5.2Excretion as an example of homeostatic control Flashcards
Define Excretion
The removal of metabolic waste from the body.
Define metabloic waste.
a substance that is produced in excess by the metabolic processes in the cells; it may become toxic.
explain why metabolic waste must be removed from the body.
almost all waste is formed from chemical processes occuring in the cells must be removed from the body, so that they do not build up and inhibit enzymes activity ot become toxic.
State the main excretory products.
Carbon dioxide,
nitrogen-containing compounds such as urea.
other compounds such as bile pigment found in faeces.
Explain how CO2 is removed from the body.
CO2 is produced by respiring cells, as CO2 builds up in tissue fluid and diffuses into capillaries assosicating with water to form carbonic acids and then dissociates to form hydrogen carbonate and a proton (HCO3- + H+).
The hydrogen ion can associate with haemoglobin to form haemoglobic acid. and the hydrogen carbonate can associate with haemoglobin to form Carboamino haemoglobin.
this then travels to the heart through the vena cava and then pulmoary system where the built up CO2 diffuses from the capillaries to the alveoli and out of the lungs.
Describe the effect of the build up CO2 in blood.
CO2 in blood forms carbonic acid, which makes blood become acidic, if the pH drops below 7.5 it may cause:
headaches,
drowsiness, reslessness tremors and confusion.
It may also lead to rapid heart rate anad changes in blood pressure.
This is called respiratory acidosis.
Explain how excess amino acids are removed from the body.
Amino acids undergo Deamination.
amino acid + oxygen -> keto acid(can be respired) + NH3.
NH3 (ammonia) is very toxic and soluble and so is turned into the less potent Urea.
The ammonia then goes into the orthinine cycle.
2NH3 + CO2 -> (NH2)2CO + H2O
Explain liver is adapted to its function.
It has a good blood supply and has an internal structure so that blood can pass over asmany hepatocytes as possible. this is done by dividing the liver into lobes which further divide into lobules which each have an intra-lobular vessel to supply blood.
State the blood vessel involved with the liver.
Hepatic portal vein -
supplys the liver with deoxygenated blood from the digestive system. it is rich in products disegned of digestion.
Hepatic Artery -
Oxygenated blood from the Aorta. This is for oxygen for respiration and deamination. The liver cells are very active and so requires alot of ATP.
Hepatic Vein -
Transports deoxygenated blood to the heart to be oxygenated by the pulmonary system.
Bile duct -
Bile is secreted from the liver which has a function for digestion and excretion. it is carried to the gall bladder where it is stored for digestion of fats in the small intestine. also contains bilirubin.
explain the histology of the liver.
The liver is divided into lobes which are further divided into lobules, as the hepatic artery and hepatic portal vein split into smaller and smaller vessels. these run inbetween parallel to the lobules (intra-lobular vessels),
At intervals, branches intra-lobular vessels enter lobules where the blood mixes and passes along the sinusiod.
Explain the function of kupffer cells.
Cells that move about within the sinusoid.
Their primary function appears to be to breakdown and recycle old red blood cells. the main product is bilerubin.
it is released to the bile canaliculi which join together to form the bile duct.
Explain how liver cells are adapted to their function.
They are relatively unspecialised. They have a simple cuboidal shape with many microvilli on their surface.
There functions are:
Protein synthesis,
Transformationa and store of Charbohydrates.
Sythesis of cholesterol and bile salts.
detoxification and many more.
This means its cytoplasm is very dense and has a large number of organelles.
Define Orthine cycle
a series of biochemical reactions that convert ammonia to urea.
List some of the livers functions.
Control fo blood glucose levels, amino acids levels, lipid levels.
synthesis of bile, plasma proteins, cholesterol
synthesis of red blood cells in the fetus
Storage of vitamins A,D and B12, iron, glycogen.
detoxification of alcohol drugs.
breakdown of hormones.
destruction of red blood cells.
