The Digestive System

The Digestive System: THE DISSAPPEARING APPLE
The food we eat travels through the alimentary canal, a path that is about 30 feet long from mouth to rectum and includes 2 large glands the liver and the pancreas.

We are food processors! We break down our food by chopping, mashing and mixing it to a nice soup that our body can absorb. Food has minerals like calcium for healthy teeth and bones. The minerals that we need come from non-livings things. Iron is a mineral required by your blood to carry the oxygen you breathe to feed every living cell in your body. Cells must have oxygen to stay alive. The iron that we get from our food originally comes from rock. The core of the earth is iron and many things are made from iron like gates and tools. Zinc and magnesium are other minerals we need.
Plants and animals that we eat contain carbohydrates, proteins, fats, minerals and vitamins like vitamin A to strengthen our eyes, vitamin C to help us heal, and B vitamins to feed our brains! Growing and doing things requires energy and energy comes from fuel! Food, water and oxygen are our fuel. The sun is the fuel for plants to grow and stay alive. In a lifetime we may eat the weight of 6 elephants. Food keeps us strong, builds cells, and allows us to grow and work and play. It helps fix our body if we are hurt or sick and it controls the systems of our body.

What happens to an apple when we eat it? Smelling and seeing food starts the process of producing saliva. The mouth releases 3 cups of saliva a day. In the mouth our teeth and tongue work together to chew food and mix it with saliva. The epiglottis trapdoor to our lungs closes and the tongue pushes the food down into the esophagus (a narrow tube 10 inches long.) It goes into the stomach where it is mashed and mixed with gastric juices and turned into a thick soup. It is in the stomach 2 to 4 hours churning. The stomach has 3 layers of muscles to help churn our food. Mucus protects the stomach from digestive acids. The food is moved into the small intestines (about 22 feet long and the longest part of the canal) where nutrition from the soup is taken into the blood stream by the tiniest blood vessels called capillaries. Then it is taken to a major checkpoint the liver to filter out any harmful substances or wastes. The nutrients are then sent to all parts of our body.

The pancreas makes juices that help the body digest fats and proteins. A juice from the liver called bile helps to absorb fats into the blood stream. The gall bladder is the storage place for the bile. Food not used goes on to the large intestines (about 5 feet long) where the rest of the liquid is absorbed. The large intestine has a tiny tube with a closed end called the appendix that doesn’t do anything. Wastes from our food travels through the colon where the rest of the water is absorbed. The solid waste accumulates in the rectum and is eliminated through the round sphincter muscle called the anus (a circular muscle is a sphincter). A meal takes from 15 hours to 2 days to go through the alimentary canal.

The body can only use one kind of sugar for energy and that is glucose. Plants make there own glucose. If there are bacteria in the food or the stomach is irritated by a germ, the stomach objects and pushes the food out and you stomach ache and you may vomit up the food.

The pancreas produces digestive juices for the small intestines and is like a giant salivary gland. It produces the hormone insulin (glucose) a type of sugar that is fuel for cells, esp. those in the brain. The liver is the largest internal organ and it makes poisons in our food less harmful and produces the green fluid called bile stored in the gall bladder. Kidneys filter and clean the fluid from the blood and sends liquid waste to our bladder and it is eliminated from the body in urination.

To keep the body in good health we must breathe clean air, keep our bodies clean, get enough rest, exercise, and eat foods that have the nutrients our bodies need. The protein we need comes from meat, fish, eggs, beans, and whole grains. Our body rearranges the protein into amino acids that our bodies use for building new cells and tissues. The carbohydrates that we need come from vegetables, fruit, bread, and cereal and the body makes glucose for energy that is stored in muscles and the liver. The fats we eat come from milk, eggs, meat, and oils. They cushion around organs and store energy in the liver and under the skin.

I use the digestive system apron with students and may have them eat an apple or pretend to eat an apple. The apron is available through one of the suppliers listed on the resource page. I may discuss animals that have 2 stomachs or a crop to store food. We may discuss herbivores, carnivores, and omnivores and those that have beaks and the differences in teeth depending on their diet. This is a good time to follow up on nutrition and the food pyramid and for very young children I have samples of food for them to identify and learn how it is good for the body.

The importance of teeth and chewing your food.

Chewing is a very important part of healthy digestion. Chew your food well. What you get in return is better health. Chew your food completely to be swallowed with ease. Digestion begins with chewing your food. Chewing breaks down food molecules to smaller particles. Increases the surface area, reduces esophageal stress and exposes food to saliva for a longer time. Saliva helps lubricate the food making it easier for foods to pass through the esophagus. The enzymes in saliva contribute to the chemical process of digestion. Carbohydrate digestion begins with saliva. The first stage of fat digestion also occurs in the mouth. Incomplete digestion can lead to bacterial growth. When food is not well chewed and food fragments are too big to be broken down, incomplete digestion occurs. Nutrients do not get extracted from the food and it becomes fodder for bacteria in the colon, which can lead to bacterial overgrowth, flatulence, and symptoms of indigestion. Chewing relaxes the lower stomach muscle. Chewing is directly connected with the movement of food through your digestive tract, and with the movement of food from your stomach to your small intestine. At the lower end of your stomach, there is a muscle called the pylorus. This muscle must relax in order for food to leave your stomach and pass into your small intestine. Sufficient saliva from optimal chewing helps relax the pylorus, and helps your food move through your digestive tract in a healthy fashion. Chewing triggers the rest of the digestive process. The process of chewing activates messages to the rest of the gastrointestinal system to begin the entire digestive process. Chewing activates taste receptors in the mouth and prompts the nervous system to relay information to the gastric system to optimize the process of digestion. Stimulation of the taste receptors can signal the stomach lining to produce hydrochloric acid that helps in the breakdown of protein. Chewing also signals the pancreas to prepare to secrete enzymes and bicarbonate into the lumen of the small intestines.