QS Study

The liver is the largest solid organ and the largest gland in the human body. It is located below the diaphragm in the right upper quadrant of the abdominal cavity. It is the largest visceral structure in the abdominal cavity and the largest gland in the human body.

Histological structure of the liver

The liver is composed of parenchymal cells (Hepatocytes), connective tissue stroma, sinusoids, bile canaliculi, numerous portal triads, and tributaries of hepatic veins. The portal vein ramifications in the portal tracts give off a series of branches between adjacent portal tracts, which in turn give rise to sinusoids draining blood towards the center of the lobule.

The outer surface is lined by a serous coat beneath which Glisson’s capsule encloses the entire organ. The microscopic organization of liver cells is grouped into three cell clusters:

(1) Classic hepatic lobule – It consists of hexagonal plates of hepatocytes stacked on top of each other. Within each plate, the hepatocytes radiate outwards from a central vein.

(2) Portal lobule – While the classic lobule view focuses on the blood supply and hepatic mass arrangement, the portal lobule view underlines the exocrine function of the liver i.e. bile secretion.

(3) Portal acinus – A liver acinus functional unit is in the shape of an oval.

Fig: (A) Histological anatomy of the liver lobule; (B) and portal triad

Hepatic lobule –

(i) There are hexagonal areas.

(ii) Diameter: Histologically, each lobule is 1 mm in diameter.

(iii) Central vein – at the center of each lobule.

(iv) Portal spaces –

  • At the corners of each lobule,
  • Occupied by the portal triads.

(v) Portal triad – Each triad contains

  1. A branch of the portal vein;
  2. A branch of hepatic artery;
  3. Interlobular bile ductules.
  4. All the structures in the portal triad are in a connective tissue sheath, the portal canal or perivascular fibrous capsule.

Portal lobule

  • These are hexagonal areas.
  • Formed by connecting adjacent three central veins.
  • These are the functional areas of the liver.
  • At the center – Portal canal.
  • At periphery – Adjoining hepatic lobules.
  • Bile – The bile from the hepatic lobule drains into a bile ductule in the portal canal.

Portal acinus –

(i) It is a diamond-shaped area,

(ii) Formed by connecting adjacent two central veins,

(iii) It is useful in considerations of blood flow, patterns of oxygenation and pathological degeneration.

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