Digestive System What happens during digestion How digestion works Digestive system problems

In digestion, foods are broken down and absorbed as nourishment or eliminated as waste Digestive system functions can be divided into three main processes: Digestion is the mechanical and chemical breakdown of foods within the stomach and intestines for use by the body’s cells Absorption is the passage of digested food from the digestive tract into the cardiovascular system Elimination is the body’s expulsion of undigested food or body wastes

The digestive system consists of the mouth, esophagus, stomach, and intestines. Digestion includes two processes: mechanical process – chewing, mashing and breaking food down; chemical process involves secretions process involves secretions produced by digestive organs Teeth – break the food you eat into smaller pieces; mastication – process of chewing prepares food to be swallowed Salivary glands – produce digestive juices, saliva contains an enzyme that begins to break down the starches and sugars in food into smaller particles Tongue – prepares chewed food for swallowing for shaping it, uvula small flap of tissue at the back of mouth, prevents food from entering the nasal passages; epiglottis, tissue covering the throat, prevents food from entering the respiratory system Esophagus – muscular tube about 10-inches long, connects pharynx with stomach, food moves through the esophagus, stomach and intestine through peristalsis a series of involuntary muscle contractions that moves food through digestive system (begins as soon as food is swallowed) sphincter muscle – circular muscle at the entrance of stomach, allows food to move from the esophagus into the stomach

Stomach is hollow, sac-like organ enclosed in a wall of muscle, flexible, can expand when you eat and has three task: Mixing foods with gastric juices – secretions from the stomach lining that contain hydrochloric acid and pepsin, an enzyme that digests protein; hydrochloric acid kills bacteria taken in with food and creates an acidic environment for pepsin to do its work; mucus produced by the stomach forms a protective lining so that the gastric juices do not harm stomach Storing partially digested food and liquid – stomach holds the food for further digestion before it is moved into the small intestine Moving food into the small intestine – food is digested in the stomach, it is converted to chyme, a creamy, fluid mixture of food and gastric juices, peristalsis moves the chyme into the small intestine through an opening controlled by another sphincter muscle

Pancreas produces enzymes that break down the carbohydrates, fats, and proteins in food, glands in the wall of the intestine produce other enzymes help this process Liver process digestive juice – bile – yellow-green, bitter fluid important in the breakdown and absorption of fats, bile is stored in gallbladder between meals, bile acids dissolve the fats inot the watery contents of the intestine, after fat is dissolved, it is digested by enzymes from the pancreas and lining of the intestine Small intestine is 20 to 23 feet in length and 1 inch in diameter; has three parts: duodenum, the jejunum and ileum About 90% of all nutrients are absorbed through the small intestine, inner wall of small intestine contains fingerlike projections called villi - lined with capillaries that absorb the nutrients, unabsorbed material leaves the small intestine in the form of liquid and fiber, moves by peristalsis into large intestine Undigested parts of food – fiber or roughage – pass into the colon or large intestine, it is about 2.5 inches in diameter and 5 to 6 feet in length, function is to absorb water, vitamins and salts and to eliminated waste

Digestive problems range from indigestion to acute conditions that require immediate medical attention. Maintain a healthy digestive system eat low-fat, high-fiber foods, wash hands before preparing or eating meals, eat slowly and chew food thoroughly, drink at least eight 8-ounce glasses of water a day Functional problems: Indigestion – discomfort in the upper abdomen, sometimes with gas and nausea, causes by eating to much food, eating too quickly, eating spicy or high-fat foods or having a stomach disorder or stress Constipation – causes the feces to become dry and hard, making bowel movements difficult, causes by not drinking enough water or not consuming enough fiber to move wastes Heartburn – burning sensation in the center of the chest may rise up to the throat, results from acid reflux, or backflow of stomach acid in the esophagus, caused by using tobacco, alcohol and aspirin, or eating spicy or greasy foods. Gas – produced from breakdown of food is normal, excessive gas results in cramps or an uncomfortable feeling of fullness in the abdomen Nausea – feeling of discomfort that sometimes precedes vomiting, motion sickness, pathogens some medications and dehydration Diarrhea – frequent passage watery feces, caused by bacterial or viral infections, some medications, a change in eating style, overeating, emotional turmoil or nutritional deficiencies, dehydration may result with some episodes.

Structural problems: some are temporary or easily treated, others are serious and require immediate medical attentions tooth decay – makes it difficult to chew food, brushing and flossing daily can prevent this, along with regular checkups. gastritis – inflammation of the mucous membrane that lines the stomach, increase in the production of stomach acid, use of tobacco or alcohol, bacterial or viral infections, some medications peptic ulcer – a sore in the lining of the digestive tract, caused by a bacterial infection or overuse of aspirin, ulcers can cause stomach bleeding Gallstones – form when cholesterol in bile crystallizes, they block the bile duct between the gallbladder and small intestine Lactose intolerance – inability to digest lactose (type of sugar in milk and other dairy products) if you are this you do not produce enough lactase Appendicitis – inflammation of the appendix, 3-to-4 inch tube at tip of the large intestine, caused by a blockage or bacterial infection

colitis – inflammation of the large intestine or colon, caused by bacterial or viral infection colon cancer – second leading cause of cancer death, develops in the lowest part of the colon, near the rectum, a low-fat, high-fiber eating plan decreases risk hemorrhoids – veins in the rectum and anus may become swollen and inflamed, occur with constipation, during pregnancy, and after childbirth Crohn’s disease – inflammation of the lining of the digestive tract, cause is unknown, seems to be associated with immune system problems cirrhosis – scarring of the liver tissue, caused by prolonged heavy alcohol use, lead to liver failure and even death