Digestive System 1-Dr Hisham Fall 2023 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 and Wednesdays 12 pm-1 pm Building I03 – Office 504 1 Learning Outcomes ...

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  Food Propulsion—Swallowing and Peristalsis  Esophagus structure and function.  Disorders of the esophageal and gastric function 2 Soft reminder Please do attendance check-in 3 Components of the Digestive System A Digestive tract (alimentary canal): B A.Oral cavity B.Pharynx C.Esophagus D.Stomach E.Small intestine G C H F. Large intestine D I J F Accessory organs are: E F G.Salivary glands H.Liver I. Pancreas J. Gall bladder 4 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 5 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 6 Organization of GIT wall 1. The mucosa: epithelium, lamina propria and smooth muscle layer. 2. The submucosa: connective tissue layer containing blood 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 cells, the visceral peritoneum which attaches to the parietal peritoneum by the mesentery. 7 General Histological Organization of the GIT 8 The peritoneum • 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 10 Some Basic Terms Retroperitoneal space Parietal peritoneum Mesentery Visceral peritoneum Intraperitoneal Organ: Retroperitoneal Organ:  Surrounded by the visceral peritoneum  Attached to the wall by a mesentery  Mobile  Liver, stomach, jejunum, ileum and transverse and sigmoid colon.  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. 11 Summary: Position of Abdominal Organs 12 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. 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. 13 Mesentery versus Omentum 14 Mesentery  The mesentery Is an organ formed by the double fold of peritoneum that attaches the jejunum and ileum of the small intestine to the posterior abdominal wall. 15 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. 16 Mesocolons  Two folds; One bind the transverse colon (transverse mesocolon) and the other binds sigmoid colon (sigmoid mesocolon) of the large intestine to the posterior abdominal wall. 17 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. 18 Innervation of the GIT 1. 2. Enteric Nervous System (ENS). The ENS is nicknamed the "second brain" Extrinsic innervation: Autonomic Nervous System (ANS) 19 Enteric nervous system (ENS) 1. 2. Myenteric plexus (Auerbach's plexus). Submucosal plexus (Meissner's plexus). 20 Enteric nervous system Submucous plexus Myenteric plexus Between the circular layer and the mucosa. Between the outer longitudinal and inner circular muscle layers Exocrine and endocrine functions of the GIT Motor function of the GIT 21 Extrinsic innervation: Autonomic nervous system 22 Autonomic Nerve Supply Sympathetic Parasympathetic -Decrease muscular activity -Increase muscular activity (peristalsis) -Decrease glandular secretion -Increase glandular secretion -Constrict sphincters -Dilate sphincters 23 24 Salivary Glands PAROTID DUCT • Three pairs: • Parotid: Anterior to ears PAROTID GLAND • Submandibular • Sublingual MASSETER MUSCLE • Secretion of saliva is under ANS control SUBLINGUAL GLAND SUBMANDIBULAR GLAND • Saliva contains water, mineral salts, enzymes and immunoglobulins • Ducts carry secretions of glands to the oral cavity SUBMANDIBULAR DUCT SUBLINGUAL DUCT 25 Saliva  A mixture of mucus and serous fluids  Digestion begins in the mouth where food is masticated and mixed with saliva.  Contains salivary amylase, lysozyme and IgA.  Has a pH 6.0 - 7.4  About 1.2 litres/day are secreted 26 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. 27 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 28 Soft reminder Please do attendance check-in 29 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 30