The Digestive System

What Happens During Digestion Foods are broken down and absorbed as nourishment or eliminated as waste. Three Main Processes of the Digestive System: ◦ Digestion  The mechanical and chemical breakdown of foods within the stomach and intestines for use by the body’s cells. ◦ Absorption  The passage of digested food from the digestive tract into the cardiovascular system. ◦ Elimination  The body’s expulsion of undigested food or body wastes.

How Digestion Works The digestive system consists: ◦ Mouth ◦ Esophagus ◦ Stomach ◦ Intestines Digestion includes two processes: ◦ Mechanical Processes  Chewing, mashing, and breaking food down. ◦ Chemical Processes  Secretions produced by digestive organs

How Digestion Works Mastication ◦ The process of chewing Salivary glands ◦ produce saliva The tongue ◦ prepares chewed food for swallowing by shaping it.

How Digestion Works Esophagus ◦ Moves food down to the stomach and intestines by peristalsis  A series of involuntary muscle contractions that moves food through the digestive tract Stomach ◦ Mixing food with gastric juices ◦ Storing partially digested food and liquid ◦ Moving food into the small intestine ◦ As food is digested in the stomach, it is converted to chyme  A creamy, fluid mixture of food and gastric juices, which is moved into the small intestine

The Pancreas and Liver Liver ◦ produces bile  A yellow-green, bitter fluid important in the breakdown and absorption of fats Pancreas ◦ produces other enzymes that break down the carbohydrates, fats, and proteins in food in the small intestine

The Small and Large Intestines The small intestine is 20 to 23 feet in length and 1 inch in diameter ◦ It consists of three parts: ◦ The duodenum ◦ The jejunum ◦ The ileum About 90 percent of all nutrients are absorbed through the small intestine Unabsorbed material leaves the small intestine in the form of liquid and fiber and moves by peristalsis into the large intestine

The Small and Large Intestines The inner wall of the small intestine contains millions of fingerlike projections called villi that are lined with capillaries that absorb the nutrients The undigested parts of the food—fiber, or roughage—pass into the colon, or large intestine Its function is to absorb water, vitamins, and salts, and to eliminate waste

Tips for Maintaining Digestive Health Eat a variety of low-fat, high-fiber foods Wash your hands before preparing or eating meals Eat slowly and chew your food thoroughly Drink at least eight 8-ounce glasses of water a day Avoid using food as a way of dealing with your emotions

Digestive System Problems Digestive problems range from indigestion to acute conditions that require immediate medical attention Functional Problems: ◦ Indigestion  Discomfort in the abdomen, sometimes with gas and nausea. ◦ Constipation  Feces become dry and hard, making bowel movements difficult. ◦ Heartburn  A burning sensation in the chest that may rise up to the throat. ◦ Gas  Cramps or an uncomfortable feeling of fullness in the abdomen. ◦ Nausea  A feeling of discomfort that sometimes precedes vomiting. ◦ Diarrhea  The frequent passage of watery feces.

Digestive System Problems Structural Problems ◦ Tooth decay  Makes it difficult to chew foods thoroughly ◦ Gastritis  Inflammation of the mucous membrane that lines the stomach ◦ Gallstones  Blockage of the bile duct between the gallbladder and the small intestine ◦ Lactose Intolerance  An inability to digest lactose, a type of sugar found in milk and other dairy products ◦ Colitis  Inflammation of the large intestine, or colon

Digestive System Problems Structural Problems ◦ Colon cancer  Cancer that usually develops in the lowest part of the colon, near the rectum. ◦ Hemorrhoids  Veins in the rectum and anus that may become swollen and inflamed ◦ Crohn’s Disease  Inflammation of the lining of the digestive tract. ◦ Cirrhosis  Scarring of the liver tissue caused by prolonged heavy alcohol use ◦ Appendicitis  Inflammation of the appendix ◦ Peptic ulcer  A sore in the lining of the digestive tract