The Digestive System Your digestive system is a group of organs that work together to digest food so that it can be used by the body

The most obvious part of your digestive system is the digestive tract The digestive tract includes your mouth, throat, esophagus, intestine, rectum, and anus

Digestive System at a Glance The human digestive tract may be more than 9 meters long Food is digested as it passes through the digestive tract The liver, gallbladder, pancreas, and salivary glands secrete substances that are used in digestion                                          

Two Types of Digestion Mechanical Chemical The breaking, crushing, and mashing of food is called mechanical digestion Chemical 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

Three major types of nutrients Carbohydrates Proteins Fats

Simple carbohydrates are sugars such as glucose, fructose, lactose, and sucrose.  Some simple sugars can be easily identified, such as honey, corn syrup, and maple syrup.  But others are tougher to find, especially in frozen dinners, white breads, cereal, and yogurt.  Excluding fruits and vegetables, most simple carbohydrates do not have much nutritional value

Complex carbohydrates are long chains of glucose molecules.  They are usually comprised of starches, which is the product of carbohydrate storage in plants.   The major source of complex carbohydrates are whole grain products, such as whole wheat bread, brown rice, pasta, and beans.

Proteins are a combination of many chemicals called amino acids Proteins are a combination of many chemicals called amino acids. Scientists have found 20 different amino acids in protein, and these 20 amino acids can combine in lots of ways - in fact, they have joined together to make thousands of different proteins! Some types of amino acids are made by your body. These are called nonessential amino acids, and there are 11 of them. The essential amino acids - all nine of them - must come from food.

Protein's biggest job is to build up, keep up, and replace the tissues in your body. Your muscles, your organs, even some of your hormones are made up mostly of protein.    Protein helps your body in other ways, too. It likes to make sure things get around by making hemoglobin, the part of red blood cells that carries oxygen to every part of your body. It even makes antibodies, the cells that fight off infection and disease. Proteins are in tasty foods like meat, chicken, fish, eggs, and nuts. Dairy products like cheese, milk, and yogurt are good sources of protein

Fats In vegetable oil you see oils created from different seeds and nuts. There is corn oil, safflower oil, peanut oil, canola oil, olive oil... All seeds and nuts contain some amount of oil, because oil is a very good way to store energy. By the way, the only difference between oil and fat is whether or not it is a solid at room temperature. In different cuts of meat you see them outlined by a layer of white, solid fat created by the animal to store energy. In dairy you see butter and margarine -- fat made from cream or vegetable oils, respectively

Special substances called enzymes break some nutrients into smaller particles that the body can use. For example, proteins are too large to be absorbed into the bloodstream, but enzymes chop up the protein chain into amino acids. These amino acids are small enough to pass into the bloodstream

Why is chewing so important? Chewing creates small, slippery pieces of food that are easier to swallow than big, dry pieces Small pieces of food are easier to digest.

Through the Teeth Teeth are very important organs for mechanical digestion With the help of strong muscles and your jaw bones, teeth are able to break and grind food The outermost layer of a tooth, the enamel, is the hardest material in the body. Enamel protects nerves and softer material inside the tooth

Different kinds of teeth The molars in the back are well suited 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

Over the gums As you chew, the food gets mixed with a liquid called saliva. Saliva is made in salivary glands located in and around the mouth Saliva contains an enzyme that begins the chemical digestion of carbohydrates. Saliva turns complex carbohydrates into simple sugars.

Look out Stomach, Here it Comes! 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 squeezed the mass of food with rhythmic muscle contractions called peristalsis Peristalsis forces the food into the stomach.

The Stomach The stomach is a muscular, baglike organ attached to the lower end of the esophagus. The stomach continues the physical digestion of your meal by squeezing its contents with muscular contractions.

While squeezing is going on in the stomach, tiny glands produce enzymes and acid. Acids and enzymes work together to break food into nutrients Stomach acid also kills most bacteria that you might swallow with your food After a few hours of combined physical and chemical action, your food is reduced to a soupy mixture called chyme.

Chyme is slowly released into the small intestine through a small ring of muscle that works like a valve. This valve keeps food in the stomach until it has been thoroughly mixed with digestive fluids Then the valve opens and closes, letting a small amount of chyme squirt into the small intestine each time. Releasing chyme slowly from the stomach give the intestine more time to mix the chyme with fluids from the liver and pancreas.

Brain Food A thick substance called mucus covers the stomach’s lining and offers some protection from its harsh environment. However, the acids still damage the lining, and the entire lining must be replaced every few days.

The small intestine is a muscular tube that is about 2 The small intestine is a muscular tube that is about 2.5 cm (about 1 inch) in diameter. If you stretched out your small intestine, it would be about 6 meters (20 feet) If you flattened out the surface of the small intestine, it would be larger than a tennis court.

The inside wall of the small intestine is covered with fingerlike projections called villi The villi are covered with tiny nutrient-absorbing cells These cells allow the nutrients to enter the bloodstream

Most chemical digestion takes place in the small intestine Chyme from the stomach moves very slowly through the small intestine by peristalsis. Proteins, carbohydrates, and fats In the chyme are digested with the help of enzymes produced in the small intestine and the pancreas.

The Pancreas The pancreas is a fish-shaped organ located between the stomach and small intestine. It makes pancreatic juice that flows into the small intestine. This juice contains digestive enzymes and bicarbonate that neutralizes the acid in chyme

Liver The liver is a large reddish brown organ that helps with digestion. A human liver can be as large as a football. Your liver is located toward your right side, slightly higher than your stomach

Functions of the Liver 1. Your liver makes a green liquid called bile that is used in fat digestion 2. Your liver stores nutrients 3. Your liver breaks down toxic substances in the blood Your liver makes cholesterol for cell membranes

Bile Breaks Up Fat Although bile is made by the liver, it is temporarily stored in a small baglike organ called the gallbladder. Bile is squeezed from the gallbladder into the small intestine, where it breaks up large fat droplets into very small droplets

After nutrients are broken down, they are absorbed into the bloodstream and carried through the body Nutrients that are not needed right away are stored in the liver. The liver then releases the stored nutrients into the bloodstream as needed. The liver also captures and detoxifies many substances in the body.

Brain Food If three-fourths of the liver were removed, the rest would go on working and would eventually grow to replace the part that was removed.

The End of the Line The large intestine is the organ of the digestive system that stores, compacts, and then eliminates indigestible material from the body The large intestine has a diameter of about 7.5cm (3 inches) and is about 1.5 meters (2 feet) long.

Undigested material enters the large intestine as a soupy mixture. The large intestine reabsorbs most of the water in the mixture, changing the liquid into a solid mass called feces or stool. Whole grains, fruits, and vegetables contain a carbohydrate, called cellulose, that humans cannot digest. We commonly refer to this material as fiber. Fiber keeps the stool soft and keeps things moving through the large intestine.

A Way Out The rectum is the last section of the large intestine. It stores feces until they can be expelled. Feces pass to the outside through an opening called the anus.

F. Y. I. It takes food approximately 24 hours to complete the digestive journey

What happens to the feces ??? Feces and other human wastes contain microorganisms and other substances that can contaminate drinking water. Every time you flush a toilet, the water and wastes go through the sewer to a sewer treatment plant. Here the disease-causing microorganisms are removed, and the clean water is released back to rivers, lakes, and streams.

Problems in the Digestive System Disorders of the digestive system are frequently related to eating behaviors. However, digestive problems can also be caused by diseases. Some common digestive disorders are Heartburn Constipation and Diarrhea Colon Cancer Gastric Ulcer

Heartburn Backflow of chyme from the stomach to the esophagus causes a burning pain in the chest called heartburn. Eating too much, eating right before going to bed, and eating very acidic foods sometimes cause heartburn.

Constipation When the body does not get enough fiber, water, or exercise, the contents of the large intestine can become dry. Bowel movements become difficult and less frequent This condition is called constipation.

Diarrhea When bowel movements are frequency and watery, the condition is called diarrhea. Diarrhea occurs when too little water is removed from digested food in the large intestine Diarrhea may cause dehydration and is especially dangerous for infants and small children

Colon Cancer Colon cancer is a serious disease of the digestive tract that can lead to death The colon is the long tubular portion of the large intestine. When certain colon cells divide uncontrollably, a tumor forms Tumors interfere with the normal functioning of organs.

Gastric Ulcer An open sore in the stomach lining is called a gastric ulcer Gastric ulcers are often caused by bacteria and can be treated successfully with antibiotics