Histological Structure of Liver
The liver is one of the largest organs in the human body and has a complex histological structure
crucial for its func on in metabolism, detoxifica on, and synthesis of vital proteins. Here’s a
breakdown of the liver’s histological structure suitable for a 15-mark answer:
1. Liver Lobules (Basic Structural Units)
The liver is organized into hexagonal units called liver lobules, which are the func onal units
of the liver.
Each lobule consists of hepatocytes (liver cells) arranged in plates radia ng from a central
vein.
Sinusoids (specialized capillaries) run between the plates of hepatocytes, facilita ng the
exchange of substances between blood and liver cells.
2. Hepatocytes
Hepatocytes are the main cells in the liver, making up about 80% of its volume.
These cells are polyhedral and have abundant mitochondria, rough and smooth
endoplasmic re culum, and glycogen deposits, enabling them to perform mul ple func ons
such as detoxifica on, metabolism, and bile produc on.
Hepatocytes are o en arranged in cords or plates that are one or two cells thick, with each
cell bordered by sinusoids.
3. Sinusoids
Sinusoids are blood channels lined by fenestrated endothelial cells that lack a basement
membrane, which allows for easy exchange between blood and hepatocytes.
They carry a mixture of oxygen-rich blood from the hepa c artery and nutrient-rich blood
from the portal vein.
Within sinusoids, Kupffer cells (liver macrophages) are present and func on to phagocy ze
debris, aged blood cells, and pathogens.
4. Portal Triad
At each corner of the hexagonal lobule is a portal triad, consis ng of three main structures:
Portal vein branch: Brings nutrient-rich blood from the diges ve tract.
Hepa c artery branch: Supplies oxygenated blood.
Bile duct: Collects bile produced by hepatocytes and transports it to the gallbladder.
Lympha c vessels and nerve fibers may also be part of the portal triad.
5. Bile Canaliculi
Small channels between hepatocytes called bile canaliculi collect bile produced by
hepatocytes.
Histological Structure of Liver
Bile flows from
hepatocytes into canaliculi,
eventually merging into
the bile ductules within
the portal triad.
6. Central Vein
The central vein runs
through the center of each
lobule, receiving blood
from the sinusoids.
Blood flows from the
periphery of the lobule
through the sinusoids
toward the central vein,
eventually draining into
the hepa c vein and then
into the inferior vena cava.
7. Space of Disse (Perisinusoidal Space)
The Space of Disse is located between the sinusoids and hepatocytes.
This space contains stellate cells (Ito cells), which store vitamin A and can transform into
myofibroblasts in response to liver damage, contribu ng to liver fibrosis.
The Space of Disse allows plasma to move from blood to hepatocytes for exchange.
8. Lobule and Acinus Models
The classic lobule model emphasizes the hexagonal structure around the central vein.
The portal lobule model focuses on bile drainage, with the portal triad at the center.
The hepa c acinus model emphasizes the metabolic gradient in liver ssue, describing
zones based on proximity to blood supply:
Zone 1 (periportal zone): Closest to the blood supply, high in oxygen and nutrients.
Zone 2 (mid-zone): Intermediate between oxygen-rich and oxygen-poor areas.
Zone 3 (centrilobular zone): Nearest to the central vein, most suscep ble to hypoxia.
Summary
The liver's unique histological structure supports its role in metabolism, detoxifica on, and bile
produc on. Through its specialized arrangement of hepatocytes, sinusoids, and portal triads, the
liver efficiently processes blood, synthesizes proteins, and excretes waste products.
Histological Structure of Liver
Structure of Liver
