The Liver

Question 0

Explain the function of the hepatic artery

Answer 0

• blood travels from the aorta into the liver via the hepatic artery
• it transports oxygenated blood as the oxygen is essential for aerobic respiration, providing plenty of energy

Question 1

Explain the function of the hepatic vein

Answer 1

• carries deoxygenated blood away from the liver - which rejoins the vena cava and normal circulation will proceed

Question 2

Explain the function on the hepatic portal vein

Answer 2

• brings blood from the small intestine, the blood is rich inter products of digestion which means that any harmful substances that were ingested will be broken down quickly by hepatocytes

Question 3

Explain the function of the bile duct

Answer 3

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

Question 4

Describe the structure of the liver

Answer 4

• the liver is made up of lobules which consists of cells called hepatocytes that are arranged in rows
• each lobule has a central vein in the middle that connects to the hepatic vein
• each single lobule has branches of the hepatic artery, hepatic portal vein and bile duct
• the hepatic artery and hepatic vein are connected to the central vein via capillaries called sinusoid
• the blood flows past every hepatocyte via the sinusoid which ensures that the harmful substances are broken down quickly, the blood also provides the hepatocytes with oxygen
• the central veins from all the lobules join up to from the hepatic vein
• cells called Kupffer cells are also attached to the walls of the sinusoids - they remove bacteria and break down old red blood cells
• the bile duct is connected to the central vein by tubes called canaliculi

Question 5

Explain the formation of urea

Answer 5

• the nitrogen containing amine groups are removed from any excess amino acids forming ammonia and keto acid (deamination)
Amino acid + oxygen –> keto acid + ammonia
• the keto acid can be respired to give ATP or converted yo carbohydrate and stored as glycogen
• ammonia is too toxic for mammals to excrete discreetly so its combined with co2 in the ornithine cycle to create urea
Ammonia + carbon dioxide –> urea + water
• the urea is then released from the liver into the blood where it is then filtered by the kidneys

Question 6

Describe the roles of the liver in detoxification

Answer 6

• alcohol (ethanol)
Ethanol –> Ethanal –> ethanoic acid –> acetyl coA
• Ethanol and ethanoic acid are dehydrogenated and the hydrogen reduces NAD
• if too many NAD are detoxifying alcohol there will be too few NAD to break down fatty acids for use in respiration so the fatty acid will be converted back to lipids which leads to fatty liver