Digestive System Notes. Biology - Mrs. Kaye

Transcription

1 Digestive System Notes Biology - Mrs. Kaye

2 Digestion There are two kinds of digestion: Mechanical digestion - the physical breakdown of food into smaller pieces to increase surface area for more enzyme action. Chemical digestion - a chemical reaction is created when enzymes break food down into smaller molecules to be absorbed.

3 Gastrointestinal Tract (GI Tract) Gastrointestinal Tract (GI Tract) - a series of hollow organs joined in a long, twisting tube from the mouth to the anus; consists of the mouth, esophagus, stomach, small intestine, large intestine, and anus.

4 The Mouth Teeth break up food into smaller pieces and increases surface area of food; mechanical digestion. Saliva softens food and secretes salivary amylase that begins to break down starch into disaccharides; chemical digestion.

5 The Mouth Epiglottis - the flap that blocks the trachea (windpipe) to prevent food and water from entering.

6 The Esophagus Esophagus - a muscular tube connecting the pharynx (throat) with the stomach. About 8 inches long. Runs behind the trachea (windpipe) and heart, and in front of the spine.

7 The Esophagus

8 The Esophagus Peristalsis - the involuntary constriction and relaxation of the muscles of the esophagus, creating wavelike movements that push the contents forward.

9 The Esophagus Medical conditions regarding the esophagus include heartburn, gastroesophageal reflux disease (GERD), achalasia, and esophageal cancer.

10 The Esophagus A Nissen fundoplication is performed to treat gastroesophageal reflux disease (GERD). The upper part of the stomach is wrapped around the lower end of the esophagus and stitched in placed, reinforcing the function of the lower esophageal sphincter.

11 The Esophagus

12 The Stomach Stomach - a muscular organ located on the left side of the upper abdomen. The stomach receives food from the esophagus. As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. Mechanical digestion occurs in the stomach as the muscles contract to churn food.

13 The Stomach Chemical digestion also occurs here. Hydrochloric acid (HCl) has a ph of 1-2 which is used to activate enzymes, dissolve minerals, and kill bacteria. Pepsin - the chief digestive enzyme in the stomach which breaks down complex proteins into smaller polypeptides and amino acids.

14 The Stomach Mucus lubricates and protects the stomach lining from acids (very acidic environment). Medical conditions regarding the stomach include gastric ulcer, dyspepsia, gastritis, and stomach cancer. Gastric ulcers occur when the bacterium H. pylori infects the stomach, causing the HCl in the stomach to destroy the mucus lining the stomach.

15 The Stomach

16 Sphincters Sphincter - A thick ring of muscle that opens and closes to allow food in and out of the stomach. Lower esophageal sphincter - lies between the esophagus and the stomach; also called the cardiac sphincter. Pyloric sphincter - lies between the stomach and the small intestine.

17 Sphincters Medical conditions regarding the lower esophageal sphincter include gastroesophageal reflux disease (GERD). If the lower esophageal sphincter does not close all the way, or opens too often, the acid produced by your stomach can move up into your esophagus.

18 The Small Intestine Small intestine - a large organ that absorbs most the nutrients from what we eat and drink. Villi - small, finger-like projections that contain capillaries and line the walls of the small intestine to increase surface area for the absorption of water and nutrients.

19 The Small Intestine The small intestine receives secretions from the gallbladder and the pancreas to complete digestion of all macromolecules.

20 The Small Intestine

21 The Liver Liver - a large, meaty organ that sits on the right side of the belly that filters and detoxifies blood, stores glycogen, and secretes bile. The liver is not apart of the digestive tract. Food does not enter this organ.

22 The Liver Bile - a fluid that aids in digestion; is secreted by the liver and stored in the gallbladder. Bile is secreted into the small intestine and breaks fat up into tiny droplets.

23 The Liver

24 The Pancreas Pancreas - a large gland behind the stomach that secretes digestive enzymes into the small intestine. The pancreas is not apart of the digestive tract. The pancreas secretes pancreatic fluid containing digestive enzymes into the small intestine and neutralizes fluids from stomach. These fluids balance out the low ph of stomach acid.

25 The Large Intestine Large intestine - a large organ in which water is absorbed and the remaining waste is stored as feces before being removed. Eliminates feces from anus through anal sphincter.

26 The Large Intestine

27 Important Digestive Enzymes Enzyme Location(s) Breakdown Pepsin Trypsin Amylase Lipase Stomach Small intestine Mouth and small intestine Small intestine Proteins into amino acids Proteins into amino acids Starch into simple sugars Fat into fatty acids and glycerol

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