Vasculature of the Abdomen

Anatomical position of the interior mesenteric

- It is the last of the three major anterior branches of the abdominal aorta (the other two are the coeliac trunk and superior mesenteric artery). - It arises at L3, near the inferior border of the duodenum, 3-4 cm above where the aorta bifurcates into the common iliac arteries. - As the artery arises from the aorta, it descends anteriorly to its parent vessel, before moving to the left side. - It is a retroperitoneal structure

what is the abdominal aorta?

- The abdominal aorta is a continuation of the thoracic aorta beginning at the level of the T12 vertebrae. - It is approximately 13cm long and ends at the level of the L4 vertebra. - At this level, the aorta terminates by bifurcating into the right and left common iliac arteries that supply the lower body.

Anatomical position of the coeliac trunk?

- The coeliac trunk is the second branch of the abdominal aorta - It arises from the anterior aspect of the aorta, at the aortic hiatus of the diaphragm (T12 level).

Common hepatic artery course and 2 main branches?

- The common hepatic artery is the sole arterial supply to the liver and the only branch of the coeliac artery to pass to the right. - As it travels past the superior aspect of the duodenum, it divides into its two terminal branches - the proper hepatic and gastroduodenal arteries. - Each of these arteries has multiple branches and variation in the arrangement of these branches is common.

Common iliac

- The common iliac vein is formed at the upper margin of the pubic symphysis by the union of the external and internal iliac veins. It receives two additional tributaries: 1) Iliolumbar vein - drains the L4 and L5 vertebrae, and the iliopsoas muscle. 2) Middle sacral veins - drain part of the sacrum. The left and right common iliac veins combine at L5 to become the inferior vena cava, which empties into the inferior aspect of the right atrium.

External iliac

- The external iliac vein is a continuation of the femoral vein, arising when the femoral vein crosses underneath the inguinal ligament. - It ascends along the medial aspect of the external iliac artery, before joining with the internal iliac vein to form the common iliac vein. - During its short course, the external iliac vein receives the inferior epigastric and deep circumflex iliac veins.

What happens if the portal veins become blocked?

Collateral circulation: When the portal circulation is obstructed, whether it is within or outside the liver, a remarkable collateral circulation develops to carry portal blood into the systemic veins.

What are the three tributaries of the portal vein?

• R and L gastric veins (Stomach) • Cystic veins (Gallbladder) • Para-umbilical veins (Skin of the umbilical region)

Internal iliac

- The internal iliac vein is responsible the majority of pelvic venous drainage, and receives numerous tributaries from veins that drain the pelvic region. - It is formed near the greater sciatic foramen, ascending anteriorly to the sacroiliac joint, before combining with the external iliac vein to form the common iliac vein. - With the exception of the iliolumbar vein (which drains into the common iliac), the tributaries of the internal iliac vein correspond with the branches of the internal iliac artery. It receives venous blood from the: 1) Superior and inferior gluteal veins - drains the buttock and upper thigh. 2) Internal pudendal vein - drains the reproductive organs and part of the rectum (via the inferior rectal vein). 3) Obturator vein 4) Lateral sacral veins - drains part of the sacrum. 5) Middle rectal vein - drains the bladder, prostate (in males only), and part of the rectum. 6) Vesical veins - drains the urinary bladder via the vesical venous plexus. 7) Uterine and vaginal veins - drain the female reproductive organs via the vaginal and uterine venous plexuses.

Common variations

- The left gastric artery often arises proximal to the bifurcation of the splenic and common hepatic arteries. This is called a false tripod. - The right gastric artery is occasionally seen as a branch of the common hepatic instead of the proper hepatic artery. - The right gastric and right hepatic arteries may arise from the SMA. - The left hepatic artery is sometimes seen as a branch of the left gastric artery. - The inferior phrenic arteries may arise from the coeliac trunk instead of the abdominal aorta

Left gastric artery

- The smallest of the three branches. - It ascends across the diaphragm, giving rise to oesophageal branches, before continuing anteriorly along the lesser curvature of the stomach. - Here, it anastomoses with the right gastric artery.

Course of the splenic artery

- The splenic artery arises from the coeliac trunk just inferior to the left gastric artery. - It then travels left towards the spleen, running posterior to the stomach and along the superior margin of the pancreas. - During its course, it is contained within the splenorenal ligament. It terminates into five branches which supply the segments of the spleen.

What are the 3 major vessels involved in venous drainage of the pelvis?

1) External iliac vein 2) Internal iliac vein 3) Common iliac vein

Major branches of the superior mesenteric

1) Inferior Pancreaticoduodenal Artery - the first branch of the SMA. - It forms anterior and posterior vessels, which anastomose with branches of the superior pancreaticoduodenal artery - This network supplies the inferior region of the head of the pancreas, the uncinate process, and the duodenum. 2) Jejunal and Ileal arteries - numerous branches supply the jejunum and ileum. - The arteries pass between the layers of the mesentery and form anastomotic arcades - from which smaller, straight arteries (known as the "vasa recta") arise to supply the organs. - The jejunal blood supply is characterised by a smaller number of arterial arcades, but longer vasa recta. - In contrast, the ileal blood supply is marked by more arterial arcades with shorter vasa recta. 3) Middle and Right Colic Arteries - arise from the right side of the superior mesenteric artery: A) Middle colic artery - supplies the transverse colon. B) Right colic artery - supplies the ascending colon. Ileocolic Artery 4) The ileocolic artery - final major branch - It passes inferiorly and to the right, giving rise to branches to the ascending colon, appendix, cecum, and ileum. - In cases of appendectomy, the appendicular artery is ligated.

List the branches of the abdominal aorta in descending order

1) Inferior phrenic arteries: Paired parietal arteries arising posteriorly at the level of T12. They supply the diaphragm. 2) Coeliac artery: A large, unpaired visceral artery arising anteriorly at the level of L1. It is also known as the celiac trunk and supplies the liver, stomach, abdominal oesophagus, spleen, the superior duodenum and the superior pancreas. 3) Superior mesenteric artery: A large, unpaired visceral artery arising anteriorly, just below the celiac artery. It supplies the distal duodenum, jejuno-ileum, ascending colon and part of the transverse colon. It arises at the lower level of L1. 4) Middle suprarenal arteries: Small paired visceral arteries that arise either side posteriorly at the level of L1 to supply the adrenal glands. 5) Renal arteries: Paired visceral arteries that arise laterally at the level between L1 and L2. They supply the kidneys. 6) Gonadal arteries: Paired visceral arteries that arise laterally at the level of L2. Note that the male gonadal artery is referred to as the testicular artery and in females, the ovarian artery. 7) Inferior mesenteric artery: A large, unpaired visceral artery that arises anteriorly at the level of L3. It supplies the large intestine from the splenic flexure to the upper part of the rectum. 8) Median sacral artery: An unpaired parietal artery that arises posteriorly at the level of L4 to supply the coccyx, lumbar vertebrae and the sacrum. 9) Lumbar arteries: There are four pairs of parietal lumbar arteries that arise posterolaterally between the levels of L1 and L4 to supply the abdominal wall and spinal cord.

What are the major branches of the coeliac trunk?

After emerging from the aorta, the coeliac trunk extends approximately 1cm before dividing into three major branches 1) left gastric 2) splenic 3) common hepatic Of these branches, two go left and one goes to the right-hand side. Collectively, they are the major arterial supply to the stomach, spleen, liver, gall bladder, abdominal oesophagus, pancreas and duodenum.

What are the 3 major branches of the inferior mesenteric?

1) Left Colic Artery - the first branch of the IMA. - supplies the distal 1/3 of the transverse colon and the descending colon. - After arising from its parent artery, it travels anteriorly to the psoas major muscle, left ureter and left internal spermatic vessels, before dividing into ascending and descending branches: A) Ascending branch - crosses the left kidney anteriorly, before entering the mesentery of the transverse colon, moving superiorly. It supplies the distal 1/3 of the transverse colon, and the upper aspect of the descending colon. B) Descending branch - moves inferiorly to supply the lower part of the descending colon. It anastamoses with the superior sigmoid artery. 2) Sigmoid Arteries - The sigmoid arteries supply the descending colon and the sigmoid colon. - There are typically 2-4 branches, with the uppermost branch termed the superior sigmoid artery. - They run inferiorly, obliquely and to the left, crossing over the psoas major, left ureter and left internal spermatic vessels. 3) Superior Rectal Artery - The superior rectal artery is a continuation of the inferior mesenteric artery, supplying the rectum. - It descends into the pelvis, crossing the left common iliac artery and vein. - At the S3 vertebral level, the artery divides into two terminal branches - one supplying each side of the rectum. - Within the walls of the rectum, smaller divisions of these branches eventually communicate with the middle and inferior rectal arteries.

In addition to supplying the spleen, the splenic artery gives rise to what important vessels?

1) Left gastroepiploic: supplies the greater curvature of the stomach. Anastomoses with the right gastroepiploic artery. 2)Short gastrics: 5-7 small branches supplying the fundus of the stomach. 3) Pancreatic branches: supply the body and tail of the pancreas.

Intra-hepatic obstruction (cirrhosis): Normally 100% of the portal venous blood can be recovered from the hepatic veins, whereas in cirrhosis only 13% is obtained. The remainder enters collateral channels which form 4 main groups.

1: Group 1 where protective epithelium adjoins absorptive epithelium. A: at the cardia of the stomach, where the left gastric vein, posterior gastric and short gastric veins of the portal system anastomose with the intercostal, diagphragmo-oesophageal and azygous minor veins . Deviation of blood into these channels leads to varicosities in the submucous layer of the lower end of the oesophagus and fundus of the stomach. B: at the anus, the superior haemorrhoidal vein of the portal system anastomoses with the middle and inferior haemorrhoidal veins of the caval system. Deviation of blood into these channels may lead to rectal varices. Group2: in the falciform ligament through the paraumbilical veins, relics of the umbilical circulation of the fetus. Group 3: where the abdominal organs are in contact with the retro-peritoneal tissues or adherent to the abdominal wall. These collateral run from the liver to the diaphragm. These include the lumbar veins. Group 4: portal venous blood is carried to the left renal vein. This may be through blood entering directly from the splenic vein or via diaphragmatic , pancreatic, left adrenal or gastric veins. Blood from the gastro-oesophageal and other collaterals ultimately reaches the SVC via the azygous or hemi-azygous system. A small volume enters the IVC.

Gastroduodenal artery branches?

The gastroduodenal artery descends posterior to the superior portion of the duodenum. Its branches are: 1) Right gastroepiploic: supplies the greater curvature of the stomach. Found between the layers of the greater omentum, which it also supplies. 2) Superior pancreaticoduodenal: divides into an anterior and posterior branch, which supplies the head of the pancreas.

What is the inferior mesenteric artery?

The inferior mesenteric artery (IMA) is a major branch of the abdominal aorta. It supplies arterial blood to the organs of the hindgut - the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum.

Pancreatic anastomoses

The pancreaticoduodenal arcade is a network of arteries that surround and supply the head of the pancreas. There are two main arteries - each has an anterior and posterior branch, that anastomose (e.g. anterior to anterior) forming a ring structure: 1) Superior pancreaticoduodenal- a branch of the gastroduodenal artery. 2) Inferior pancreaticoduodenal - branch of superior mesenteric artery (SMA)

What is the portal venous system?

The portal system includes all the veins that carry blood from the abdominal part of the alimentary tract, the spleen, pancreas and the gall bladder. The portal vein enters the liver at the "porta hepatis" in 2 main branches, one to each lobe.

What forms the portal vein?

The portal vein is formed from the union of the superior mesenteric vein and the splenic vein just posterior to the head of the pancreas at about L2. • The splenic veins originate at the splenic hilum and join near the tail of the pancreas with the short gastric vessels to form the main splenic vein. • The inferior mesenteric vein bringing blood back from the left part of the colon and rectum.

Proper hepatic artery branches?

The proper hepatic artery ascends through the lesser omentum towards the liver. It gives rise to: 1) Right gastric: supplies the pylorus and lesser curvature of the stomach. 2) Right and left hepatic: divide inferior to the porta hepatis and supply their respective lobes of the liver. 3) Cystic: branch of the right hepatic artery - supplies the gall bladde

What is special about the splenic flexure?

The splenic flexure can be described as a watershed area - a term used when an area has dual blood supply from the most distal branches of two large arteries. Whilst this has the advantage of being more resistant to ischaemia if one of the arteries becomes occluded, it makes the area more sensitive to systemic hypoperfusion.

Stomach anastamoses

The stomach is the only organ to receive arterial supply from all three branches of the coeliac trunk. This is achieved through a system of anastomoses along the greater (gastroepiploic arteries) and lesser (gastric arteries) curvatures

What is the superior mesenteric artery?

The superior mesenteric artery (SMA) is a major artery of the abdomen. It arises from the abdominal aorta, and supplies arterial blood to the organs of the midgut - which spans from the major duodenal papilla (of the duodenum) to the proximal 2/3 of the transverse colon.

Anatomical position and relations of the superior mesenteric artery

The superior mesenteric artery is the second of the three major anterior branches of the abdominal aorta (the other two are the coeliac trunk and inferior mesenteric artery). It arises anteriorly from the abdominal aorta at the level of the L1 vertebrae, immediately inferior to the origin of the coeliac trunk. After arising from the abdominal aorta, the superior mesenteric artery descends down the posterior aspect of the abdomen. At this point, it has several important anatomical relations: 1) Anterior to the SMA - pyloric part of the stomach, splenic vein and neck of the pancreas. 2) Posterior to the SMA - left renal vein, uncinate process of the pancreas and inferior part of the duodenum. - The uncinate process is the only part of the pancreas that hooks around the back of the SMA.

What are the 2 major anastamoses of the IMA?

They both involve a union with branches of the SMA Marginal artery (of Drummond) - forms a continuous arterial circle along the inner border of the colon. Straight vessels (vasa recta) arise from the artery to supply the colon. It is formed by the union of several branches; the ileocolic, right colic and middle colic of the SMA and left colic and sigmoid branches of the IMA. Arc of Riolan - anastomosis between the middle colic branch of SMA and the left colic branch of IMA. It is less common than the marginal artery, and indeed its existence has been questioned by some surgeons.

Name the porto-systemic anastomoses

• This is when the portal venous system communicates with the systemic venous system • Between the oesophageal veins, draining into the azygous vein (systemic) or left gastric vein (portal). When dilated these cause oesophageal varices • Between rectal veins, between the inferior and middle veins draining into the IVC (Systemic) and the superior rectal vein as the inferior mesenteric vein (IMV) (portal) - giving heammorhoids • Para-umbillical veins (portal) anastomosing with peri-umbilical superficial epigastic veins (systemic). When dilated these form caput medusae - varicose veins arising from the umbillicous • Twigs of colic veins (portal) anastomosing with retroperitoneal veins (Systemic)