1.2.2 The LiverOCR – A2 – Module 2

10/04/20

151By Piril Erel

The structure of the liver

The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis. Therefore it is essential for a continuous supply of blood. The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible

10/04/20

152By Piril Erel

Blood flow to the liver

TO:

The liver has two blood supplies

Oxygenated blood from the heart. Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER.

This supplies the oxygen essential for aerobic respiratory. Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply.

Deoxygenated blood from the digestive system. This enters the liver via the HEPATIC PORTAL VEIN. This blood is rich in the products of digestion. The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine.

10/04/20

153By Piril Erel

Blood flow from the liver

FROM:

Blood leaves the liver via the HEPATIC VEIN. This re-joins the vena cava and the blood returns to normal circulation

A Fourth vessel connected to the liver is not a blood vessel. It is the bile duct. Bile is a secretion from the liver. It has both a digestive function and an excretory function. The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine.

10/04/20

154By Piril Erel

The arrangement of cells

inside the liver

The liver is divided into lobes and further divided into cylindrical lobules.

As the hepatic artery and hepatic portal vein enter the liver, they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels.

The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein.

The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver.

As blood moves along the sinusoid it is in very close contact with the liver cells. They are able to remove molecules from the blood and pass molecules into the blood.

One of the many functions of the liver cells is to manufacture bile. This is released into the bile canaliculi (small canals). These join together to form the bile duct, which transports the bile to the gall bladder.

10/04/20

155By Piril Erel

Liver Cells

Hepatocytes are unspecialised simple cuboidal shaped

cells which have many microvilli on their surface

They are however involved in many metabolic functions

including;

Protein synthesis

Transformation

Storage of carbohydrates

Synthesis of cholesterol and bile salts

Detoxification and other processes

This means that their cytoplasm must be very dense and

is specialised in the amounts of certain organelles that it

contains 10/04/20

156By Piril Erel

Kupffer cells

Kupffer cells are specialised macrophages

moving about in the sinusoids involved in

the breakdown and recycling of red blood

cells. A product it produces during

breakdown is bilirubin which is excreted as

part of the bile and in faces. Bilirubin is the

brown pigment is faeces.

Application Scenario:

A common condition in newborns,

jaundice refers to the yellow color of

the skin and whites of the eyes caused by

excess bilirubin in the blood.

It is also seen in adults where an excess

chronic consumption of alcohol can have

damaging effects on your liver meaning

that you are not removing bilirubin from

your liver and bile ducts quickly enough,

as it builds up in the blood it is deposited

in the skin… The resulting is jaundice.

10/04/20

157By Piril Erel