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1. Overview of The Digestive system by D Siwale.pptx
- 1. GASTRO-INTESTINAL PHYSIOLOGY Mr D.R Siwale (MSc. Human physiology, BSc Biological sciences, BSc Human Biology, Dip.Ed.)
- 3. Organs of the digestive system Organs of the gastrointestinal (GI) tract are the • mouth, • pharynx, • esophagus, • stomach, • small intestine • large intestine. • Accessory digestive organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
- 4. Cont’d
- 6. 4 activities (GIT= Gastro Intestinal Tract) • D= Digestion (How are C/hydates, Lipids, Proteins) • A= Absorption (How are C/hydates, Lipids, Proteins, Iron, Calcium etc) • M= Motility (Mastication, Swallowing, peristalsis, Vomiting, defecation) • S= Secretion (saliva, gatric juice, pancreatic, intestinal juices, Bile)
- 7. • Tone • Ca++, ATP, Neurostimulation
- 8. Length of GIT • The length of the GI tract is about 5–7 meters (16.5–23 ft) in a living person. • It is longer in a cadaver (about 7–9 meters or 23–29.5 ft) because the muscles along the wall of the GI tract organs are not in a state of tonus (sustained contraction).
- 9. layers that form the wall of the GIT
- 11. Summary of the layers of GIT….
- 12. Nerve supply to GIT
- 13. Nerve Supply to the Digestive system • GI tract has two types of nerve supply: • I. Intrinsic nerve supply: Intrinsic nerves to GI tract form the enteric nervous system that controls all the secretions and movements of GI tract. (submucosal plexus and Myenteric plexus) • II. Extrinsic nerve supply: Extrinsic nerves that control the enteric nervous system are from autonomic nervous system. (vagus and pelvic nerve). Parasympathetic (rest and digest) and sympathetic ( FLIGHT AND FIGHT RESPONSE)
- 14. Intrinsic nerve supply • Intrinsic nerves to GI tract form the enteric nervous system. It comprose of two nerve plexuses: • 1. Auerbach plexus (Myenteric plexus) • 2. Meissner plexus • These nerve plexus contain nerve cell bodies, processes of nerve cells and the receptors. The receptors in the GI tract are stretch receptors and chemoreceptors. • Enteric nervous system is controlled by extrinsic nerves.
- 16. Enteric nervous system • It is an extensive network of neurons and nerve networks located in the walls of the digestive tract. • The ENS controls most function of the GI tract, especially Motility and Secretion, even in the Absence of Extrinsic innervation. • The two major Networks of the Nerve fibre are: The Myenteric Plexus and Submucosal plexus
- 17. Features of ENS • It is part of the ANS • It is viewed as a displaced part of the CNS and it is sometimes referred to as Little Brain. • The Neurotransmitters in the ENS include Ach, the amines, Norepinephrine, serotonin, GABA, NO, CO etc. has all the Neurotransmitter found in the brain. • The ENS has about 100 million Neurons. • The two major Networks of the Nerve fibre are: The Myenteric Plexus and Submucosal plexus
- 18. • The Myenteric Plexus (auerbach’s plexus) innervates the longitudinal and circular smooth muscle layers. It controls the motility of the GI smooth muscle. • The Submucosal plexus (Meissner’s plexus) innervates the glandular epithelium, intestinal endocrine cells and sub mucosal blood vessel and is involved in the control of intestinal secretion.
- 19. EXTRINSIC Nerve supply • Extrinsic nerves that control the enteric nervous system are from autonomic nervous system. • Both sympathetic and parasympathetic divisions of autonomic nervous system innervate the GI tract.
- 20. Extrinsic nerve
- 21. Sympathetic Nerve FIBERS • Preganglionic sympathetic nerve fibers to GI tract arise from lateral horns of spinal cord between fifth thoracic and second lumbar segments (T5 to L2). • From here, the fibers leave the spinal cord, pass through the ganglia of sympathetic chain without having any synapse and then terminate in the celiac and mesenteric ganglia. • The postganglionic fibers from these ganglia are distributed throughout the GI tract.
- 22. Functions of sympathetic nerve fibers • Sympathetic nerve fibers inhibit the movements and decrease the secretions of GI tract by secreting the neurotransmitter noradrenaline. • It also causes constriction of sphincters.
- 23. Parasympathetic Nerve Fibers • Parasympathetic nerve fibers to GI tract pass through some of the cranial nerves and sacral nerves. • The preganglionic and postganglionic parasympathetic nerve fibers to mouth and salivary glands pass through facial and glossopharyngeal nerves.
- 24. Cont’d… • Preganglionic parasympathetic nerve fibers to esophagus, stomach, small intestine and upper part of large intestine pass through vagus nerve. • Preganglionic nerve fibers to lower part of large intestine arise from second, third and fourth sacral segments (S2, S3 and S4) of spinal cord and pass through pelvic nerve. • All these preganglionic parasympathetic nerve fibers synapse with the postganglionic nerve cells in the myenteric and submucus plexus
- 25. Cont’d.. • Functions of parasympathetic nerve fibers • Parasympathetic nerve fibers accelerate the movements and increase the secretions of GI tract. • The neurotransmitter secreted by the parasympathetic nerve fibers is acetylcholine (Ach).
- 27. Review 1. Mention any 6 functions of the GIT? 2. What is the length of GIT? Why is it longer in a cadaver? 3. Mention the 4 layers of the GIT 4. Which layer of the mucosa has fibroblasts, macrophages, lymphocytes and eosinophils? 5. State the functions of the extrinsic innervation of the GIT? 6. State functions of the Intrinsic nerve supply to the GIT 7. Mention any 3 features of the Enteric Nervous system Intrinsic (submucosal plexuas and Myenteric plexus) 1. Whats the effect of Atropine on the nerve supply to the GIT?
- 28. • D- diges • A- absorpt • M- moitil • S- seccretio
- 29. END
Editor's Notes
- The outline is as follows INTRODUCTION FUNCTIONAL ANATOMY WALL OF GASTROINTESTINAL TRACT NERVE SUPPLY TO GASTROINTESTINAL TRACT INTRINSIC NERVE SUPPLY EXTRINSIC NERVE SUPPLY
- Major internal organs in the viscera
- 1. Why is the GIT longer in candavers than in a living person?
- 1. Give examples of secretion and movements controlled by intrinsic nerve supply
- It is an extensive network of neurons and nerve networks located in the walls of the digestive tract. The ENS controls most function of the GI tract, especially Motility and Secretion, even in the Absence of Extrinsic innervation. The two major Networks of the Nerve fibre are: The Myenteric Plexus and Submucosal plexus FEATURES OF ENS It is part of the ANS It is viewed as a displaced part of the CNS and it is sometimes referred to as Little Brain. The Neurotransmitters in the ENS include Ach, the amines, Norepinephrine, serotonin, GABA, NO, CO etc. has all the Neurotransmitter found in the brain. The ENS has about 100 million Neurons. The two major Networks of the Nerve fibre are: The Myenteric Plexus and Submucosal plexus FUNCTION The Myenteric Plexus (auerbach’s plexus) innervates the longitudinal and circular smooth muscle layers. It controls the motility of the GI smooth muscle. The Submucosal plexus (Meissner’s plexus) innervates the glandular epithelium, intestinal endocrine cells and sub mucosal blood vessel and is involved in the control of intestinal secretion.
- Show how the nervous system is organised
- (1) SYMPATHETIC NERVE FIBERS Preganglionic sympathetic nerve fibers to GI tract arise from lateral horns of spinal cord between fifth thoracic and second lumbar segments (T5 to L2). From here, the fibers leave the spinal cord, pass through the ganglia of sympathetic chain without having any synapse and then terminate in the celiac and mesenteric ganglia. The postganglionic fibers from these ganglia are distributed throughout the GI tract. FUNCTION: Sympathetic nerve fibers inhibit the movements and decrease the secretions of GI tract by secreting the neurotransmitter noradrenaline. It also causes constriction of sphincters. (2) PARASYMPATHETIC Parasympathetic nerve fibers to GI tract pass through some of the cranial nerves and sacral nerves. The preganglionic and postganglionic parasympathetic nerve fibers to mouth and salivary glands pass through facial and glossopharyngeal nerves. Preganglionic parasympathetic nerve fibers to esophagus, stomach, small intestine and upper part of large intestine pass through vagus nerve. Preganglionic nerve fibers to lower part of large intestine arise from second, third and fourth sacral segments (S2, S3 and S4) of spinal cord and pass through pelvic nerve. All these preganglionic parasympathetic nerve fibers synapse with the postganglionic nerve cells in the myenteric and submucus plexus Functions of parasympathetic nerve fibers: Parasympathetic nerve fibers accelerate the movements and increase the secretions of GI tract. The neurotransmitter secreted by the parasympathetic nerve fibers is acetylcholine (Ach).
- The enteric nervous system (ENS) is sometimes referred to as the third division of the nervous system (central, peripheral, and enteric). This system is composed of a nerve plexus or a meshwork of fibers innervating the digestive tract from the esophagus to the distal colon. The ENS includes the myenteric plexus and the submucosal plexus which receive preganglionic fibers from the parasympathetic division and postganglionic fibers from the sympathetic division of the ANS. Innervation from the ANS and sensory input from within the wall of the gut work together to control smooth muscle motor activity and gut secretory actions. However, the ENS releases a variety of neurotransmitters and is capable of controlling digestive functions independently of the CNS by way of local reflexes. When food is introduced into the digestive tract, stretch receptors in the gut are activated and send action potentials through afferent enteric sensory neurons. These neurons synapse with entericinterneurons which are capable of activating efferent enteric motor neurons. These neurons innervate glands and smooth muscle. Their increased activity enhances digestive enzyme secretions and gut contraction to cause mixing and propulsion of food. The ENS is particularly important in providing synchronous peristaltic movements ensuring propulsion of food in one direction (see figure below).