Human Anatomy and Physiology - N. I. Fedyukovich 2003

Internal Organs
Digestive System
Liver. Gallbladder

The Liver (hepar) is the largest gland in The Human Body (Fig. 78). It weighs approximately 1500 g. It performs several primary Functions: digestive, Protein Synthesis, detoxification, hematopoiesis, Metabolic Regulation, and others.

The liver is located in the right hypochondriac and epigastric regions. It is wedge-shaped and has superior and inferior surfaces. The superior (diaphragmatic) surface is convex and lies against the Inferior surface of the Diaphragm; the inferior (visceral) surface faces downward and toward the underlying Organs. It is concave, featuring fissures and impressions from adjacent Internal Organs. The superior and inferior surfaces meet to form a sharp inferior border and a blunt posterior border. There are three fissures on the visceral surface of the liver: one frontal and two sagittal; the right and left lobes are also distinguished. The right and left sagittal fissures are joined by a deep transverse fissure called the porta hepatis. The visceral surface of the liver is divided into the right, left, quadrate, and caudate lobes. On the diaphragmatic surface, only the right and left lobes can be seen, separated by the falciform ligament of the liver.

On the diaphragmatic surface, impressions from adjacent organs (The Heart, INFERIOR VENA CAVA, and Vertebral Column) are visible, while the visceral surface shows impressions from the right Kidney, Adrenal gland, right colic flexure, and duodenum. The left lobe of the liver is in contact with The Stomach and Esophagus.

The Peritoneum covers the liver almost entirely, with the exception of the porta hepatis, the posterior border, and the transverse fissure. Where the peritoneum reflects from the liver onto the diaphragm, ligaments are formed that help hold the liver in its proper position.

Beneath the peritoneum lies a thin, dense fibrous capsule; it enters the parenchyma of the organ through the porta hepatis, accompanying the Blood Vessels and forming interlobular septa with them. Based on the distribution of blood vessels and Bile ducts, the liver is divided into two lobes, five sectors, and 8 segments. Structurally, the liver is a complex branched tubular gland, with the bile ducts serving as its excretory ducts. The morphofunctional unit of the liver is the hepatic lobule. It is prism-shaped, measuring from 0,5 to 2,0 mm in diameter; there are about 500 000 of them in humans. Each lobule consists of interconnected hepatic plates, or "cords," arranged in double, radially directed rows of hepatic Cells. At the center of each lobule is a central vein.

The inner ends of the hepatic plates are directed toward the central vein, while the outer ends point toward the periphery of the lobule. Within each hepatic plate, between the two rows of hepatic cells, lies a bile canaliculus, which gives rise to the biliary tract. At the center of the lobule, the bile canaliculi are closed, while at the periphery they empty into the interlobular bile ducts. The latter join to form larger ducts, which then merge into the right and left hepatic ducts emerging from the respective lobes of the liver. At the porta hepatis, they form the common hepatic duct, which is 4— б cm long. This duct then joins the cystic duct to form the common bile duct, which empties into the duodenum.

The liver lies in the right hypochondrium and does not extend beyond the costal margin. On the right, the inferior border of the right lobe crosses the costal margin at the level of the VIII rib. From the end of this rib, the inferior border of the right lobe, followed by the left, crosses the epigastric region toward the VI rib and ends along the midclavicular line. The superior border on the right along the midclavicular line corresponds to the V rib, and on the left, to the fifth-sixth intercostal space. In elderly individuals and women, the inferior border of the liver is located somewhat lower than in young individuals and men.

The Gallbladder (vesica fellea, biliaris) is a reservoir where bile is stored and concentrated through Water absorption. It is located in the anterior part of the right longitudinal groove of the liver, is pear-shaped, and holds about 40—60 ml of bile. It consists of a fundus, body, and neck. The neck of the gallbladder continues into the cystic duct, which joins the common hepatic duct. The Cytology/practical/108.html">Fundus of the gallbladder is in contact with the parietal peritoneum, while the body is in contact with the inferior part of the stomach, the duodenum, and the transverse colon.

The wall of the gallbladder consists of mucosal and muscular layers and is covered by the peritoneum. The mucosa in the neck and cystic duct forms a spiral fold; the muscular layer consists of smooth Muscle fibers.