Lesson Plan - Get It!
Have you ever watched a plant eat? How are plants and humans different in the way they obtain nutrients?
Plants obtain nutrients from the sun through chemical reactions called photosynthesis.
Humans and other animals must consume food products in order to survive. Our bodies process food through the digestive system. In the first lesson of our Digestive System series, found under Related Lessons in the right-hand sidebar, you learned about the major organs and tissues of the digestive system. This system processes all the food products you take in by eating. Let's follow a cheeseburger as it moves through the digestive system to learn how food is processed.
Once the burger has arrived at your house, digestion begins. You start to produce saliva in your mouth because of the smell. After you take a big bite of the burger, the saliva starts to break down the food into smaller chemical compounds. Chewing helps the process by turning a large bite into many smaller pieces.
Now that food is broken into smaller pieces and softened, it becomes a bolus. A bolus is a small ball of churned up food product ready to be swallowed. It moves down the back of your throat and through the epiglottis into the esophagus. Remember that the epiglottis is the small flap that prevents your food from entering your windpipe. If you have ever laughed while drinking and experienced something "going down the wrong way," you've experienced what can happen when food goes down the windpipe!
In the esophagus, food is slowly moved from the throat to the stomach through muscular contractions.
Sometimes, people have problems in the esophagus that make moving food harder. You might have heard of GERD, or gastroesophageal reflux disease, where the end of esophagus does not close properly. When that happens, the stomach leaks acidic juices back, causing irritation. This can increase issues related to heartburn.
Once the cheeseburger reaches the stomach through the esophagus, it meets up with specialized acidic juices that break down food into usable nutrients. These gastric juices also kill bacteria that may be living in the cheeseburger and toppings. The muscular stomach contracts to mix and churn food products together into a liquidy mix. In the stomach, your cheeseburger loses the typical appearance as the meat, bun, cheese, and toppings become mixed together. It becomes a mix of chemical components ready to be digested.
Your burger may stay in the stomach for storage before being passed to the small intestine. The stomach depends on nerve signals to contract and release the nutrient mixture. If these nerves are damaged, the stomach cannot empty and becomes hard and painful. Individuals who experience this condition must take medication to regulate the contraction of the stomach.
Now that food has moved into the small intestine, it is mixed with juices from the pancreas, liver, and the gallbladder. The pancreas produces fluid full of enzymes that remove fats and proteins from the food. Your cheeseburger has fats in the cheese and mayonnaise, and protein in the meat patty. These nutrients are then used by your body to cushion joints and organs, and produce molecules that help you heal from injury and make up the cell membrane.
Your liver makes bile, a substance that moves fats into the blood stream so that it can be moved throughout the entire body. The liver is also responsible for identifying if nutrients are moved throughout the body or stored for later use. It also helps to turn waste into bile. Not all the bile is used immediately, so it is stored in the gallbladder.
The small intestines then remove additional nutrients like vitamins, minerals, and carbohydrates from the nutrient mix. Your cheeseburger would contain vitamins like potassium, B12, calcium, and folate. These compounds are used to help move muscles, fortify bones, and assist with the development of new tissues. Carbohydrates extracted from the bun would help build new cell membranes and provide quick energy to your growing body. It takes about four hours for food to move through the small intestine and be absorbed.
- Did you know there are some compounds that people are not able to digest?
Celiac's disease occurs when an individual is unable to digest gluten, a protein found in wheat products. When the body is unable to digest gluten, the small intestine begins to degrade and is unable to process any nutrition. This can lead to health issues like weight loss and fatigue. Individuals with Celiac's must avoid gluten to prevent damage.
Food leaves the small intestine and enters the large intestine. At this point in the digestive system, most usable nutrients have been removed and have left a waste product. In the large intestine, water is removed from the waste of the cheeseburger. The water is then distributed to the body for use. There are also minerals, like zinc, sodium, and phosphorus, that are removed and absorbed from the cheeseburger waste for use in the body. The large intestine prepares your cheeseburger for excretion.
What is left of your cheeseburger leaves your digestive system through the rectum and anus. By this point, you are probably ready for the next meal!
You have to eat in order to survive, and all food is processed through the digestive system. As food moves through your body, nutrients are removed and absorbed so they can be used to drive other body processes, like growth and development.
- How might this process change if the meal were different, maybe higher in protein and lower in fat?
Middle school students, discuss what you have learned with a parent or teacher.
High school students, write a one-paragraph reflection in your notebook.
In the Got It? section, you will learn more about the juices that assist organs and tissues to process nutrition in the body.