Accessory Organs to the Digestive Tract Pages 473

Accessory Organs to the Digestive Tract Pages 473 -476 and 494 -497

Accessory Digestive Organs � Teeth – mechanical digestion through mastication � Salivary glands – parotid, submandibular, sublingual ◦ Secrete saliva, a bicarbonate rich juice ◦ chemical digestion via secretions of enzymes �Salivary amylase begins starch digestion ◦ Saliva also contains lysozyme and antibodies to inhibit bacteria � Pancreas � Liver � Gallbladder © 2015 Pearson Education, Inc.

Figure 14. 1 The human digestive system: Alimentary canal and accessory organs. Mouth (oral cavity) Tongue Parotid gland Sublingual gland Submandibular gland Salivary glands Pharynx Esophagus Stomach Pancreas Liver Gallbladder Small intestine Anus Duodenum Jejunum Ileum Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Appendix Anal canal Large intestine

Pancreas Produces digestive enzymes that break down all categories of food ◦ releases into the duodenum via the hepatopancreatic ampulla ◦ Alkaline (bicarbonate) fluid with these enzymes neutralizes the acidic chyme Produces hormones: (negative feedback loops) ◦ Insulin – reduces blood glucose ◦ Glucagon – raises blood glucose © 2015 Pearson Education, Inc.

Liver largest gland in the body; consists of four lobes can regenerate if part is damaged/removed suspended from the diaphragm and abdominal wall by the falciform ligament Connected to the gallbladder via the common hepatic duct © 2015 Pearson Education, Inc.

The Central Role of the Liver in Metabolism the body’s key metabolic organ � After the GI tract, blood travels to liver via the hepatic � portal circulation � Roles in digestion: ◦ ◦ Manufactures bile and blood clotting proteins Detoxifies drugs and alcohol Degrades hormones Produces cholesterol: �Low Density Lipoproteins: transport cholesterol/lipids to the cells; large amounts circulating can build up in vessel lumen (BAD GUYS) �High Density Lipoproetins: transport cholesterol from the cells to the liver for disposal in bile (GOOD GUYS) © 2015 Pearson Education, Inc.

The Liver and Blood Glucose � The liver manages blood glucose levels through: ◦ Glycogenesis: “Building glycogen” ◦ Glucose is removed from the blood (via insulin) ◦ Converted to glycogen and stored in the liver ◦ Glycogenolysis: “Splitting glycogen” ◦ Glucose is released into the blood (via glucagon) ◦ Glycogen is “split” and put back into blood ◦ Gluconeogenesis: “Building glycogen from other sources” ◦ The Liver can make glucose using fats and amino acids

Bile produced by the liver a yellow-green, watery solution containing: ◦ Bile salts and bile pigments (mostly bilirubin from the breakdown of hemoglobin) ◦ Cholesterol, phospholipids, and electrolytes leaves the liver via the common hepatic duct ◦ enters duodenum through the bile duct Function: emulsify fats ◦ Chemically breaks down large fat globules © 2015 Pearson Education, Inc.

Gallbladder Sac found in shallow fossa of liver When no digestion is occurring: ◦ bile backs up the cystic duct for storage in the gallbladder Water is removed at this time to concentrate it Gallstones ◦ crystallized cholesterol that can cause blockages Result from removal of too much water Prolonged storage in gallbladder © 2015 Pearson Education, Inc.

Figure 14. 6 The duodenum of the small intestine and related organs. Right and left hepatic ducts from liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Pancreas Gallbladder Jejunum Duodenal papilla Hepatopancreatic ampulla and sphincter Main pancreatic duct and sphincter Duodenum