Chapter 22 (Digestive System) PDF

CHAPTER 23 The Digestive System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. Overview of the Digestive System Organs are divided into two groups The alimentary canal Mouth, pharynx, and esophagus Stomach, small intestine, and large intestine (colon) Acces...

CHAPTER 23 The Digestive System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. Overview of the Digestive System Organs are divided into two groups The alimentary canal Mouth, pharynx, and esophagus Stomach, small intestine, and large intestine (colon) Accessory digestive organs Teeth and tongue Gallbladder, salivary glands, liver, and pancreas The Alimentary Canal and Accessory Digestive Organs Mouth (oral cavity) Tongue Esophagus Liver Parotid gland Sublingual gland Salivary glands Submandibular gland Pharynx Stomach Pancreas (Spleen) Gallbladder Duodenum Small intestine Jejunum Ileum Anus Transverse colon Descending colon Ascending colon Cecum Large intestine Sigmoid colon Rectum Vermiform appendix Anal canal Digestive Processes Ingestion Propulsion Mechanical digestion Chemical digestion Absorption Defecation Peristalsis Major means of propulsion Adjacent segments of the alimentary canal relax and contract Segmentation Rhythmic local contractions of the intestine Mixes food with digestive juices The Peritoneal Cavity and Peritoneum Peritoneum – a serous membrane Visceral peritoneum – surrounds digestive organs Parietal peritoneum – lines the body wall Peritoneal cavity a slit-like potential space The Peritoneal Cavity and Peritoneum Mesentery – a double layer of peritoneum Holds organs in place Sites of fat storage Provides a route for circulatory vessels and nerves The Peritoneal Cavity and Peritoneum Retroperitoneal organs Behind the peritoneum Peritoneal organs Digestive organs that keep their mesentery Mesenteries Superficial view of the abdominal organs Liver Gallbladder Lesser omentum Stomach Duodenum Transverse colon Small intestine Cecum Urinary bladder (b) Mesenteries Greater omentum and transverse colon reflected Greater omentum Transverse colon Transverse mesocolon Descending colon Jejunum Mesentery Sigmoid mesocolon Sigmoid colon Ileum Mesenteries Sagittal section through Liver Lesser omentum the abdominopelvic cavity Pancreas Stomach Duodenum Transverse mesocolon Transverse colon Mesentery Greater omentum Jejunum Ileum Visceral peritoneum Parietal peritoneum Urinary bladder Rectum (d) Histology of the Alimentary Canal Wall Same four layers from esophagus to anus The mucosa – innermost layer Consists of: Epithelium Absorption/secretion Lamina propria Capillaries MALT Muscularis mucosae Local movement Histology of the Alimentary Canal Wall The submucosa – external to the mucosa Contains major blood and lymphatic vessels, nerve fibers Many elastic fibers The muscularis externa – external to the submucosa Two layers Circular muscularis Longitudinal muscularis Histology of the Alimentary Canal Wall The serosa – the outermost layer The visceral peritoneum Nerve plexuses Myenteric nerve plexus Submucosal nerve plexus Histology 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 Connective tissue Nerve Artery Gland in mucosa Vein Duct of gland outside Lymphatic vessel alimentary canal Lumen Mucosa-associated lymphoid tissue (a) Longitudinal and cross-sectional views through the small intestine Mesentery The Mouth and Associated Organs The mouth – oral cavity Mucosal layer Stratified squamous epithelium Lamina propria The lips and cheeks Formed from orbicularis oris and buccinator muscles, respectively Anatomy of the Mouth 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 Anatomy of the Mouth The labial frenulum Connects lips to gum The palate Forms the roof of the mouth Upper lip Gingivae (gums) Palatine raphe Hard palate Soft palate Superior labial frenulum Palatoglossal arch Palatopharyngeal arch Uvula Palatine tonsil Posterior wall of oropharynx Tongue Sublingual fold with openings of sublingual ducts Lingual frenulum Opening of submandibular duct Gingivae (gums) Vestibule Lower lip (b) Anterior view Inferior labial frenulum The Tongue Interlacing fascicles of skeletal muscle Grips food and repositions it Helps in speech production Intrinsic muscles – within the tongue Extrinsic muscles – external to the tongue The Superior Surface of the Tongue Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil Palatoglossal arch Terminal sulcus Vallate papilla Midline groove of tongue Fungiform papilla Filiform papilla The Teeth Deciduous teeth – 20 teeth First appear at 6 months of age Permanent teeth – 32 teeth Most erupt by the end of adolescence Dental formula—shorthand Way to indicate number and position of teeth 2I, 1C, 2P, 3M The Teeth Incisors Central (7 yr) Lateral (8 yr) Canine (eyetooth) (11 yr) Premolars (bicuspids) First premolar (11 yr) Second premolar (12–13 yr) Molars First molar (6–7 yr) Incisors Central (6–8 mo) Lateral (8–10 mo) Canine (eyetooth) (16–20 mo) Molars First molar (10–15 mo) Second molar (about 2 yr) (a) Second molar (12–13 yr) Deciduous (milk) teeth Third molar (wisdom tooth) (17–25 yr) Permanent teeth The Teeth Deciduous teeth (b) Permanent teeth Tooth Structure Enamel Dentin Crown Longitudinal section of tooth in alveolus Neck Dentinal tubules Pulp cavity (contains blood vessels and nerves) Gingiva (gum) Cementum Root Root canal Periodontal ligament Apical foramen Bone The Salivary Glands Produce saliva Compound tubuloalveolar glands Parotid Submandibular Sublingual Moistens mouth Dissolve food Taste Neutralize acid Oral bacteria Kill microorganisms Starch digestion The Pharynx Oropharynx and laryngopharynx Passages for air and food Lined with stratified squamous epithelium External muscle layer superior, middle, and inferior pharyngeal constrictors The Esophagus Gross anatomy – muscular tube Begins as continuation of pharynx Joins stomach inferior to diaphragm The Esophagus Microscopic anatomy Epithelium is stratified squamous epithelium When empty – mucosa and submucosa in longitudinal folds Mucous glands lubrication Muscularis externa – skeletal muscle first third of length Most external layer – adventitia The Stomach Temporary storage tank Food churned into chyme Protein digestion begins Secretes pepsin Functions under acidic conditions Absorption The Stomach Cardia Fundus Esophagus Serosa Muscularis externa Longitudinal layer Circular layer Oblique layer Body Lumen Lesser curvature Rugae of mucosa Greater curvature Duodenum (a) Pyloric canal Pyloric sphincter (valve) at pylorus Pyloric antrum The Stomach – Microscopic Anatomy The Small Intestine – Gross Anatomy Longest portion of the alimentary canal Site of most enzymatic digestion and absorption Three subdivisions Duodenum Jejunum Ileum The Duodenum and Related Organs Duodenum Receives digestive enzymes and bile Main pancreatic duct and common bile duct Right and left hepatic ducts of liver Common hepatic duct Cystic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Gallbladder Major duodenal papilla Hepatopancreatic ampulla and Duodenum sphincter Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas The Small Intestine – Microscopic Anatomy Modifications for absorption Circular folds (plicae circulares) Transverse ridges of mucosa and submucosa Villi Projections of the mucosa Covered with simple columnar epithelium Microvilli Further increase surface area for absorption Enzymes Histology of the Intestinal Wall Absorptive cells uptake digested nutrients Goblet cells secrete mucus that lubricates chyme Enteroendocrine cells secrete hormones Intestinal crypts epithelial cells secrete intestinal juice The Small Intestine – Structural Features Vein carrying blood to hepatic portal vessel Muscle layers Lumen Microvilli (brush border) Circular folds Absorptive cells Villi Lacteal Goblet cell Blood capillaries (a) (b) Mucosa associated lymphoid tissue Intestinal crypt Muscularis mucosae Duodenal gland Absorptive cells Vilus Goblet cells Villi Enteroendocrine cells Venule Lymphatic vessel Submucosa (c) Intestinal crypt The Large Intestine Digested residue contains few nutrients Small amount of digestion by bacteria Absorbs water and electrolytes Mass peristaltic movements force feces toward rectum Gross Anatomy of Large Intestine Cecum a blind pouch Vermiform appendix contains lymphoid tissue neutralizes pathogens Colon Divided into distinct segments Ascending, transverse, descending, and sigmoid colon Gross Anatomy of Large Intestine Rectum descends along the inferior half of the sacrum Anal Canal the last subdivision of the large intestine Gross Anatomy of Large Intestine Left colic (splenic) flexure Transverse colon Transverse mesocolon Epiploic appendages Superior mesenteric artery Descending colon Right colic (hepatic) flexure Haustrum Ascending colon IIeum Cut edge of mesentery IIeocecal valve Teniae coli Sigmoid colon Cecum Vermiform appendix Rectum Anal canal (a) External anal sphincter Microscopic Anatomy of Large Intestine Villi are absent Contains numerous goblet cells Lined with simple columnar epithelial tissue Epithelium changes at anal canal Becomes stratified squamous epithelium The Liver Largest gland in the body Performs over 500 functions Digestive function – bile production Performs many metabolic functions Visceral Surface of the Liver Hepatic portal vein Caudate lobe Hepatic veins Inferior vena cava Bare area Left lobe Ligamentum venosum in fissure Porta hepatis Right hepatic artery Left hepatic artery Right hepatic duct Left hepatic duct Cystic duct Common hepatic duct Gallbladder Fissure (b) Falciform ligament Ligamentum teres Right lobe Quadrate lobe Microscopic Anatomy of Liver (a) (b) Lobule Central vein Connective tissue septum 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 Hepatic macrophages in sinusoid walls Portal vein (c) Bile duct Portal venule Portal arteriole Portal triad The Gallbladder Stores and concentrates bile Expels bile into duodenum Bile emulsifies fats The Gallbladder Right and left hepatic ducts of liver Common hepatic duct Cystic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Gallbladder Major duodenal papilla Hepatopancreatic ampulla and Duodenum sphincter Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas The Pancreas Exocrine function Acinar cells make, store, and secrete pancreatic enzymes Enzymes are activated in the duodenum Endocrine function Produces insulin and glucagon Regulates blood sugar The Pancreas Right and left hepatic ducts of liver Common hepatic duct Cystic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Gallbladder Major duodenal papilla Hepatopancreatic ampulla and Duodenum sphincter Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas The Exocrine Pancreas: Histology Diaphragm Liver Spleen Pancreas Tail Body Head Duodenum Acinar cells (b) Photomicrograph of the exocrine acinar cells of the pancreas (160) Small duct Acinar cells (a) Dissection illustrating the pancreas and its relationship to surrounding organs in the superior abdomen Basement membrane Zymogen granules Rough endoplasmic reticulum (c) Illustration of the pancreatic acinar cells