Gastrointestinal Tract in Health: Basic Anatomy and Physiology- Esophagus and Stomach Gastrointestinal Tract Esophagus Liver Stomach Gallbladder Large intestine Pancreas Small intestine Digestive Organs Digestive Tract Digestion • Breakdown of food into smaller components • Allows the body to absorb the nutrients and minerals in food • Necessary for growth, metabolism, body maintenance, and reproduction Mechanisms of Digestion Mechanical Chemical • Mastication • Saliva • Peristalsis • Gastric acid • Segmentation • Bile • Pancreatic enzymes Process of Digestion 1. Motility • Muscular movements of the GI tract • Peristalsis – propels food forward via contractions • Segmentation – mixes food with simultaneous contraction Motility Peristalsis Segmentation Process of Digestion 1. Motility - Muscular movements of the GI tract - Peristalsis – propels food forward via contractions - Segmentation – mixes food with simultaneous contractions 2. Secretion - Release of acid/enzymes to mix with food 3. Absorption - Nutrients and water absorbed by GI tract into blood Journey Through Digestion Mouth Esophagus Stomach Liver Small Intestine Pancreas Gallbladder Large Intestine Mouth • Chewing mechanically breaks down food • Presence of food stimulates saliva production • Tongue helps to arrange food bolus for swallowing Saliva • Produced by salivary glands in mouth Parotid gland • Moistens food to assist in swallowing Sublingual gland • Amylase – initiates carbohydrate digestion Submandibular gland • Antibacterial effect Gastrointestinal Tract Esophagus Liver Stomach Gallbladder Large intestine Pancreas Small intestine Digestive Organs Digestive Tract Esophagus • Hollow muscular tube connecting the mouth to the stomach • 18-26 cm in length • Transports saliva and food from the mouth to the stomach Esophageal Wall Layers Cross-Section Mucosa Submucosa Circular muscle Longitudinal muscle Mucosa Stratified squamous epithelium Musculature Inner Circular Outer Muscle Longitudinal • Contracts Muscle esophagus • Shortens • Moves food bolus esophagus down esophagus Musculature • Upper 1/3 of esophagus - Skeletal muscle Skeletal - “voluntary muscle” muscle • Lower 2/3 of esophagus Smooth - Smooth muscle muscle - “involuntary muscle” Gastroesophageal Junction Esophagus Squamocolumnar junction (Z-line) Diaphragm Stomach Gastroesophageal Junction • Lower esophageal sphincter - Located where esophagus meets the stomach Diaphragm - Relaxes with swallows Esophagus Z-line - Contracts to prevent backflow of stomach acid and food back into the esophagus Stomach Gastroesophageal Junction Esophagus Stomach Esophagus Stomach Endoscopy Pathology Stomach • J-shaped reservoir of digestive tract • Food mixes in acid and enzymes that breaks down food • Small amounts of partially digested food released into the small intestine Parts of the Stomach Fundus Lower esophageal sphincter Cardia Body Lesser curvature Greater curvature Pylorus Antrum Stomach Mucosa Rugae Rugae (or gastric folds) Stomach Mucosa Rugae Columnar epithelium Stomach Musculature 3 Muscle Layers Longitudinal layer Circular layer Oblique layer Stomach Layers Surface Gastric epithelium pit Parietal cell Mucosa Gastric Enteroendocrine gland Lamina cell propria Chief cell Muscularis mucosa Submucosa Oblique layer Muscularis Circular layer externa Longitudinal layer Serosa Endoscopic Ultrasound Mucosa (M) Mucularis mucosa Submucosa (SM) Muscularis propria (MP) Serosa (S) Stomach Acid Physiology Parietal cell H+/K+ H2R ATPase Acid Histamine ECL cell -ve G cell Gastrin Gastrointestinal Tract in Health Basic Anatomy and Physiology- Esophagus and Stomach Questions? Gastrointestinal Tract in Health: Basic Anatomy and Physiology- Small and Large Intestine Gastrointestinal Tract Esophagus Liver Stomach Gallbladder Large intestine Pancreas Small intestine Digestive Organs Digestive Tract Small Intestine • 5-25 feet long • Stomach contents empty into small intestine • Important functions - Digestion of food - Absorption of nutrients Small Intestine Duodenum Jejunum Ileum Duodenum 1. Bulb Pylorus Major papilla • First section and 4. Ascending 2. Descending shortest segment - ~ 12 inches in length • 4 sections 3. Horizontal Jejunum Duodenum Common bile duct Gallbladder Pancreas Duodenum Jejunum • Mid-portion of small intestine • ~8-10 feet in length Jejunum • No clear demarcation between the jejunum and ileum Jejunum Columnar epithelial cell Mucous cell • Function: Nerve absorption Lacteal Capillary of nutrients network Lamina propria Arteriole Lymphatic vessel Venule Villi Endoscopy Endoscopy Electron microscope Ileum • Final section of small intestine • 8-15 feet in length • Connects to the colon at the ileocecal valve Ileum Ileum • Function: absorption of nutrients Villi - Anything not absorbed by jejunum - Vitamin B12 - Bile salts Large Intestine • Last part of the gastrointestinal tract • ~4-5 feet in length • Function - Absorption of water and salt - Elimination of solid wastes Large Intestine Transverse colon Ascending colon Descending colon Rectum Sigmoid colon Anus Colon Motility Reverse peristalsis Mass Peristalsis peristalsis Rectum and Anus Rectum Rectum • Retains stool until appropriate time Sigmoid Colon to release Rectum Anus External anal sphincter • Internal anal sphincter Internal anal sphincter - Involuntary control Dentate line • External anal sphincter - Voluntary control Anus Defecation At Rest Straining Pubis Puborectalis External anal Anorectal Angle Anorectal Angle sphincter Internal anal sphincter Descent of the pelvic floor Gastrointestinal Tract in Health Basic Anatomy and Physiology- Small and Large Intestine Questions? Gastrointestinal Tract in Health: Basic Anatomy and Physiology- Liver, Gallbladder and Pancreas Gastrointestinal Tract Esophagus Liver Stomach Gallbladder Large intestine Pancreas Small intestine Digestive Organs Digestive Tract Liver • Vital organ • Right upper abdomen • 3.2-3.7 pounds • 2 blood supplies - Hepatic artery - Portal vein Liver Anatomy Hepatic veins Left lobe Right lobe Hepatic artery Portal vein Bile duct Biliary Anatomy Intrahepatic bile ducts Cystic duct Common hepatic duct Common Gall bladder bile duct Ampulla Function of Liver and Bile • Liver produces bile • Bile stored in the gallbladder • Bile released in response to a fatty meal via CCK • Absorption of fat and fat- soluble vitamins (A,D,E,K) Liver Function • Synthesize - Clotting Factors - Glucose - Proteins - Cholesterol Liver Function • Storage - Glucose - glycogen - Vitamins A, D, B12 and K - Iron - Copper Liver Function • Breakdown - Medications - Drugs - Alcohol - Toxins Pancreas • Small glandular organ • ~8 inches long • Embryology - Starts as two separate buds that join together Pancreas Anatomy Minor pancreatic duct Major pancreatic duct Tail Body Ampulla Neck Head Uncinate Pancreatic Function Exocrine (GI) Endocrine (non-GI) • Produce and secrete enzymes that break down: - Fats - Carbohydrates - Proteins • Neutralize acid by releasing bicarbonate into duodenum Secretin Pancreas stimulated Bicarbonate neutralizes to secrete bicarbonate acid in duodenum Acid from stomach enters duodenum Secretin stimulates pancreas Duodenum Bloodstream releases secretin into blood Pancreatic Function Exocrine (GI) Endocrine (non-GI) • Produce and secrete enzymes • Produce hormones that act that break down: on other parts of the body - Fats - Insulin - Carbohydrates - Glucagon - Proteins - Somatostatin • Neutralize acid by releasing bicarbonate into duodenum GI Tract in Health • Breakdown and absorption of food and nutrients • Absorption of water and minerals • Movement of contents via coordinated motility • Storage of waste until elimination Gastrointestinal Tract in Health Basic Anatomy and Physiology- Liver, Gallbladder and Pancreas Questions? .