Unit 2.07 & 2.08 Digestive System

Overview Digestive System aka Alimentary Canal, Digestive Tract, GI Tract is a 30 ft. tube extending from mouth to anus. Its function is the physical and chemical breakdown of food. Mechanical digestion is the breaking down of food into progressively smaller and smaller particles through tearing, shredding, cutting and grinding and the moving of food along the GI tract. Chemical digestion is the process where food is converted to substances that the body can use. This is done with enzymes that speeds up the digestive process. The end product of digestion is waste and the elimination from the body. The process of digestion involves chemical, physical, absorption and elimination properties. It starts in the mouth with the formation of a Bolus — soft, pliable ball of semi-digested food. Ptyalin — in saliva in the mouth, converts starches to simple sugars and wavelike motions, known as peristalsis, moves the food along the esophagus, stomach and intestines. Once it reaches the stomach, gastric juices are released and the stomach churns and mixes food and juice into a substance known as chyme. It takes 2-4 hours for stomach to empty. Small amounts chyme enter the duodenum. In small intestine, digestion is completed, absorption occurs and you have the addition of enzymes from the pancreas and liver (via gallbladder). In the large intestine, large quantities of H20 are absorbed back into the bloodstream and bacteria help break down undigested food. Gas formation (flatulence) from bacterial action occurs and feces is formed— undigested semi-solid waste. Defecation then occurs— colon and rectal muscles contract, external anal sphincter under conscious control

I.Structure and Functions of Digestive System

A. Mouth - entrance way to digestive system 1. Tongue - attached to the floor of the mouth and made of skeletal muscle. Helps in chewing and swallowing and the taste buds are on the surface. 2. Teeth - used for mastication (chewing) a. gingiva – gums support the teeth b. deciduous – baby teeth c. Adult mouth has 32 teeth 3. Salivary glands - Three pairs that secrete saliva that aid in liquefying food making it easier to digest. Saliva is 99% water but also contains the enzymes ptyalin, or salivary amylase that begins the breakdown of carbohydrates d. Parotid — largest- located anterior and inferior to your ears. These glands swell when you have the mumps virus b. Sub-maxillary or Submandibular glands – found near the inner surface of your lower jaw. c. Sublingual glands are located under the tongue. 4. Palate – roof of your mouth 5. Uvula – prevents food from going up nose when swallowing B. Esophagus – 10 ft. long muscular tube connecting pharynx and stomach C. Stomach – sac-like structure located in the ULQ of the abdomen filled with gastric juices and mucus. Contains hydrochloric acid which destroys unwanted bacteria and other microorganisms. It has a mucus lining which acts as a protective barrier. Food becomes a semi-liquid, creamy, homogeneous substance called chime. Chyme leaves the bottom of the stomach through the pyloric sphincter and travels to the small intestine. 1. Cardiac sphincter - Circular layer of muscle controlling passage of food into stomach 2. Pyloric sphincter - regulates entrance of food into duodenum 3. Rugae - Mucous coated lining that folds when stomach is empty. Peristalsis pushes food into small intestine D. Pancrease - located behind the stomach and produces pancreatic juice which contains digestive enzymes (exocrine function). They travel through the pancreatic duct and common bile duct to reach the duodenum and help digest fats and proteins and control blood glucose levels by producing insulin. 1. Exocrine function — secretes digestive enzymes 2. Also has endocrine function

E. Liver - largest organ in the body located in the URQ below the diaphragm. Connected to the gall bladder and the intestine by ducts 1. Manufactures bile needed for the digestion & utilization of fats. 2. Produces and stores glucose in the form of glycogen 3. Detoxifies alcohol, drugs and other harmful substances 4. Filters out & destroys old RBC’s and saves the iron to be used again. 5. Stores vitamin K, A, D E and B 12 complex.

F. Gallbladder - small green organ on the inferior surface of the liver 1. Stores bile 2. When fatty foods are digested, bile released by gallbladder breaks down fat which is then stored in the intestinal wall and used by the body. G. Small Intestine - about 1” in diameter and 23 ft. long, coiled up in the abd. cavity. Digested foods (nutrients) pass into the bloodstream and on to body cells. About 10 liters of water is absorbed here daily. Undigested food passes on to the large colon

1. Duodenum — 12’ long. Pancreas and liver empty here. Most chemical digestion occurs here. Also the site of frequent ulceration 2. Jejunum —8 ft. long 3. lleum—10—l2ft.long H. Large Intestine (Colon) Approx 2” in diameter and 5 ft long. Nutrients not absorbed in small intestine are absorbed here and some water. Water and salts are absorbed here as needed and it serves as a storage and elimination structure for indigestible substances. This is where E-Coli is and works on undigested matter and is needed to synthesize B complex vitamins and Vit. K. Chyme enters but is converted to feces. Takes longer for food to pass through the large intestine, with mass movements occurring every 3 to 4 times a day. 1. Cecum - - beginning portion of the large colon receiving chyme from the ileum and connecting to the ascending colon of the large colon. 2. Appendix – narrow pouch of tissue resembling a worm. Exact function unclear. 3. Rectum - end portion of the large colon that connects the colon to the anus 4. Anus - external opening of the rectum with two sphincters controlling the exit of feces from the body during defecation II. Processes of Digestion A. Mechanical/Physical – digestion begins in the mouth with the teeth tearing, shredding, cutting and grinding down food into smaller and smaller pieces and the moving along the GI tract B. Chemical – process where food is converted to substances that the body can use through the use of enzymes which speeds up the digestive process C. Absorption – Food that has been broken down sufficiently to substances the tissues can use through the villa that line the wall of the intestine and enter into the bloodstream or put into storage D. Elimination – the process of defecation or the elimination of fecal material via the external anal sphincter. Feces is undigested semi-solid waste.

III. Relevance of Nutrition to the Digestive System A. Electrolytes – are nutrients/substances responsible for the acidity and alkalinity of solutions and can conduct an electrical charge. Major ones are calcium, magnesium, potassium, sodium, phosphate and chloride. They are responsible for regulating your heartbeat to allowing your muscles to contract for movement. Must maintain homeostasis. B. Vitamins – organic compounds that often functions as a coenzyme that is necessary for normal growth and health. A dietary deficiency of a vitamin results in a specific disorder. Vitamins that are not produced by the body must be obtained from dietary intake. The circulatory system transports vitamins to all the tissues of the body.

IV. Common Disorders and Treatments of the Digestive System

A. Anorexia Nervosa – an illness in which a person refuses to eat

B. Bulimia Nervosa – frequently binge eating, purges w/laxatives, & vomiting

C. Caries – tooth or bone decay

D. Cholecystitis - inflammation of the gallbladder

E. Cholecystectomy – surgical removal of gall bladder

F. Cirrhosis - liver disease from excessive alcohol consumption

G. Jaundice – results from blockage of common bile duct

H. Cleft Palate – an opening in the roof of the mouth when the two maxillae fail to unite

I. Constipation – infrequent bowel movements or hard to pass fecal material

J. Diarrhea – having 3 or more loose or watery stools in a day

K. Gastroenteritis - inflammation of the mucous membrane lining of stomach, & intestine. Treated w/IV fluids and prevented with hand-washing

L. Obesity – results from over-eating & lack of exercise and high BMI

M. Heartburn – prevention – avoid lying down 2-3 hours after eating

N. Colostomy – structure that compensates for the removal of large intestine

O. Peritonitis – spread of bacteria into the abdominal cavity

P. Gastroesphageal Reflux Disease - characterized by epigastric pain while lying down

Q. Hepatitis - inflammation of the liver caused by a virus

R. Hepatitis A – can get from contaminated food & water

S. Hepatitis B – can get from contaminated needle, healthcare workers can receive this vaccination

T. Colitis – inflammation of large intestine w/ constipation & diarrhea

U. Cholelithiasis – Gall Stones. s/s abd pain & nausea from high fat intake. Large stones require surgical removal. Small stones may pass on their own.

V. H Pylori – bacteria that can cause an ulcer

W. Pyloric Stenosis – symptom with projectile vomiting in babies

X. Pylorospasm – small quantities of stomach acid are regurgitated into the esophagus

Y. Diverticulosis – pouches or pockets in the mucosa of the digestive tract. Symptoms usually occurs when you’re 60 or older

Z. Irritable Bowel Syndrome

AA. Peptic Ulcers - sore or lesion on mucosal lining of stomach