Liver在线视频

Hello everyone.

The following topic is about an important organ,

the liver.

First let's review a well-known Greek story.

Because of stealing fire for human beings,

Prometheus was chained on the cliff

of the Caucasus Mountains by Zeus.

Every morning an eagle was sent to eat his liver.

However,

his liver grew back at night!

It is a myth that the liver could grow overnight,

while it is a fact that

the liver has great potential to regenerate.

the liver has great potential to regenerate.

the liver has great potential to regenerate.

In animal experiments,

after 70% of the rat's liver was removed,

the liver grew back to its normal size

in about 20 days.

Similarly,

in human liver transplantation,

liver regeneration was assessed

by magnetic resonance imaging (MRI)

in living donors and the recipients.

The results indicated that

human liver regeneration is also very rapid.

Why does the liver have

such a strong proliferation ability?

At the end of this session,

you should be able to describe the structures

and functions of liver,

list the composition of hepatic lobules

and portal triad,

and relate these

to some relevant clinical phenomena.

The liver sits on the top right side of the belly,

has two large sections

called the right and the left lobes.

The gallbladder hides under the liver.

The functions of liver include several aspects.

First is the secretion and delivery of bile

to the duodenum for digestion.

Secondly,

it take part in metabolism of nutrition,

including lipid, carbohydrate and protein.

It is the site for detoxification of some

harmful substances and drugs.

During fetal stage,

liver is also an organ for hematopoiesis.

Under light microscope,

it is easy to identify that

the structures of liver

which is covered by connective tissue

that form the capsule.

Connective tissues also extend deeply

into the organ

to divide it into typical hepatic lobules.

The histology of hepatic lobules

is different from the anatomic lobes of the liver:

is different from the anatomic lobes of the liver:

lobules are the smaller divisions of the lobes.

lobules are the smaller divisions of the lobes.

The lobules are polyhedral structures

with a diameter of 1-2 mm.

They form the building blocks

of the liver consisting of hepatocytes

arranged in plates

between a capillary network sinusoid

and a central vein.

They are the basic structural

and functional units of the liver.

Between the hepatic lobules is the portal area

with connective tissue and the portal triad

A portal triad has a branch of the hepatic artery,

a branch of the portal vein and a small bile duct.

The bile duct

in portal area is lined

by simple cuboidal epithelium,

which carries bile products

away from the hepatocytes,

to the larger ducts and gall bladder.

Bile can be stored in the gallbladder

and discharged into the small intestine

through the ampulla of Vater.

The function of bile is to help lipid digestion.

Patients with hepatits

have reduced bile secretion,

often associated with digestive disorders,

such as decreased appetite,

nausea, and vomiting.

Branches of the hepatic artery

carry oxygenated blood

to the hepatocytes.

The lumen of the arteriole is small and regular;

the diameter is similar to the bile duct

while the wall

is composed of several layers of smooth muscle

in addition to the innermost endothelium.

in addition to the innermost endothelium.

Branches of the portal vein in the portal triad

have big and irregular lumens,

and a relative thin wall.

One end of the portal vein

is the superior mesenteric vein,

which collects the substances

absorbed by the GI tract,

while the other end branches out in the liver.

Blood from the branches of the portal vein

and branches of the hepatic artery

form the sinusoids between hepatic plates

within the hepatic lobules,

Within the sinusoid,

specialized stellate macrophages,

called Kupffer cells,

are there to phagocytose

aged erythrocytes and bacteria,

thus helping to filter and clean the blood.

The blood always flows from the periphery,

through hepatic sinusoid to the central vein

in each lobule.

Consequently, oxygen and metabolites,

as well as all other toxic or nontoxic

substances absorbed in the intestines,

reach the lobule's peripheral cells

before the more central cells.

The main components of the hepatic lobules

--the hepatocytes are the real site for metabolism.

Hepatocytes adhere to each other firmly

with desmosomes and junctional complexes

that form the hepatic plates.

Between the lateral hepatic plates

are the hepatic sinusoids.

Hepatocytes are large polygonal cells,

with large nuclei and eosinop hilic cytoplasm

rich with organelles.

The cells are frequently bi-nucleated,

which indicates active cell proliferation.

This diagram shows the organelles

in the cytoplasm of hepatocyte.

in the cytoplasm of hepatocyte.

There is a great deal of

rough endoplasmic reticulum

for protein and smooth endoplasmic reticulum

for lipid metabolism

as well as bile synthesis.

Glucose is stored in the glycogen granules.

Most of the material for metabolism are taken up

from the perisinusoidal space for processing,

and will be released back to the same space.

Bile will be secreted into the bile canaliculi,

which flows from the center

to periphery of the lobule

and form the bile duct in the portal area.

There are foreign and sometimes harmful materials

that need to be metabolized

or detoxified by the hepatocytes.

For example,

alcohol and therapeutic medications.

The detoxification process of these materials

may also be harmful

and may result in the necrosis of hepatocytes.

To sustain the overall function of the liver,

the hepatocytes are active in proliferation

for cellular repair and functional recovery.

That's why we can see the bi-nucleated liver cells

under the microscope.

Now let's summarize

Division and proliferation are responses

of hepatocytes to injuries,

and also the basis for the repair of

Prometheus' liver.

Due to the active regeneration of hepatocytes,

unlike other organ transplants,

reduced-size liver can be used

in living donor transplantation.

Here are the references.

Thank you,

see you next time!