23 The Digestive System: Part A

Two groups of organs Digestive System 1. Alimentary canal (gastrointestinal or GI tract) Mouth to anus Digests food and absorbs fragments Mouth, pharynx, esophagus, stomach, small intestine, and large intestine © 2013 Pearson Education, Inc.

2. Accessory digestive organs Digestive System 2. Accessory digestive organs Teeth, tongue, gallbladder Digestive glands Salivary glands Liver Pancreas © 2013 Pearson Education, Inc.

Mouth (oral cavity) Parotid gland Sublingual gland Salivary Tongue* Figure 23.1 Alimentary canal and related accessory digestive organs. Mouth (oral cavity) Parotid gland 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 Appendix Anus Anal canal © 2013 Pearson Education, Inc.

Six essential activities Digestive Processes Six essential activities Ingestion Propulsion Mechanical breakdown Digestion Absorption Defecation © 2013 Pearson Education, Inc.

Ingestion Food Mechanical breakdown Pharynx Esophagus Chewing (mouth) Figure 23.2 Gastrointestinal tract activities. Ingestion Food Mechanical breakdown Pharynx Esophagus Chewing (mouth) Churning (stomach) Propulsion Segmentation (small intestine) • Swallowing (oropharynx) • Peristalsis (esophagus, stomach, small intestine, large intestine) Digestion Stomach Absorption Lymph vessel Small intestine Blood vessel Large intestine Mainly H2O Feces Anus Defecation © 2013 Pearson Education, Inc.

Figure 23.3 Peristalsis and segmentation. From mouth Peristalsis: Adjacent segments of alimentary tract organs alternately contract and relax, moving food along the tract distally. Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving food forward then backward. Food mixing and slow food propulsion occur. © 2013 Pearson Education, Inc.

Homeostatic Imbalance Peritonitis Inflammation of peritoneum Causes by e.g., piercing abdominal wound, perforating ulcer, ruptured appendix Peritoneal coverings stick together, localizing infection Dangerous and lethal if widespread Treated with debris removal and antibiotics © 2013 Pearson Education, Inc.

Histology of the Alimentary Canal Four basic layers (tunics) Mucosa Submucosa Muscularis externa Serosa © 2013 Pearson Education, Inc.

Myenteric nerve plexus Figure 23.6 Basic structure of the alimentary canal. 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 Epithelium (mesothelium) Nerve Connective tissue Artery Gland in mucosa Lumen Vein Duct of gland outside alimentary canal Mucosa-associated lymphoid tissue Mesentery Lymphatic vessel © 2013 Pearson Education, Inc.

Sagittal section of the oral cavity and pharynx Figure 23.7a Anatomy of the oral cavity (mouth). 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 © 2013 Pearson Education, Inc.

Upper lip Gingivae (gums) Superior labial frenulum Palatine raphe Figure 23.7b Anatomy of the oral cavity (mouth). Upper lip Gingivae (gums) Superior labial frenulum Palatine raphe Palatoglossal arch Hard palate Palatopharyngeal arch Soft palate Uvula Palatine tonsil Posterior wall of oropharynx Tongue Sublingual fold with openings of sublingual ducts Lingual frenulum Opening of Submandibular duct Gingivae (gums) Oral vestibule Inferior labial frenulum Lower lip Anterior view © 2013 Pearson Education, Inc.

Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil Figure 23.8 Dorsal surface of the tongue, and the tonsils. Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil Palatoglossal arch Terminal sulcus Foliate papillae Vallate papilla Medial sulcus of the tongue Dorsum of tongue Fungiform papilla Filiform papilla © 2013 Pearson Education, Inc.

Salivary Glands Major salivary glands Minor salivary glands Produce most saliva; lie outside oral cavity Parotid Submandibular Sublingual Minor salivary glands Scattered throughout oral cavity; augment slightly © 2013 Pearson Education, Inc.

Salivary Glands Function of saliva Cleanses mouth Dissolves food chemicals for taste Moistens food; compacts into bolus Begins breakdown of starch with enzymes © 2013 Pearson Education, Inc.

Figure 23.9 The salivary glands. Tongue Teeth Parotid gland Ducts of sublingual gland Parotid duct Masseter muscle Frenulum of tongue Body of mandible (cut) Sublingual gland Posterior belly of digastric muscle Mylohyoid muscle (cut) Submandibular duct Anterior belly of digastric muscle Submandibular gland Mucous cells Serous cells forming demilunes © 2013 Pearson Education, Inc.

97–99.5% water, slightly acidic Composition of Saliva 97–99.5% water, slightly acidic Electrolytes—Na+, K+, Cl–, PO4 2–, HCO3– Salivary amylase and lingual lipase Mucin Metabolic wastes—urea and uric acid Lysozyme, IgA, defensins, and a cyanide compound protect against microorganisms PLAY Animation: Rotating head © 2013 Pearson Education, Inc.