Liver structure, function and adaptation
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Summary
Liver structure, function and adaptation
In a nutshell
The liver has many important functions including removal of harmful products and regulation of different levels in the blood. The liver structure is highly specialised to carry out these tasks. Different structures within the liver are responsible for certain aspects of these tasks.
Liver functions
Amino acids
Excess amino acids are broken down in the liver. Amino acids are nitrogenous compounds which cannot be stored easily so excess amino acids must be broken down to prevent damage.
| 1. | The groups are removed from the amino acid creating ammonia () and organic acids. This process is called deamination. Organic acids are either respired to become ATP or transformed to carbohydrates which can be easily stored as glucagon. |
| 2. | Ammonia is converted to urea through combination with carbon dioxide in the ornithine cycle. Urea can be removed from the body by the kidneys. The liver uses the blood stream to transport urea to the kidneys. |
Detoxification
Detoxification is a process controlled by the liver where harmful substances are broken down by the liver and excreted.
Substance | detoxification |
| Alcohol | Alcohol is a toxic substance. The liver breaks alcohol down into ethanal and further digests it into acetic acid. Acetic acid is then sent to the kidneys. |
| Paracetamol | High levels of paracetamol in the blood can induce kidney and liver failure. |
| Insulin | High levels of insulin in the blood can lead to chronically low blood glucose concentration. Therefore, the liver digests excess insulin in the blood to prevent hypoglycaemia. |
Storage
Glucose is very important for all bodily functions, however, too much glucose in the blood is harmful. Glucose needs to be stored. The liver oversees the conversion of glucose into glycogen which is stored as granules in liver cells until glucose is required again.
Structure
| 1. | Hepatic vein | Transports deoxygenated blood away from the liver. |
2. | Hepatic artery | Transports oxygenated blood from the heart to the liver so it is well supplied with oxygen for respiration. |
| 3. | Hepatic portal vein | Transports blood to the liver from the duodenum and ileum which are parts of the small intestine. Therefore, the blood is rich in products from digestion. Harmful products can be filtered from the blood and broken down very soon after ingestion. |
| 4. | Gall bladder | Stores bile which is used to emulsify fats. |
5. | Bile duct | Transports bile from the liver to the gall bladder. |
6. | Duodenum | Part of the small intestine. |
7. | Ileum | Part of the small intestine. |
| 8. | Pancreas | Gland of the endocrine system. |
The liver is made up of liver lobules which are cylindrical structures formed with cells called hepatocytes. The hepatocyte cells are organised into rows which radiate out from the centre.
The central vein is found in the middle of the liver lobules and is linked to the hepatic vein. The hepatic artery, hepatic portal vein and bile duct provide many branches which connect to liver lobules.
| 1. | Branch of hepatic artery | Transport oxygenated blood to the liver lobules from main hepatic artery. |
| 2. | Branch of hepatic portal vein | Transports blood to the liver lobules from main hepatic portal vein. |
| 3. | Brach of bile duct | Drain bile from hepatocytes and transport the bile to the bile duct. |
| 4. | Hepatocytes | Remove harmful products and oxygen from the blood. Hepatocytes break down harmful products which are returned to the blood for excretion. |
| 5. | Kupffer cells | Remove bacteria from the blood and break down old and faulty red blood cells. |
| 6. | Sinusoid | Capillaries which connect branches of hepatic artery and hepatic portal vein to the central vein. Transport blood to the hepatocytes and Kupffer cells. |
| 7. | Bile canaliculi | Transport bile produced by the bile canaliculi to branches of the bile duct. |
| 8. | Central vein | Transports blood away from hepatocytes. |
FAQs - Frequently Asked Questions
What do hepatocytes do?
Hepatocytes remove harmful products and oxygen from the blood. Hepatocytes break down harmful products which are returned to the blood for excretion.
What happens to excess amino acids in the blood?
Excess amino acids are broken down in the liver. Amino acids are nitrogenous compounds which cannot be stored easily so excess amino acids must be broken down to prevent damage.
How does the liver break down alcohol?
The liver breaks alcohol down into ethanal and further digests it into acetic acid. Acetic acid is then sent to the kidneys for excretion.