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Home , Anal columns, Anal sinuses, External anal sphincter, Haustrum (anatomy), Pectinate line

Business  Reminder: No class Monday (Memorial Day)  Midterm 2 is Tuesday 5/28/13  Optional review session tomorrow @ 5pm  Homework due in Lab 1. PreLab 8 (1pt) 2. Replace a Missing Assignment (4 pts)  Homework page 17 Digestive System

Part 2 Digestive System   Major organ of digestion and absorption  2 - 4 m long; from pyloric to  Subdivisions  Digestive System  Small intestine  Structural modifications  Villi  Intestinal glands  Mucosa 

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

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

Figure 23.1 carrying blood to hepatic portal vessel

Muscle layers Lumen Villi

(a)

Figure 23.22a Microvilli (brush border)

Absorptive cells

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

Figure 23.22b Microvilli

Absorptive cell (b)

Figure 23.3b Digestive System  Chemical digestion in the small intestine  Food entering SI = partially digested  Intestinal juice  Water, 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 Digestive System  Chemical digestion in the small intestine  Pancreatic juice  Enzymes  Amylase o Carbohydrates  Lipase o Fats  Trypsinogen, chymotrypsinogen, carboxypeptidase o Activated to digest protein  Sodium bicarbonate  Neutralize stomach acid

Stomach

Pancreas

Epithelial cells

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

Figure 23.27 Digestive System  Chemical digestion in the small intestine  Bile  Emilsify lipids  Disaccharidases 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 Digestive System  Accessory digestive organs  Liver  Pancreas  Gallbladder

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 ) 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 Digestive System  Accessory digestive organs  Liver  Microscopic compartments = lobules  Lined by hepatocytes = screen blood o Store nutrients 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 Digestive System  Accessory digestive organs  Liver  Hepatocyte functions  Process blood borne nutrients  Store fat-soluble vitamins  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 Digestive System  Accessory digestive organs  Liver  Bile  Yellow-green, alkaline solution  Bile salts o Cholesterol derivatives that function in fat emulsification & absorption  Bilirubin o Pigment formed from heme o Metabolized to form urobilinogen → stercobilin  Lack of bile = grayish stools with fatty streaks (acholic feces)

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 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

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 Digestive System  Accessory digestive organs  Pancreas  Secretion mediated by hormones  Secretin o Released in response to acid o Stimulates release of base from pancreas o Also stimulates release of pancreatic secretions and bile  Cholecystokinin o Released when protein and fat enter intestine o Stimulates the release of pancreatic secretions and bile

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 endoplasmic reticulum (a)

Figure 23.26a Digestive System  Large intestine  About 1.5 meters in length in a cadaver (SI about 6m long)  Functions  Vitamins, water, and electrolytes 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 mesentery IIeum Teniae coli IIeocecal valve Sigmoid Cecum colon Vermiform appendix Rectum

Anal canal (a)

Figure 23.29a Digestive System

 Regions  Cecum  Colon  Rectum  Anal canal

Digestive System

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

Digestive System

 Regions  Colon  Ascending  Retroperitoneal  Transverse  Anchored via mesocolons (mesenteries)  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 Greater omentum Jejunum Ileum Visceral peritoneum Parietal peritoneum Rectum (d)

Figure 23.30d Digestive System

 Regions  Rectum  Rectal valves stop feces from being passed with gas  Anal canal  Last segment of the large intestine   Smooth muscle (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 Digestive System

 Mass movements force feces into rectum  Distension initiates spinal defecation 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 fibers spinal cord 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