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The Digestive System
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Parotid gland Mouth (oral cavity) Sublingual gland Salivary glands Tongue Submandibular gland Pharynx Esophagus Stomach Pancreas (Spleen) Liver Gallbladder Transverse colon Duodenum Descending colon Small intestine Jejunum Ascending colon Ileum Cecum Large intestine Sigmoid colon Rectum Vermiform appendix Anus Anal canal
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Intrinsic nerve plexuses
• Myenteric nerve plexus • Submucosal nerve plexus Glands in submucosa Mucosa • Epithelium • Lamina propria • Muscularis mucosae Submucosa Muscularis externa • Longitudinal muscle • Circular muscle Serosa Nerve • Epithelium Artery • Connective tissue Vein Gland in mucosa Lumen Lymphatic vessel Duct of gland outside alimentary canal Mucosa-associated lymphoid tissue Mesentery
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From mouth (a) Peristalsis: Adjacent segments of alimentary tract organs alternately contract and relax, which moves food along the tract distally. (b) Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving the food forward then backward. Food mixing and slow food propulsion occurs.
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Sagittal section of the oral cavity and pharynx
Soft palate Palatoglossal arch Uvula Hard palate Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Esophagus Trachea Sagittal section of the oral cavity and pharynx
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Enamel Dentin Crown Dentinal tubules Pulp cavity (contains blood vessels and nerves) Neck Gingiva (gum) Cementum Root Root canal Periodontal ligament Apical foramen Bone
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Upper lip Gingivae (gums) Superior labial frenulum Palatine raphe Palatoglossal arch Hard palate Palatopharyngeal arch Soft palate Uvula Posterior wall of oropharynx Palatine tonsil Tongue Sublingual fold with openings of sublingual ducts Lingual frenulum Opening of submandibular duct Gingivae (gums) Vestibule Inferior labial frenulum Lower lip
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Bolus of food Tongue Uvula Pharynx Bolus Epiglottis Epiglottis Glottis Trachea Bolus Esophagus Upper esophageal sphincter is contracted. During the buccal phase, the tongue presses against the hard palate, forcing the food bolus into the oropharynx where the involuntary phase begins. 1 The uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. 2 The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after entry. 3 Relaxed muscles 4 Food is moved through the esophagus to the stomach by peristalsis. Relaxed muscles 5 The gastroesophageal sphincter opens, and food enters the stomach. Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Gastroesophageal sphincter opens Stomach
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Bolus of food Tongue Pharynx Epiglottis Glottis Trachea
1 Upper esophageal sphincter is contracted. During the buccal phase, the tongue presses against the hard palate, forcing the food bolus into the oropharynx where the involuntary phase begins.
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Uvula Bolus Epiglottis Esophagus
2 The uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus.
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Bolus 3 The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after entry.
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Food is moved through the esophagus to the stomach by peristalsis.
Relaxed muscles Food is moved through the esophagus to the stomach by peristalsis. 4 Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Stomach
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The gastroesophageal sphincter opens, and food enters the stomach.
5 The gastroesophageal sphincter opens, and food enters the stomach. Relaxed muscles Gastroesophageal sphincter opens
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Cardia Fundus Esophagus Muscularis externa Serosa • Longitudinal layer • Circular layer Body • Oblique layer Lumen Lesser curvature Rugae of mucosa Greater curvature Pyloric canal Pyloric antrum Duodenum Pyloric sphincter (valve) at pylorus
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Liver Gallbladder Lesser omentum Stomach Duodenum Transverse colon Small intestine Cecum Urinary bladder
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Hepatic macrophages in sinusoid walls
Interlobular veins (to hepatic vein) Central vein Sinusoids Bile canaliculi Plates of hepatocytes Bile duct (receives bile from bile canaliculi) Fenestrated lining (endothelial cells) of sinusoids Bile duct Hepatic macrophages in sinusoid walls Portal venule Portal triad Portal arteriole Portal vein (c) Figure 23.25c
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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 Pancreas Gallbladder Jejunum Major duodenal papilla Main pancreatic duct and sphincter Hepatopancreatic ampulla and sphincter Duodenum Head of pancreas
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Right colic (hepatic) flexure Left colic (splenic) flexure Transverse mesocolon Transverse colon Epiploic appendages Superior mesenteric artery Descending colon Haustrum Ascending colon Cut edge of mesentery IIeum Teniae coli IIeocecal valve Sigmoid colon Cecum Vermiform appendix Rectum Anal canal External anal sphincter
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Carbon atom Phosphate Glucose Phase 1 Sugar Activation Glucose is
Electron trans- port chain and oxidative phosphorylation Glycolysis Krebs cycle Carbon atom Phosphate Glucose Phase 1 Sugar Activation Glucose is activated by phosphorylation and converted to fructose-1, 6-bisphosphate 2 ADP Fructose-1,6- bisphosphate
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Carbon atom Phosphate Fructose-1,6- bisphosphate Phase 2 Sugar
Electron trans- port chain and oxidative phosphorylation Glycolysis Krebs cycle Carbon atom Phosphate Fructose-1,6- bisphosphate Phase 2 Sugar Cleavage Fructose-1, 6-bisphosphate is cleaved into two 3-carbon fragments Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate
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Carbon atom Phosphate Dihydroxyacetone phosphate Glyceraldehyde
Glycolysis Electron trans- port chain and oxidative phosphorylation Krebs cycle Carbon atom Phosphate Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Phase 3 Sugar oxidation and formation of ATP The 3-carbon frag- ments are oxidized (by removal of hydrogen) and 4 ATP molecules are formed 2 NAD+ 4 ADP 2 NADH+H+ 2 Pyruvic acid 2 NADH+H+ 2 NAD+ 2 Lactic acid To Krebs cycle (aerobic pathway)
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Mitochondrion (matrix)
Cytosol Glycolysis Krebs cycle Electron trans- port chain and oxidative phosphorylation Pyruvic acid from glycolysis NAD+ CO2 Transitional phase NADH+H+ Carbon atom Acetyl CoA Mitochondrion (matrix) Inorganic phosphate Coenzyme A Oxaloacetic acid Citric acid (pickup molecule) NADH+H+ (initial reactant) NAD+ Malic acid Isocitric acid NAD+ Krebs cycle CO2 NADH+H+ Fumaric acid -Ketoglutaric acid CO2 FADH2 NAD+ Succinic acid Succinyl-CoA NADH+H+ FAD GTP GDP + ADP
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Chemical energy (high-energy electrons)
Electron transport chain and oxidative phosphorylation Glycolysis Krebs cycle Pyruvic acid Glucose Mitochondrial cristae Mitochondrion Cytosol Via oxidative phosphorylation Via substrate-level phosphorylation During glycolysis, each glucose molecule is broken down into two molecules of pyruvic acid in the cytosol. 1 The pyruvic acid then enters the mitochondrial matrix, where the Krebs cycle decomposes it to CO2. During glycolysis and the Krebs cycle, small amounts of ATP are formed by substrate- level phosphorylation. 2 Energy-rich electrons picked up by coenzymes are transferred to the elec- tron transport chain, built into the cristae membrane. The electron transport chain carries out oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration. 3
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(a glycolysis intermediate)
Lipids Lipase Glycerol Fatty acids H2O Coenzyme A Glyceraldehyde phosphate (a glycolysis intermediate) NAD+ NADH + H+ b Oxidation in the mito- chondria Glycolysis FAD Pyruvic acid FADH2 Cleavage enzyme snips off 2C fragments Acetyl CoA Krebs cycle
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Ketogenesis (in liver) Acetyl CoA bodies CO2 + H2O +
Glycolysis Glucose Stored fats in adipose tissue Glycerol Glyceraldehyde phosphate Triglycerides (neutral fats) Lipogenesis Dietary fats Fatty acids Pyruvic acid Certain amino acids b Ketone Ketogenesis (in liver) Acetyl CoA bodies CO2 + H2O + Steroids Electron transport Cholesterol Bile salts Krebs cycle Catabolic reactions Anabolic reactions
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Proteins Carbohydrates Fats Glycogen Proteins Triglycerides (neutral fats) Glucose Amino acids Glucose-6-phosphate Glycerol and fatty acids Glyceraldehyde phosphate Keto acids Pyruvic acid Lactic acid NH3 Acetyl CoA Ketone bodies Urea Krebs cycle Excreted in urine
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Food Pyramid
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