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Digestive System

Part 2 and Physiology of the Digestive System   Major of and absorption  2–4 m long; from pyloric to  Subdivisions  Anatomy and Physiology of the Digestive System  Small intestine  Structural modifications  Villi  Intestinal  Mucosa 

Parotid (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland

Esophagus Pancreas () Gallbladder Duodenum Small Jejunum intestine Ileum Large intestine Vermiform

Figure 23.1 carrying blood to hepatic portal vessel

Muscle layers Villi

(a)

Figure 23.22a Microvilli (brush border)

Absorptive cells

Lacteal Blood Vilus Mucosa associated lymphoid tissue Enteroendocrine Intestinal crypt cells Muscularis Venule mucosae Duodenal gland Submucosa (b)

Figure 23.22b Microvilli

Absorptive cell (b)

Figure 23.3b Anatomy and Physiology of the Digestive System  Chemical digestion in the small intestine  Food entering SI = partially digested  Intestinal juice  , mucous  Crypt cells produce lysozyme

Microvilli (brush border)

Absorptive cells

Lacteal Goblet cell Blood Villus capillaries Mucosa associated lymphoid tissue Enteroendocrine Intestinal crypt cells Muscularis Venule mucosae Lymphatic vessel Duodenal gland Submucosa (b)

Figure 23.22b Anatomy and Physiology of the Digestive System  Chemical digestion in the small intestine   Amylase o Carbohydates  Lipase o Fats  Trypsinogen, chymotrypsinogen, carboxypeptidase o Activated to digest protein  bicarbonate  Neutralize stomach

Stomach

Pancreas

Epithelial cells

Membrane-bound enteropeptidase Trypsinogen Trypsin (inactive) Chymotrypsinogen Chymotrypsin (inactive) Procarboxypeptidase Carboxypeptidase (inactive)

Figure 23.27 Anatomy and Physiology of the Digestive System  Chemical digestion in the small intestine   Emilsify lipids  Disaccharides and peptidases  Protective mucous secreted as well Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct

Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas

Figure 23.21 Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Pancreas  Gallbladder

Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Largest internal surface area of any body organ  Blood supply  Hepatic  Hepatic-portal vein  Hepatic vein

Inferior vena cava (not part of hepatic portal system) Gastric Hepatic veins Spleen

Inferior vena cava Liver Splenic vein

Right gastroepiploic Hepatic portal vein vein Inferior mesenteric vein Superior mesenteric vein Small intestine

Rectum

(c) The hepatic portal circulation.

Copyright © 2010 Pearson Education, Inc. Figure 19.29c Interlobular veins (to hepatic vein) Central vein

Sinusoids Plates of Bile canaliculi hepatocytes

Bile duct (receives bile from bile canaliculi) Fenestrated lining (endothelial cells) of sinusoids

Bile duct Hepatic Portal venule Portal triad macrophages Portal arteriole in sinusoid walls Portal vein

(c)

Copyright © 2010 Pearson Education, Inc. Figure 23.25c Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Microscopic compartments = lobules  Lined by hepatocytes = screen blood o Store o Manage toxins

Sternum Bare area Nipple Falciform Liver ligament Left lobe of liver Right lobe of liver

Round ligament Gallbladder (ligamentum (a) teres)

Figure 23.24a (a) Lobule (b) Central vein Connective tissue septum

Copyright © 2010 Pearson Education, Inc. Figure 23.25a, b Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Hepatocyte functions  Process blood borne nutrients  Store fat-soluble  Perform detoxification  Produce ~900 ml bile per day  Glucose is stored as glycogen

Cystic, Hepatic and Bile ducts Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct

Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas

Copyright © 2010 Pearson Education, Inc. Figure 23.21 Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Bile  Yellow-green, alkaline solution  Bile o Cholesterol derivatives that function in fat emulsification and absorption  o Pigment formed from heme  Metabolized to form urobilinogen → stercobilin  Lack of bile = grayish stools with fatty streaks (Acholic )

Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Other functions  Makes heparin and other plasma proteins  Stores vitamins, minerals and lipid soluble toxins  Stores nutrients  Catabolizes nitrogenous wastes Anatomy and Physiology of the Digestive System  Accessory digestive organs  Liver  Gallbladder  Thin-walled muscular sac on the ventral surface of the liver  Stores and concentrates bile by absorbing its water and ions  Releases bile via the cystic duct o Flows into the bile duct

Anatomy and Physiology of the Digestive System  Accessory digestive organs  Pancreas  Function

 Delivers digestive fluids and NaHCO3 to duodenum via pancreatic duct  Tissue types  Endocrine o Islets of Langerhans → insulin and glucagon  Exocrine o Acinar tissue → pancreatic juice

Parotid gland Mouth (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland

Esophagus Pharynx Stomach Pancreas Liver (Spleen) Gallbladder Transverse colon Duodenum Descending colon Small Jejunum Ascending colon intestine Ileum Cecum Large Sigmoid colon intestine Rectum Vermiform appendix Anus Anal canal

Figure 23.1 Anatomy and Physiology of the Digestive System  Accessory digestive organs  Pancreas  Secretion mediated by hormones  o Released in response to acid o Stimulates release of base  o Released when protein and fat enter intestine o Stimulates the release of bile and pancreatic juice

Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct

Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas

Figure 23.21 Small duct Acinar cells

Basement membrane Zymogen granules

Rough (a)

Figure 23.26a Slide 1

1 enter- 4 Bile salts and, ing duodenum to a lesser extent, causes release of secretin cholecystokinin transported via bloodstream (CCK) and stimulate liver to secretin from produce bile duodenal more rapidly. enteroendocrine cells. 5 CCK (via bloodstream) 2 CCK (red causes dots) and gallbladder to secretin (yellow contract and dots) enter the hepatopancreatic bloodstream. sphincter to relax; bile enters duodenum. 3 CCK induces secretion of 6 During -rich cephalic and gastric phases, pancreatic juice. vagal Secretin causes stimulation secretion of causes weak – HCO3 -rich contractions of pancreatic juice. gallbladder.

Figure 23.28 Anatomy and Physiology of the Digestive System  Large intestine  About 1.5 meters in length in a cadaver (SI about 6m long)  Functions  Vitamins, water, and are reclaimed  Propulsion of feces toward the anus  Colon is not essential for life

Right colic Left colic (hepatic) (splenic) flexure flexure Transverse Transverse mesocolon colon Epiploic Superior appendages mesenteric artery Descending colon Ascending Cut edge of colon IIeum Teniae coli IIeocecal valve Sigmoid Cecum colon Vermiform appendix Rectum

Anal canal (a)

Figure 23.29a Anatomy and Physiology of the Digestive System

 Regions  Cecum  Colon  Rectum  Anal canal

Anatomy and Physiology of the Digestive System

 Regions  Cecum  Blind pouch  Appendix attaches to this area   Immune function

Anatomy and Physiology of the Digestive System

 Regions  Colon  Ascending  Retroperitoneal  Transverse  Anchored via mesocolons ()  Descending  Retroperitoneal  Sigmoid  Anchored via mesocolons (mesenteries)

Greater omentum

Transverse colon

Transverse mesocolon

Descending colon Jejunum Mesentery Sigmoid mesocolon Sigmoid colon

Ileum

(c)

Figure 23.30c Liver Lesser omentum Pancreas Stomach Transverse mesocolon

Duodenum Transverse colon Mesentery Jejunum Ileum Visceral Parietal peritoneum Rectum (d)

Figure 23.30d Anatomy and Physiology of the Digestive System

 Regions  Rectum  Rectal valves stop feces from being passed with gas  Anal canal  Last segment of the large intestine  (involuntary)  Spinal reflex arcs  External anal sphincter  (voluntary)

Rectal valve Rectum Hemorrhoidal veins muscle Anal canal

External anal sphincter Internal anal sphincter Anus (b)

Figure 23.29b Anatomy and Physiology of the Digestive System

 Defectation  Mass movements force feces into rectum  Distension initiates spinal reflex  Parasympathetic signals  Stimulate contraction of the sigmoid colon and rectum  Relax the internal anal sphincter  Conscious control allows relaxation of external anal sphincter  Valsalva’s maneuver

Impulses from 1 Distension, or stretch, of the cerebral cortex rectal walls due to movement of feces into the rectum (conscious stimulates stretch receptors control) Sensory there. The receptors transmit signals along afferent fibers to nerve fibers neurons. Voluntary motor 2 A spinal reflex is initiated in nerve to external which parasympathetic motor anal sphincter Sigmoid (efferent) fibers stimulate colon contraction of the rectal walls and relaxation of the internal anal sphincter. Stretch receptors in wall Rectum Involuntary motor nerve External anal (parasympathetic division) sphincter Internal anal sphincter (skeletal muscle) (smooth muscle) 3 If it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so that feces may pass.

Figure 23.31 Questions?