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F214 Communication, Homeostasis and Energy

Module 2 Excretion

4.2.1 Excretion

a. Define the term excretion

Excretion-The removal of metabolic waste from the body which are by products
or unwanted substances from cell processes.

b. Explain the importance of removing metabolic wastes, including carbon dioxide and
nitrogenous waste from the body…

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Hepatic portal vein
o This carries oxygenated blood to the liver.
o The blood is rich in the products of digestion some of which may be toxic
Hepatic vein
o This is where blood leaves the liver which then re-joins the vena cava.
Bile duct
o Bile is secreted…

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d. Describe the formation of urea in the liver including an outline of the ornithine cycle

o Amino acid + O2 Keto acid + ammonia
Ornithine cycle
o 2NH3 + CO2 CO(NH2)2 + H2O
o Ammonia + carbon dioxide Urea + water

e. Describe the roles of the liver…

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o E.g. Catalase which converts hydrogen peroxide to oxygen and water.
Detoxification of alcohol
o Ethanol contains chemical potential energy that can be used in respiration.
o It is broken down in the hepatocytes using ethanol dehydrogenase.
o This makes ethanal which is dehydrogenated further using ethanal dehydrogenase.
o Then…

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3. The blood pressure in the glomerulus is higher than in the Bowman's
4. So fluid from the blood is pushed in the Bowman's capsule.
5. Molecules with a higher molecular mass than 69,000 cannot get through
the basement membrane so are held in the capillaries of the glomerulus.…

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Active transport is used to adjust the concentrations of various
o Collecting duct
Water moves by osmosis from the tubule fluid into the
surrounding tissue. It then enters the blood capillaries.
Antidiuretic hormone (ADH)
o Cells in the wall of the collecting duct have receptors for ADH.
o ADH…

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Blood from a vein is passed through a machine that has an
artificial membrane.
Heparin is added to avoid clotting.
It is usually performed at a clinic, three times a week for several
o Peritoneal dialysis
The filter is the body's own abdominal membrane (peritoneum).
A permanent tube is…

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This is analysed to create a chromatogram.
Standard examples are then run so that the drugs can be
identified and quantified in the chromatograms.
o Mass spectrometry can also be used to analyse a urine sample.




I've found a few errors in your notes :/ for instance the hepatic portal vein doesn't carry oxygenated blood but deoxy from the digestive system, full of nutrients. I'm not saying your wrong but you may have made some typo's and I would recommend you check it again before publishing it again :S 



but appologise if I'm indeed wrong.

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