Fig. 15-2, Vander’s Human Physiology, 11th edition (2008)

Actions of the digestive system

• secretion• digestion • absorption • motility

Internal vs. external environment

Overview of digestive tract function

Figure 21.6, p. 667

Components of the digestive system

GI TRACTmouth and pharynx

esophagus

stomach

small intestineduodenumjejunumileum

large intestine

rectum

ACCESSORY GLANDSsalivary glands

livergallbladderpancreas

Figure 21.1a, p. 656

Structure of the stomach

Figure 21.1c, p. 656

Structure of the small intestine

Figure 21.1d, p. 656

Digestive secretions entering the duodenum

pancreas: • digestive enzymes• bicarbonateliver: • bile salts (solubilize fats)• bicarbonate(gallbladder stores bile)

Duodenal papilla: outlet for pancreatic duct andcommon bile duct

Figure 4.109, Gray’s Anatomy for Students

Anatomy of the bile ducts

Adapted from Figure 4.111, Gray’s Anatomy for Students

cystic bile duct hepatic bile duct

common bile duct

Anatomy of the large intestine

From Figure 21.21, p. 686

Structures to identify on the large model of the digestive tract:

hard palatesoft palatetonguesalivary glandsepiglottisesophagusstomach

greater curvaturelesser curvaturefundusbodyantrum (pylorus)pyloric sphincter (pyloric valve)

pancreaspancreatic duct

liver

common bile ductsmall intestine

duodenumduodenal papillajejunum/ileum

large intestinececum

ileocecal valveappendixascending colontransverse colondescending colonsigmoid colonrectum

anal canalexternal anal sphincter

Blood flow to the liver

Structures to identify on the model of the liver with gallbladder and duodenum

duodenumjejunumgallbladderbile ducts

hepatic bile ductcystic bile ductcommon bile duct

pancreaspancreatic duct

hepatic portal veincommon hepatic artery

Structures to identify on the model of the pancreas with spleen and part of the duodenum

duodenumplicae circularesduodenal papilla

jejunumpancreas

pancreatic ductcommon bile ducthepatic portal veincommon hepatic artery

Clinical example: bariatric surgery

bariatric surgery à weight loss surgery

two most common procedures• sleeve gastrectomy• Roux-en-Y gastric bypass

treatment for type 2 diabetes mellitus: remission rates following surgery

Sleeve gastrectomy

“restrictive”—smaller stomach reduces food intake↓ ghrelin secretionghrelinàhormone secreted by stomach cells that increases appetite

Roux-en-Y gastric bypass (RYGB)

Configuration of GI tract after RYGB

Endocrine changes after RYGB

àreduction or removal of stomach decreases ghrelin secretion

àbypass of stomach and upper intestine changes secretion of an unknown hormone

àfaster delivery of chyme to distal small intestine increases secretion of GLP-1 and PYY

• secreted by endocrine cells in small intestine epithelium

• secretion stimulated by glucose, fats in small intestine

• increase glucose-dependent insulin secretion

• incretin-based drugs used in the treatment of type 2 diabetes mellitus

• GLP-1 also has effects on CNS controlof appetite

GLP-1 is an incretin

Secretion and Action of Incretins

incretins: GIP, GLP-1

*look for a web page about bariatric surgery by next week