Physiology Lecture: 46 Gastrointestinal Physiology Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT Propulsive movements or Peristalsis Mixing movements Moves food forward along GIT at an appropriate rate for digestion and absorption Mixing movements Keeps intestinal contents thoroughly mixed at all times Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT: Peristalsis Requires active myenteric plexus Congenital absence of myenteric plexus Peristalsis is depressed or absent Atropine (paralyzes cholinergic nerve endings) Directional movement toward Anus Can occur in either direction but normally occurs towards anus Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT: Peristalsis Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT: Mixing Movement Differs in different parts Peristaltic contractions causing mixing Occurs when forward progression is blocked by sphincter. Peristaltic wave can then only churn the contents, rather than propelling them Local intermittent constrictive contractions Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT: Mixing Movement Differs in different parts Peristaltic contractions causing mixing Local intermittent constrictive contractions Occurs every few centimeters in gut wall. Usually last only 5-30 seconds; then new constrictions occur at other points, "chopping" & "shearing" the contents first here and then there Tanveer Raza MD MS MBBS razajju2@yahoo.com

Movement in GIT: Mixing Movement Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Gut to prevertebral sympathetic ganglia and then back to GIT Gut to the spinal cord or brain stem and then back to the GIT Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Much GI secretion Peristaltic reflex Mixing contractions Local inhibitory effects Gut to prevertebral sympathetic ganglia and then back to GIT Gut to the spinal cord or brain stem and then back to the GIT Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Gut to prevertebral sympathetic ganglia and then back to GIT Reflexes transmit signals long distances to other areas of GIT Gastrocolic reflex Enterogastric reflex Colonoileal reflex From gut to the spinal cord or brain stem and then back to the GIT Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Gut to prevertebral sympathetic ganglia and then back to GIT Gastrocolic reflex From stomach, causes colon evacuation Defecation after meal is rule for children In adults, habits and culture play a rule Maybe due to action of gastrin acting on colon, not neurally mediated Gut to the spinal cord or brain stem and then back to the GIT Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Gastrocolic reflex may affect Irritable Bowel Syndrome (IBS) or spastic colon Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Gut to prevertebral sympathetic ganglia and back to GIT Enterogastric reflex From colon and small intestine, inhibits stomach motility and secretion Initiated by Product of protein digestion hydrogen ions bathing the duodenal mucosa Duodenal distention Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Gut to prevertebral sympathetic ganglia and then back to GIT Colonoileal reflex From colon, inhibits emptying of ileal contents into colon Gut to the spinal cord or brain stem and then back to the GIT Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Integrated entirely within the gut wall enteric nervous system Gut to prevertebral sympathetic ganglia and then back to GIT Gut to the spinal cord or brain stem and then back to the GIT Reflexes controlling gastric motor and secretory activity Pain reflexes Defecation reflexes Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Gut to the spinal cord or brain stem and then back to the GIT Reflexes controlling gastric motor and secretory activity From stomach and duodenum to brain stem and back to stomach-by way of vagus nerves Tanveer Raza MD MS MBBS razajju2@yahoo.com

Gastrointestinal Reflexes: 3 types Gut to the spinal cord or brain stem and then back to the GIT Pain reflexes General inhibition of the entire GIT Defecation reflexes From colon and rectum to spinal cord and back again to produce the powerful colonic, rectal, and abdominal contractions required for defecation Tanveer Raza MD MS MBBS razajju2@yahoo.com

CHEWING (MASTICATION) Tanveer Raza MD MS MBBS razajju2@yahoo.com

Mastication: Chewing reflex Chewing is a reflex action Voluntarily chewing can occur Tongue and to a lesser extent lips and cheeks acts to keep food between the grinding surfaces of teeth Tanveer Raza MD MS MBBS razajju2@yahoo.com

Mastication: Chewing reflex Food in mouth Reflex inhibition of lower jaw muscles. Lower jaw drops Stretch reflex causes muscle contraction Closure of mouth Tanveer Raza MD MS MBBS razajju2@yahoo.com

Mastication: Importance Breaks indigestible cellulose membrane Fruits and raw vegetables Breaks large pieces into small pieces  surface area for digestive enzymes to work Breaks food into very fine particulate and mixes with salivary secretion Tanveer Raza MD MS MBBS razajju2@yahoo.com

Mastication: Importance Breaks indigestible cellulose membrane Breaks large pieces into small pieces Breaks food into very fine particulate and mixes with salivary secretion Helps in deglutition and digestion Prevents excoriation of GIT Eases passage of food Tanveer Raza MD MS MBBS razajju2@yahoo.com

SWALLOWING

Sword Swallowing: Lessons Tanveer Raza MD MS MBBS razajju2@yahoo.com

Sword Swallowing: Lessons Tanveer Raza MD MS MBBS razajju2@yahoo.com

Sword Swallowing: Lessons Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Stages Voluntary Stage Involuntary Stage Pharyngeal stage Initiates Swallowing process Involuntary Stage Pharyngeal stage Esophageal stage Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Voluntary Stage Food ready for swallowing “Voluntarily" squeezed or rolled posteriorly into pharynx by pressure of the tongue upward and backward against the palate From here on, swallowing normally cannot be stopped Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Stages Involuntary Stage Pharyngeal stage Esophageal stage Passage of food through pharynx into esophagus In less than 6 seconds Esophageal stage Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Once food bolus reaches pharynx several actions are initiated: Closure of Nasal Aperture Closure of Trachea Swinging back of Epiglottis Opening of Esophagus Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage of Swallowing Animation (Must go to Slide show to see animation) Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Closure of nasal aperture Soft palate is pulled upward to close the posterior nares Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Closure of the trachea Vocal cords are strongly approximated Larynx is pulled upward and anteriorly by the neck muscles Swinging back of epiglottis Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Closure of the trachea Vocal cords are strongly approximated Most important Destruction of vocal cords or the muscles that approximate them can cause strangulation Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Closure of the trachea Larynx is pulled upward and anteriorly by the neck muscles Upward movement also lifts glottis out of main stream of food flow, so food passes on each side of epiglottis rather than over its surface. Protects against entry of food into trachea Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal Stage Closure of the trachea Swinging back of epiglottis Epiglottis swing backward over the opening of the larynx Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Pharyngeal stage Opening of esophagus Upward movement of larynx pulls up and enlarges the esophageal opening. The upper esophageal sphincter (also called the pharyngoesophageal sphincter) relaxes Tanveer Raza MD MS MBBS razajju2@yahoo.com

Swallowing: Stages Involuntary Stage Esophageal stage Pharyngeal stage Esophageal stage Transport of food from pharynx to stomach Tanveer Raza MD MS MBBS razajju2@yahoo.com

Thank You