excretion Flashcards
define excretion
is the removal of metabolic waste from the body ,this means the removal from the body of the unwanted products of cell metabolism
what products must be excreted
- carbon dioxide from
- nitrogen containing compounds such as urea
- other compounds such as bile pigments found in faeces
name the excretory organs
- lungs
- liver
- the skin
- kidneys
describe the lungs as an excretory organs
every living cell in the body produces carbon dioxide as a result of respiration, carbon dioxide is passed from the cells of respiring tissues into the bloodstream, where it is transported to the lungs . in the lungs the carbon dioxide diffuse into the alveoli to be excreted as you breathe out
describe the kidneys as an excretory organ
the urea is passed into the bloodstream to be transported to the kidneys. urea is transported in solution - dissolved in the plasma. in the kidneys the urea is removed from the blood to become a part of the urine. urine is stored in the bladder before being excreted from the body via the urethra
describe the liver as a excretory organ
the liver directly involved in excretion . it has many metabolic roles and some of the substances produced will be passed into the bile for excretion with the faeces , for example the pigment bilirubin
the liver is also involved in converting excess amino acids to urea. amino acids are broken by the process of deaminatiom . the nitrogen containing part of the molecule is then combined with carbon dioxide to mla eurea
describe the skin as an excretory organ
the skin is also involved in excretion , but excretion is not the primary function of the skin. sweat contains a range of substances including salts, urea, water, uric acid and ammonia. urea, uric acid and ammonia are all excretory products. the loss of water and salts may be important part of homeostasis - maintaining the body temperature and the water potential of the blood
describe the importance of excretion
allowing the products of metabolism to build up could be fatal, some metabolic products such as carbon dioxide and ammonia are toxic. they interfere with cell processes by altering the PH , so that normal metabolism is prevented. other metabolic products may act as inhibitors and reduce the activity of essential enzymes .
the aorta splits into this so carries oxygen to the liver
hepatic artery
this comes from the digestive system so bring glucose to the liver
hepatic portal vein `
takes blood away from the liver to join the vena cava
hepatic vein
carries bile from the liver to the gall bladder
bile duct
what is the liver divided into and then what is it further divided into
lobes
lobules
what is the hepatic artery and hepatioc portal #vein split into
interlobular vessels
what are the special chambers in the liver called
sinusoid
what goes on to from the hepatic veins
intralobular vessels
what are the liver cells with many microvilli
hepatocytes
what are the specialised macrophages called in the liver
kupffer cells
what does heamoglobin break down form in the liver
bilirubin
where is the bile released into initially prior to the bile duct
bile canaliculi
where is bile stored
gall bladder
what are the two sources of blood suppiled to the liver
the hepatic artery
the hepatic portal vein
describe the hepatic artery
oxygenated blood from the heart travels from the aorta via the hepatic artery to the liver . this supplied the oxygen that is essential for aerobic respiration
describe the hepatic portal vein
deoxygenated blood from the digestive system enters the liver via the hepatic portal vein . the blood is rich in the products of digestion . the blood may also contain toxic compounds that have been absorbed from the intestines
what are the functions of the liver
- control of blood , glucose levels, amino acids, lipid levels
- synthesis of bile, plasma proteins , cholesterol
- synthesis of red blood cells in the fetus
- storage of vitamins A, B, B12, iron and glucose
- detoxification of alcohol and drugs
- breakdown of hormones
- destruction of red blood cells
describe detoxification
toxins need to be rendered harmless by oxidation , reduction , methylation or by combination with another molecule
describe catalase
converts hygrogen peroxide to oxygen and water . catalase has a particularly high turnover number of five million
describe cytochrome p4500
which is a group of enzymes used to break down drugs including cocaine . the cytochromes are also use din other metabolic reactions such as electron transport during respiration . their role in metabolising drugs can interfere with other metabolic roles and causes the unwanted side effects of some medicinal drugs
what are the two types of enzymes involved in detoxification
catalase
cytochrome p4500
alcohol or ethanol is a drug that …..
alcohol or ethanol is a drug that depresses nerve activity . in addition alcohol contains chemical potential energy which can be used for respiration
describe detoxification of alcohol
alcohol is broken own in the hepatocytes by the action of the enzyme ethanol dehydrogenase . the resulting compound is ethanal . this is dehydrogenated further by the enzyme ethanal dehydrogenase . the final compound produced is ethanoate . this joins with co-enzyme A to form acetyl co-enzyme A , which enters the process of aerobic respiration . the hydrogen atoms release from alcohol are combined with another co-enzyme called NAD, to form reduced NAD
NAD is also required to oxidise and breakdown fatty acids for use in respiration.
what happens if the liver has to detoxify too much alcohol
it uses up its store of NAD and has insufficient left to deal with the fatty acids . these fatty acids are then converted back to lipids and stored as fat in the hepatocytes , causing the liver to become enlarged. this is a condition known as fatty liver which can lead to alcohol related hepatitis or to cirrhosis
describe the formation of urea
everyday we need 40-60g of protein . however most people in developed countries eat far more than this. excess amino acids cannot be stored, because the amino group make them toxic. however the amino acid molecule contains a lot of energy so it would be wasteful to excrete the whole molecule . therefore excess amino acids undergo treatment in the liver to remove and excrete the amino component . this treatment consists of two processes , deamination and ornithine cycle