Digestive System 1-Dr Hisham Fall 2024 PDF

Anatomy and Physiology of the Digestive System - 1 Dr Hisham Alshaikhli M.B.Ch.B, M.Sc, Ph.D, PGCertMedTech - New Zealand Assistant Professor College of Nursing – Qatar University [email protected] Office hours: Mondays...

Anatomy and Physiology of the Digestive System - 1 Dr Hisham Alshaikhli M.B.Ch.B, M.Sc, Ph.D, PGCertMedTech - New Zealand Assistant Professor College of Nursing – Qatar University [email protected] Office hours: Mondays and Wednesdays 12 pm-1 pm Building I03 – Office 504 1 Learning Outcomes  Organs of the gastrointestinal system  General organization of walls in the gastrointestinal system  Functions of the gastrointestinal tract  Mesentery and omentum  Salivary glands 2  "What are the key functions of the gastrointestinal tract, and how do you think its physiology contributes to maintaining overall health? Consider both digestive processes and the absorption of nutrients.“ 2 minutes 4  Components of the Digestive System A B Digestive tract (alimentary canal): G A.Oral cavity C B.Pharynx C.Esophagus D.Stomach E.Small intestine H F. Large intestine D I J Accessory organs are: F E G.Salivary glands F H.Liver I. Pancreas J. Gall bladder 5  Surface Anatomy: Abdominal Regions Midclavicular planes: Midpoint of clavicles to midinguinal points Subcostal plane: Through IV disc between L1/L2 Transtubercular plane: Through body of L5 Specific clinical description 6  Functions of the GIT Main functions of the GIT involve: 1. Ingestion 2. Propulsion 3. Mechanical breakdown 4. Digestion 5. Absorption 6. Defecation 7. Host defence 7 1. The mucosa: epithelium, lamina propria and smooth muscle layer. 2. The submucosa: connective tissue layer containing blood Organization of GIT wall vessels, nerve endings, lymphoid tissue, glands, and lymphatic vessels. 3. The muscularis externa is a muscle layer typically made up of an inner circular layer and an outer longitudinal layer of smooth muscle cells. 4. The serosa is the outermost layer of the wall. It consists of a single layer of flat, serous fluid–producing 8 cells, the visceral peritoneum which attaches to the parietal peritoneum by the mesentery.  The peritoneum Please watch the video on BB The largest serous membrane of the body (mesothelium) The peritoneum is divided into the 1. Parietal peritoneum, which lines the wall of the abdominal cavity. 2. Visceral peritoneum, which covers some of the organs in the cavity (serosa). The space between the layers is called the peritoneal cavity which contains serous fluid known as the peritoneal fluid. In certain diseases, serous fluid is accumulated known as ascites. large folds of peritonium bind the organs to one another and to the walls of the abdominal cavity including the greater omentum, lesser omentum, falciform ligament, mesentery and mesocolons 9  Retroperitoneal space Parietal peritoneum Mesentery Visceral peritoneum Retroperitoneal Organ:  Incompletely surrounded by peritoneum  Does not have a mesentery  Fixed to the posterior abdominal wall  kidneys, ascending and descending colons of the large intestine, duodenum of the small intestine, rectum, and pancreas. Intraperitoneal Organ:  Surrounded by the visceral peritoneum  Attached to the wall by a mesentery  Mobile  Liver, stomach, jejunum, ileum and transverse and sigmoid colon. 10  Omentums 1. The greater omentum: the longest peritoneal fold, drapes over the transverse colon and coils of the small intestine as a double sheet that folds back on itself, giving it a total of four layers. Contains fat, which helps to insulate, cushion, and protect the abdominal organs. Large collections of lymphoid follicles which play important role in immune response. 2. The lesser omentum, arises as an anterior fold in the serosa of the stomach and duodenum, and it connects the stomach and duodenum to the liver. 12  Mesentery  The mesentery Is double fold of peritoneum that attaches the jejunum and ileum of the small intestine to the posterior abdominal wall. Functions of the Mesentery 1. Attaches your intestines to the wall abdomen keeping the intestines in place, preventing it from twisting or collapsing down into the pelvic area. 2. Stores fat 3. Provided lymphatic and blood supply to the intestines and other GIT organs. 14  Mesocolons  Two folds of peritonium; One bind the transverse colon (transverse mesocolon) and the other binds sigmoid colon (sigmoid mesocolon) of the large intestine to the posterior abdominal wall. 15  Falciform ligament  The only organ that attaches to the anterior abdominal wall is the liver. The falciform ligament attaches the liver to the diaphragm and the anterior abdominal wall. 16  Innervation of the GIT 1. Enteric Nervous System (ENS). The ENS is nicknamed the "second brain" 2. Extrinsic innervation: Autonomic Nervous System (ANS) 1- Enteric nervous system (ENS) A. Submucosal plexus (Meissner's plexus) - Between the circular layer and the mucosa. - Exocrine and endocrine functions of the GIT. B. Myenteric plexus (Auerbach's plexus). - Between the outer longitudinal and inner circular muscle layers. - Motor function of the GIT. 17  Extrinsic innervation: Autonomic Nervous System (ANS) Sympathetic Parasympathetic  Increase muscular activity  Decrease muscular activity (peristalsis)  Decrease glandular secretion  Increase glandular  Constrict sphincters secretion  Dilate sphincters 18 19  Salivary Glands Three pairs: Parotid: Anterior to ears Submandibular Sublingual Secretion of saliva is under ANS control Saliva contains water, mineral salts, enzymes and immunoglobulins Ducts carry secretions of glands to the oral cavity Saliva  A mixture of mucus and serous fluids  Digestion begins in the mouth where food is masticated and mixed with saliva.  Contains salivary amylase (Start Carb digestion), lysozyme and IgA.  Has a pH 6.0 - 7.4 20  About 1.2 litres/day are secreted  Control of salivation Parasympathetic stimulation evokes a copious flow of saliva (increase salivation). In contrast, sympathetic stimulation produces either a small flow, which is rich in protein, or no flow at all. Salivary center in medulla 21  Formation of Bolus Food is chewed by teeth Moved around by tongue and muscles of cheeks Mixed with saliva to form a bolus ready for swallowing 22  The Pharynx (“the throat”) A funnel shaped muscular tube, extends from base of skull to inferior border of larynx Subdivisions: Nasopharynx, Oropharynx Laryngopharynx  The pharynx is composed of involuntary skeletal muscles (inner longitudinal and outer circular) and is lined by mucous membrane,  While most skeletal muscles are under voluntary control, the pharyngeal muscles represent a unique category as they are a blend of both voluntary and involuntary muscles.  They contain a mix of skeletal muscle fibers that are under voluntary control and fibers that are involuntary. smooth muscle  This combination allows for conscious initiation of the swallowing process, followed by a largely involuntary phase of muscle contractions that move the food bolus through the pharynx and into the esophagus. 23  Swallowing  Initiated voluntarily by muscles of the tongue and cheeks  The bolus is pushed backwards into the pharynx  The presence of bolus in the pharynx stimulates wave of peristalsis 24  Swallowing (deglutition)  The process of swallowing [deglutition] is controlled by the deglutition centre in the medulla oblongata of the brain stem. Food is swallowed in three stages: 1. Voluntary swallowing process – involving the tongue which moves the bolus of food into the back of the mouth. 2. Pharyngeal involuntary process ‐ series of reflex actions which close the larynx and propel the food into the top of the oesophagus. 3. Oesophagal involuntary stage ‐ food bolus moved down the oesophagus actively by peristalsis. 25 Swallowing disorders  Dysphagia is the medical term for swallowing difficulties  Cough is an important reflex that helps protect your airway and lungs against irritants and foreign particles - Talking during eating 26  Peristalsis  Contraction and relaxation of these muscles occur in waves  Pushes the content forward  (Also contraction mixes food with digestive juices in other parts of GIT) 27 Dr Hisham Alshaikhli M.B.Ch.B, M.Sc, Ph.D, PGCertMedTech - New Zealand Assistant Professor College of Nursing – Qatar University [email protected] Office hours: Mondays and Wednesdays 12 pm-1 pm Building I03 – Office 504 31