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?