Digestive System Anatomy

Digestive System Anatomy  Digestive tract   Alimentary tract or canal GI tract Primarily glands Mouth or oral cavity Pharynx Esophagus Stomach Small intestine Large intestine Anus   Accessory organs  Regions        Digestive Tract Histology Digestive System Regulation  Nervous regulation  Involves enteric nervous system   Chemical regulation  Production of hormones  Types of neurons: sensory, motor, interneurons Gastrin, secretin  Coordinates peristalsis and regulates local reflexes  Production of paracrine chemicals   Histamine Help local reflexes in ENS control digestive environments as pH levels Peritoneum and Mesenteries  Peritoneum    Visceral: Covers organs Parietal: Covers interior surface of body wall Retroperitoneal: Behind peritoneum as kidneys, pancreas, duodenum Routes which vessels and nerves pass from body wall to organs Greater omentum Lesser omentum  Mesenteries    Oral Cavity  Mouth or oral cavity   Vestibule: Space between lips or cheeks and alveolar processes Oral cavity proper   Lips (labia) and cheeks Palate: Oral cavity roof  Hard and soft   Palatine tonsils Tongue: Involved in speech, taste, mastication, swallowing Teeth  Two sets   Primary, deciduous, milk: Childhood Permanent or secondary: Adult (32) Incisors, canine, premolar and molars  Types  Tooth structure: Salivary Glands  Produce saliva    Prevents bacterial infection Lubrication Contains salivary amylase  Breaks down starch  Three pairs    Parotid: Largest Submandibular Sublingual: Smallest Pharynx and Esophagus   Esophagus   Pharynx    Nasopharynx Oropharynx: Transmits food normally Laryngopharynx: Transmits food normally Transports food from pharynx to stomach Passes through esophageal hiatus (opening) of diaphragm and ends at stomach  Hiatal hernia Upper Lower  Sphincters   Deglutition (Swallowing)  Three phases  Voluntary  Bolus of food moved by tongue from oral cavity to pharynx  Pharyngeal Reflex: Upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus  Esophageal  Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx Phases of Deglutition (Swallowing) Functions    Ingestion: Introduction of food into stomach Mastication: Chewing Propulsion   Deglutition: Swallowing Peristalsis: Moves material through digestive tract Stomach Anatomy:  Openings   Gastroesophageal: To esophagus Pyloric: To duodenum  Regions     Cardiac Fundus Body Pyloric Stomach Histology:  Layers   Serosa or visceral peritoneum: Outermost Muscularis: Three layers    Outer longitudinal Middle circular Inner oblique   Submucosa Mucosa Stomach Histology   Rugae: Folds in stomach when empty Gastric pits: Openings for gastric glands  Contain cells      Surface mucous: Mucus Mucous neck: Mucus Parietal: Hydrochloric acid and intrinsic factor Chief: Pepsinogen Endocrine: Regulatory hormones Hydrochloric Acid Production Phases of Gastric Secretion Movements in Stomach Small Intestine   Site of greatest amount of digestion and absorption Divisions    Duodenum Jejunum Ileum: Peyer’s patches or lymph nodules Circular folds or plicae circulares, villi, lacteal, microvilli  Modifications   Cells of mucosa  Absorptive, goblet, granular, endocrine Small Intestine Secretions   Mucus  Protects against digestive enzymes and stomach acids Disaccharidases: Break down disaccharides to monosaccharides Peptidases: Hydrolyze peptide bonds Nucleases: Break down nucleic acids Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa Digestive enzymes     Duodenal glands  Duodenum and Pancreas Duodenum Anatomy and Histology Liver  Lobes   Major: Left and right Minor: Caudate and quadrate Common hepatic Cystic   Ducts   From gallbladder  Common bile  Joins pancreatic duct at hepatopancreatic ampulla Functions of the Liver      Bile production  Salts emulsify fats, contain pigments as bilirubin Glycogen, fat, vitamins, copper and iron Storage  Nutrient interconversion Detoxification  Hepatocytes remove ammonia and convert to urea Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria Albumins, fibrinogen, globulins, heparin, clotting factors Phagocytosis   Synthesis  Blood and Bile Flow Duct System Gallbladder     Bile is stored and concentrated Stimulated by cholecystokinin and vegal stimulation Dumps into small intestine Production of gallstones possible  Drastic dieting with rapid weight loss Pancreas  Anatomy   Secretions  Endocrine  Pancreatic juice (exocrine)     Pancreatic islets produce insulin and glucagon Acini produce digestive enzymes  Exocrine     Regions: Head, body, tail Trypsin Chymotrypsin Carboxypeptidase Pancreatic amylase Pancreatic lipases Enzymes that reduce DNA and ribonucleic acid Bicarbonate Ion Production Gastric hormones: Movement in small intestine:      Mixing: Segmental contraction that occurs in small intestine Secretion: Lubricate, liquefy, digest Digestion: Mechanical and chemical Absorption: Movement from tract into circulation or lymph Elimination: Waste products removed from body Large Intestine:    Extends from ileocecal junction to anus Consists of cecum, colon, rectum, anal canal Movements sluggish (18-24 hours) Large Intestine     Cecum  Blind sac, vermiform appendix attached Ascending, transverse, descending, sigmoid Colon  Rectum  Straight muscular tube Internal anal sphincter (smooth muscle) External anal sphincter (skeletal muscle) Anal canal    Hemorrhoids: Vein enlargement or inflammation Secretions of Large Intestine  Mucus provides protection  Parasympathetic stimulation increases rate of goblet cell secretion  Pumps Exchange of bicarbonate ions for chloride ions  Exchange of sodium ions for hydrogen ions   Bacterial actions produce gases called flatus Histology of Large Intestine Movement in Large Intestine  Mass movements  Common after meals Gastrocolic: Initiated by stomach Duodenocolic: Initiated by duodenum Distension of the rectal wall by feces Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration  Local reflexes in enteric plexus     Defecation reflex  Defecation  Reflexes in Colon and Rectum: Digestion, Absorption, Transport  Digestion  Breakdown of food molecules for absorption into circulation Mechanical: Breaks large food particles to small  Chemical: Breaking of covalent bonds by digestive enzymes   Absorption and transport  Molecules are moved out of digestive tract and into circulation for distribution throughout body Liver Histology portal triad Figure 24.20a, b 3. Architecture of the Hepatic Parenchyma The hepatic lobule is the structural unit of the liver. Portal vein Bile duct Sinusoids Central vein Portal area Hepatic artery Liver cells (Hepatocytes) Bile …each day around 600 ml of bile is produced…        Bile acid Phospholipids Cholesterol Bilirubin Waste products Electrolytes Mucin Functions of the Liver      Bile production  Salts emulsify fats, contain pigments as bilirubin Glycogen, fat, vitamins, copper and iron Storage  Nutrient interconversion Detoxification  Hepatocytes remove ammonia and convert to urea Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria Albumins, fibrinogen, globulins, heparin, clotting factors Phagocytosis   Synthesis  Exocrine Pancreas – Enzymes        Trypsinogen Chymotrysinogen Carboxypeptidases Pro-elastase Phospholipase pancreatic lipase Pancreatic amylase Bicarbonate Ion Production Lipoproteins  Types  Chylomicrons  Enter lymph   VLDL LDL  Transports cholesterol to cells Transports cholesterol from cells to liver  HDL  Water and Ions:  Water  Can move in either direction across wall of small intestine depending on osmotic gradients Sodium, potassium, calcium, magnesium, phosphate are actively transported  Ions  Effects of Aging   Decrease in mucus layer, connective tissue, muscles and secretions Increased susceptibility to infections and toxic agents  Ulcerations and cancers