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Major Abdominal Vessels. Abdomen, Pelvis & Perineum Unit Lecture 7 د. حيدر جليل الأعسم. Aorta.
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Major Abdominal Vessels Abdomen, Pelvis & Perineum Unit Lecture 7 د. حيدر جليل الأعسم
Aorta It enters the abdomen through aortic opening of diaphragm (aortic hiatus) in front of T12 thoracic vertebra. It descends behind peritoneum on anterior surface of bodies of lumbar vertebrae. At the level of L4 lumbar vertebra, it divides into two common iliac arteries. Relations: On its right side: inferior vena cava, cisterna Chyli & beginning of azygos vein. On its left side: left sympathetic trunk. Branches: 3 Anterior visceral branches: celiac trunk, superior mesenteric, & inferior mesenteric arteries 3 Lateral visceral branches: suprarenal, renal & testicular (or Ovarian) arteries. 5 Lateral abdominal wall branches: inferior phrenic & 4 lumbar arteries 3 Terminal branches: two common iliac arteries & median sacral artery
Common Iliac Arteries Right and left common arise at level of L4 lumbar vertebra and run downward and laterally along medial border of psoas muscle. Each artery ends in front of sacroiliac joint by dividing into external and internal iliac arteries. At the bifurcation, common iliac artery on each side is crossed anteriorly by the ureter. External Iliac Artery It lies on medial border of psoas muscle. It gives off inferior epigastric and deep circumflex iliac branches. It enters the thigh by passing under inguinal ligament to become femoral artery. Internal Iliac Artery It passes down into pelvis in front of sacroiliac joint to supply pelvic organs.
Arterial Supply of GIT During embryonic development, gut is divided into three parts: foregut, midgut and hindgut. Each part has its own arterial supply and venous drainage. Celiac artery is the artery of foregut and supplies GIT from lower 1/3 of esophagus till middle of 2nd part of duodenum. Superior mesenteric artery is artery of midgut & supplies GIT from middle of 2nd part of duodenum till distal 1/3 of transverse colon. Inferior mesenteric artery is artery of hindgut & supplies large intestine from distal 1/3 of transverse colon to halfway down anal canal.
A. Celiac Artery arises from abdominal aorta at level of T12. It is surrounded by celiac plexus & lies behind lesser sac. It has three terminal branches: left gastric, splenic, and hepatic arteries. Splenic Artery: Splenic artery runs to the left in a tortuous coursealong upper border of pancreas & behind stomach. On reaching left kidney, it enters splenicorenal ligament and runs to hilum of spleen. Branches: 1. Pancreatic branches 2. Left gastroepiploic artery: along greater curvature of stomach in the gastrosplenic omentum. 3. Short gastric arteries: 5-6 in number, Supply fundus of stomach in gastrosplenic omentum.
Hepatic Artery Medium-size hepatic artery runs forward and to the right and ascends between layers of lesser omentum. It lies in hepatic triad in front of the opening into lesser sac and is placed to left of bile duct and in front of portal vein. At porta hepatis it divides into right and left branches. Branches Right gastric artery:along lesser curvature of stomach & anastomoses with left gastric a. Gastroduodenal artery:is a large branch that descends behind 1st part of duodenum. It divides into right gastroepiploic artery (along greater curvature) and superior pancreaticoduodenal artery that descends between 2nd part of duodenum & head of pancreas. Right and left hepatic arteries:enter porta hepatis. Right hepatic artery usually gives off cystic artery.
B. Superior Mesenteric Artery It supplies distal part of duodenum, jejunum, ileum, cecum, appendix, ascending colon, and right 2/3 transverse colon. It runs downward & to the right behind neck of pancreas and in front of 3rd part of duodenum. It continues downward between layers of mesentery of small intestine. Branches: Inferior pancreaticoduodenal artery: To pancreas & adjoining part of duodenum. Middle colic artery: runs forward in transverse mesocolon. Right colic artery: is often a branch of ileocolic artery. It supplies ascending colon. Ileocolic artery: gives rise to superior branch that anastomoses with right colic artery and an inferior branch that gives rise to anterior & posterior cecal arteries; appendicular artery is a branch of posterior cecal artery. Jejunal and ileal branches:form a series of arcades. From terminal arcades, small straight vessels supply the intestine (vasa recta).
C. Inferior Mesenteric Artery supplies distal 1/3 of transverse colon, left colic flexure, descending and sigmoid colons, rectum & upper half of anal canal. It runs left downward and crosses left common iliac artery to become superior rectal artery. Branches Left colic artery:runs upward and to the left and supplies distal 1/3 of transverse colon, left colic flexure & upper part of descending colon. Sigmoid arteries:are 2-3 in number and supply descending & sigmoid colon. Superior rectal artery:is a continuation of inferior mesenteric artery as it crosses left common iliac artery. It descends into pelvis behind rectum. It supplies rectum and upper half of anal canal and anastomoses with middle rectal and inferior rectal arteries. Marginal Artery: single artery that formed by anastomosis of colic arteries around margins of large intestine. It anastomoses with ileal branches of superior mesenteric & with superior rectal arteries.
Inferior Vena Cava It conveys most of the blood from body below diaphragm to right atrium It is formed by union of common iliac veins behind right common iliac artery at level of L5. It ascends on right side of aorta, pierces central tendon of diaphragm at level of T8, & drains into right atrium. Right sympathetic trunk lies behind its right margin & right ureter lies close to its right border. Tributaries: 2 Anterior visceral tributaries: right and left hepatic veins 3 Lateral visceral tributaries: right suprarenal vein, renal veins, and right testicular or ovarian vein. 5 Lateral abdominal wall tributaries: inferior phrenic & 4 lumbar veins 3 Veins of origin: 2 common iliac veins & median sacral veins.
Venous drainage of GIT Venous drainage of most of GIT and its accessory organs is drained into liver by portal venous system. Proximal tributaries drain directly into portal vein, but distal tributaries correspond to branches of celiac artery and superior and inferior mesenteric arteries. Portal Vein: It drains blood from abdominal part of GIT from lower third of esophagus to halfway down anal canal; it also drains blood from spleen, pancreas & gallbladder. Portal is short and formed behind neck of pancreas by union of superior mesenteric & splenic veins. It ascends to the right, behind 1st part of duodenum, and enters lesser omentum. It then runs upward in front of opening into lesser sac to porta hepatis, where it divides into right and left terminal branches.
Tributaries of Portal Vein Splenic vein:begins at hilum of spleen by union of several veins & is joined by short gastric & left gastroepiploic veins. It passes to right within splenicorenal ligament and runs behind pancreas. It unites with superior mesenteric vein behind neck of pancreas to form portal vein. Inferior mesenteric vein:ascends on posterior abdominal wall and joins splenic vein behind body of pancreas. It receives superior rectal veins, sigmoid veins, and left colic vein. Superior mesenteric vein:ascends in root of mesentery of small intestine. It passes in front of 3rd part of duodenum & joins splenic vein behind neck of pancreas. It receives jejunal, ileal, ileocolic, right colic, middle colic, inferior Pancreaticoduodenal & right gastroepiploic veins. Left gastric vein:drains left portion of lesser curvature of stomach & distal part of esophagus. Right gastric vein:drains right portion of lesser curvature of stomach. Cystic veins:either drain gallbladder directly into liver or join portal vein.
Lymphatics on Posterior Abdominal Wall Lymph Nodes:are closely related aorta and form a preaortic and right & left lateral aortic (para-aortic or lumbar) chain. Preaortic lymph nodes lie around origins of celiac, superior mesenteric & inferior mesenteric arteries and drain lymph from GIT. Para-aortic (or lumbar) lymph nodes drain lymph from kidneys & suprarenals; from testes in male & from ovaries, uterine tubes & fundus of uterus in female. Lymph Vessels: Thoracic duct commences in abdomen as an elongated lymph sac called cisterna chyli. It lies just below diaphragm in front of 1st two lumbar vertebrae and on right side of aorta. Cisterna chyli receives intestinal trunk, right & left lumbar trunks, & small lymph vessels that descend from lower part of thorax.
Nerves on Posterior Abdominal Wall Aortic Plexuses They are regional concentrations of nerves at the origins of celiac, renal, superior mesenteric & inferior mesenteric arteries to form celiac, renal, superior mesenteric & inferior mesenteric plexuses. Aortic plexuses receive preganglionic sympathetic fibers from greater and lesser splanchnic nerves while Parasympathetic fibers are from vagi except inferior mesenteric plexus which receives parasympathetic fibers from sacral parasympathetic plexus. Lumbar Plexus formed in psoas muscle from anterior rami of upper four lumbar nerves. Iliohypogastric nerve, ilioinguinal nerve, lateral cutaneous nerve of thigh & femoral nerve emerge from lateral border of psoas. Obturator nerve and 4th lumbar root of lumbosacral trunk emerge from medial border of psoas at pelvic brim. Genitofemoral nerve (L1 and 2) emerges on anterior surface of psoas. Sympathetic Trunk (Abdominal Part) Abdominal part of sympathetic trunk is continuous above with thoracic and below with pelvic parts of sympathetic trunk. It enters abdomen from behind medial arcuate ligament and gains entrance to pelvis by passing behind common iliac vessels.
