Digestive System
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Transcript of Digestive System
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Digestive System
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Digestive System
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Functions of The Digestive System
All the food you eat goes through a process with four steps — ingestion, digestion, absorption, and elimination.
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Functions of The Digestive System
• Food is INGESTED. Ingestion is the act of eating, or putting food in your mouth.
• Food is DIGESTED. Digestion is the mechanical and chemical breakdown of food into small particles and molecules that your body can absorb and use.
• Nutrients and water in the food are absorbed, or taken in, by cells. ABSORPTION occurs when the cells of the digestive system take in small molecules of digested food.
• Undigested food is eliminated. ELIMINATION is the removal of undigested food and other wastes from your body.
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Types of Digestion
• Before your body can absorb nutrients from food, the food must be broken into small molecules by digestion.
• There are TWO types of digestion:
MECHANICAL CHEMICAL
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Types of Digestion
• In mechanical digestion, food is physically broken into smaller pieces.
• Mechanical digestion happens when you chew, mash, and grind food with your teeth and tongue.
• Smaller pieces of food are easier to swallow and have more surface area than larger pieces. This helps with chemical digestion.
• In chemical digestion, chemical reactions break down pieces of food into small molecules.
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Types of Digestion - Enzymes
• Chemical digestion cannot occur without substances called ENZYMES.
• Enzymes are proteins that help break down larger molecules into smaller molecules.
• Enzymes also speed up, or catalyze, the rate of chemical reactions.
• Without enzymes, some chemical reactions would be too slow or would not occur at all.
• There are many kinds of enzymes. Each one is specialized to help break down a specific molecule at a specific location.
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• Nutrients in food are made of different molecules, such as carbohydrates, proteins, and fats. Many of these molecules are too large for your body to use.
• But, because these large molecules are made of long chains of smaller molecules joined together, they can be broken down into smaller pieces.
The Role of enzymes in Digestion
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• The digestive system produces enzymes that are specialized to help break down each type of food molecule.
• The enzyme AMYLASE helps break down carbohydrates.
• The enzymes PEPSIN and PAPAIN help break down proteins.
• Fats are broken down with the help of the enzyme LIPASE.
The Role of enzymes in Digestion
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The Role of enzymes in Digestion
• Notice that the food molecule breaks apart, but the enzyme does not change. Therefore, the enzyme can immediately be used to break down another food molecule.
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Organs of the digestive system
• There are TWO parts to your digestive system: the digestive tract and the other organs that help the body break down and absorb food.
• The digestive track extends from the mouth to the anus. It has different organs that are connected by tubelike structures. Each of these organs is specialized for a certain function.
• The other organs, include the tongue, salivary glands, liver, gallbladder, and pancreas.
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Mouth
• Mechanical digestion of food begins in your mouth.
• Your teeth and tongue mechanically digest food as you chew.
• But even before chewing begins, your salivary glands produce saliva at the thought of food.
• They produce more than 1 L of saliva every day. Saliva contains an enzyme that helps break down carbohydrates.
• It also contains substances that neutralize acidic foods and a slippery substance that makes food easier to swallow.
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Esophagus
• When you swallow a bite of food, it enters your esophagus.
• The esophagus is a muscular tube that connects the mouth to the stomach.
• Food moves through the esophagus and the rest of the digestive tract by waves of muscle contractions called peristalsis.
• Muscles in the esophagus contract and relax. This action pushes partially digested food down the esophagus and into the stomach.
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Esophagus
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Esophagus
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Stomach
• Partially digested food leaves the esophagus and enters the stomach.
• The stomach is a large, hollow organ.
• One function of the stomach is to store food. This allows you to go many hours between meals.
• The stomach is like a balloon. It can stretch when filled.
• An adult stomach can hold about 2 L of food and liquid.
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Stomach
• The stomach also helps with chemical digestion.
• The walls of the stomach are extremely folded. These folds enable the stomach to expand and hold large amounts of food.
• The cells in these folds produce chemicals that help break down proteins.
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Stomach
• The stomach contains an acidic fluid called gastric juice.
• Gastric juice makes the stomach acidic. Acid helps break down some of the structures that hold plant and animal cells together.
• Gastric juice also contains pepsin. Pepsin is an enzyme that helps break down the proteins in foods into amino acids.
• Food and gastric juices mix as muscles in the stomach contract through peristalsis. As food mixes with gastric juice in the stomach, it forms a thin, watery liquid called CHYME.
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Stomach
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Small Intestine
• Chemical digestion begins in the mouth and the stomach. But most chemical digestion occurs in the small intestine.
• The small intestine is a long tube that is connected to the stomach.
• Chemical digestion and nutrient absorption take place in the small intestine.
• The small intestine is named for its small diameter — about 2.5 cm. The small intestine is about 7 m long.
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Small Intestine
• Chemical digestion takes place in the first part of the small intestine, called the duodenum.
• The remainder of the small intestine absorbs nutrients from food.
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Small Intestine • Like the stomach, the wall of the intestine has many folds.
These fingerlike projections called villi.
• Each villus contains small blood vessels. Nutrients in the small intestine diffuse into the blood through these blood vessels.
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Small Intestine IF YOU WERE TO STRETCH OUT THE VILLI OF THE SMALL INTESTINE THEY WOULD COVER......
...a tennis court!!!!
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Pancreas and Liver
• The pancreas and liver produce substances that enter the small intestine and help with chemical digestion.
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Pancreas and Liver
• The pancreas produces the enzyme amylase and a substance that neutralizes stomach acid. The enzyme amylase helps break down carbohydrates.
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Pancreas and Liver
• The liver produces bile. Bile makes it easier to digest fats. The gallbladder stores bile until it is needed in the small intestine.
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Small Intestine
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Large Intestine • Any food that is not absorbed in the small intestine moves by
peristalsis into the large intestine.
• The large intestine is also called the colon.
• The large intestine has a larger diameter (about 5 cm) than the small intestine. It is much shorter than the small intestine, however. It is only about 1.5 m long.
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Large Intestine
• Most of the water in ingested foods and liquids is absorbed in the small intestine. As food travels through the large intestine, even more water is absorbed.
• Materials that pass through the large intestine are the waste products of digestion.
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Large Intestine • The waste products become more solid as even more water is
absorbed.
• Peristalsis continues to force the semisolid waste into the rectum, the last section of the large intestine.
• Muscles in the rectum and anus control the release of this semisolid waste, called feces.
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Bacteria and Digestion• You might think that all bacteria are harmful. However, some
bacteria have an important role in the digestive system.
• Bacteria in the intestines digest food and produce important vitamins and amino acids.
• Bacteria in the intestines are necessary for proper digestion. Without these bacteria, food would not be digested well.
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Homeostasis and the Digestion System
• Recall that nutrients from food are absorbed in the small intestine. The digestive system must be functioning properly for this absorption to occur.
• The nutrients that are absorbed are needed for other body systems to maintain homeostasis.
• For example, the blood in the circulatory system absorbs the products of digestion. The blood carries the nutrients to all other body systems, providing them with materials that contain energy.