The Digestive System

The digestive system is a group of organs that work together to digest food so that it can be used by the body The digestive tract is a series of tubelike organs that include your mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus The liver, gall bladder, pancreas and salivary glands are part of the digestive system, but food does not pass through these organs

Breaking Down Food

Digestion is the process of breaking down food into a form that can pass from the digestive tract to the bloodstream Two types of digestion – mechanical and chemical Mechanical digestion – the breaking, crushing and mashing of food Chemical digestion – large molecules are broken down into nutrients Enzymes – substances that break down larger molecules into smaller units

Nutrients

Three major nutrients – carbohydrates, proteins and fats – make up most of the food you eat Enzymes break some nutrients into smaller particles that the body can use For example – proteins are too big to be absorbed into the bloodstream – enzymes break them up into amino acids which can be absorbed

Digestion Begins in the mouth

Teeth – very important for mechanical digestion – break and grind food – makes smaller pieces of food easier to digest Saliva – made in the salivary glands located in the mouth - contain enzymes that begins the chemical digestion of carbohydrates Esophagus – a long straight tube that squeezes the mass of food with rhythmic muscle contractions called peristalsis – peristalsis forces food into the stomach

The Harsh Environment of the Stomach

The stomach is a muscular, saclike digestive organ attached to the lower end of the esophagus Continues mechanical digestion by squeezing food with muscle contractions Tiny glands in the stomach produce enzymes and acid – work together to break down food Stomach acid kills bacteria that might be in food Food reduced to soupy mixture called chyme

The Pancreas

Most chemical digestion takes place after the food leaves the stomach When the chyme leaves the stomach, it is very acidic The pancreas makes fluids that protect the small intestine from the acid Pancreas – oval organ located between the stomach and the small intestine Pancreatic fluid flows into the small intestine – contains enzymes to break down chyme and bicarbonate to neutralize acid Pancreas is part of the endocrine system by making hormones that regulate blood sugar

Small intestine

Small intestine is a muscular tube that is about 2.5 cm in diameter Stretched out, it is usually about 6 m long Inside wall of the small intestine is covered with fingerlike projections called villi Villi are covered with tiny nutrient – absorbing cells Once nutrients are absorbed, they enter the bloodstream

The Liver

The liver is a large, reddish brown organ that helps with digestion Located toward your right side, slightly higher than your stomach Liver helps make bile to break up fat Liver stores nutrients Liver breaks down toxins Bile that is made by the liver is temporarily stored by the gall bladder Gall bladder squeezes bile into the small intestine to break down fat droplets

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 Has a larger diameter than the small intestine (7.5 cm) Undigested material enters the large intestine as a soupy material from the body Most of water is absorbed from the mixture by the large intestine

Changes the mixture to a semi – solid called feces Whole grains, fruits and vegetables contain cellulose, or fiber, that cannot be digested The rectum is the last part of the large intestine – it stores feces until it can be expelled through the anus It takes your sandwich about 24 hours to make the journey through your digestive system