Gastrointestinal Physiology Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction Gastrointestinal system Portal through which nutritive substances, vitamins, minerals, and fluids enter the body Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction Digestion Absorption Complex food particles are broken down to simple form (absorbable units) Absorption Products of digestion and the vitamins, minerals and water cross the mucosa and enter the lymph or the blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction Alimentary tract Digestive tract Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction Alimentary tract Mouth to Anus Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction Gastrointestinal tract Stomach to Anus Tanveer Raza MD MS MBBS razajju2@yahoo.com

Physiologic Anatomy

Parts of digestive system Mouth or buccal cavity with tongue Oropharynx Oesophagus Stomach Small Intestine Large Intestine Tanveer Raza MD MS MBBS razajju2@yahoo.com

Parts of digestive system Mouth or buccal cavity with tongue Oropharynx Oesophagus Stomach Small Intestine Duodenum Jejunum Ileum Large Intestine Tanveer Raza MD MS MBBS razajju2@yahoo.com

Parts of digestive system Mouth or buccal cavity with tongue Oropharynx Oesophagus Stomach Small Intestine Large Intestine Caecum Ascending Colon Transverse Colon DescendingColon Sigmoid Colon Rectum Anal Canal Tanveer Raza MD MS MBBS razajju2@yahoo.com

Parts of digestive system Accessory parts Teeth Salivary glands Liver Pancreas Gall Bladder Other digestive glands in the wall of the digestive tract Tanveer Raza MD MS MBBS razajju2@yahoo.com

Parts of digestive system Accessory parts Teeth Salivary glands Major Salivary Glands Parotid Submandibular Sublingual Minor Salivary Glands Liver Pancreas Gall Bladder Other digestive glands in the wall of the digestive tract Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall From outer surface inward Serosa Muscular layer Longitudinal Circular Submucosa & Mucosa Sparse bundles of smooth muscle fibers (mucosal muscle) lie in the deeper layers of mucosa Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall Muscular layer Arranged in bundles Within each bundle Fibers connected through gap junctions Low resistance movement of ions Electrical signals travel easily Each muscle layer functions as a syncytium Excitation of one layer excites the other Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall Resting membrane potential Voltage can change to different levels At rest Depolarization Hyperpolarization less negative -56mv more negative Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall Resting membrane potential Depolarization of membrane Less negative More excitable Factors Stretching of muscle Stimulation by Acetylcholine (Ach) Stimulation by Parasympathetic nerves Stimulation by several GI hormones Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall Resting membrane potential Hyperpolarization of membrane More negative Less excitable Factors Effect of norepinephrine or epinephrine Stimulation of Sympathetic nerves Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System

Enteric Nervous System Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System In GIT wall, from Esophagus to Anus Two plexuses Myenteric or Auerbach’s plexus Submucosal plexus or Meissner’s plexus Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System Connected to and influenced by Sympathetic Nervous System Parasympathetic Nervous System Receives sensory nerve endings Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System Myenteric or Auerbach’s plexus Submucosal plexus or Meissner’s plexus Outer plexus Inner plexus Between longitudinal and circular muscle layers In submucosa Controls GI movements Controls GI secretion and Local blood flow Tanveer Raza MD MS MBBS razajju2@yahoo.com JEJUNUM Cross section

Enteric Nervous System Neurotransmitters Acetylcholine (Ach) Most often excites GI activity Norepinephrine (NE) Almost always inhibits GI activity Adenosine triphosphate Serotonin Dopamine Cholecystokinin Substance P Vasoactive intestinal polypeptide Somatostatin Leu-enkephalin Metenkephalin Bombesin Tanveer Raza MD MS MBBS razajju2@yahoo.com

Autonomic Nervous System Sympathetic Spinal Cord T5-L2 Postganglionic neuron Celiac ganglion Mesenteric ganglion Inhibits GI activity Tanveer Raza MD MS MBBS razajju2@yahoo.com

Autonomic Nervous System Parasympathetic Cranial: Vagus Sacral: Pelvic Sacral 2nd, 3rd & 4th Postganglionic neurons Myenteric & Submucosal plexuses Effect Mainly Excitatory Tanveer Raza MD MS MBBS razajju2@yahoo.com

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