L44 - Physiology of Gastrointestinal System PDF

L44- PHYSIOLOGY OF GASTROINTESTINAL SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua The Human Digestive System The alimentary tract provides the body with a continual supply of water, electrolytes, vitamins, and nutrient...

L44- PHYSIOLOGY OF GASTROINTESTINAL SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua The Human Digestive System The alimentary tract provides the body with a continual supply of water, electrolytes, vitamins, and nutrients. 3  The Human Digestive System This requires : 1. movement of food through the alimentary tract. 2. secretion of digestive juices and digestion of food. 3. absorption of digestive products ،water, electrolytes, and vitamins. 4. circulation of blood to carry away absorbed Substances. 5. nervous and hormonal control of all these functions 4  The Human Digestive System Main organs of the Digestive System:  Mouth  Pharynx  Esophagus  Stomach  Small intestine  Large intestine. Together this makes a tube called the Digestive tract 5  The Human Digestive System Accessory organs of the Digestive System: 1) Teeth 2) Tongue 3) Liver 4) Pancreas 5) Gall Bladder 6) Salivary Gland 6  The Human Digestive System Functions of Digestive System:- 1-Ingestion. 2-Secretion. 3-Mixing & Propulsion. 4-Digestion A-Mechanical :-Food is broken down mechanically, with movement. B-Chemical:- Food is broken down with a chemical or enzyme 5-Absorption. 6-Defecation. 7 The Human Digestive System The Gastrointestinal Tract Has Its Own Nervous System Called the: ( Enteric Nervous System) in the wall of the gut beginning in the esophagus and extending all the way to the anus. The enteric system is composed mainly of two plexuses: 1-The Myenteric plexus, or Auerbach’s plexus outer plexus located between the muscle layers, Stimulation cause : 8  The Human Digestive System The Myenteric plexus, or Auerbach’s plexus Stimulation cause : 1. Increased intensity of rhythmical contraction. 2. Increased rate of contraction. 3. Increased velocity of conduction. 4. The myenteric plexus is also useful for inhibiting the pyloric sphincter which controls emptying of the stomach. 9 The Myenteric plexus, or Auerbach’s plexus The Myenteric Plexus 10 2-The Submucosal plexus, or Meissner’s plexus: is an inner plexus that lies in the submucosa. 1. Controls function within small segments of the Gastrointestinal wall. 2. Helps control local intestinal secretions, absorption, blood flow and local contraction of the muscularis mucosa. 11 Submucosal plexus, or Meissner’s plexus 12  The Human Digestive System Autonomic Control of the Gastrointestinal Tract: 1-The Parasympathetic Nerves Increase the Activity of the Enteric Nervous System. The parasympathetic supply to the gut is made up of cranial and sacral divisions: The cranial parasympathetics innervate, by way of the vagus nerves, the esophagus, stomach, small intestine ،pancreas, and first half of the large intestine. The sacral parasympathetics innervate, by way of the pelvic nerves, the distal half of the large intestine 13 The Human Digestive System 2- The Sympathetic Nervous System Usually Inhibits Activity in the Gastrointestinal Tract, Causing Many Effects Opposite to Those of the Parasympathetic System 14  The Human Digestive System Ingestion of food: followed by Mastication (Chewing) and Swallowing (Deglutition). Mastication (Chewing): The teeth are designed for chewing, the anterior teeth (incisors) providing a strong cutting action and the posterior teeth (molars), a grinding action 15 The Human Digestive System Part: 1 Mouth  Digestion actually begins in the mouth. Food enters in the mouth or oral cavity. Tasting, Mechanical breakdown of food. , and the tongue moves the pieces around so that saliva can be mixed with them, this begins the digestion. 16  The Human Digestive System Part: 1 Structures in the mouth that helps digestion:  Teeth-cut, tear, crush and grind food.  Salivary glands- produce and secrete saliva into oral cavity.  Parotid (beneath the cheeks).  Submaxillary (below the jaw bone).  Sublingual(below the tongue). 17 18  The Human Digestive System Part: 1 Functional Movements in the Gastrointestinal Tract Two types of movement occur in the gastrointestinal tract:- 1-Propulsive (Peristalsis) movements 2- Mixing movements Peristalsis is the basic propulsive movement of the gastrointestinal tract 19 20 Chewing is important for: 1.Digestion of all foods, but especially important for most fruits and raw vegetables because these have indigestible cellulose membranes around their nutrient portions that must be broken before the food can be digested. 2.Chewing the digestion of food for simple reason: Digestive enzymes (in saliva) act only on the surfaces of food particles; therefore the rate of digestion is absolutely dependent on the total surface area exposed to the digestive secretions 21 Saliva & Salivary glands: The principal glands of salivation are the parotid, submandibular ،and sublingual glands. Saliva contains two major types of protein secretion: 1- The serous secretion (watery saliva) contains ptyalin (α-amylase),which is an enzyme for digesting starches. 2-The mucous secretion contains mucin for lubrication and for surface protection. Saliva Contains low Concentrations of potassium and Bicarbonate Ions and high Concentrations of sodium and chloride Ions. 22 Swallowing (Deglutition) Swallowing is a complicated mechanism, principally because the pharynx subserves respiration as well as swallowing. In general, swallowing can be divided into: 1. A voluntary stage in oral cavity which initiates the swallowing process; When the food is ready for swallowing, it is voluntarily pushed into the pharynx by the tongue. 2. A pharyngeal stage, which is involuntary and constitutes passage of food through the pharynx into the esophagus. 3. An esophageal stage, involuntary phase that transports food from the pharynx to the stomach 23 Stomach There Are Three Functions of the Stomach:- 1- Storage of food until the food can be processed in the duodenum 2 Mixing of food with gastric secretions until it forms a semifluid mixture called chyme. 3 Emptying of food into the small intestine at a rate suitable for proper digestion and absorption. 24 Stomach 25  Tongue  Mixes and rolls food into tiny mashed up bits (Bolus).  Pushes the bolus toward the pharynx and into the esophagus when swallowing.  REFERENCES  Drake R.L., Gray’s Anatomy for Students, 2nd Edition, 2009, Churchill Livingstone  Moore, Clinically Oriented Anatomy, 6th Edition, 2009, Lippincott Williams & Wilkins  Textbook of Medical Physiology – Guyton & Hall  Medical Physiology – R.K Marya  Essentials of Physiology for Dental Students. K Sembulingam and Prema Sembulingam ,2016, four Edition , Jaypee Brothers Medical Publishers.  Human Physiology. Stuart Ira Fox., TWELFTH EDITION,2017. Published by McGraw-Hill 27 19-Nov-24