Digestive - Oesophagus, Stomach & Intestines II PDF

Digestive: Oesophagus, Stomach & Intestines II YBOD200 Mr J Naidoo  Learning Objectives Describe the anatomy of the peritoneum, mesentery and lesser and greater omentum Describe the following in relation to the gastrointestinal tract: o Arterial blood supply - coel...

Digestive: Oesophagus, Stomach & Intestines II YBOD200 Mr J Naidoo  Learning Objectives Describe the anatomy of the peritoneum, mesentery and lesser and greater omentum Describe the following in relation to the gastrointestinal tract: o Arterial blood supply - coeliac artery and branches, superior and inferior mesenteric arteries and branches, the 3 rectal arteries and the supply to the anal and perianal region o The portal venous drainage system o The rectal and anal venous drainage o Innervation - sympathetic and parasympathetic o Lymph drainage and regional nodes Peritoneum  Peritoneum Thin membrane, lining walls of abdominal cavity, covers viscera Parietal peritoneum – lines abdominal walls Visceral peritoneum – lines viscera o Between these layers is the peritoneal cavity Viscera are suspended in cavity by mesentery which are folds of peritoneum o These viscera are referred to as intraperitoneal Viscera that lie outside the cavity, or are only partially covered by peritoneum are referred to as retroperitoneal  Peritoneal Cavity Subdivided into greater sac and omental burse GREATER SAC Most space in peritoneal cavity Begins superiorly at diaphragm, continues inferiorly to pelvic cavity OMENTAL BURSA Smaller subdivision of peritoneal cavity Lies posterior to stomach Continuous with greater sac via omental foramen (epiploic foramen)  Peritoneal Cavity Structures surrounding omental foramen are covered with peritoneum: Anteriorly o Portal vein o Hepatic artery proper o Bile duct Posteriorly o Inferior vena cava Superiorly o Caudate lobe of liver Inferiorly o First part of duodenum Omenta, Mesenteries & Ligaments  Omenta Numerous peritoneal folds connect viscera to each other or to abdominal wall Namely: Omenta, mesenteries and ligaments o Some contain neurovasculature supplying the viscera Develop from original dorsal and ventral mesenteries Consist of two layers of peritoneum Greater omentum – derived from dorsal mesentery Lesser omentum – derived from ventral mesentery  Greater Omentum “policeman of abdomen” Large, apron-like fold Attached to greater curvature of stomach and first part of duodenum Drapes over transverse colon, jejunum and ileum Also attached to peritoneum on superior surface of transverse colon before attaching to posterior abdominal wall Contains an accumulation of fat Contains right and left gastro-omental vessels in relation to its attachment to the greater curvature of stomach  Lesser Omentum Attached to lesser curvature of stomach and first part of duodenum Attached to inferior surface of liver Continuous with peritoneum covering anterior and posterior wall of stomach Divided into: o Hepatogastric ligament – medially, between stomach and liver o Hepatoduodenal ligament – laterally, between duodenum and liver, contains portal vein, hepatic artery proper and bile duct Contains gastric vessels near lesser curvature of stomach  Mesentery Peritoneal folds attaching viscera to posterior abdominal wall Allow for movement, transports neurovasculature Large fan-shaped, double layered fold of peritoneum Connects jejunum and ileum to posterior abdominal wall Superior attachment: Duodenojejunal junction Inferior attachment: Ileocaecal junction  Mesentery TRANSVERSE MESOCOLON Connects transverse colon to posterior abdominal wall Crosses anterior surface of head and body of pancreas Anterior layer attached to greater omentum SIGMOID MESOCOLON V-Shaped peritoneal fold Apex of V is near division of left common iliac artery into external and internal branches Limbs of V related to left psoas major muscle (medially) and ends at S3 in pelvis (laterally) MESOAPPENDIX  Blood Supply of Gastrointestinal Tract  Blood Supply of Gastrointestinal Tract Via branches of: o Coeliac Trunk – foregut o Superior Mesenteric Artery – midgut o Inferior Mesenteric Artery – hindgut Revise notes from CVS: Major Arterial Systems on these three arteries  Stomach Receives blood supply from the following arteries: o Left gastric artery – branch of coeliac trunk, lies on lesser curvature of stomach o Right gastric artery – branch of hepatic artery proper, lies on lesser curvature of stomach o Left gastro-omental/gastro-epiploic artery – branch of splenic artery, lies on greater curvature of stomach o Right gastro-omental/gastro-epiploic artery – branch of gastroduodenal artery, lies on greater curvature of stomach o Posterior gastric artery – variation, not always present, branch of splenic artery, lies on posterior wall of stomach  Duodenum Receives blood supply from the following arteries: o Gastroduodenal artery via ▪ Supraduodenal artery ▪ Anterior superior pancreaticoduodenal artery ▪ Posterior superior pancreaticoduodenal artery  Duodenum Receives blood supply from the following arteries: o Superior mesenteric artery via ▪ First jejunal branch ▪ Anterior inferior pancreaticoduodenal artery ▪ Posterior inferior pancreaticoduodenal artery  Jejunum & Ileum Receives blood supply from the following arteries: o Superior mesenteric artery via jejunal and ileal arteries  Caecum & Appendix Receives blood supply from the superior mesenteric artery via the branches of the ileocolic artery: o Anterior caecal artery o Posterior caecal artery o Appendicular artery  Ascending Colon Receives blood supply from the superior mesenteric artery and the ileocolic artery: o Colic branch – of ileocolic artery o Posterior caecal artery – of ileocolic artery o Appendicular artery – ileocolic artery o Right colic artery – from superior mesenteric artery  Transverse Colon Receives blood supply from the following arteries: o Right colic artery – from superior mesenteric artery o Middle colic artery – from superior mesenteric artery o Left colic artery – from inferior mesenteric artery  Descending Colon & Sigmoid Colon Receives blood supply from the following arteries: DESCENDING COLON o Left colic artery – from inferior mesenteric artery SIGMOID COLON o Sigmoidal arteries – from inferior mesenteric artery Marginal artery – anastomotic connections between arteries supplying  Rectum & Anal Canal Receives blood supply from the following arteries: o Superior rectal artery – from inferior mesenteric artery o Middle rectal artery – from internal iliac artery o Inferior rectal artery – from internal pudendal artery  Venous Drainage of Gastrointestinal Tract  Portal System of Veins Mainly through portal system of veins Portal vein formed by union of splenic vein and superior mesenteric vein posterior to neck of pancreas at level of L2 Portal vein passes superior to superior part of duodenum Enters right margin of lesser omentum Lies anterior to omental foramen Receives: o Right and left gastric veins o Cystic veins ( from gallbladder) o Para-umbilical veins Revise notes from CVS: Major Venous Systems  Splenic Vein Forms from smaller vessels leaving hilum of spleen Passes through splenorenal ligament Lies posterior to body of pancreas Joins superior mesenteric vein to form portal vein, posterior to neck of pancreas Tributaries: o Short gastric veins – drains fundus of stomach and left part of greater curvature of stomach o Left gastro-omental/gastro-epiploic vein – related to greater curvature of stomach o Pancreatic vein – drains body and tail of pancreas o Inferior mesenteric vein  Superior Mesenteric Vein Drains small intestine, caecum, ascending colon and transverse colon Begins as fusion of veins draining terminal ileum, caecum and appendix Ascends to form portal vein with splenic vein Has tributaries that accompany superior mesenteric artery branches – e.g. jejunal veins, middle colic veins Additional tributaries: o Right gastro-omental/gastro-epiploic vein – related to greater curvature of stomach o Anterior & Posterior inferior pancreaticoduodenal veins  Inferior Mesenteric Vein Drains splenic flexure, descending colon, sigmoid colon and rectum Begins as superior rectal vein and ascends Receives tributaries from sigmoid veins and left colic vein o These veins accompany arteries with similar names Drains into splenic vein o Alternatively: ▪ Ends at junction of splenic vein and superior mesenteric vein ▪ Or drains into superior mesenteric vein Lymphatic Drainage & Innervation of Gastrointestinal Tract  Lymphatic Drainage All drainage is to pre-aortic lymph nodes Via: o Coeliac, superior mesenteric & inferior mesenteric groups ROUTE: Lymph from inferior mesenteric group drains to superior mesenteric group Lymph from superior mesenteric group drains to coeliac group Lymph from coeliac group drains into cysterna chyli  Innervation Abdominal viscera innervated by extrinsic and intrinsic components: o Extrinsic – receives motor impulses and sends sensory impulses to central nervous system ▪ Via visceral efferent and visceral afferent fibres ▪ Visceral efferent fibres are part of sympathetic and parasympathetic system ▪ Structural components include anterior and posterior rami, rami communicantes, splanchnic nerves, sympathetic ganglia, prevertebral plexus o Intrinsic – regulation of digestive system via the enteric nervous system ▪ Enteric system found in walls of gastrointestinal tract ▪ System contains motor and sensory neurons ▪ Neurons co-ordinate contraction and relaxation of smooth muscle and regulate gastric secretion and blood flow  Innervation – Sympathetic & Parasympathetic SYMPATHETIC Abdominal prevertebral plexus – branches from ganglia Has three divisions: o Coeliac plexus o Aortic plexus o Superior hypogastric plexus PARASYMPATHETIC Vagus nerve association with prevertebral plexus Pelvic splanchnic nerves carry impulse to inferior hypogastric plexus  Innervation – Enteric System Consists of motor and sensory neurons organised into two plexuses: o Myenteric o Submucosal Generally independent of CNS but receives input from sympathetic and parasympathetic systems Regulates and co-ordinates gastrointestinal tract activities o Gastric secretory activity o Gastrointestinal blood flow o Peristalis That’s All Folks! For any queries or questions please feel free to contact me: [email protected]  RESOURCES Grays Anatomy for Students, 6th Edition Chapter 4 – Abdomen Peritoneum, Peritoneal Cavity, Mesenteries & Omenta https://www.clinicalkey.com/student/content/book/3-s2.0- B9780323934237000046#hl0002706 Organs https://www.clinicalkey.com/student/content/book/3-s2.0- B9780323934237000046#hl0002854 Arterial Supply, Venous Drainage, Lymphatics & Innervation https://www.clinicalkey.com/student/content/book/3-s2.0- B9780323934237000046#hl0003717