Digestive System Physiology

Overall Steps Ingestion Secretion (of enzymes) Digestion Absorption Elimination

Mechanical Digestion Mastication- chewing Deglutination- swallowing Peristalsis & Segmentation

Chemical Digestion Enzymes work to digest food by hydrolysis The function with a negative feedback loop They are continually being eliminated The have specific pH under which they function Examples amylase, slightly acidic in saliva pepsin, highly acidic stomach

Digestive juices and Enzymes Chemical Digestion Location Digestive juices and Enzymes Substance Digested Mouth (Saliva) Amylase Starch (polysaccharides) Stomach (Gastric juice) Pepsin (protease) Proteins HCL Pancreatic juice Trypsin (protease) Lipases Fats, lipids Starch Intestinal Enzymes Peptidases Peptides, proteins Sucrase Sucrose Lactase Lactose Maltase Maltose

Digestive juices and Enzymes Chemical Digestion Location Digestive juices and Enzymes Substance Digested Mouth (Saliva) Amylase Starch (polysaccharides) Stomach (Gastric juice) Pepsin (protease) Proteins HCL Pancreatic juice Trypsin (protease) Lipases Fats, lipids Starch Intestinal Enzymes Peptidases Peptides, proteins Sucrase Sucrose Lactase Lactose Maltase Maltose

Macromolecule Digestion Starches(carbohydrates)monosaccharides(glucose) Proteins(polypeptides) amino acids Lipids  fatty acids, glycerols

Nutrient Digestion Nutrients include Carbohydrates Fats Minerals Proteins Vitamins include are made of are made using include include Simple Complex Amino acids Calcium Iron Fatty Acids Glycerol such as such as Sugars Starches Fat-soluble Water-soluble

Emulsification of Fats Micelle (fat droplet in water) Fats are insoluble in water and must be broken down into small droplets, or emulsified Lecithin and bile salts found in bile both act as emulsifying agents Micelles, tiny fat droplets are formed with lots of surface area Lipases from pancreatic enzymes can then breakdown fats

Digestive Secretions Saliva is mostly water but also contains digestive enzymes Mucus is a mixture of water and glycoproteins Chief cells in stomach secrete gastric enzymes(pepsin) Parietal cells secrete HCL (activates pepsin) and intrinsic factor into the stomach

Absorption Stomach 20% alcohol Aspirin Small Intestines Ca, Mg, Fe Glucose Vitamins, Na, K, B12 80% alcohol Fats H2O Colon Na, K Rectum Elimination of feces

Elimination Defecation is the process of eliminating feces Defection reflex is triggered by a filling of the rectum Constipation results of slow movement of feces causes a high rate of water absorption Diarrhea is caused by a rapid movement of stool that does not allow for absorption of water, can be fatal is severe and untreated

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Disorders of the Digestive System Gastroenteritis- inflammation of the stomach Anorexia- chronic loss of appetite Emesis- vomiting Nausea- unpleasant feeling before vomiting Diverticulosis- saclike pouches in the intestines that can become inflamed and infected.

Disorders of the Digestive System Ulcer- open wound or sore in the stomach or small intestine, Caused by H. pylori Irritable bowel syndrome, IBS- (spastic colon) stress causes diarrhea or constipation Cirrhosis- when the liver is damaged faster than it can regenerate it develops scar tissue.