GIT I - Introduction to GI Tract & Saliva - Physical Therapy Notes - PDF

Faculty of Physical Therapy  The alimentary canal or gastrointestinal (GI) tract digests and absorbs food.  Alimentary canal – mouth, pharynx, esophagus, stomach, small intestine, and large intestine  Accessory digestive organs – teeth, tongue, gallbladder, salivary gland...

Faculty of Physical Therapy  The alimentary canal or gastrointestinal (GI) tract digests and absorbs food.  Alimentary canal – mouth, pharynx, esophagus, stomach, small intestine, and large intestine  Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas Figure 23.1  There are six essential activities: ▪ Ingestion, ▪ propulsion, ▪ mechanical digestion ▪ Chemical digestion, ▪ absorption, and ▪ defecation Figure 23.2  Ingestion – taking food into the digestive tract  Propulsion – swallowing and peristalsis ▪ Peristalsis – waves of contraction and relaxation of muscles in the organ walls  Mechanical digestion – chewing, mixing, and churning food  Chemical digestion – catabolic breakdown of food by enzymes  Absorption – movement of nutrients from the GI tract to the blood or lymph  Defecation – elimination of indigestible solid wastes  It is a specific nervous system of GIT  It is formed of about 100 millions of neurons lying along the wall of gut, beginning from oesophagus till the anus.  It is divided into 2 plexuses:  An outer plexus called the meyenteric plexuses responsible for movement of GIT  An inner plexus called submucosal pexuses which regulate GIT secretions. Salivation Taste Swallowing Salivation  Three pairs of extrinsic glands – parotid, submandibular, and sublingual  Intrinsic salivary glands (buccal glands) – scattered throughout the oral mucosa  Produce and secrete saliva that: ▪ Cleanses the mouth ▪ Moistens and dissolves food chemicals ▪ Aids in bolus formation ▪ Contains enzymes that break down starch  Parotid – lies anterior to the ear between the masseter muscle and skin ▪ Parotid duct – opens into the vestibule next to the second upper molar  Submandibular – lies along the medial aspect of the mandibular body ▪ Its ducts open at the base of the lingual frenulum  Sublingual – lies anterior to the submandibular gland under the tongue ▪ It opens via 10-12 ducts into the floor of the mouth Figure 23.9a  Secreted from serous and mucous cells of salivary glands  A 97-99.5% water, hypo-osmotic, slightly acidic solution containing ▪ Electrolytes – + + – 2– Na , K , Cl , PO4 , HCO3– ▪ Digestive enzyme – salivary amylase ▪ Proteins – mucin, lysozyme, defensins, and IgA ▪ Metabolic wastes – urea and uric acid Sympathetic regulation  Sympathetic nerves arise from T1,2 passing through the superior cervical ganglion terminate at the salivary glands.  Sympathetic stimulation produce: ▪ Trophic (concentrated) saliva rich in mucus and enzymes ▪ vasoconstriction Parasympathetic regulation Facial n.: submandibular and sublingual glands Glossoph-: parotid gland Action: increase salivary secretions  Conditioned reflexes ▪ Acquired reflexes by learning & training ▪ Sight, smell, thinking of food stimulate the salivary nucleus in brainstem which through parasympathetic efferent stimulate salivation.  Unconditioned reflexes ▪ Inherent reflexes, don’t need learning or intact cerebral cortex ▪ Mechanical stimulation (presence of food in mouth) of buccal cavity stimulate taste receptors afferent 7,9 CN salivary n. increase salivation Taste  Most of the 10,000 or so taste buds are found on the tongue  Taste buds are found in papillae of the tongue mucosa Figure 15.1  There are four basic taste sensations ▪ Sweet – sugars, saccharin, alcohol, and some amino acids ▪ Salt – metal ions ▪ Sour – hydrogen ions ▪ Bitter – alkaloids such as quinine and nicotine  Cranial Nerves VII and IX carry impulses from taste buds to the solitary nucleus of the medulla  These impulses then travel to the thalamus, and from there fibers branch to the: ▪ Gustatory cortex (taste) ▪ Hypothalamus and limbic system (appreciation of taste) Figure 15.2  Deglutition is the act of transforming food from the buccal cavity to the stomach.  This process is divided into 3 stages: 1-Buccal 2-Pharyngeal 3-Esophageal 1-Buccal 2-Pharyngeal 3-Esophageal  Deglutition  Swallowing is initiated by presence of food particles in the mouth.  First, the food is masticated and lubricated by secretions in buccal cavity to facilitate its swallowing.  The tongue rolled and squeezed the bolus of food posterior to the pharynx.  Stimulation of mucosal mechanoreceptors in the pharynx activate afferent nerves traveling through the glossopharyngeal, vagus nerve to the swallowing center. Then efferent motor nerves run through the vagi to control the contractile state of the pharyngeal muscles. Innervation  summary Salivary secretion: Afferent: facial, glossopharyngeal Efferent: facial, glossopharyngeal Taste: Afferent: facial, glossopharyngeal Swallowing: Afferent: glossopharyngeal, vagus Efferent: vagus THANK YOU