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Digestive System 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 1 Introduction Every cell requires a constant energy source Ingested food is complex Modification is needed to utilize Introduction Digestive system is a tube Gastrointestinal tract Specialized regions Mouth Pharynx Esophagus Stomach Small intestine Large intestine 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 Copyright © 2010 Pearson Education, Inc. Figure 23.1 Introduction Digestive processes 1. Ingestion 2. Propulsion 3. Mechanical digestion 4. Chemical digestion 5. Absorption 6. Defecation Ingestion Food Mechanical digestion Pharynx • Chewing (mouth) Esophagus • Churning (stomach) Propulsion • Segmentation • Swallowing (small intestine) (oropharynx) Chemical • Peristalsis digestion Stomach (esophagus, stomach, small intestine, large intestine) Absorption Lymph vessel Small intestine Large Blood intestine vessel Mainly H2O Feces Defecation Anus Copyright © 2010 Pearson Education, Inc. Figure 23.2 Introduction Histology of the alimentary canal Four basic layers (tunics) Tunica mucosa Protection and absorption Epithelium and connective tissue Tunica submucosa Connective tissue Tunica muscularis (externa) Double layer of muscle Tunica serosa Visceral peritoneum Single layer of epithelium Introduction Peritoneum Parietal peritoneum Mesentery Visceral peritoneum Omentum 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 Nerve Serosa Artery • Epithelium Vein • Connective tissue Gland in mucosa Lumen Lymphatic Duct of gland outside Mucosa-associated Mesentery vessel alimentary canal lymphoid tissue Copyright © 2010 Pearson Education, Inc. Figure 23.6 Abdominopelvic Peritoneum cavity Vertebra Dorsal mesentery Parietal peritoneum Ventral mesentery Visceral peritoneum Peritoneal Alimentary Liver cavity canal organ (a) Schematic cross sections of abdominal cavity illustrate the peritoneums and mesenteries. Copyright © 2010 Pearson Education, Inc. Figure 23.5a Omentia and Mesentery Liver Gallbladder Lesser omentum Stomach Duodenum Transverse colon Small intestine Cecum Urinary bladder (b) Copyright © 2010 Pearson Education, Inc. Figure 23.30b Digestive System Mouth Cheek, palate, tongue Opens into oropharynx Salivary glands Soft palate Palatoglossal arch Uvula Hard palate Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Esophagus Trachea (a) Sagittal section of the oral cavity and pharynx Figure 23.7a Salivary glands secrete about 1250 ml of saliva per day! Tongue Teeth Parotid Ducts of gland sublingual gland Parotid duct Masseter muscle Frenulum of tongue Body of Sublingual mandible (cut) gland Posterior belly Mylohyoid of digastric muscle (cut) muscle Submandibular Anterior belly of Submandibular duct digastric muscle gland Mucous Serous cells (a) cells forming demilunes (b) Copyright © 2010 Pearson Education, Inc. Figure 23.9 Digestive System Teeth Held in place by periodontal ligaments Gingiva covers bone 2 dentitions Deciduous Permanent Teeth 20 deciduous 32 permanent Incisors Incisors Central (6–8 mo) Central (7 yr) Lateral (8 yr) Lateral (8–10 mo) Canine (eyetooth) Canine (eyetooth) (11 yr) (16–20 mo) Premolars Molars (bicuspids) First molar First premolar (10–15 mo) Deciduous (11 yr) Second molar (milk) teeth Second premolar (about 2 yr) (12–13 yr) Molars First molar (6–7 yr) Second molar (12–13 yr) Third molar Permanent (wisdom tooth) teeth (a) (17–25 yr) Copyright © 2010 Pearson Education, Inc. Figure 23.10a Digestive System Teeth Anatomy Crown covered by enamel Pulp cavity Dentin Roots Function Break down food Mixed with saliva to form bolus Enamel Dentin Crown Dentinal tubules Pulp cavity (contains blood vessels and Neck nerves) Gingiva (gum) Cementum Root canal Root Periodontal ligament Apical foramen Bone Copyright © 2010 Pearson Education, Inc. Figure 23.11 Digestive System Esophagus Pharynx to stomach Moves bolus to stomach Peristalsis Cardiac (gastroesophageal) sphincter Heartburn Histology Mucosa Stratified squamous epithelium Abundant mucous glands Serosa Connective tissue 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 Relaxed muscles 4 Food is moved through Circular muscles the esophagus to the contract stomach by peristalsis. Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Stomach Figure 23.13, step 4 Relaxed 5 The gastroesophageal muscles sphincter opens, and food enters the stomach. Gastroesophageal sphincter opens Figure 23.13, step 5 Mucosa (contains a stratified squamous epithelium) Submucosa (areolar connective tissue) Lumen Muscularis externa • Longitudinal layer • Circular layer Adventitia (fibrous connective tissue) (a) Figure 23.12a simple columnar epithelium Mucosa (contains a stratified squamous epithelium) Esophagus stomach junction (b) Copyright © 2010 Pearson Education, Inc. Figure 23.12b Cardia Fundus Esophagus Muscularis externa Serosa • Longitudinal layer • Circular layer Body • Oblique layer Lesser Lumen curvature Rugae of mucosa Greater curvature Pyloric Pyloric Duodenum canal antrum Pyloric sphincter (a) (valve) at pylorus Figure 23.14a Digestive System Stomach From cardiac orifice to pyloric sphincter Rugae Greater curvature Convex lateral surface Greater omentum Lesser curvature Concave medial surface Lesser omentum Falciform ligament Liver Gallbladder Spleen Stomach Ligamentum teres Greater omentum Small intestine Cecum (a) Figure 23.30a Liver Gallbladder Lesser omentum Stomach Duodenum Transverse colon Small intestine Cecum Urinary bladder (b) Figure 23.30b Digestive System Stomach Four tunics Muscularis Additional layer of muscle in an oblique orientation Three layers of smooth muscle Cardia Fundus Esophagus Muscularis externa Serosa • Longitudinal layer • Circular layer Body • Oblique layer Lesser Lumen curvature Rugae of mucosa Greater curvature Pyloric Pyloric Duodenum canal antrum Pyloric sphincter (a) (valve) at pylorus Figure 23.14a Digestive System Stomach Four tunics Mucosa Gastric glands o Mucous cells = Mucous o Parietal cells = Intrinsic factor and HCL o Zymogenic (chief) cells = Pepsinogen o Enteroendocrine cells = Gastrin and cholecystokinin Surface epithelium Mucosa Mucosa contains gastric glands Lamina propria Muscularis mucosae Submucosa (contains submucosal plexus) Oblique layer Muscularis externa Circular layer (contains myenteric Longitudinal plexus) layer Serosa Stomach wall (a) Layers of the stomach wall (l.s.) Figure 23.15a Gastric pits Surface epithelium (mucous cells) Gastric pit Mucous neck cells Parietal cell Chief cell Gastric gland Enteroendocrine cell (b) Enlarged view of gastric pits and gastric glands Figure 23.15b Pepsinogen Pepsin HCl Mitochondria Parietal cell Chief (Zymogenic) cell Enteroendocrine cell (c) Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland Figure 23.15c Digestive System Chemical digestion in the stomach Protein catabolism → polypeptides Secretions HCl Pepsinogen → pepsin HCl pH 1.5–3.5 Denatures protein in food Kills many bacteria Intrinsic factor Required for absorption of vitamin B12 in small intestine Pepsinogen Pepsin HCl Mitochondria Parietal cell Chief (Zymogenic) cell Enteroendocrine cell (c) Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland Figure 23.15c Digestive System Chemical digestion in the stomach Enteroendocrine cells Secrete hormone like substances Gastrin Cholecystokinin o Actually produced by enteroendocrine cells in the duodenum Digestive System Chemical digestion in the stomach Chyme Product of stomach digestion Prevention of autodigestion Mucous Gastritis Peptic ulcers Gastric ulcers Duodenal ulcers Bacteria Mucosa layer of stomach (a) A gastric ulcer lesion (b) H. pylori bacteria Figure 23.16 Digestive System Control of gastric secretions Neural control Vagus nerve Enteric nervous system Hormonal control Gastrin Digestive System Control of gastric secretions Stimulatory and inhibitory events occur in three phases 1. Cephalic 2. Gastric 3. Intestinal Stimulatory events Inhibitory events Cephalic 1 Sight and thought Cerebral cortex Lack of Cerebral 1 Loss of phase of food Conditioned reflex stimulatory cortex appetite, impulses to depression 2 Stimulation of Hypothalamus Vagus parasym- taste and smell and medulla nerve pathetic receptors oblongata center 1 Stomach Vagovagal Medulla Vagus Gastrin G cells 1 Excessive distension reflexes nerve secretion acidity activates declines (pH <2) stretch in stomach Gastric receptors Local Overrides Sympathetic 2 Emotional phase reflexes
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