I./1. Anatomy of the human liver

I./1.1.: Surface antomy of the liver

I./1.1.1.: The liver in general

The liver (hepar) is the largest parenchymal organ int he abdominal cavity. It lies largely in the right hypochondrium, under the right dome of the diaphragm. Smaller part of the liver extends across the epigastrium into the left hypochondrium, reaching the left medioclavicular line or crossing it. A dense connective tissue capsule known as Glisson’s capsule covers the hepatic surface. Its superior, anterior and right margins are rounded, thus no definite borders can be described between them. These margins are continouos.

In contrast, the inferior margin is sharp, the lower visceral surface separated in front from the diaphragmatic surface by the sharp inferior margin. In the median sagittal plane, a notch in the inferior border of the liver accommodates the round ligament (incisura umbilicalis). In the right medioclavicular line, in the region of gallbladder fossa, another shallow notch on the inferior margin may be present.

Two hepatic surfaces can be defined distinctly. (i) The right, upward and anteriorly facing convex surface constitutes the diaphragmatic surface of which the smooth larger part is covered by peritoneum and a smaller supero-posterior one is devoid of peritoneal covering (bare area). The important structures related to the diaphragmatic surface are peritoneal ligaments and the inferior vena cava in the left part of the bare area. (ii) The visceral surface or inferior surface of the liver is concave, directed downward, backward, and to the left. Deep fissures and the impressions of the adjacent organs make this surface uneven. These two surfaces join antero-laterally in acute angle forming the inferior margin. Behind, the diaphragmatic and visceral surfaces are separated by the coronary ligaments.

I./1.1.2.: Diaphragmatic surface

I./1.1.2.1.: Anterior Part

Peritoneal ligaments are double layers of peritoneum that attach the liver to the anterior abdominal wall and to the diaphragm.

Peritoneal ligaments of the liver:

• - falciform ligament of the liver,

• - right and left triangular ligaments

• - coronary ligaments

The falciform ligament connects the liver to the diaphragm and to the supra-umbilical part of the anterior abdominal wall. From the distal surface of the diaphragm and posterior surface of the anterior abdominal wall down to the umbilicus, it passes to the liver and attaches to the notch for the round ligament, and then its attaching line extends to antero-superior surface of the liver. The falciforme ligament has a sickle shaped free margin.

It is of note; the falciform ligament does not run in the midsagittal plane but it reaches the liver by deviating to the right, therefore the left layer of the ligament lies to the left anterior hepatic surface, while right one facing anteriorly, abuts the diaphragm. The left and right layers at the lower free margin are folded upon each other. This thickened free edge of the falciforme ligament, between the umbilicus and the liver contains the remnant of the left umbilical vein (round ligament of the liver), small paraumbilical veins, and lymph vessels. On the two sides of the ligament, between the liver and diaphragm, narrow peritoneal recesses form: right and left subphrenic recesses. On the superior hepatic surface, the falciform ligament eventually splits into two layers, which are continued into the anterior layers of the right and left coronary ligaments.

I./1.1.2.2.: Superior part

This surface is convex, except to the left of the inferior vena cava, it bears a depression corresponding to the position of the heart (cardiac impression), lying on the central tendon of the diaphragm.

On the superior surface, and in the left portion of the bare area, in a deep groove, the inferior vena cava is embedded in the liver.

The left and right coronary ligaments suspend the liver from the diaphragm, in the frontal plane and limit superiorly the subphrenic recesses.

The left coronary ligament is a true peritoneal duplication, its anterior layer doubles back on itself and forms the left triangular ligament and it continues to the right as the posterior layer of the left coronary ligament extending to the proximal border of the caudate lobe.

The right triangular ligament is in the same way shaped, but the posterior layer shortly separates from the anterior one, enclosing the large bare area. On the left side of the inferior vena cava, it ascends and meet the posterior layer of the left coronary ligament at the proximal end of the fissure for ligamentum venosum. The posterior layers of the coronary ligaments form then another peritoneal duplication: the lesser omentum.

The posterior layer of the right coronary ligament descends on the posterior slope of the right dome of the diaphragm and abuts the antero-superior surface of right kidney forming the hepatorenal ligament. The posterior layer of the right coronary ligament continues as the visceral peritoneal covering of the liver, on its visceral surface.

The medially meeting anterior layers of the coronary ligaments continue in the left and right layers of the falciform ligament and are continuous with one another around the inferior border of the falciform ligament.

I./1.1.2.3.: Lateral part

In the right dome of the diaphragm, the lateral part of the superior hepatic surface is related to the costodiaphragmatic recess and the base of the right lung, through the diaphragm. This topographical relationship provides the possibility for the liver biopsy.

I./1.1.2.4.: Posterior part

On the right side, the backward facing surface is convex and large. The most notable structures are the wide part of the bare area and in its left extension, in a deep vertical sulcus that gives passage to the peritoneum-free inferior vena cava (sulcus for vena cava). On the left side, only a narrow stripe faces posteriorly.

I./1.1.3.: Visceral surface

Lifting upwards the inferior margin of the liver, an H-shaped group of deep fissures and fossae comes into view. Its left and right proximal limbs and in between the caudate lobe are practicably parts of the posterior part of the diaphragmatic surface; it is also supported by the fact that the caudate lobe abuts the crura of the diaphragm above the aortic hiatus. Since there is no definite border between the posterior part of the diaphragmatic and the visceral surfaces, we describe the proximal and distal sets of grooves together, similarly to several anatomical descriptions.

The inferior vena cava lies in the proximal groove of the postero-inferior right limb (groove for inferior vena cava). Inferiorly a shallow elongated fossa accommodates the gallbladder running from the inferior margin toward the inferior vena cava. The groove for the inferior vena cava and the fossa for the gallbladder are not continuous with each other. The part of the fossa for the gallbladder housing the cystic duct narrows and curves into the porta hepatis.

The left limb is a deep cleft, in the proximal part of which the ligamentum venosum, in the antero-inferior part the ligamentum teres are buried.

Between the neck of the gallbladder and the junction of the fissures for ligamentum teres and ligamentum venosum, a cross-bar of H forms the porta hepatis through wich the left and right branches of the proper hepatic artery and the portal vein enter, while left and right hepatic ducts leave the liver.

I./1.1.3.1.: Fissure for ligamentum venosum

The fissure for ligamentum venosum extends vertically from the porta hepatis to the inferior vena cava between the caudate lobe and the left lobe. Continuations of the posterior leaves of the left and right coronary ligaments attach in the fissure for ligamentum venosum and leave it for the superior part of the lesser curvature of the stomach as the lesser omentum. At the portal end of this cleft, the two layers separate and enclosing the leaving and entering vessels of the porta hepatis, form the hepatoduodenal ligament. Deep in the fissure, the fibrous remnant or the highly narrowed ductus venosus of Arantius runs from the the left branch of the portal vein to the terminal branch of left hepatic vein or directly to the inferior vena cava. Antero-inferiorly it is continuous with the round ligament of liver (remnant of left umbilical vein. The ligamentum venosum is invested by the peritoneal layers of the lesser omentum.

I./1.1.3.2.: Fissure for ligamentum teres

In antero-inferior direction, the left anterior limb of the H, known as fissure for round ligament (fissure for ligamentum teres) joins the distal end of the fissure for ligamentum venosum and the left extremity of the porta hepatis. This fissure is often obscured by bridging of liver tissue across the quadrate and left lobes.

The deep cleft lodges the obliterateded or highly narrowed remnant of the left umbilical vein known as the round ligament of the liver. The round ligament lies in its fissure, in a peritoneal fold that is connected to the falciforme ligament. In the subserous loose connective tissue, lymphatic vessels and paraumbilical veins run along the round ligament.

The round ligament extends from the navel on the anterior body wall to the notch of the inferior margin, in the free edge of the falciform ligament then it courses further in the fissure for the round ligament and joins the left branch of the portal vein.

I./1.1.3.3.: Gallbladder fossa

A shallow depression (gallbladder fossa) on the visceral surface, between the quadrate and right lobes lodges the gallbladder. The fundus is the blunt anterior end of the gallbladder projecting beyond the inferior margin of the liver; it is fully covered by peritoneum. The antero-superior, non-peritoneal surface of its body and neck is attached by connective tissue to the fossa, while their infero-posterior surface has peritoneal covering which is continuous with the layer investing the visceral surface of the liver. The body of the gallbladder gradually tapers towards the neck. More often an angular junction is present between the neck and the body then the neck turns sharply downward connecting it to the common hepatic duct via the cystic duct. Usually under the porta hepatis, the cystic duct joins the right side of the common hepatic duct in acute angle marking the border between the common hepatic duct and common bile duct. The common bile duct runs toward the major duodenal papilla in the right free border of the hepatoduodenal ligament (part of the lesser omentum).

I./1.1.3.4.: Groove for inferior vena cava

Between the caudate and right lobes, in the left portion of the bare area, a deep groove houses the inferior vena cava. This groove is separated from the gallbladder fossa and the porta hepatis by the caudate process that is covered with peritoneum. A collagenous connective tissue band frequently bridges the inferior vena cava lying in its groove, known as inferior vena cava ligament. Occassionally it may contain hepatic parenchyma or only hepatic tissue bridges over the vein transforming the groove into a tunnel.

The hepatic veins comprise three large hepatic veins which empty into the upper segment of the inferior vena cava, in contact with the bare area of the liver.

The right, left and middle hepatic veins join immediately under the diaphragma.

The terminal segments of the left and right hepatic veins display extrahepatic course prior to its confluence with the inferior vena cava. The left and middle hepatic veins frequently unite in the liver parenchyma and a common stem enters the inferior vena cava. Below these veins several small veins from the right liver lobe and some veins from the caudate lobe drain directly into the inferior vena cava.

In 20-25% of cases an accessory vein, from a large portion of the right lobe, called inferior hepatic vein or Makuuchi vein, drains into the vena cava, some cm below right hepatic vein.

I./1.1.3.5.: Porta hepatis (hilum of the liver)

The porta hepatis is a deep transverse fissure, bordered by the caudate lobe from behind, while the quadrate lobe is located in front of it. This horizontal fissure connects the proximal ends of the fossa for the gallbladder and the fissure for the round ligament.

To the right, the left and right hepatic ducts emerge in front from the hilum, to the left and behind the left hepatic duct the left and right hepatic arteries enter, and the portal vein enters behind and between the duct and the artery. At the porta hepatis, the bifurcation of the portal vein (occasionally trifurcation) may occur in extra- or intrahepatic position (~50-50%).

A part of both the superficial and deep lymphatic vessels leave the liver through the hilar nodes to follow the proper hepatic artery toward the aortic nodes.

The hepatic plexus beginning at the porta hepatis contains sympathetic and parasympathetic (vagal) fibres. They mostly accompany the hepatic arteries then ramify giving off branches to the hepatic ducts.

I./1.1.3.6.: Caudate lobe

Next to the porta hepatis, the caudate lobe displays two protrusions: on the left side the papillary process and on the right the caudate process. The narrow caudate process bends to the right below the inferior vena cava separating it from the porta hepatis; it joins the parenchyma of the right lobe. The caudate process forms the proximal boundary of the epiploic foramen. A slit-like superior recess (superior omental recess) situated between the caudate lobe of the liver and the diaphragm is an upward extension of the omental bursa.

I./1.1.3.7.: Quadrate lobe

The quadrate lobe is bounded on the right by the fossa for the gallbladder, on the left, by the fissure for the round ligament, behind by the porta hepatis, and in front by the inferior margin of the liver. On its posterosuperior surface, impressions of the pyloric part of the stomach and the superior part of the duodenum can be observed. The anteroinferior surface comes in contact with the transverse colon.

I./1.1.3.8.: Impressions on the posterior part of the diaphragmatic surface and on the left and right portions of the visceral surface

To the right of the inferior vena cava, on the non-pertoneal surface, the suprarenal gland forms an impression (suprarenal impression). Behind the posterior layer of the right coronary ligament the renal impression is situated. Between the liver and the right kidney, the hepatorenal recess or Morison’s pouch communicating with the omental bursa is of clinical importance. The colic impression is produced by the right colic flexure in front of the renal impression. The duodenal impression lying medial from the renal impression and between the neck and partly the body of the gallbaladder is caused by the descending portion of the duodenum.

To the left from the fissure for the ligamentum venosum, the esophageal groove and further to the left, the gastric impressions are located. To the right of the gastric impression, the tuber omentale protrudes posteriorly, which fits into the lesser curvature of the stomach and lies in front of the lesser omentum.

I./1.1.3.9.: Peritoneal ligaments attaching on the visceral surface of the liver

The attachments of the right and left coronary ligaments, which are continued into the fissure for the ligamentum venosum, and then into the porta, from where an extremely thin peritoneal duplication, the lesser omentum extends to the esophagus and descends to the lesser curvature of the stomach. At the right border of the lesser omentum, its anterior and posterior layers are continuous, forming a free margin. The lesser omentum can be divided int o two parts: the hepatogastric ligament connects the liver to the lesser curvature of the stomach and the hepatoduodenal ligament attaches the liver to the superior part of the duodenum and constitutes the anterior boundary of the epiploic foramen.

Between the anterior and posterior layers of the hepatoduodenal ligament, running parallel to its free margin are the hepatic artery, the common hepatic duct or the common bile duct, the portal vein, the efferent lymphatic vessels, some primary lymph nodes and the hepatic plexus surrounded by loose connective tissue constituting the hepatic pedicle. This connective tissue derives from the fibrous capsule of Glisson, its distal extension ensheaths the portal structures between the two layers of the hepatoduodenale ligament.

I./1.1.4.: Glisson’s capsule (fibrous capsule of Glisson)

The thin fibrous capsule of Glisson containing collagen and elastic fibers covers the external surface of the liver. At the hilum of the liver, the Glisson’s capsule fuses with the connective tissue enclosing the bile ducts and vascular elements in the intersegmental space (invagination of the fibrous capsule of Glisson). On the undersurface of the liver this connective tissue thickens constituting connective tissue plate system: the hilar plate, the cystic plate, and the umbilical and arantian plates. The hilar plate is of a firm tissue in the transverse fissure (porta hepatis); the cystic plate (gallbladder plate) is the thickened dense connective tissue in the fossa for the gallbladder, above the gallbladder; the umbilical plate is the the firm tissue in the fissure for the round ligament, while the arantian plate is present in the fissure for the ligamentum venosum.

The hilar plate covers the long left and the short right hepatic pedicles of the hilum and is prolonged as the cystic plate on the right and umbilical plate on its left end. A loose areolar connective tissue surrounds the portal vein, which is the histological explanation for its easy dissection. The individual dissection of the hepatic artery and hepatic duct is always more difficult because of the denser fibrous tissue by which they are ensheathed. The anterior cranial border of the hilar plate can easily be separated from the hepatic parenchyma, since on the superior surface of the hilar plate there are no vascular structures; there is little risk of bleeding. The hilar plate separates the confluence of the left and right hepatic ducts from the posterior surface of the quadrate lobe, thus lifting upward the quadrate lobe in order to expose the biliary confluence and the left hepatic duct, incision is made at the junction of the hilum and the liver parenchyma.

The umbilical plate blends with the left paramedian pedicle covering the initial portion of the left bile duct and the umbilical part of the portal vein and is continuous with the round ligament of the liver.

The knowledge of the anatomy of Glisson’s capsule and its extensions into the liver surrounding the hepatic triad structures (portal vein, hepatic artery, bile duct), and its thickened four fibrous connective tissue plates is indispensable in surgical interventions at the hilar region and in gallbladder surgery.