The Digestive System

Intro to the digestive system. Watch the video and answer the questions as an introduction or overview to the digestive system. How your digestive system works. Watch the video and answer the questions that follow. The digestive system is 9m long and contains 20 different cells types. The overall function of the digestive system is to turn the raw materials of your food into nutrients and energy that keep you alive. Food is broken from polymers into monomers but secretions of the digestive system. The types of molecules that compose food are carbohydrates or sugars, fats or lipids, proteins, and vitamins and minerals.The 4 main components of the digestive system are: 1. Gastrointestinal tract, which is 30-40 square meters and spans the entire length of your upper body.2. Pancreas, gallbladder and liver- a trio of organs that break down food using an array of special juices.3. Enzymes, hormones, nerves, and blood- all work to breakdown food, modulate the digestive process, and deliver its final products.4. Mesentary- a large stretch of tissue that supports and positions the digestive organs in the abdomen.The Digestive ProcessJust the thought of food can get the juices flowing for the digestive process. Glands in your mouth will begin to secrete saliva in anticipation of food that is on its way. About 1.5 L of this liquid per day. Chewing and mixing food with the saliva turns the food into a bolus. Enzymes in your saliva begin to break down any starch. This is why the longer you chew a piece of bread the sweater it will taste because more and more sugar molecules are released to stimulate the taste buds. The bolus is pushed to the pharynx (back of the throat) by the tongue and a reflex action and peristalsis takes over to push the food down the 25 cm long esophagus. The esophagus delivers the food to the stomach were powerful muscle action churns and crushes the bolus into a paste called chyme. Amino acids in the food you eat and stretching of the stomach lining triggers the release of hormones that stimulate the secretion of acids and enzymes from specialized cells in the gastric pits lining the stomach. The protein content of the food is digested by the enzymes and the hormones also stimulate the pancreas, liver and gallbladder to secrete digestive juices. Bile is also transferred from the gallbladder to the small intestine in preparation for the next stage.Now that the bolus has been processed in the stomach we refer to it as chyme. The chyme will slowly leave the stomach and enter the first part of the small intestine; the duodenum. Bile that was produced in the liver and stored in the gallbladder enters the duodenum in response to the fat content of the food. The bile begins to emulsify the fats in the chyme and turn them from large globules into smaller droplets in order for enzymes to more easily interact with the fats and digest them. At the same time the pancreas secretes pancreatic juice that contains bicarbonate that neutralizes the stomach acid, and pancreatic enzymes that continue to digest carbohydrates and proteins, and begin to digest fats. Fats are digested into fatty acids and glycerol, proteins into amino acids, and carbohydrates into glucose. This happens in the later regions of the small intestine, the jejunum and ileum. The surface area of the small intestine is increased because of billions of tiny little folds called villi that help increase the surface area of the small intestine for digestion and absorption of nutrients. The monomers of carbs, proteins, and lipids are absorbed into the bloodstream to be distributed to the body. By the end of the small intestine all we are left with is a watery sludge that needs some final processing in the large intestine before it is eliminated from the body.The watery liquid called feces, or stool,enters the large intestine (colon) and begins a short journey to recover excess water and absorb vitamins made by bacteria that live in the large intestine. At the end of the large intestine is the rectum, a holding pouch for the feces. As it fills, nerves are stimulated that deliver the defecation message to the brain. When the urge is strong enough the feces is eliminated through the anus; a small muscular segment of the tube that opens and closes to eliminate the waste.