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Gastrointestinal Physiology
Tanveer Raza MD MS MBBS
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Introduction Gastrointestinal system
Portal through which nutritive substances, vitamins, minerals, and fluids enter the body Tanveer Raza MD MS MBBS
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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
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Introduction Alimentary tract Digestive tract Tanveer Raza MD MS MBBS
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Introduction Alimentary tract Mouth to Anus Tanveer Raza MD MS MBBS
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Introduction Gastrointestinal tract Stomach to Anus
Tanveer Raza MD MS MBBS
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Physiologic Anatomy
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Parts of digestive system
Mouth or buccal cavity with tongue Oropharynx Oesophagus Stomach Small Intestine Large Intestine Tanveer Raza MD MS MBBS
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Enteric Nervous System
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Enteric Nervous System
Tanveer Raza MD MS MBBS
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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
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Enteric Nervous System
Connected to and influenced by Sympathetic Nervous System Parasympathetic Nervous System Receives sensory nerve endings Tanveer Raza MD MS MBBS
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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 JEJUNUM Cross section
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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
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Autonomic Nervous System
Sympathetic Spinal Cord T5-L2 Postganglionic neuron Celiac ganglion Mesenteric ganglion Inhibits GI activity Tanveer Raza MD MS MBBS
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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
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Thank You
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