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The Digestive System-7th Grade
Transcript of The Digestive System-7th Grade
that work together to digest food
so that it can be used by the body. The Digestive System DIGESTIVE SYSTEM AT A GLANCE BREAKING DOWN THE FOOD
There are two types of digestion—mechanical and chemical. The breaking, crushing, and mashing of food is called mechanical digestion. In chemical digestion, large molecules are broken down into nutrients. Nutrients are substances in food that the body needs for normal growth, maintenance, and repair. The three main types of nutrients—carbohydrates, proteins, and fats—make up most of the food you eat. Substances called enzymes break some nutrients into smaller molecules that the body can use.
Example: Proteins are chains of amino acids. The proteins are too large to be absorbed into the bloodstream. So, enzymes-scissors- cut up the chain of amino acids. The individual amino acids are small enough to enter the bloodstream, where they can be used to make new proteins. Digestion: The Beginning Sources-
Grade 7 "Tennessee Holt Science & Technology" Science Book
http://www.nature.ca/discover/exm/blddgstvsystm/index_e.cfm - Putting together the Digestive System
http://www.softschools.com/quizzes/science/digestive_system/quiz751.html - Digestive System Quiz Once the food has been reduced to a soft mush, the tongue pushes it into the throat, which leads to a long, straight tube called the esophagus. The esophagus squeezes the mass of food with rhythmic muscle contractions called peristalsis (PER uh STAL sis). Peristalsis forces the food into the stomach. Esophagus Down the esophagus The stomach is a muscular, saclike, digestive organ attached to the lower end of the esophagus. It continues the mechanical digestion of your meal by squeezing the food with muscular contractions. Squeezing mixes the food with enzymes and acids produced by tiny glands in the stomach. The enzymes and acid work together to break food into nutrients. After a few hours of both mechanical and chemical digestion, your peanut butter and jelly sandwich has been reduced to a soupy mixture called chyme (KIEM) The Stomach The stomach slowly releases the chyme into the small intestine through a small ring of muscle that works like a valve. This valve keeps food in the stomach until the food has been thoroughly mixed with digestive fluids. Each time the valve opens and closes, it lets a small amount of chyme into the small intestine. Because the stomach releases chyme slowly, the intestine has more time to mix the chyme with fluids from the liver and pancreas. The fluids help digest food and stop the harsh acids in chyme from hurting the small intestine. Leaving the Stomach The small intestine is a hollow tube about 20 feet long that runs from the stomach to the beginning of the large intestine. The small intestine breaks down food from the stomach and absorbs much of the nutrients from the food.
The small intestine has three parts:
Ileum The Small Intestine We'll take a short cut....... Undigested material enters the large intestine as
a soupy mixture. The large intestine absorbs most
of the water in the mixture and changes the liquid
into a semisolid waste materials called feces, or stool. The Large Intestine The rectum is the last part of the large intestine and the digestive system. The rectum stores the feces until they can be expelled. Feces pass to the outside of the body through an opening called the anus. Your sandwich has now traveled a long 24 hour journey through your digestive system. & The Anus Presented By:
Corinne Fann Chewing is important for two reasons. First, chewing creates small, slippery pieces of food that are easier to swallow than big, dry pieces are. Second, small pieces of food are easier to digest.
Teeth are very important organs for mechanical digestion. With the help of strong jaw muscles, teeth break and grind food.
Have you ever noticed that your teeth have different shapes? The molars are well made for grinding food. The premolars are perfect for mashing food. The sharp teeth at the front of your mouth, the incisors and canines, are for shredding food. Saliva
As you chew, the food mixes with a liquid called saliva. Saliva contains an enzyme that begins the chemical digestion of carbohydrates. Saliva changes complex carbohydrates into simple sugars. TEETH The Rectum The Liver The liver is a large, reddish brown organ that helps with digestion. Your liver is located toward your right side, slightly higher than your stomach. The liver helps with digestion by:
Making bile to break up fat
It stores nutrients
It also breaks down toxins The Gallbladder Although bile is made by the liver, bile is temporarily stored in a small saclike organ called the gallbladder. Bile is squeezed from the gallbladder into te small intestine, where it breaks large fat droplets into very small droplets. This mechanical process allows more fat molecules to be exposed to digestive enzymes. The Pancreas When the chyme leaves the stomach, it is very acidic. The pancreas makes fluids that protect the small intestine from the acid. The pancreas is an oval organ located between the stomach and the small intestine. The chyme never enters the pancreas. Instead, the pancreatic fluid flows into the small intestine. This fluid contains enzymes that chemically digest chyme and contains bicarbonate, which neutralizes the acid in chyme. The pancreas also functions as a part of the endocrine system by making hormones that regulate blood sugar. Before we leave the stomach, we must learn about the other organs in you digestive system. These organs are not included in the digestive tract. That means that food does not pass through anytime during the digestive process. We will learn about the organs in the following order:
The Pancreas The Three Parts of
the Small Intestine Duodenum
The duodenum is the first part of the small intestine. The main role of the duodenum is to complete the first phase of digestion. In this section of the intestine, food from the stomach is mixed with enzymes from the pancreas and bile from the gallbladder. The enzymes and bile help break down food.
The jejunum is the second part of the small intestine. Once the food is broken down in the duodenum, it moves to the jejunum, where the inside walls absorb the food’s nutrients. The inside walls of the jejunum have many circular folds, which make its surface area large enough to absorb all of the nutrients that the body needs.
The ileum is the third part of the small intestine. It absorbs bile acids, which are returned to the liver to be made into more bile, then stored in the gallbladder for future use in the duodenum. The ileum also absorbs vitamin B12, which the body uses to make nerve cells and red blood cells.After the food is processed in the small intestine, it passes into the large intestine, also called the large bowel or colon. The large intestine, which is about 5 feet long, extracts most of the water from this food and distributes it to the body; the remaining material passes through the colon and out of the body as feces. The most obvious part of your digestive system is the digestive tract, a group of tube-like organs. This is where the food passes through. The digestive tract includes:
The Liver, Gallbladder, Pancreas, and Salivary Glands are also part of the digestive system, but food does not pass through them. Before we move on to the small intestine, we must learn about the other organs in the digestive system. These organs are not part of the digestive tract, so no food passes through them at any time during the digestive process. Even so, they all play important roles in the digestive system. There are two types of digestion—mechanical and chemical. The breaking, crushing, and mashing of food is called mechanical digestion. In chemical digestion, large molecules are broken down into nutrients. Nutrients are substances in food that the body needs for normal growth, maintenance, and repair. The three main types of nutrients—carbohydrates, proteins, and fats—make up most of the food you eat. Substances called enzymes break some nutrients into smaller molecules that the body can use.
Example: Proteins are chains of amino acids. The proteins are too large to be absorbed into the bloodstream. So, enzymes-scissors- cut up the chain of amino acids. The individual amino acids are small enough to enter the bloodstream, where they can be used to make new proteins. Now let's put together a digestive system http://www.nature.ca/discover/exm/blddgstvsystm/index_e.cfm
5. B. Thanks For Watching!!!
Tyler, Janie, & Corinne Time to take the Quiz :) Questions??