4.2.1 EXCRETION
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- Created by: upsidedown1004
- Created on: 02-06-16 13:31
What is excretion?
the removal of metabolic waste and substances that are in excess of the requirements
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Outline the importance of excretion
many products of metabolism are toxic, which if built up in the body will cause damage
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Why must Carbon Dioxide be excreted?
dissolves in blood to form hydrogen carbonate ions which compete with oxygen for space on haemoglobin // CO2 can also bind directly with Hb which has a low affinity for O2// carbonicA can causes respiratory acidosis, breathing problems and headaches
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Why must nitrogenous waste be excreted?
amino group is highly toxic// proteins and amino A are high in energy so wasteful to remove // ornithine cycle removes amino group to form ammonia --> urea
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Where is the liver?
lies below the diaphragm and just to the right
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Describe the bile duct of the liver, what does bile do?
bile is secreted// made up of water and bile salts // carries to the gall bladder where it is stored until required by intestines via bile canaliculi// emulsifies fats
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What doe the hepatic portal vein do?
brings blood from the small intestine // is rich in nutrients from digestion // any harmful substances broken down by hepatocytes// low O2 conc
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Describe the lobular structure of the liver
maximise blood flow/ made up of hepatocytes in rows// each has a central view in the middle that connect to the hepatic vein// every lobule has branches to hepatic artery, HPV and bile duct
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What are sinusoids?
capillaries lined with hepatocytes which connect to hepatic artery and vein to the central vein
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Briefly outline the production of urea
Deamination --> ornithine cycle
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What is deamination?
the process by which nitrogen-containing amino groups are removed from amino acids, forming ammonia and organic keto acids
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Describe the process of deamination
amino group removed to form ammonia// rest of molecules form keto acid which can be respired/ cholesterol or lipids// Amino acid + O2 --> Keto acid + ammonia
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Why must ammonia be excreted?
highly soluble and toxic so must not be allowed to accumulates
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Describe the ornithine cycle
ammonia is quickly converted into less soluble and less toxic urea CO(NH2)2// requires ATP
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Explain the role of the liver in detoxification
detoxifies drugs // broken down into less harmful compounds so they can be excreted from the body
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How is alcohol detoxified?
broken down into ethanoate by enzymes alcohol dehydrogenase and aldehyde dehydrogenase// ethanoate then enters the krebs cycle // reduced NADs are produced
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How is a fatty liver produced?
if too many NAD are detoxifying, there is not enough to break down fatty acids for respiration// causes fatty acids to be converted back into lipids in the liver (fatty liver)
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Why must excess insulin be broken down (detoxified)
excess insulin can cause blood sugar level problems
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describe the histology of the kidneys
supplied with blood from the renal artery and drained by renal vein // surrounded by a tough capsule, outer region is the cortex and inner is the medulla// central region is the pelvis which leads to the ureter
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what is the nephron?
a filtering unit of the kidney, responsible for removing waste substances from the blood // each kidney is made up of thousands of nephrons
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What is the role of the nephron?
filters blood to produce a liquid (filtrate) from the plasma // reabsorb useful substances into the blood and control vol of water loss in urine
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Outline ulterfiltration
...
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How is ultrafiltration made more efficient?
by the arrangement of capillaries and podocytes// endothelial cells line capillaries contain pores and podocytes have slit pores that reduce resistance to the flow of filtrate - they support the capillaries
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Outline selective reabsorption
...
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describe the structure of the cells in the proximal convoluted tubule
microvilli increase SA for reabsorption // co-transporter proteins in cell surface mem transports proteins and aminoA// Na/K pump // many mitochondria provides energy for selective reabsorption
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what are the consequences of kidney failure?
unable to remove excess water and waste products// inability to regulate salt levels // death
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Outline dialysis
waste, excess fluids and salts are removed from the body by passing the blood over a dialysis mem. this allows the exchange of substances// dialysis fluid has same conc of substances as blood plasma
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Outline haemodialysis
blood is passed through a machine that contains an artificial dialysis mem // heparin is used to avoid clotting // 3x weekly several hour long sessions
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what is peritoneal dialysis?
the body own abdominal membrane is used as a filter
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What are the advantages of kidney transplants?
no dialysis/ less limited diet/ better physical feeling/ better quality of life/ no longer 'chronically ill'
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What are the disadvantages of kidney transplants?
need immunosuppresents for life/ major surgery/ risk of infection/ need frequent checks incase of rejection/ side effects of medication
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What is tested for in pregnancy tests?
human chorionic gonadotrophin (hCG) is produced by human embryos when implanted on uterine lining, is excreted in the urine
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outline how a pregnancy test works
urine passes into reaction zone, some of the monoclonal antibodies bind to the hCG/ urine carrying the antibodies reaches testing zone, hCG binds to immobilised antibodies (gold beads) zone changes colour// monoclonal antibodies w/o hCG control regio
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What are anabolic steroids?
stimulate anabolic reactions in the body/ derived from cholesterol/ lipid soluble/ increase protein synthesis inside cells
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How are anabolic steroids tested for?
urine samples vaporised with gaseous solvent/ passed down tube with absorbing agent/ each substance dissolves differently in gas and gas different retention t/ substance will leave gas and is absorbed then analysed and compared to standard
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What are the disadvantages of using anabolic steroids?
high blood pressure/ hair loss/ CV diseases/ acne
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Other cards in this set
Card 2
Front
Outline the importance of excretion
Back
many products of metabolism are toxic, which if built up in the body will cause damage
Card 3
Front
Why must Carbon Dioxide be excreted?
Back
Card 4
Front
Why must nitrogenous waste be excreted?
Back
Card 5
Front
Where is the liver?
Back
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