Digestive Systems

Digestive Systems by Nabiya, Annika, & Zaina

Summary of Lesson

Vocabulary • Digestive system: an organ system that breaks down food to release nutrients • Esophagus: a muscular tube that pushes food toward the stomach • Large intestine: the organ into which food and other substances pass and where water and minerals from the food are absorbed – most of the large intestine is a tube called the colon • Small intestine: in humans, a long, coiled organ where most digestion takes place • Stomach: a muscular organ that mixes and stores food and passes it to the small intestine

Nutrients

Carbohydrates Carbohydrates are the main source of energy for the body. • Sources • Whole-grain bread • Pasta • Rice and other grains • Potatoes

Proteins Proteins are used to replace, repair, and grow new cells and tissue • Sources • Fish • Beef • Chicken • Beans

Vitamins and Minerals Vitamins and minerals help in various ways, including helping nerves work • Sources • Fruits • Vegetables • Fortified milk

Fats Fats provide energy and keep skin healthy. They also help the body use vitamins and cushion body organs. • Sources • Butter • Oil • Salad dressing • Ice cream

Energy From Nutrients Food provides nutrients that your body can use. Your body uses different kinds of nutrients for different purposes.

Animal Digestive Systems Grazing Animals • Cows, horses and other grazing animals have unusually long and complex digestive systems so they can digest the tough plant matter found in leaves and grass (the food they eat). Meat-Eating Animals • Animals that eat meat normally have short and simple digestive systems because meat breaks down much easier than plant matter. Other Animals • Some animals, such as sea sponges, don’t have digestive systems. Instead, they use a layer of cells to digest their food without the aid of organs or an organ system.

Stages of Digestion

Digestion begins in your mouth. While chewing, your teeth grind the food into tiny pieces. This allows the food to easily move through your digestive system. Your tongue pushes around the food, mixing it with saliva. Saliva is the watery liquid in your mouth that moistens the food and begins to break it down into tiny pieces. Saliva is produced by salivary glands at the back and bottom of your mouth. • The enzymes in saliva break down the starch in foods like bread and potatoes. After the enzymes do their job, the starch is converted to sugar. If you chew something salty for a long time, you may notice the salty taste changes to a sweet taste. • The enzymes in saliva break down the starch in foods like bread and potatoes. After the enzymes do their job, the starch is converted to sugar. If you chew something salty for a long time, you may notice the salty taste changes to a sweet taste. • The stomach squeezes the food and mixes it with these digestive fluids. The fluids contain multiple enzymes and an acid. This acid is a strong chemical that breaks down food. The proteins found in the food you eat are partially digested in your stomach.

After you swallow chewed foods, it moves into the esophagus. This tube pushes food towards the stomach. The stomach mixes and stores food, turning it into a soupy mix. When food enters the stomach, cells lining the stomach release fluids, breaking down the food further. • The stomach squeezes the food and mixes it with these digestive fluids. The fluids contain multiple enzymes and an acid. This acid is a strong chemical that breaks down food. The proteins found in the food you eat are partially digested in your stomach. • After the food you have eaten has been in your stomach for one to three hours, the food (now a soupy liquid) leaves your stomach. The food is on its way to becoming nutrients your cells can use. • Leaving the stomach, the food makes its way to the small intestine. The food remains in the small intestine from one to six hours. Chemicals from the liver and pancreas enter the first part of the small intestine. Here, they continue to break down the food. These chemicals digest fats, carbs, and proteins.

The small intestine is lined with billions of tiny, fingerlike folds called villi, plural for villus. Nutrients from the digested foods pass from villi into the blood, which passes them on to every cell in the body. • Food that hasn’t yet been digested moves on to the large intestine, where water and minerals from the foods are absorbed into the blood. Food stays in the large intestine for 12 – 36 hours. Any remaining food leaves the body as solid waste.

Beyond the Book

Tongue: organ that mixes food in the mouth Mouth: the first part of the digestive system, where food enters the body Salivary glands: produce saliva – help soften foods Bacteria: live in the small intestine and help digest food Beyond the book vocabulary

Fun Facts • We make one to three pints of saliva every day • Food stays in your stomach for two to three hours • In the mouth, food is either cooled or warmed to a more suitable temperature

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Digestive Systems