Flashcards in Unit 1, Module 2 - Liver Deck (16):
What are the main substances that need to be excreted?
Carbon dioxide from respiration.
Nitrogen containing compounds such as urea.
Where is are carbon dioxide and urea produced?
Carbon dioxide - every living cell in the body as a result of respiration.
Urea - liver from excess amino acids.
Where is carbon dioxide excreted from?
It is passed from the cells of respiring tissues into the bloodstream.
It is transported in the blood to the lungs.
It diffuses into the alveoli to be excreted as we breathe out.
Where is urea excreted?
It is produced by breaking down excess amino acids on the liver by deamination.
It is passed into the bloodstream to be transported to the kidneys.
It is removed from the blood to become a part of urine.
It is stored in the bladder before being excreted via the urethra.
What are the three main effects of high levels of carbon dioxide?
Reduces oxygen transport.
Carbaminohaemoglobin has a lower affinity for oxygen than normal haemoglobin.
Can cause respiratory acidosis.
How does excess carbon dioxide cause respiratory acidosis?
Carbon dioxide can combine with water to produce carbonic acid.
This dissociates to release hydrogen ions.
These lower the pH and make the blood more acidic.
If the pH drops below 7.35 it results in slowed or difficult breathing, headache, drowsiness, restlessness, tremor and confusion. There may also be a rapid heart rate and changes in blood pressure.
Why are excess amino acids not simply excreted?
It would be wasteful as they contain almost as much energy as carbohydrates.
What happens to amino acids before they are excreted?
They are transported to the liver and the potentially toxic amino group is removed.
It initially forms the very soluble and highly toxic compound ammonia.
This is converted to a less toxic compound - urea.
The remaining keto acid can be used directly in respiration to release energy
How is the liver supplied with blood?
Oxygenated blood from the heart - It travels from the aorta via the hepatic artery into the liver.
Deoxygenated blood from the digestive system - Enters the liver via the hepatic portal vein.
What is the fourth vessel connected to the heart?
The bile duct.
Bile is a secretion from the liver.
It has a digestive function and an excretory function.
What are Kupffer cells?
Specialised macrophages that move about in sinusoids and are involved in the breakdown and recycling of old red blood cells.
Which organelles are particularly common in the cytoplasm of hepatocytes?
What metabolic functions does the liver carry out?
Control of: Blood glucose levels, amino acid levels, lipid levels.
Synthesis of: Red blood cells in the foetus, bile, plasma proteins, cholesterol.
Storage of: Vitamins A, D and B12, iron, glycogen.
Detoxification of: Alcohol, drugs
Breakdown of hormones
Destruction of red blood cells
What are the two parts of the treatment that amino acids undergo before being excreted?
Deamination - The removal of the amine group from an amino acid to produce ammonia.
Ornithine cycle - Conversion of toxic substances, such as alcohol, to less toxic substances.
Why must ammonia not be allowed to accumulate?
It is very soluble and highly toxic.