Lecture 26: Anatomy of the Abdomen II PDF

Lecture 26 Anatomy of the Abdomen II Abdominal Viscera  Neural tube Notochord Mesoderm Parietal Dorsal...

Lecture 26 Anatomy of the Abdomen II Abdominal Viscera  Neural tube Notochord Mesoderm Parietal Dorsal Coelomic peritoneum mesentery Peritoneal cavity cavity Digestive tract Developing Visceral liver peritoneum Digestive tract 4 weeks Ventral mesentery 5 weeks During embryonic development, the digestive tube is initially suspended by dorsal and ventral mesenteries. In adults, the ventral mesentery is lost, except where it connects the stomach to the liver (at the lesser omentum) and the liver to the anterior body wall and diaphragm (at the falciform ligament). 2 Week 5 Week 6-10 Week 11 Week 12 3  Abdominal Cavity Peritoneum – The abdominal cavity is lined with a mesothelium called peritoneum; the peritoneum reflects off the abdominal wall to form folds called mesenteries that suspend abdominal organs – Parietal peritoneum lines the abdominal wall – Visceral peritoneum covers suspended organs – In general, the GIT consists of a central tube suspended from the posterior abdominal wall and from the anterior abdominal wall by mesenteries Ventral mesentery: attach to proximal part of gut tube Dorsal mesenteries: attach along the entire length of system – Mesenteries are named according to the organs they cover or with which they are associated 4  Greater omentum (cut) Lesser omentum Transverse mesocolon Transverse Mesocolon of ascending colon and descending colons fused to posterior portion Ascending of the parietal peritoneum colon Mesentery Descending proper colon (mesenterial sheet) Small intestine Sigmoid colon A diagrammatic view of the organization of mesenteries in an adult. As the digestive tract enlarges, mesenteries associated with the proximal portion of the small intestine, the pancreas, and the ascending and descending portions of the colon fuse to the body wall. 5  Falciform Diaphragm ligament Liver Lesser omentum Stomach Pancreas Transverse Duodenum mesocolon Transverse Mesentery colon proper Greater omentum Sigmoid mesocolon Parietal peritoneum Rectum Small Urinary intestine bladder Uterus A sagittal section showing the mesenteries of an adult. Notice that the pancreas, duodenum, and rectum are retroperitoneal. 6 Intraperitoneal structures Retroperitoneal structures (e.g. stomach) are suspended (e.g. kidneys) are not suspended from from the abdominal wall by the abdominal wall by mesenteries. mesenteries. They lie between the parietal peritoneum and the abdominal wall. 7  Abdominal Viscera Stomach – The most dilated part of the GIT between abdominal oesophagus and small intestines; J-shaped – 4 regions: Cardia – surrounds opening of oesophagus into stomach Fundus – area above the cardiac orifice Body – largest region Pylorus – pyloric antrum and canal – 2 openings: cardiac and pyloric orifices – 2 curvatures: greater and lesser – 2 surfaces: anterior and posterior 8  Diaphragm Liver and gallbladder Liver Greater omentum Lesser omentum Lesser Spleen omentum Transverse colon Oesophagus Greater omentum Lesser curvature Duodenum Greater curvature 9  Abdominal Viscera Small intestine – Longest part of GIT ~7m long; from pyloric orifice to ileocaecal valve; diameter of tube narrows distally – 3 parts: duodenum, jejunum and ileum I. Duodenum – first part; 25cm long; C-shaped and adjacent to head of pancreas; receives ducts of liver and pancreas II. Jejunum – middle portion, represents most of proximal 2/5 of small intestine; larger diameter and thicker walls than ileum III.Ileum – distal 3/5 of small intestine; opens into large intestine where caecum and ascending colon join together 10 Duodenum Jejunum Plica Ileum circulares Large intestine A representative view of the jejenum Rectum The positions of the duodenum, jejunum, and ileum in the abdominopelvic cavity Longitudinal andand Longitudinal smooth muscle smooth muscle layer layers Plica circulares 11  The duodenum is the shortest, widest and most predictably placed part of the small intestine. It is 25cm long, C-shaped and adjacent to the head of the pancreas. It has four parts: superior, descending, inferior and ascending. It joins the jejunum at the duodenojejunal flexure. The duodenum is retroperitoneal except for initial portion which is attached to the liver by part of the lesser omentum (hepatoduodenal ligament). Superior part Descending part Body of pancreas Pylorus Duodenum Head of pancreas Jejunum Inferior Ascending part part 12  The descending part of the duodenum contains the major duodenal papilla, which is the Liver common entrance for the bile and pancreatic ducts, and the minor duodenal papilla, which is the entrance for the accessory pancreatic duct. Bile duct Accessory pancreatic duct Minor Pancreas duodenal papilla Major Main pancreatic duct duodenal papilla Johns Hopkins Medicine: Gastroenterology & Hepatology A peptic ulcer is a break in the mucosa of the stomach or Duodenum duodenum. Duodenal ulcers (4x more common than gastric ulcers) arise in the superior part of the duodenum and are mostly caused by the bacteria Helicobacter pylori. 13  The jejunum and ileum (~7m long) make up the last sections of the small intestine. There’s no clear distinction between the two parts, but a gradual change in morphology from proximal to distal. The jejunum, representing the proximal 2/5, is mostly in the left upper quadrant and is a larger diameter and has thicker walls than the ileum. The ileum is the distal 3/5 of the small bowel and is located in the right lower quadrant. Jejunum Ileum Fewer More arterial arterial arcades. arcades. Short Longer vasa vasa recta. recta. More mesenteric fat Larger lumen. Lymphoid aggregates Less prominent (Peyer’s patches). circular folds. More circular folds (plicae circulares). 14 Jejunum Ileum Ileum Ileocaecal fold flaps 15  Abdominal Viscera Large Intestine – Extends from caecum to the anus; ~1.5 m long – Consists if: Caecum – most dilated part, below ileocaecal valve; appendix Ascending colon – ends at right colic flexure, under liver Transverse colon – crosses abdomen from right to left; ends at left colic flexure Descending colon – from left colic flexure, ends at pelvic inlet Sigmoid colon – S-shaped; begins at pelvic inlet, ends anterior to sacrum Rectum – dilated; begins at level of S3 vertebra Anal canal – begins at anorectal junction; most distal part of large intestine 16  Left colic flexure Large Intestine Right colic flexure Transverse colon Ascending colon Caecum Appendix Sigmoid colon Rectum Anal canal 17  Appendix Appendix A narrow, hollow tube (9cm long) attached to posteromedial aspect of caecum. It contains large aggregations of lymphoid tissue in its walls and is suspended from the terminal ileum by the mesoappendix, which carries appendicular blood vessels. Although its base (attachment to caecum) is consistent, the location of the rest of the appendix varies considerably. Caecum Preileal Postileal Caecum Large blind pouch; lies below ileocaecal opening in the right iliac fossa. It is intraperitoneal, in contact with anterior abdominal wall, and continuous with Retrocecal Pelvic ascending colon superiorly. 75% Subcecal 18  Colon The colon consists of the ascending, The sigmoid colon is highly mobile; runs transverse, descending, and sigmoid colon. posterior to urinary bladder; ends at level The ascending and descending segments of vertebra S3. The rectum is expandable are retroperitoneal and its transverse for temporary storage of faeces, located and sigmoid parts are intraperitoneal. in front of the sacrum. Descending colon Sigmoid colon Rectum Right colic flexure Left colic flexure Anal canal 10  Right colic (hepatic) flexure Left colic (splenic) flexure Greater omentum (cut) TRANSVERSE COLON DESCENDING COLON Anal Canal ASCENDING COLON Last portion of large Fatty appendices Haustra intestine; contains small longitudinal folds called Ileocecal valve Ileum anal columns. Anus (or anal Caecum orifice) – exit of anal canal. Appendix Taenia coli Sigmoid flexure SIGMOID COLON The gross anatomy and regions of the large intestine Anal sphincter Rectum Ileocecal Internal – smooth muscle Rectum valve (involuntary), Cecum (cut open) Anal canal External – skeletal muscle Anal columns (voluntary). Internal anal Appendix sphincter External anal sphincter The caecum and appendix Anus The rectum and anus 20  Abdominal Viscera Liver 2% of body mass – Largest visceral organ in the body; lies primarily in right hypochondrium and epigastric region of body – Surfaces: diaphragmatic and visceral Diaphragmatic surface: lie against diaphragm; smooth, domed; parts of this surface are not covered by peritoneum (called bare area of the liver) Visceral surface: inferior surface, covered by visceral peritoneum except for fossa for the gallbladder and porta hepatis; related to many structures of the abdomen – Porta hepatis: point of entry into liver for hepatic arteries and portal vein, exit for hepatic ducts – Lobes: larger right lobe; smaller left lobe which includes the quadrate and caudate lobes 21  Coronary ligament Right lobe Left lobe Falciform ligament Coronary ligament Gallbladder Bare area Round ligament 22  Bare area Left hepatic vein Coronary ligament Inferior vena cava Left lobe Caudate lobe Common bile duct Hepatic portal vein Hepatic artery proper Right lobe Porta hepatis Quadrate lobe Gallbladder Quadrate lobe: only visible from inferior surface. Fissure for Boundaries: right – gallbladder fossa, left – ligamentum teres fissure, posterior – porta hepatis. ligamentum venosum Caudate lobe: visible on lower part of visceral surface. Boundaries: right – groove for inferior vena cava; left – fissure for ligamentum venosum; anterior – porta hepatis. 23  Gallbladder Round ligament Right hepatic duct Left hepatic duct Left hepatic artery Cystic duct Pear-shaped sac lying on Common hepatic duct Fundus visceral surface of right lobe Body Cut edge of lesser of liver, in a fossa between Gallbladder omentum Neck right and quadrate lobes. Function: it receives, Hepatic portal vein concentrates and stores bile Common bile from the liver. duct Common hepatic artery Liver Duodenum Right gastric artery Stomach Pancreas Bile Duct System The right and left hepatic ducts come together as the common hepatic duct, and join the cystic duct to form the common bile duct. This duct descends to the 2nd part of the duodenum, is joined by the pancreatic duct, and empties its contents into the duodenal lumen via the major duodenal papilla. 24  Abdominal Viscera Pancreas – Elongated gland; lies posterior to the stomach, from duodenum to spleen; retroperitoneal – Four parts: Head – lies within C-shaped concavity of duodenum; a process (uncinate process) projects inferiorly from head Neck – narrow region anterior to superior mesenteric vessels Body – longest portion, progressively thinner towards tail Tail – narrowest, ends at hilum of spleen – Pancreatic ducts Main pancreatic duct – drains most of exocrine part; joins common bile duct to form hepatopancreatic ampulla (of Vater) which empties at the major duodenal papilla Accessory pancreatic duct – empties into duodenum at minor duodenal papilla, just above major duodenal papilla 25  Tail Head Hepatopancreatic sphincter (of Oddi) Common bile duct Hepatopancreatic ampulla (of Vater) Main pancreatic duct Major duodenal papilla Duodenum lumen Pancreas 26  Abdominal Viscera Spleen – Consists of largest collection of lymphoid tissue in the body; ~size of a cupped hand – Located in left upper quadrant, lies along greater curvature of stomach, between ribs 9-11 – 2 surfaces: diaphragmatic and visceral – 2 borders: superior (notched) and inferior – 2 poles: anterior and posterior – The spleen is connected to surrounding organs by peritoneal folds: Gastrosplenic ligaments – to greater curvature of stomach Splenorenal ligaments – left kidney 27  Liver Spleen Superior border (notched) Stomach Posterior pole Hilum Inferior Spleen border Anterior pole Splenic vessels Pancreas Left kidney 28  Stomach Gastrosplenic ligament Diaphragm Liver Gallbladder Spleen Epiploic foramen Splenomegaly Phrenicocolic ligament Transverse mesocolon Pancreas 29  GIT Blood Supply Arterial Supply – Abdominal aorta: Begins at aortic hiatus (T12) and ends at level of L4 vertebra by terminating into Rt & Lt common iliac arteries It gives off anterior, lateral and posterior branches; anterior branches supply GIT organs – Anterior branches: Celiac trunk – supplies foregut – abdominal oesophagus, stomach, duodenum (superior to major papilla), liver, pancreas, gallbladder, and spleen Superior mesenteric artery – supplies midgut – Duodenum (inferior to major papilla), jejunum, ileum, caecum, ascending colon, and proximal ⅔ of transverse colon Inferior mesenteric artery – supplies hindgut – Distal ⅓ of transverse colon, descending colon, sigmoid colon, rectum, and upper ½ of anal canal 30 Foregut Midgut Hindgut 31  GIT Blood Supply Celiac trunk – Supplies the foregut; arises from abdominal aorta immediately below aortic hiatus of diaphragm (L1) – Branches: Left gastric artery – smallest branch of celiac trunk; gives off oesophageal branches; supplies anterior and posterior surfaces of stomach Splenic artery – largest branch of celiac trunk; has a tortuous course to the left; divides into many branches to pancreas, stomach and spleen Common hepatic artery – medium-sized; passes to the right, its branches supply the liver, gallbladder, stomach, proximal duodenum, and pancreas 32 Common hepatic artery Left gastric artery Splenic artery 33  Left gastric artery Common hepatic artery Celiac trunk Splenic artery 34  GIT Blood Supply Superior mesenteric artery – Supplies the midgut; arises from abdominal aorta immediately below celiac trunk (L1) – Branches: Inferior pancreaticoduodenal artery – first branch; supplies distal duodenum and pancreas Jejunal and ileal branches – arise from the left, and form arches or arcades which supply the small intestine Middle colic artery – arises from right of main trunk; supplies right ⅔ of transverse colon Right colic artery – arises from right side of main trunk; supplies the ascending colon Ileocolic artery – last branch; from right side, supplies terminal ileum, caecum, appendix, and distal ascending colon 35  Inferior pancreaticoduodenal artery Jejunal arteries Middle colic artery 36  Inferior Middle colic artery pancreaticoduodenal artery Superior mesenteric artery Right colic artery Jejunal arteries Ileocolic artery Jejunal and Ileal arteries: These branches leave the main trunk of the superior mesenteric artery, and form arcades as they pass outward to supply the small intestine. The number of arterial arcades increases distally along the gut. Vasa recta (straight Ileal arteries arteries) extend from the terminal arcade to reach the walls of the small intestine. 37  GIT Blood Supply Inferior mesenteric artery – Supplies the hindgut; arises from abdominal aorta at level of L3 vertebra; smallest of the 3 anterior branches – Branches: Left colic artery – first branch; supplies left ⅓ of transverse colon and descending colon Sigmoid arteries – 2 to 4 branches; supply lowest part of descending colon and sigmoid colon Superior rectal artery – terminal branch of inferior mesenteric artery; descends into pelvis; supplies the rectum and upper part of anal canal – Lower part of anal can is supplied by the middle rectal (internal iliac artery) and the inferior rectal (internal pudendal artery) 38  Left colic artery Superior mesenteric artery Superior rectal artery Sigmoid arteries 40  Arteries Supplying the Abdominopelvic Organs Branches of the The Celiac Trunk Common Hepatic Artery Hepatic artery proper (liver) Common hepatic Gastroduodenal (stomach Liver Left gastric and duodenum) Splenic Cystic (gallbladder) Right gastric (stomach) Spleen Right gastroepiploic Stomach Branches of the (stomach and duodenum) Splenic Artery Superior pancreatico- Left gastroepiploic duodenal (duodenum) (stomach) Pancreatic Ascending colon (pancreas) Pancreas Superior Mesenteric Artery Inferior Mesenteric Inferior pancreatico- Artery duodenal (pancreas and Left colic (colon) duodenum) Middle colic (cut) Sigmoid (colon) (large intestine) Right colic (large intestine) Rectal (rectum) Ileocolic (large intestine) Small intestine Intestinal arteries (small intestine) Sigmoid colon Rectum 40  GIT Blood Supply Venous Drainage – Venous blood from the spleen, pancreas, gallbladder, and the abdominal part of the GIT (abdominal oesophagus to upper rectum) drains towards the hepatic portal vein: hepatic portal v. >> portal sinusoids >> hepatic v. >> IVC – Hepatic portal vein Final common pathway for venous blood from GI tract and accessory organs to liver Formed by union of the splenic vein and the superior mesenteric vein It passes through the porta hepatis together with the hepatic artery and bile duct Divides into right and left branches which enter the liver 41 Hepatic portal vein Splenic vein Superior mesenteric vein 42 Porto-Systemic Anastomosis Caput medusae 1 Oesophageal varices 2 Haemorrhoids 3 43 Notes & Figures Adapted From: 1. Gray’s Anatomy For Students 2. Netter’s Atlas for Human Anatomy 3. Clinical Oriented Anatomy by Moore, Dalley & Agur 4. Anatomy and Physiology – Seeley et al. (7th Edition) 5. Fundamentals of Anatomy & Physiology – Martini et al. (9th Edition) 44