Chap 19 The Digestive System Memmler’s A&P Chap 19 The Digestive System

Digestion p410 Every body cell needs a constant supply of nutrients. The food we eat is too large to enter the cells. It must be digested, or broken down into particles small enough to cross the plasma membrane, before it is usable.

Functions of digestive system p410 Digestion Absorption Elimination

Digestive system p410 The digestive tract Accessory organs Salivary glands Liver Gallbladder Pancreas

Wall of the digestive tract p410 Where absorption happens From innermost layer to outermost layer: Mucous membrane Submucosa Smooth muscle Serous membrane visceral peritoneum

The Peritoneum p411 Serous membrane that lines the wall of the abdominal cavity and covers the outer surface of abdominal organs Parietal peritoneum Visceral peritoneum

Digestive Tract p412 Mouth Pharynx Esophagus Stomach Small intestine Large intestine

Mouth p412 Oral cavity Functions Ingestion Mastication Saliva Deglutition

The Pharynx p413 The throat Uvula Epiglottis

The Esophagus p414 Smooth muscle Mucosa Lubricates food with mucus and moves it to the stomach with peristalsis Esophageal hiatus Hiatal hernia

The Stomach p414 3 smooth muscle layers for mixing food with digestive juices Rugae Gastric juice Hydrochloric acid Pepsin Chyme

The Small Intestine p414 Functions: digestion and absorption of nutrients Sections of small intestine Duodenum Jejunum Ileum Special features Villi Lacteals

Wall of small intestine 411, 416

The Large Intestine p415 Functions: Sections: Reabsorption of water Storage of food wastes Elimination Growth of Vit K and some B vitamins by normal flora Sections: Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anus

Accessory organs p417 Liver Gallbladder Pancreas Salivary glands

The liver p418 Manufactures bile Storage glycogen Modification of fats Stores some vitamins and iron Formation plasma proteins Destruction of old RBCs Synthesis of urea Detoxification of blood

The Gallbladder p418 Stores bile Secretes bile into the duodenum Function of bile: emulsification of fat Secretes bile into the duodenum

The Pancreas p418 Produces enzymes that digest fats, proteins, carbohydrates Releases sodium bicarbonate to neutralize chyme Secretes into the duodenum

Enzymes and digestion p418 Catalysts to speed digestion Pancreatic amylase: splits carbohydrates into monosaccharides Trypsin: splits proteins into amino acids Lipase: splits fats into glycerol and fatty acids

The role of water p419 Hydrolysis: splitting by means of water. 7 liters of water a day are secreted into the digestive tract in addition to what is eaten or consumed by drinking Water dilutes food and digestive juices for easier passage through the digestive tract.

Absorption p420 Absorption site: villi in the mucosa of the small intestine Each villus contains blood vessels and a lacteal After absorption, nutrients go to the liver via the hepatic portal system

Control of digestion p420 Regulation is by the Autonomic Nervous System Parasympathetic nervous system promotes digestion and peristalsis Sympathetic nervous system inhibits peristalsis, digestion, and mucus production

Hunger and appetite p421 Hunger Appetite Anorexia desire for food because nutrition is needed to fuel cells Appetite desire for food without relationship to the need for food Anorexia loss of appetite

Digestive system disorders p422 Peritonitis Gastroesophageal reflux disease (GERD) Nausea Vomiting Diarrhea Flatus Peptic ulcer Appendicitis Constipation

Constipation p424 Hard stools or difficulty with defecation

Cancer p424 Colon or rectal cancer can be detected by colonoscopy. Occult blood

Liver diseases p425-426 Cirrhosis: active liver cells are replaced by scar tissue Jaundice: damage to liver can cause bile pigment to accumulate in the blood Stool becomes light clay colored Skin and sclera become yellow Hepatitis: inflammation of liver (can be caused by drugs, alcohol, or infection.

Disease of gallbladder p426 Gallstones: cholelithiasis Inflammation of gallbladder: cholecystitis Surgical removal of gallbladder: cholecystectomy

Aging and digestive system p426 Receptors for taste and smell deteriorate, loss of appetite Decrease in saliva Poor gag reflex Tooth loss Poor absorption Slowed peristalsis Constipation