The Digestive System

The Gastrointestinal Tract (GIT)

The Mouth

·  The mouth: the oral( buccal) cavity is the entrance of the digestive system.

·  The initiation of digestion for the carbohydrates occurs in the mouth by the secretion of the saliva.

·  The mouth opens posteriorly at the pharynx by the oropharynx, which leads to the esophagus inferiorly.

·  During the swallowing, the epiglottis closes the larynx to prevent the leakage of any drink or food particles to the trachea.

·  The bolus: ground food mixed with the saliva.

The Esophagus

·  The esophagus: a muscular tube extends from the laryngopharynx passes through the mediastinum anterior to the vertebral column, pierces the diaphragm through the esophageal hiatus.

The Stomach

·  J-shaped enlargement of the GIT.

·  The Cardia: surrounds the superior opening of the stomach.

·  The Fundus: rounded portion superior and left to the cardia.

·  The body: largest central portion of the stomach.

·  The pylorus: region of the stomach connects to the duodenum.

·  Cardiac valve( sphincter): between the esophagus and stomach.

·  Pyloric valve( sphincter): between the stomach and the duodenum.

·  Lesser curvature: concave medial border of the stomach.

·  Greater curvature: convex lateral border of the stomach.

·  The chyme: macerated food and mixed with the gastric secretion.

·  The smooth muscles are oriented into three layers: the circular, longitudinal and oblique.

·  The rugae: the large folds of the stomach mucosal layer.

The Small Intestine

·  The site of major events of digestion and absorption.

·  The duodenum: the proximal shortest part(25cm)

·  The jejunum: the middle part of the small intestine, found empty at death.

·  The ileum: the distal part connected to the large intestine by the ileocecal sphincter.

The large Intestine

·  The terminal part of GIT which surrounds the small intestine.

·  The eliocecal sphincter separates between the small and large intestine.

·  The cecum: blind pouch inferior to the eliocecal valve.

·  The vermiform appendix: twisted tube attached to the cecum.

·  The ascending colon: ascends at the right side of the abdomen, reaching the inferior surface of the liver.

·  The transverse colon: extends from the most left side to the most right side of the abdominal cavity superiorly.

·  The descending colon: descends inferior to the spleen to the level of iliac crest.

·  The sigmoid colon: begins near the left iliac crest, projest medially to the midline.

·  The rectum: the last 20 cm of GIT, lies anterior to sacrum and coccyx.

·  The hepatic flexure: the right curvature of the colon.

·  The splenic flexure: the left curvature of the colon.

·  The anal canal: the last2-3cm of the rectum.

·   The anal column: longitudinal folds of the mucous membrane of the anal canal.

·  The anus: the external opening of the anal canal.

·  The Haustra: pouch-like structures give the colon the puckered appearance.

·  The  Tenia coli: three thickened portions of the large intestine longitudinal smooth muscles.

The Accessories of the GIT

         The Pancreas

·        12-15cm long,2.5cm thick gland.

·        The head: the expanded portion near the duodenum

·        The body: lateral to the head.

·        The tail: lateral to the body.

·        Pancreatic duct (Duct of Wirsung): the larger duct of pancreas to the small intestine.

·        Hepatopancreatic ampulla( ampulla of Vater): the shared space in the small intestine between the pancreatic duct and common bile duct from the liver and gall bladder.

·        The accessory duct( duct of Santorini): the smaller duct of the pancreas, superior to hepatopancreatic ampulla.

The Liver and the gall bladder

·        The heaviest gland of the body.

·        Lies inferior to the diaphragm at the right side.

·        The larger right lobe is connected with the smaller left lobe by the falciform ligament.

·        Inferiorly the quadrate lobe and posteriorly the caudate lobe are found.

·        Ligament teres: between the liver and the umbilicus.

·        Right and left coronary ligaments: suspend the liver from the diaphragm.

·        The gallbladder: the fundus, body and the neck.

** the right hepatic duct and the left hepatic duct open at the common hepatic duct.

**the common hepatic duct and the cystic duct open in the common bile duct.

** the common bile duct and the pancreatic duct open in the hepatopancreatic ampulla.