The Digestive System

Introduction The digestive system is used for breaking down food into nutrients which then pass into the circulatory system and are taken to where they are needed in the body.

Components Esophagus Stomach Small Intestine Large Intestine Gall bladder Liver Pancreas

There are four stages to food processing: Ingestion: taking in food Digestion: breaking down food into nutrients Absorption: taking in nutrients by cells Egestion: removing any leftover wastes

I. The Digestive Process Begins         1. Digestion: The process by which your body breaks down food into small nutrient molecules. (mechanical and chemical)

2. Absorption: The process by which nutrient molecules pass through the wall of your digestive system into your blood.

3. Elimination: Materials that are not absorbed are eliminated from the body as waste (ie. Fiber)

Diagram of Digestive System

Mouth Chemical and mechanical digestion. Food is chewed (masticated) mechanically. A bolus (lump) is formed with saliva and the tongue.

B. Mouth Saliva: Fluid released when your mouth waters and plays an important part in both mechanical and chemical digestion. Types of Digestion Mechanical Digestion- Teeth begin digestion by cutting, tearing, and grinding food

mouth break up food digest starch kill germs moisten food

C. Esophagus- Total Time 10 seconds. 1.           1. Epiglottis: Flap of tissue that seals off your windpipe preventing food from entering. 2. Esophagus: Food enters a muscular tube that connects the mouth to the stomach. 3. Mucus: Thick, slippery substance that lines the esophagus in order to make food easier to swallow and move along

You have a trap door called the epiglottis to cover your windpipe when you swallow.

Peristalsis series of involuntary wave-like muscle contractions which move food along the digestive tract

Stomach Food is temporarily stored here. Gastric juices are secreted. Has layers of muscle that line the inside. Mechanically and chemically breaks down food.

Mechanical Digestion: Three strong layers of smooth muscle contract to produce a churning motion. (similar to a washing machine) 2. Chemical Digestion: Churning food makes contact with digestive juices. a. Enzyme Pepsin- Works best in an acid environment.     b. Hydrochloric Acid (HCl).-Kills many bacteria that you swallow with food, mucus protects stomach lining from this acid. c. Food remains in the stomach until the entire solid has been broken down.

Your stomach mashes your food the way a baker kneads dough for bread.

Your stomach stretches when you eat like a balloon being filled with air

mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food sphincter sphincter

Small Intestine Most chemical digestion takes place here. Simple sugars and proteins are absorbed into the inner lining. Fatty acids and glycerol go to lymphatic system. Lined with villi, which increase surface area for absorption, one cell thick.

3. Absorption in the Small Intestine Villi: Fingerlike structures increase the surface area of the small intestines and allow nutrient molecules to pass into the blood

Small Intestine Tube that is 20 feet long. Continues to digest food Food stays in your small intestine for 4 to 8 hours

Large Intestine Solid materials pass through the large intestine. These are undigestible solids (fibers). Water is absorbed. Vitamins K and B are reabsorbed with the water. Rectum- solid wastes exit the body.

Large intestines (colon) Function re-absorb water use ~9 liters of water every day in digestive juices > 90% of water reabsorbed not enough water absorbed diarrhea too much water absorbed constipation

B. The Large Intestine -The last section of the digestive system that contain bacteria that feed on material and make vitamins (1.5 meters long) -The role is absorb water into the bloodstream and get remaining material ready for elimination.

Large Intestine Tube that is 5 feet long Gets waste from small intestine Waste stays for 10 to 12 hours

Rectum Last section of colon (large intestines) eliminate feces undigested materials extracellular waste mainly cellulose from plants roughage or fiber masses of bacteria

Accessory Organs Pancreas Gall Bladder Spleen

Pancreas An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine) ** Pancreatic juice digests all major nutrient types. Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.

Gall bladder Pouch structure located near the liver which concentrates and stores bile Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

BILE Bile emulsifies lipids (physically breaks apart FATS) Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats pancreas produces enzymes to digest proteins & starch

Healthy Habits Eat foods that are high in fiber like fruits and vegetables

Drink plenty of water

Chew your food completely before you swallow

Avoid foods high in fat

Interesting Facts Food is in your digestive system for about 24 hours