Human Liver

 Human Liver

The liver is an organ that is present in both humans and other vertebrate animals. The human liver has an average weight of 1500 g,[1]​ it is located in the upper right part of the abdomen, below the diaphragm, it secretes bile, essential for the digestion of fats, it also has many other functions,[2 ]​ among them the synthesis of plasma proteins, storage of vitamins and glycogen and detoxifying function. Its main cells are hepatocytes and one of its most characteristic features is that it has the ability to regenerate.

The liver is responsible for eliminating different substances from the blood that may be harmful to the body, including alcohol, converting them into harmless ones. The absence of a liver or its lack of functioning is incompatible with life.

Etymology

 The word "liver" does not derive from its Latin homonym jecur, nor from the Greek hepatos. It comes from the Latin expression ficatum jecur which literally means “liver fattened with figs.” In ancient times, the inhabitants of Rome had the custom of feeding certain birds with figs in order to obtain a gastronomic delight, since the liver of these animals acquired a delicious flavor in this way. Over time, ficatum jecur came to simply mean liver and the expression was abbreviated, becoming first ficatum, then fegado and finally liver.

Liver anatomy

The liver has a triangular shape, red-brown color, smooth surface and soft, depressible consistency. In the human adult, it measures on average 26 cm wide, 15 cm high and 8 cm thick at the level of the right lobe, its approximate weight is 1.5 kg.

 Location

The liver is located in the upper right region of the abdomen, below the diaphragm, it occupies the right hypochondrium and part of the epigastrium. Under normal conditions it does not exceed the limit of the costal margin. It fills the space of the diaphragmatic dome, where it can reach up to the fifth rib, and is close to the heart, from which it is separated by the diaphragm. It is covered by a fibrous capsule, Glisson's capsule, on which the peritoneum is applied.

Facesedit

 The liver is surrounded by the visceral peritoneum and has two faces:

 Anterosuperior face. It has a convex shape and is in contact with the diaphragm that separates it from the lung bases and the phrenic surface of the heart.

 posterior inferior face. Also called the visceral surface because in it the liver is related to structures located on the right side of the abdomen, many of which leave an impression on the lower surface of the right lobe of the liver. Thus, we have from back to front the colic impression determined by the hepatic angle of the colon, the duodenal impression marked by the duodenum, attached to the cystic fossa where the gallbladder is housed, the less marked renal impression formed by the upper pole of the kidney right and further ahead a very deep groove marked by the inferior vena cava. On the lower surface of the left lobe are the gastric impression and the notch of the esophagus, on the posterior edge.

 At the base of the liver is the gallbladder and the hepatic hilum, which is the entrance area of ​​the portal vein, the hepatic artery, and the exit of the hepatic duct. The structure of the liver will follow the divisions of the hepatic portal vein. After the division of segmental branches, the branches of the portal vein, accompanied by those of the hepatic artery and the divisions of the hepatic ducts, are found together in the portal space.

 Liver lobes

 The liver is divided by the falciform ligament into two main lobes, right and left. There are two other smaller lobes, the quadrate lobe and the caudate lobe, which for many anatomists belong to the left lobe, although other texts consider that the liver has four lobes.

 Right lobe, located to the right of the falciform ligament;

 Square lobe, visible only on the lower surface of the liver; It is limited by the umbilical groove on the left, the gallbladder bed on the right, and the hilum of the liver behind;

 Spigelian lobe (caudate lobe), located between the posterior edge of the hepatic hilum in front, the vena cava behind.

 Left lobe, extended over the stomach and located to the left of the falciform ligament:

 There are frequent anatomical variants such as Riedel's Hepatic Lobe where there is a right infracostal prolongation that can be confused with hepatomegaly (increased liver size).

liver segments

Couinaud's classification divides the liver into eight segments that are functionally independent, each of these segments has a branch of the hepatic portal vein, a branch of the hepatic artery, an outflow venous branch that contributes to the hepatic veins and a bile duct through which bile reaches the hepatic duct. Segments 5, 6, 7 and 8 correspond to the right lobe, 2, 3 and 4 to the left lobe and 1 to the caudate lobe.

 Ligaments

 The liver is covered by the visceral peritoneum, it has several connections with the parietal peritoneum that are called liver ligaments, which are not actually true ligaments, but rather fibrous tracts that support it and support it on adjacent structures. These hepatic ligaments are the following:

 Round ligament of the liver. It comes from the obliteration of the umbilical vein, it joins the liver to the umbilical area of ​​the anterior abdominal wall.

 Coronary ligament. It joins the posterior portion of the diaphragmatic surface of the liver with the diaphragm, and is extended on both sides by the left and right triangular ligaments, which have the same function.

 falciform ligament. It joins the diaphragmatic surface of the liver to the diaphragm and the anterior abdominal wall. It marks the division between the right and left lobes.

 Gastrohepatic ligament. Joins the lesser curvature of the stomach to the liver

 Venous duct ligament. It is the fibrosed remnant of the venous duct that during the fetal period connects the umbilical vein directly to the inferior vena cava.

 Hepatoduodenal ligament. It joins the duodenum to the hepatic hilum and acts as support for the portal vein, hepatic artery, and main bile duct.

 Blood circulation of the liver

 Blood reaches the liver through the portal vein and hepatic artery. The portal vein system makes up 70-75 percent of blood flow and contains low-oxygenated, nutrient-rich blood from the gastrointestinal tract and spleen.

 Arterial blood arrives through the hepatic artery, a branch of the celiac trunk that contains oxygenated blood.

 Blood from both sources mixes in the hepatic sinusoids and leaves the organ through the hepatic veins, also called suprahepatic, which finally drain into the inferior vena cava.

 Lymphatic drainage of the liver

 The liver is one of the organs that produces the largest amount of lymph. The lymphatic vessels converge in the region of the hepatic hilum from where they reach the cisterna chyli in the thoracic duct that finally empties into the inferior vena cava.

 Innervation of the liver

 The liver receives sympathetic and parasympathetic innervation from the celiac plexus and the left and right vagus nerves. Both innervations form the hepatic plexus, a mixture of sympathetic and parasympathetic fibers.