scn

See videos of astronauts eating in outer space at https://www.nasa.gov/audience/foreducators/stem-on-station/ditl_eating

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.