DEVELOPMENT OF THE LIVER

THE LIVER

DEVELOPMENT OF THE LIVER

THE LIVER The hepa-c diver-culum develops as an outgrowth of the endoderm of the foregut in the region of the second por-on of duodenum. This diver-culum enters the ventral mesentery. This diver-culum enters the ventral embryonic mesentery and distally becomes the liver and gallbladder and proximately becomes the biliary duct system. The part of the ventral embryonic mesentery between the liver and gut tube becomes the lesser omentum, and the part between the liver and ventral body wall becomes the falciform ligament.

The liver is the body s largest internal organ (1.2 1.5 kg) and is situated in the right hypochondrium. THE LIVER A funcbonal division into the larger right lobe (containing caudate and quadrate lobes) and the lel lobe is made by the middle hepabc vein. The liver is further subdivided into eight segments by divisions of the right, middle and lel hepa-c veins. Each segment has its own portal pedicle, permimng individual segment resecbon at surgery.

The liver has 2 surfaces: a superior or diaphragmabc surface and an inferior or a visceral surface. lt lies mostly in the right aspect of the abdominal cavity and is protected by the rib cage. THE LIVER The reflec-on of visceral peritoneum between the diaphragma-c surface of the liver and the diaphragm forms the falciform ligament, which con-nues onto the liver as the coronary ligament and the right and lel triangular ligaments.

THE LIVER The extension of visceral peritoneum between the visceral surface of the liver and the first part of the duodenum and the lesser curvature of the stomach forms the hepatoduodenal and hepatogastric ligaments of the lesser omentum, respec-vely. The liver is divided into 2 lobes Fissures for the ligamentum teres and the ligamentum venosum, the porta hepabs, and the fossa for the gallbladder further subdivide the right lobe into the right lobe proper, the quadrate lobe, and the caudate lobe.

THE LIVER The quadrate and caudate lobes are anatomically part of the right lobe but func-onally part of the lel. They receive their blood supply from the lel branches of the portal vein and hepa-c artery and secrete bile to the lel hepa-c duct. The liver has a central hilus, or porta hepabs, which receives venous blood from the portal vein and arterial blood from the hepa-c artery.

THE LIVER The central hilus also transmits the common bile duct, which collects bile produced by the liver. The bile duct, hepa-c artery, and hepa-c portal vein, known collec-vely as the portal triad, are located in the hepatoduodenal ligament, which is the right free border of the lesser omentum. The hepabc veins drain the liver by collec-ng blood from the liver sinusoids and returning it to the inferior vena cava.

THE LIVER The liver has a convex diaphragmabc surface and a rela-vely flat or even concave visceral surface. Subphrenic recesses, superior extensions of the peritoneal cavity (greater sac) - between diaphragm and the anterior and superior aspects of the diaphragma-c surface of the liver. The subphrenic recesses are separated into right and lel recesses by the falciform ligament, which extends be tween the liver and the anterior abdominal wall. The hepatorenal recess (hepatorenal pouch; Morison pouch) is the posterosuperior extension of the subhepa-c space, lying between the right part of the visceral surface of the liver and the right kidney and suprarenal gland.

THE LIVER The diaphragma-c surface of the liver is covered with visceral peritoneum, except posteriorly in the bare area of the liver The bare area is demarcated by the reflec-on of peritoneum from the diaphragm to it as the anterior (upper) and posterior (lower) layers of the coronary ligament. The layers of the coronary ligaments meet: on the right to form the right triangular ligament on the lel meet to form the lek triangular ligament

THE LIVER The liver is surrounded by the peritoneum and is atached to the diaphragm by the coronary and falciform ligaments and the right and lel triangular ligaments. The IVC traverses a deep groove for the vena cava within the bare area of the liver.

The visceral surface of the liver is also covered with visceral peritoneum except in the: fossa for the gallbladder porta hepa-s hepa-c nerve plexus hepa-c ducts THE LIVER

THE LIVER Two sagimally oriented fissures, linked centrally by the transverse porta hepa-s, form the lemer H on the visceral surface. The right sagimal fissure is the con-nuous groove formed anteriorly by the fossa for the gallbladder and posteriorly by the groove for the vena cava.

THE LIVER The umbilical (lek sagimal) fissure is the con-nuous groove formed anteriorly by the fissure for the round ligament and posteriorly by the fissure for the ligamentum venosum. The round ligament of the liver is the fibrous remnant of the umbilical vein The ligamentum venosum is the fibrous remnant of the fetal ductus venosus, which shunted blood from the umbilical vein to the IVC.

The lesser omentum, enclosing the portal triad (bile duct, hepa-c artery, and hepa-c portal vein) passes from the liver to the: lesser curvature of the stomach first 2 cm of the superior part of the duodenum THE LIVER The hepatoduodenal ligament, free edge of the lesser omentum, encloses the structures that pass through the porta hepa-s.

THE LIVER In addi-on to the fissures, impressions on (areas of) the visceral surface reflect the liver s rela-onship to the: Right side of the anterior aspect of the stomach (gastric and pyloric areas). Superior part of the duodenum (duodenal area). Lesser omentum (extends into the fissure for the ligamentum venosum). Gallbladder (fossa for gallbladder). Right colic flexure and right transverse colon (colic area). Right kidney and suprarenal gland (renal and suprarenal areas).

The liver is divided into two anatomical lobes (right & lel) and two accessory lobes (quadrate & caudate) THE LIVER The essen-ally midline plane defined by the atachment of the falciform ligament and the lel sagital fissure separates a large right lobe from a much smaller lek lobe. the quadrate lobe anteriorly and inferiorly and the caudate lobe posteriorly and superiorly

THE LIVER The liver has funcbonally independent right and lel livers that are much more equal in size than the anatomical lobes. Each part receives its own primary branch of the hepabc artery and hepabc portal vein and is drained by its own hepabc duct. The liver can be further subdivided into four divisions and then into eight surgically resectable hepabc segments, each served independently by a secondary or ter-ary branch of the portal triad.

The liver, like the lungs, has a dual blood supply THE LIVER The hepabc portal vein brings 75 80% of the blood to the liver. The hepabc portal vein brings 75 80% of the blood to the liver. Arterial blood from the hepa-c artery, accoun-ng for only 20-25% of blood received by the liver.

THE LIVER The hepa-c artery, a branch of the celiac trunk, may be divided into the common hepa-c artery, from the celiac trunk to the origin of the gastroduodenal artery and the hepabc artery proper, from the origin of the gastroduodenal artery to the bifurca-on of the hepa-c artery The hepabc artery and hepabc portal vein terminate by dividing into right and lel branches.

ARTERIAL SUPPLY OF THE LIVER The arterial supply of the liver is from the right hepa-c artery and lel hepa-c artery: abdominal aorta celiac trunk common hepa-c artery proper hepa-c artery right hepa-c artery and lel hepa-c artery hepa-c sinusoids THE LIVER

VENOUS DRAINAGE OF THE LIVER The venous drainage of the liver is to the central veins central veins hepa-c veins inferior vena cava THE LIVER

PORTAL SUPPLY 1. The portal supply of the liver is from the portal vein superior mesenteric vein, inferior mesenteric vein, and splenic vein portal vein hepa-c sinusoids THE LIVER 2. The portal vein is formed by the union of the splenic vein and superior mesenteric vein. 3. The inferior mesenteric vein joins the splenic vein. 4. The arterial blood and portal blood mix in the hepa-c sinusoids.

THE LIVER The liver is a major lymph-producing organ. Hepa-c collec-ng vessels are divided into superficial and deep systems. The lympha-c vessels of the liver occur as superficial lympha-cs in the subperitoneal fibrous capsule of the liver and drain to the hepa-c lymph nodes scatered along the hepa-c vessels and ducts in the lesser omentum. Superficial lympha-cs from the posterior aspects of the diaphragma-c and visceral surfaces of the liver drain toward the bare area of the liver and drain into phrenic lymph nodes.

The nerves of the liver are derived from the hepabc plexus, the largest deriva-ve of the celiac plexus. THE LIVER

BILIARY DUCTS AND GALLBLADDER

THE GALLBLADDER The biliary ducts convey bile from the liver to the duodenum. Bile is produced con-nuously by the liver and stored and concentrated in the gallbladder, which releases it when fat enters the duodenum. Each lobule has a central vein running through its center from which sinusoids and plates of hepatocytes radiate toward from surrounding interlobular portal triads. The hepatocytes secrete bile into the bile canaliculi. The canaliculi drain into the small interlobular biliary ducts and then into large collec-ng bile ducts of the intrahepa-c portal triad, which merges to form the hepabc ducts.

THE GALLBLADDER The right and lek hepabc ducts join together aler leaving the liver to form the common hepabc duct. The common hepa-c duct is joined at an acute angle by the cys-c duct to form the common bile duct. The cysbc duct drains bile from the gallbladder. The mucosa of the cysbc duct is arranged in a spiral fold with a core of smooth muscle known as the spiral valve (valve of Heister). The spiral valve keeps the cys-c duct constantly open so that bile can flow freely in either direc-on.

THE GALLBLADDER The common bile duct passes posterior to the pancreas and ends at the hepatopancreabc ampulla (ampulla of Vater), where it joins the pancreabc duct. The sphincter of Oddi is an area of thickened smooth muscle that surrounds the bile duct as it traverses the ampulla. The sphincter of Oddi controls bile flow (sympathe-c innerva-on causes contrac-on of the sphincter).

THE GALLBLADDER The gallbladder is divided into the fundus (anterior por-on), body, and the neck (posterior por-on). Fundus: usually projects from the inferior border of the liver Body: contacts the visceral surface of the liver, transverse colon, and superior part of the duodenum. Neck: makes an S-shaped bend and joins the cys-c duct A small pouch (Hartmann pouch) may extend from the neck as a sequela to pathologic changes and is a common site for gallstones to lodge.

THE GALLBLADDER ARTERIAL SUPPLY. The arterial supply of the gallbladder is from the cysbc artery: abdominal aorta celiac trunk common hepa-c artery proper hepa-c artery right hepa-c artery cys-c artery

THE GALLBLADDER VENOUS DRAINAGE. The venous drainage of the gallbladder is to the cysbc vein cys-c vein portal vein hepa-c sinusoids central veins hepa-c veins inferior vena cava

THE GALLBLADDER INNERVATION ParasympatheBc Preganglionic neuronal cell bodies are located in the dorsal nucleus of the vagus. Preganglionic axons run in CN X. Postganglionic neuronal cell bodies are located within the wall of the gallbladder. Postganglionic parasympathe-c axons terminate on smooth muscle and s-mulate gallbladder contrac-on.

THE GALLBLADDER INNERVATION SympatheBc Preganglionic neuronal cell bodies are located in the intermediolateral cell column of the spinal cord (T5 9). Preganglionic axons form the greater splanchnic nerve. Postganglionic neuronal cell bodies are located in the celiac ganglion. Postganglionic axons terminate on smooth muscle and inhibit gallbladder contrac-on. SomaBc. Sensory neuronal cell bodies located in dorsal root ganglion (C3 5) of the right phrenic nerve send peripheral processes to the gallbladder. These sensory nerve fibers are probably responsible for the soma-c referred pain associated with gallbladder disease.

Portal Hypertension Portal hypertension is indicated by a rise in pressure in the portal vein and is olen caused by cirrhosis, characterized by scarring and fibrosis of the liver. This causes blood to flow into the systemic (caval) system at sites of portal-systemic anastomosis, producing varicose veins. THE LIVER

THE PORTAL-SYSTEMIC ANASTOMOSES Portal-systemic anastomoses, in which the portal venous system communicates with the systemic venous system: in the submucosa of the inferior esophagus, in the submucosa of the anal canal, in the peri-umbilical region (caput meduse) on the posterior aspects (bare areas) of secondarily retroperitoneal viscera, or the liver The blood from the gastrointes-nal tract can s-ll reach the right side of the heart through the IVC by way of these collateral routes.

THE LIVER Liver biopsies are frequently performed by needle puncture through the right intercostal space 8, 9, or 10 when the pa-ent has exhaled. Liver biopsies. The needle will pass through the following structures: skin superficial fascia external oblique muscle intercostal muscles costal parietal pleura costodiaphragma-c recess diaphragma-c parietal pleura diaphragm peritoneum.

Gallstones form when bile salts and lecithin are overwhelmed by cholesterol. Most stones consist of cholesterol (major component), bilirubin, and calcium. There are three main types of gallstones: Cholesterol stones are yellow, large, smooth, and composed mainly of cholesterol. Pigment (bilirubin) stones are brown or black, smooth, and composed mainly of bilirubin salts. Calcium bilirubinate stones are associated with infec-on and/or inflamma-on of the biliary tree.

Gallstone ObstrucBon. There are three clinically important sites of gallstone obstruc-on: Within the cysbc duct. A stone may transiently lodge within the cys-c duct and cause pain (biliary colic) within the epigastric region due to the disten-on of the duct. If a stone becomes entrapped within the cys-c duct, bile flow from the gallbladder will be obstructed, resul-ng in inflamma-on of the gallbladder (acute cholecys--s) and pain will shil to the right hypochondriac region.

Gallstone ObstrucBon. There are three clinically important sites of gallstone obstruc-on: Within the common bile duct. If a stone becomes entrapped within the common bile duct, bile flow from both the gallbladder and liver will be obstructed, resul-ng in inflamma-on of the gallbladder and liver. Jaundice is frequently observed and is first observed clinically under the tongue. The jaundice is moderate and fluctuates since a stone rarely causes complete blockage of the lumen.

Gallstone ObstrucBon. There are three clinically important sites of gallstone obstruc-on: At the hepatopancreabc ampulla. If a stone becomes entrapped at the ampulla, bile flow from both the gallbladder and liver will be obstructed. In addi-on, the pancrea-c duct may be blocked. In this case, jaundice and pancrea--s are frequently observed.

THE PANCREAS

THE PANCREAS In the adult, the pancreas is a retroperitoneal organ that measures 15 to 20 cm in length and weighs about 85 to 120 g. The pancreas is both an exocrine gland and an endocrine gland. HEAD OF THE PANCREAS The head is the expanded part of the pancreas that lies in the concavity of the C-shaped curve of the duodenum and is firmly atached to the descending and horizontal parts of the duodenum. The uncinate process is a projec-on from the inferior por-on of the pancrea-c head. The head of the pancreas is related posterior to the IVC, right renal artery, right renal vein, and lek renal vein.

NECK OF THE PANCREAS The neck is related posteriorly to the confluence of the superior mesenteric vein and splenic vein to form the portal vein. THE PANCREAS BODY OF THE PANCREAS The body is related posteriorly to the: aorta superior mesenteric artery lel suprarenal gland lel kidney renal artery renal vein. TAIL OF THE PANCREAS The tail is related to the splenic hilum and the lel colic flexure.

ARTERIAL SUPPLY The arterial supply of the pancreas is from the: Anterior and posterior superior pancrea-coduodenal arteries Anterior and posterior inferior pancrea-coduodenal arteries Dorsal pancrea-c artery Great pancrea-c artery Caudal pancrea-c arteries THE PANCREAS

THE PANCREAS ARTERIAL SUPPLY Anterior and posterior superior pancrea-coduodenal arteries, which supply the head and neck of the pancreas abdominal aorta celiac trunk common hepa-c artery gastroduodenal artery anterior and posterior superior pancrea-coduodenal arteries ARTERIAL SUPPLY Anterior and posterior inferior pancrea-coduodenal arteries, which supply the head and neck of the pancreas abdominal aorta superior mesenteric artery anterior and posterior inferior pancrea-coduodenal arteries

ARTERIAL SUPPLY Dorsal pancrea-c artery, which supplies the body and tail of the pancreas abdominal aorta celiac trunk splenic artery dorsal pancrea-c artery THE PANCREAS Great pancrea-c artery, which supplies the body and tail of the pancreas: abdominal aorta celiac trunk splenic artery great pancrea-c artery

ARTERIAL SUPPLY Caudal pancrea-c arteries, which supply the body and tail of the pancreas: abdominal aorta celiac trunk splenic artery caudal pancrea-c arteries THE PANCREAS

VENOUS DRAINAGE The venous drainage of the pancreas is to the: Splenic vein Superior mesenteric vein THE PANCREAS

VENOUS DRAINAGE The venous drainage of the pancreas is to the: Splenic vein splenic vein portal vein hepa-c sinusoids central veins hepa-c veins IVC THE PANCREAS

VENOUS DRAINAGE The venous drainage of the pancreas is to the: Superior mesenteric vein superior mesenteric vein portal vein hepa-c sinusoids central veins hepa-c veins IVC THE PANCREAS

The main pancreabc duct begins in the tail of the pancreas, THE PANCREAS The main pancreabc duct begins in the tail of the pancreas, which opens into the descending part of the duodenum at the summit of the major duodenal papilla (of Vater). The sphincter of the pancrea-c duct (around the terminal part of the pancrea-c duct), the sphincter of the bile duct (around the termina-on of the bile duct), and the hepatopancrea-c sphincter (of Oddi, around the hepatopancrea-c ampulla) are smooth muscle sphincters that control the flow of bile and pancrea-c juice into the ampulla and prevent reflux of duodenal content into the ampulla.

THE PANCREAS The accessory pancreabc duct opens into the duodenum at the summit of the minor duodenal papilla Usually, the accessory duct communicates with the main pancrea-c duct.

THE PANCREAS The nerves of the pancreas are derived from the vagus and abdominopelvic splanchnic nerves passing through the diaphragm The parasympathebc and sympathebc fibers reach the pancreas by passing along the arteries from the celiac plexus and superior mesenteric plexus

THE SPLEEN

THE SPLEEN The spleen is located in the lel hypochondriac region posterior to the 9th, 10th, and 11th ribs. The spleen does not extend below the costal margin and therefore is not palpable unless splenomegaly is present. The spleen is atached to the stomach by the gastrosplenic ligament, which contains the short gastric arteries and veins and the lel gastroepiploic artery and vein. The spleen is atached to the kidney by the splenorenal ligament, which contains the five terminal branches of the splenic artery, tributaries of the splenic vein, and the tail of the pancreas.

ARTERIAL SUPPLY The arterial supply is from the splenic artery (the largest branch of the celiac trunk), which gives off the following branches: dorsal pancrea-c artery great pancrea-c artery caudal pancrea-c arteries short gastric arteries lel gastroepiploic artery, it ends with about five terminal branches. THE SPLEEN

THE SPLEEN ARTERIAL SUPPLY The five terminal branches of the splenic artery supply individual segments of the spleen with no anastomosis between them (i.e., end arteries) so that obstruc-on or liga-on of any terminal branch will result in splenic infarcbon (i.e., the spleen is very prone to infarc-on).

VENOUS DRAINAGE THE SPLEEN The venous drainage is to the splenic vein via tributaries. The splenic vein joins the superior mesenteric vein to form the portal vein. The inferior mesenteric vein usually joins the splenic vein. VENOUS DRAINAGE SPLENIC VEIN THROMBOSIS is most commonly associated with pancrea--s and shows the following clinical signs: gastric varices and upper gastrointes-nal bleeding.