ORGANS SUPPLIED BY THE CELIAC AXIS Dr. Milton M. Sholley SUGGESTED READING

Essential Clinical Anatomy 3 rd ed. (ECA): pp. 142­152 and 159­174 Head to Toe Questions in Gross Anatomy: Continue questions #607­756.

OBJECTIVE

This lecture is designed to explain the distribution of the celiac axis (i.e. the celiac ). Additionally, it is designed to provide an understanding of the organs supplied by the celiac axis and their relationships.

LECTURE OUTLINE

I. Celiac artery or axis ­ an unpaired artery from the anterior surface of the abdominal aorta (Fig. 1 and ECA, Fig. 2.16A, p. 147)

A. The celiac artery has branches which supply organs derived from the distal portion of the embryological foregut. These organs include the:

1. Distal part of

2.

3. Liver and gall bladder

4. Pancreas

5. Cranial portion of the (parts I and II)

B. The celiac artery also has a branch that supplies the spleen, an organ which develops within the dorsal mesogastrium and therefore is closely related to the stomach.

C. The celiac artery (axis) has three branches (which radiate from the axis like spokes from the hub of a wheel):

1. Left gastric artery ­ This artery gives off an esophageal branch and then runs inferiorly along the lesser curvature of the stomach to anastomose with the right gastric artery.

2. Common hepatic artery ­ This artery has three branches:

a. Right gastric artery ­ This relatively small artery runs superiorly along the lesser curvature of the stomach to anastomose with the left gastric artery. b. Gastroduodenal artery ­ This large branch passes posterior to the first part of the duodenum, where it sometimes is the source of fatal bleeding after perforation of a duodenal ulcer. The gastroduodenal artery then gives off:

(1) Right gastroepiploic artery ­ An artery which follows the greater curvature of the stomach and anastomoses with the left gastroepiploic artery (a branch of the splenic artery).

(2) Anterior superior pancreaticoduodenal artery ­ An artery which anastomoses with the anterior inferior pancreaticoduodenal artery, which is a branch of the superior mesenteric artery, and supplies primarily the duodenum.

(3) Posterior superior pancreaticoduodenal artery ­ An artery which anastomoses with the posterior inferior pancreaticoduodenal artery, which is a branch of the superior mesenteric artery, and supplies primarily the pancreas.

c. Proper hepatic artery ­ This artery is the continuation (i.e. third branch) of the common hepatic artery. It divides into:

(1) Right hepatic artery ­ An artery which supplies the right functional lobe of the liver and also gives off the cystic artery to the gall bladder.

(2) Left hepatic artery ­ An artery which supplies the left functional lobe of the liver.

C

Fig. 1 The celiac artery (C) and its branches (From Textbook of Anatomy by W. Henry Hollinshead) 3. Splenic artery ­ This large, tortuous branch runs to the left along the superior border of the pancreas and gives off:

a. Pancreatic branches

b. Short gastric branches ­ to the fundic stomach

c. Left gastroepiploic artery ­ An artery which runs along the greater curvature of the stomach and anastomoses with the right gastroepiploic artery.

II. Stomach ­ an intraperitoneal organ

A. For description, the stomach is divided into a number of parts:

1. Cardiac portion ­ the area around the entrance of the esophagus

2. Fundus ­ the area superior and to the left of the entrance of the esophagus

3. Body ­ the major portion of the stomach

4. Pyloric portion ­ the narrow end which connects with the duodenum and is demarcated from the body of the stomach by the angular incisure, a notch on the lesser curvature. The angular incisure is easily discernable on a barium X­ ray.

a. Pyloric antrum ­ the wider, more proximal part of the pyloric portion

b. Pyloric canal ­ the narrow, more distal part of the pyloric portion, which connects with the

c. Pylorus ­ the opening into the duodenum, constricted by a heavy layer of circular smooth muscle, the pyloric sphincter

5. Gastric canal ­ formed by pronounced mucosal folds on the interior of the stomach along the lesser curvature. The incomplete canal formed by these folds tends temporarily to trap fluids entering the stomach, although these fluids soon mix with the remainder of the gastric contents. Consequently, when caustic liquids are accidentally swallowed, the lesser curvature tends to be more damaged than other areas of the stomach's interior.

B. One minor and four major sources of blood supply to the stomach can be deduced from your knowledge of the branches of the celiac artery (see Fig. 1). C. Lymphatic drainage ­ areas of lymphatic drainage of the stomach correspond to its four major arterial supplies. The areas are numbered in order of decreasing size, area 1 being the largest.

1. Area 1 ­ lymph vessels follow the left gastric artery

2. Area 2 ­ lymph vessels follow the right gastroepiploic artery (carcinoma of the stomach most frequently originates in this area)

3. Area 3 ­ lymph vessels follow the left gastroepiploic artery

4. Area 4 ­ lymph vessels follow the right gastric artery

5. Lymph vessels from all four areas eventually reach the lymph nodes at the base of the celiac axis.

D. supply

1. Anterior vagal trunk ­ provides parasympathetic primarily derived from the left vagus nerve. The anterior trunk follows the anterior side of the lesser curvature, although it also sends a branch through the lesser omentum to supply the liver and gall bladder.

2. Posterior vagal trunk ­ provides parasympathetic nerves primarily derived from the right vagus nerve. The posterior trunk runs along the posterior side of the lesser curvature. Both vagal trunks are involved in stimulation of peristalsis and acid secretion.

3. Sympathetic innervation is supplied by periarterial plexuses of postganglionic fibers having their cell bodies in the celiac ganglia. Preganglionic fibers reach the celiac ganglia through the greater splanchnic nerves. Visceral afferent fibers follow the greater splanchnic nerves in a reverse direction.

III. Spleen

A. It lies along the midaxillary line against ribs 9,10, and 11 in the upper left quadrant.

B. It is an intraperitoneal organ, suspended within the greater omentum, which connects it to the greater curvature of the stomach (gastrolienal ligament) and to the left kidney (lienorenal ligament).

C. It receives branches of the splenic artery at an indentation (hilum) on its concave side. IV. Pancreas

A. For purposes of description this secondarily retroperitoneal organ is divided into several parts:

1. Head ­ the part lying within the C­shaped curve of the duodenum

a. Uncinate process ­ a part of the head which hooks posteriorly to lie behind the superior mesenteric vessels

2. Neck – the part lying anterior to the superior mesenteric vessels

3. Body – the part between the neck and the tail

4. Tail – the leftmost tip, which is closely related to the hilum of the spleen

B. The blood supply to the pancreas can be deduced from your knowledge of the branches of the celiac (primarily) and superior mesenteric .

C. The main pancreatic duct joins the common bile duct, and they have a common opening into the second part of the duodenum. The pancreatic juice contains a number of important digestive enzymes. It also contains bicarbonate, which buffers the acidic gastric juice.

V. Duodenum – the first and shortest segment (~12 inches) of the

A. For purposes of description this first part of the small intestine is divided into four parts numbered I, II, III, and IV (Fig. 2).

1. Part I (superior part) is the part which connects to the pylorus and it is intraperitoneal, being connected to the liver by the hepatoduodenal ligament (a part of the lesser omentum). This part of the duodenum receives the highly acidic contents of the stomach and, like the pyloric region of the stomach, it is prone to ulceration.

2. Part II (descending part) is retroperitoneal and receives the combined opening of the common bile duct and main pancreatic duct.

3. Part III (horizontal part) is retroperitoneal and is crossed anteriorly by the superior mesenteric vessels.

4. Part IV (ascending part) is retroperitoneal and connects with the , which is intraperitoneal.

5. The , an acute bend, is supported by the attachment of the suspensory muscle of the duodenum (ligament of Treitz). 6. There are other important relationships of the duodenum to surrounding structures. Please learn about these using ECA, Table 2.6, p. 151.

I

II

IV III Grant’s Atlas, 12 th ed. Fig. 2.54A, p. 156 Fig. 2. Duodenum, gallbladder, bile and pancreatic ducts

B. The is a cone­shaped mound projecting through the wall and seen on the interior surface of the second part of the duodenum (See Grant’s Atlas, 12 th ed., Figs. 2.54B&C, page 156). The papilla contains a dilated chamber called the hepatopancreatic ampulla. The common bile duct and the main pancreatic duct both empty into the hepatopancreatic ampulla, hence its name. The walls of the ampulla contain a smooth muscle sphincter called the hepatopancreatic sphincter. The sphincter is contracted most of the time, thus closing off the lumen of the ampulla and preventing passage of bile and pancreatic juice through the opening of the ampulla at the apex of the major duodenal papilla. The sphincter relaxes under the influence of the hormone cholecystokinin. Relaxation of the sphincter allows bile and pancreatic juice to flow through the ampulla into the duodenum.

The following eponyms are commonly used by clinicians: Ampulla of Vater = Hepatopancreatic ampulla Sphincter of Oddi = Hepatopancreatic sphincter

C. The blood supply of the duodenum can be deduced from your knowledge of the branching of the celiac and superior mesenteric arteries.

VI. Liver ­ an intraperitoneal organ (except for the bare area)

A. Study relationships of the liver shown in ECA, Figs. 2.24 and 2.25, pp. 164­165. B. For purposes of description the liver is divided into four anatomical lobes.

1. Left anatomical lobe (radiologists call this the lateral segment of the left lobe) ­ This lobe lies to the left of the plane of the falciform ligament. In an inferior view it is obvious that it lies to the left of the fissures for the ligamentum teres and the ligamentum venosum.

2. Quadrate lobe (radiologists call this the medial segment of the left lobe) ­ This lobe is obvious only in an inferior view. It lies between the fissure for the ligamentum teres and the fossa for the gall bladder, anterior to the porta hepatis (the area where vessels and ducts attach).

3. Caudate lobe ­ This lobe is obvious only in an inferior view. It lies between the fissure for the ligamentum venosum and the groove for the inferior vena cava, posterior to the porta hepatis.

4. Right anatomical lobe ­ This large lobe lies to the right of the fossa for the gall bladder and the groove for the inferior vena cava.

C. The liver can also be divided into two functional lobes, supplied by the right and left branches of the proper hepatic artery, the portal , and the common hepatic duct.

1. Left functional lobe ­ consists of the left anatomical lobe, the quadrate lobe, and most of the caudate lobe

2. Right functional lobe ­ consists of the right anatomical lobe (and a small part of the caudate lobe)

D. Within the "free edge" of the lesser omentum, or hepatoduodenal ligament, run the portal vein, the common bile duct, and the proper hepatic artery. The portal vein is located posteriorly, the common bile duct is located anteriorly and to the right, and the proper hepatic artery is located anteriorly and to the left.

E. Triangle of Calot ­ This triangle is bounded by the cystic duct laterally, the common hepatic duct medially, and the liver superiorly. Through this triangle normally passes the cystic artery (the branch of the right hepatic artery which supplies the gall bladder). The cystic artery must be ligated during removal of the gall bladder. The arterial supply of this area is subject to many variations.

VII. Hepatic portal system (Fig. 3 and ECA, Fig. 2.30, p. 172 and pp.173­174)

A. A portal system consists of interposed between two capillary beds. In the case of the hepatic portal system, capillary beds (first bed) within the gut and its associated organs (except the liver) connect to tributaries of the hepatic portal vein. The hepatic portal vein (Fig. 3) eventually enters the liver, where it breaks up into the second capillary bed (formed by the sinusoids of the liver). Because of the hepatic portal system, materials absorbed from the gut are passed through the circulation of the liver (where they can be biochemically modified) before entering the systemic circulation.

Portal Vein and its Branches

Left gastric vein (Coronary vein)

Splenic vein

Portal vein Inferior mesenteric vein Superior mesenteric vein

Grant’s Atlas, 12t h ed. Fig. 2.60, p. 160 Fig. 3

B. The hepatic portal vein is formed in a location posterior to the pancreas by the merger of the splenic and superior mesenteric veins. The inferior mesenteric vein normally enters the splenic vein just before the latter merges with the superior mesenteric vein. Just before entering the liver, the portal vein divides into right and left branches, one to each of the functional lobes of the liver.

C. There are also smaller branches of the portal vein (Fig. 3). One important smaller branch is the left gastric vein, also called the coronary vein. The left gastric vein has an esophageal branch which has anastomotic connections to higher esophageal veins derived from the azygos system (a systemic venous system). Because there are no valves in the portal system, if pressure builds up (portal hypertension), as it does in certain pathological conditions (notably cirrhosis of the liver), excessive blood will flow into the anastomotic connections. Because the connections are made through thin­ walled veins lying within the of the esophagus, the veins become dilated and tortuous, forming esophageal varices (Grant’s Atlas, 12 th Ed., Figs. 2.61A&B, p. 161). Esophageal varices bulge into the lumen of the esophagus, where they are subject to the mechanical trauma of passing food and may rupture. Fatal exsanguination (i.e. complete loss of blood) may result. Figures from Grant's Atlas of Anatomy

(11 th ed.) (12 th ed.)

2.28A, page122 2.29A, page130 2.28B, page 122 2.29B, page 130 2.30, page 123 2.31, page 131 2.27A, B&C, page 121 2.28A, B&C, page 129 2.49A, page 142 and 2.51A, page 144 2.45A, page 146 and 2.47A, page 148 2.50A, page 143 and 2.51B, page 144 2.46A, page 147 and 2.47B, page 148 2.54B, page 148 2.52A, page 154 2.50B, page 143 2.46C, page 147 2.55A, page 149 2.53A, page 155 2.35A&B, page 128 2.51A&B, page 152 2.36, page 129 2.51, page 153 2.53B,C,D,&E, page 147 2.49B,C,D,&E, page 150 2.53A, page 146 2.49A, page 150 2.60, page 152 2.60, page 160 2.61A&B, page 153 2.61A­C, page 161 2.33A&B, page 126 2.33A&B, page 134 2.34A&B, page 127 2.34A&B, page 135 2.37A, page 130 2.54A, page 156 2.37B, page 130 2.54B&C, page 156