The Digestive System

The Digestive System Digestion is the process of breaking down food into nutrients that can be absorbed by cells. 1. Tongue 10. Anal Canal 2. mouth 11. Parotid gland 3. Tooth 12. Pharynx 4. Sublingual gland 13. Esophagus 5. Submandibular gland 14. Stomach 6. Liver 15. Pancreas 7. Gallbladder 16. Small Intestine 8.Duodenum 17. Rectum 9. Large Intestine

Gastrointestinal Tract The Mouth Digestion begins in the mouth with mastication. Three sets of salivary glands surrounding the oral cavity secrete saliva. Saliva contains enzymes that break down food and begin the digestion of carbohydrates. Three pairs of glands with ducts: parotid, submandibular, and sublingual glands. Mastication- the use of your teeth to chew food Enzymes- are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place

Gastrointestinal Tract The Mouth (cont.) 1. Parotid gland. 2. Submandibular gland. 3. Tongue. 4. Tooth. 5. Sublingual gland. 1 2 3 4 5

Gastrointestinal Tract The Pharynx Passageway for food and air. Epiglottis covers the trachea when we swallow. The Esophagus Muscular tube that connects the throat to the stomach. Contracts rhythmically to move food to stomach. The cardiac sphincter, a group of muscles, closes the entrance to the stomach to prevent backflow of food.

Gastrointestinal Tract The Stomach Pouchlike organ with four regions. Receives food from the esophagus and mixes it with gastric juice to form chyme. Regions of Stomach: Cardiac region: closest to the heart Fundus: upper, rounded portion Body: middle portion Pylorus: the narrowed bottom part Muscles of the stomach move, the food is then mixed with the gastric juice to form chime. The stomach releases the chime in small portions in regular intervals into the small intestine, where more digestion takes place. CHYME: the pulpy acidic fluid that passes from the stomach to the small intestine, consisting of gastric juices and partly digested food thick semifluid mass of partially digested food and digestive secretions

The Gastrointestinal Tract Small Intestines About 20 feet long from the stomach to the large intestine. Receive chyme from the stomach. Absorption occurs over 1 to 6 hours. Has 3 parts: Duodenum Jejunum Ileum Receives chime from the stomach, bile from the liver, and pancreatic juice from the pancreas. Bile is a substance secreted by the liver stored in the gallbladder. a bitter greenish-brown alkaline fluid that aids digestion Absorption begins in the small intestine. Most of the digestive products pass into the bloodstream in the small intestine. Its walls are lined with tiny, thread-like projections called villi Duodenum- 10 inches long, where the chime, bile, pancreatic juice, and intestinal juice mixes. Bile aids in fat digestion. Jejunum- 8 ft. long, continues the digestive process Ileum- 3rd section, connects the small intestine to the large intestine. Digestion time depends on the food and the health of the digestive system.

The Gastrointestinal Tract Large Intestines About 5 feet long and forms a rectangle around the small intestine. Waste products from digestion stay here for 12 to 24 hours. Has 4 main parts: Cecum Colon Sigmoid colon Rectum Most of the water from ingested food is absorbed back into the bloodstream in the large intestine 4 Parts: Cecum: first part and has 3 openings. From the Ileum into the Cecum, from the Cecum into the Colon, and from the Cecum to the Appendix. Colon: Divided into 3 parts to form a horseshoe in the abdominal cavity. Sigmoid Colon: S-shaped body that goes across the pelvis to the middle of the sacrum, where it connects to the rectum. Rectum: Attaches tot eh anal canal. The Sphincter muscle at the opening of the anus opens during release of feces.

The Digestive System The Liver Not within the GI tract, but performs digestive functions. Changes food nutrients into useable substances. Secretes bile to break down fat. Stores glucose and certain vitamins. Secretes bilirubin. Important digestive organ, located in the upper right quadrant of the abdominal cavity. Large organ weighs about 3 lbs in the average adult. Changes food nutrients into useable substances. Secretes bile to break down fat. Stores glucose and certain vitamins and releases them when the body needs them. Secretes bilirubin, a bile pigment that is combined with bile and excreted into the duodenum.

The Digestive System Gallbladder Bile from the liver goes into the gallbladder. It stores bile until its needed for digestion. Then its released into the duodenum, where it aids in the breaking down of fats. Pancreas 5-6 inches long and lies across the posterior side of the stomach. Part of the digestive system because it secretes pancreatic juice (that contains enzymes) into the small intestine through the system of ducts. Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place

The Process of Digestion: The mouth Mechanical Digestion: Process of physically breaking down food through chewing. Chemical Digestion: Occurs when food molecules are further broken down with the help of enzymes

With the help of strong jaw muscles, the teeth are capable of breaking down food

While mechanically breaking down food in the mouth, enzymes in the saliva begin to chemically break the food molecules down into useable nutrients Once the food has been reduced to a soft mush, the tongue pushes the food to the back of the mouth, causing the swallowing reflex

Food is pushed to the esophagus, where it slides to the stomach in less than 10 seconds. Small glands in the stomach produce enzymes and acid which further break down food particles into nutrients After a few hours of being broken down, the food exits the stomach as a soupy mixture called chyme

After leaving the stomach, chyme is pushed into the small intestine, where the process of absorption will begin. At this point, fluids produced by the pancreas to protect the small intestine from the acid in the chyme are released

The Small Intestine is the MAIN point of absorption of nutrients into the blood (and eventually the cells). Numerous small, finger-like projections called villi poke out into the tube of the small intestine, greatly increasing its surface area. The increase in surface area allows for more absorption to occur here

While traveling along the digestive tract, bile is secreted into the small intestine, breaking up fats Bile is produced in the liver, although it is stored and secreted into the small intestine through the gallbladder

Food that cannot be directly absorbed into the blood is pushed from the small intestine into the large intestine The large intestine is capable of absorbing most of the water from the food remains, turning them into a semi-solid mass known as feces, or stool. Feces are stored in the rectum until they can be expelled.

The Digestive System (cont.) Diseases and Disorders Anorexia nervosa – refusing to eat in order to be thin. Bulimia nervosa – binging on food and then purposely vomiting for weight loss. Obesity – usually caused by overeating, possibly a heredity defect. Can contribute to heart disease and diabetes. Halitosis – bad breath. Esophageal varices – twisted veins in the esophagus.

The Digestive System (cont.) Diseases and Disorders (cont.) Gastroenteritis – inflammation of the stomach and small intestines. Flatulence – gas. Eructation – belching. Nausea – sick feeling in stomach. GI ulcer – sores on the mucous membrane of the GI tract. Hiatal hernia – protrusion of the stomach through an opening in the diaphragm.

The Digestive System (cont.) Diseases and Disorders (cont.) Jaundice – yellow discoloration of the skin. Cirrhosis – chronic liver disease. Cholecystitis – inflammation of the gall bladder. Appendicitis – inflammation of the appendix. Ulcerative colitis and Crohn’s disease – chronic inflammatory diseases of the intestines.

The Digestive System (cont.) Diseases and Disorders (cont.) Diverticulitis – inflammation of the pouches in the intestinal wall. Constipation – infrequent or difficult release of bowel movements. Diarrhea – loose, watery stools. Hemorrhoids – swollen, twisted, painful veins in the internal and external anal area.

Jobs and Professions Gastroenterologist- Physician who specializes in the digestive system. Dietician- Plan food and nutrition programs that help treat and prevent disease.