Gastrointestinal Physiology - Weebly

Gastrointestinal Physiology - Weebly

Gastrointestinal Physiology Tanveer Raza MD MS MBBS [email protected] Introduction Gastrointestinal system Portal through which nutritive substances, vitamins, minerals, and fluids enter the body Tanveer Raza MD MS MBBS [email protected]

Introduction Digestion 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 [email protected] Introduction Alimentary Digestive tract tract Tanveer Raza MD MS MBBS [email protected] Introduction Alimentary tract Mouth

to Anus Tanveer Raza MD MS MBBS [email protected] Introduction Gastrointestinal tract Stomach to Anus Tanveer Raza MD MS MBBS [email protected] Physiologic Anatomy

Parts of digestive system Mouth or buccal cavity with tongue Oropharynx Oesophagus Stomach

Small Intestine Large Intestine Tanveer Raza MD MS MBBS [email protected] 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 [email protected] 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 [email protected] 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 [email protected] Parts of digestive system Accessory parts Teeth Salivary glands Major Salivary Glands Parotid Submandibular Sublingual

Minor Salivary Glands Liver Pancreas Gall Bladder Tanveer Raza MD MS Other digestive glands in the wall of the digestive tract MBBS [email protected] 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 [email protected] 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 [email protected] Cross Section of Intestinal wall Resting

membrane potential Voltage can change to different levels less negative Depolarization -56mv At rest more negative Hyperpolarization Tanveer Raza MD MS MBBS [email protected] Cross Section of Intestinal wall Resting

membrane potential Depolarization of membrane Less negative More excitable Factors I. Stretching of muscle II. Stimulation by Acetylcholine (Ach) III. Stimulation by Parasympathetic nerves IV. Stimulation by several GI hormones Tanveer Raza MD MS MBBS

[email protected] 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 [email protected] Enteric Nervous System Enteric Nervous System Tanveer Raza MD MS MBBS [email protected] Enteric Nervous System In GIT wall, from Esophagus to Anus

Two plexuses 1. Myenteric or Auerbachs plexus 2. Submucosal plexus or Meissners plexus Tanveer Raza MD MS MBBS [email protected] Enteric Nervous System Connected to and influenced by

Sympathetic Nervous System Parasympathetic Nervous System Receives sensory nerve endings Tanveer Raza MD MS MBBS [email protected] Enteric Nervous System Myenteric or Auerbachs plexus Submucosal plexus or

Meissners plexus Outer plexus Inner plexus Between longitudinal and circular muscle layers In submucosa Controls GI movements Controls GI secretion and Local blood flow

JEJUNUM Cross section Tanveer Raza MD MS MBBS [email protected] 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 [email protected] Autonomic Nervous System

Sympathetic Spinal Cord T5-L2 Postganglionic Celiac ganglion Mesenteric neuron ganglion Inhibits GI activity

Tanveer Raza MD MS MBBS [email protected] 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 [email protected] Thank You

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