5.2.2: The structure of the liver

Question 1

Why is it essential that the liver has a good supply of blood?

Answer 1

Because the liver cells (hepatocytes) carry out many hundreds of metabolic processes.

Question 2

The internal structure of the liver ensures that as much blood as possible flows past as many liver cells as possible. What does this allow liver cells to do?

Answer 2

Remove as excess or unwanted substances from the blood and return substances to the blood to ensure concentrations are maintained.

Question 3

Which two sources supply the liver with blood?

Answer 3

• The hepatic artery

- The hepatic portal vein

Question 4

What does the hepatic artery do?

Answer 4

• Oxygenated blood from the heart travels from the aorta via the hepatic artery into the liver.
• Supplies oxygen (essential for aerobic respiration)

Question 5

Why is it important that the liver has a good supply of oxygen?

Answer 5

• The liver carries out many metabolic processes.
• Many of these processes require energy, in the form of ATP, so.
• the liver needs a good supply of oxygen for aerobic respiration.

Question 6

What does the hepatic portal vein do?

Answer 6

-deoxygenated blood from the digestive system enters the liver via the hepatic portal vein.

Question 7

Describe the content of the blood that enters the liver via the hepatic portal vein.

Answer 7

-Rich in the products of digestion.
-The concentrations of various substances will be uncontrolled as they have just entered the body from the products of digestion.
-May also contain toxic compounds that have been absorbed from the intestine.
It is important that such substances do no continue to circulate until their concentrations have been adjusted.

Question 8

How does blood leave the liver?

Answer 8

• Via the hepatic vein.

- The hepatic vein rejoins the vena cave and the blood returns to the body’s normal circulation.

Question 9

What is bile?

Answer 9

Bile is a secretion from the liver which has functions in digestion and excretion.

Question 10

What is the function of the bile duct?

Answer 10

The bile duct carries bile from the liver to gall bladder, where it is stored until required to aid digestion of fats in the small intestine.

Question 11

What other excretory products does bile contain?

Answer 11

bile pigments like bilirubin, which will leave the body with the faeces.

Question 12

How are the cells, the blood vessels and the chambers inside the liver arranged to ensure the greatest possible contact between the blood and the liver cells?

Answer 12

The liver is divided into lobes which are further divided into lobules.
Lobules are cylindrical.

Question 13

What are inter-lobular vessels?

Answer 13

As the hepatic artery and hepatic portal vein enter the liver, they split into smaller and smaller vessels. These vessels run between and are parallel to the lobules.

Question 14

At intervals, branches from the hepatic artery and the hepatic portal vein enter the lobules. What happens to the blood from the two vessels?

Answer 14

• They are mixed and passed along a special chamber called the sinusoid, which is lined with liver cells.
• As blood flows along the sinusoid it is in close contact with the liver cells.
• These cells are able to remove substances from the blood and return other substances to the blood.

Question 15

What is the function of Kupffer cells?

Answer 15

• They are specialised macrophages that move around in the sinusoids.
• Their primary function appears to be to breakdown and recycle old red blood cells.

Question 16

What is one of the products of haemoglobin breakdown?

Answer 16

Bilirubin, which is one of the bile pigments that is excreted as part of the bile.

Question 17

Where does the bile go once made in the liver cells?

Answer 17

• bile is made in the liver cells and released into the bile canaliculi.
• The bile canaliculi join together to form the bile duct, which transports bile in the gall bladder.

Question 18

When blood reaches the end of the sinusoid, the concentrations of many of its components have been modified and regulated. What happens next?

Answer 18

• At the centre of each lobule is a branch of the hepatic vein called the intra-lobular vessel.
• The sinusoids empty into this vessel.
• The branches of the hepatic vein from different lobules join together to form the hepatic vein, which drains the blood from the liver.

Question 19

what is the shape/structure of a hepatocyte?

Answer 19

hepatocytes have a simple, cuboidal shape with many microvilli on their surface.

Question 20

What do the many metabolic functions of hepatocytes include?

Answer 20

protein synthesis, transformation and storage of carbohydrates, synthesis of cholesterol and bile salts, detoxification and many other processes.

Question 21

How does a hepatocyte need to be specialised to carry out so many metabolic functions?

Answer 21

Their cytoplasm must be very dense and be specialised in the number of organelles it contains.