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BRIEF Physiology of Gastrointestinal System For the students of physio therapy

Dr. GUL MUHAMMAD, KGMC, PESHAWAR. BRIEF Physiology of Gastrointestinal System For the students of physio therapy. General Functions. Provides the body with water, electrolytes and nutrients Requires:. Movement of food Break down the food to absorbable materials

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BRIEF Physiology of Gastrointestinal System For the students of physio therapy

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  1. Dr. GUL MUHAMMAD, KGMC, PESHAWAR BRIEF Physiology of Gastrointestinal SystemFor the students of physio therapy www.doctorsherwan.com

  2. General Functions • Provides the body with water, electrolytes and nutrients Requires: • Movement of food • Break down the food to absorbable materials • Digestion of food by different juices • Absorption of digestive materials • Neural control www.doctorsherwan.com

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  4. SMOOTH MUSCLE OF GIT TWO SMOOTH MUSCLE CLASSIFICATIONS • Unitary type - Contract spontaneously in the absence of neural or hormonal influence but in response to stretch (such as in stomach and intestine) - Cells are electrically coupled via gap junctions • Multiunit type - Do not contract in response to stretch or without neural input (such as in esophagus & gall bladder) www.doctorsherwan.com

  5. SMOOTH MUSCLE OF G.I.T • Phasic contractions - periodic contractions followed by relaxation; such as in gastric antrum, small intestine and esophagus • Tonic contractions - maintained contraction without relaxation; such as lower esoghageal, ileocecal and internal anal sphincter - not associated with slow waves www.doctorsherwan.com

  6. SMOOTH MUSCLE OF G.I.T • Tonic contractions (continued): - Caused by: • Continuous repetitive spike potential • Hormonal effects • Continuous entery of Ca www.doctorsherwan.com

  7. The Musculature of the Digestive Tract • Two main muscle layers: • Longitudinal muscle layer • Circular muscle layer • Oblique muscle layer (stomach only) www.doctorsherwan.com

  8. The Musculature of the Digestive Tract • Longitudinal Muscle: • Contraction shortens the segment of the intestine and expands the lumen • Innervated by ENS, mainly by excitatory motor neuron • Ca influx from out side is important www.doctorsherwan.com

  9. The Musculature of the Digestive Tract • Circular muscle: • Thicker and more powerful than longitudinal • Contraction reduces the diameter of the lumen and increases its length • Innervated by ENS, both excitatory and inhibitory motor neurons • More gap junctions than in longitudinal muscle • Intracellular release of Ca is more important www.doctorsherwan.com

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  14. Electromechanical & Pharmacomechanical Coupling Trigger Contractions in GI Muscles • Depolarization opens the voltage-gated Ca channels (electromechanical coupling) • Ligands open the ligand-gated Ca channels (pharmacomechanical coupling) www.doctorsherwan.com

  15. Gastrointestinal Peptides • Hormones - endocrine cells - via portal circulation and liver - e.g., gastrin, CCK, secretin and GIP • Paracrines - endocrine cells - thru diffusion at the same tissue - e.g., somatostatin (mucosa), to inhibit gastric H secretion • Neurocrines - neuronal cells in GI tract - e.g., VIP, GRP and Enkephalins www.doctorsherwan.com

  16. Slow Waves & Action potentials are Forms of Electrical Activity in GI Muscles • Factors that depolarize the membrane: • Stretching of the muscle • Ach • Parasympathetic stimulation • Hormonal stimulation • Factors that hyperpolarize the membrane: • Norepinephrine • Sympathetic stimulation www.doctorsherwan.com

  17. CONTROL OF DIGESTIVE FUNCTIONSBY NERVOUS SYSTEM • Autonomic nervous system (ANS) is divided into - Parasympathetic - Sympathetic - ENS (Enteric Nervous System) www.doctorsherwan.com

  18. CONTROL OF DIGESTIVE FUNCTIONSBY NERVOUS SYSTEM • Parasympathetic Nerves: • Located in brain stem & sacral region • Projection to the G.I. are preganglionic efferents • Vagus & pelvic nerves • Vagus nerves synapse with neurons of ENS in esophagus, stomach, small intestine, colon, gall bladder & pancreas • Pelvic nerves synapse with ENS in large intestine • Neurotransmitter is Ach www.doctorsherwan.com

  19. CONTROL OF DIGESTIVE FUNCTIONSBY NERVOUS SYSTEM • Sympathetic nerves: • Located in thoracic & lumbar regions • Neurotransmitter is NE • NE increases sphincter tension • Inactivate the motility www.doctorsherwan.com

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  21. Excitatory Motor Neurons Evoke Muscle Contraction & Intestinal Secretion • Neurotransmitters of motor neurons: • Substance P • Ach • Neurotransmitters of secretomotor neurons (releasing of water, electrolytes and mucus from crypts of Lieberkuhn): • Ach • VIP • Histamine (neurogenic secretory diarrhea) www.doctorsherwan.com

  22. Inhibitory Motor Neurons Suppress Muscle Contraction • Neurotransmitters: • ATP • NO • VIP N.B. Longitudinal muscles do not have inhibitory motor innervation www.doctorsherwan.com

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