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F214 Module 2: Excretion
4.2.1 Excretion

(a) define the term excretion
Excretion the removal of metabolic waste from the body , of byproducts or unwanted substances from normal
cell processes.

Functions of the Liver:
control of: blood glucose levels, amino acid levels, lipid levels
synthesis of: red blood cells in…

Page 2

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F214 Module 2: Excretion
3. The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a
carbohydrate or fat for storage.

(c) describe, with the aid of diagrams and photographs, the histology and gross structure of the liver


















































Page 3

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F214 Module 2: Excretion




(d) describe the formation of urea in the liver, including an outline of the ornithine cycle
Most people in the developing world eat more than the 4060g of protein we need every day. Excess amino acids
cannot be stored, as the amine groups make them toxic.…

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F214 Module 2: Excretion













(g) describe, with the aid of diagrams and photographs, the detailed structure of a nephron and its associated
blood vessels




































(h) describe and explain the production of urine, with reference to the processes of ultrafiltration and selective
reabsorption
Ultrafiltration:

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F214 Module 2: Excretion
The afferent arteriole is wider than the efferent arteriole which is wider than the capillaries. Therefore there is a
higher blood pressure in the capillaries to push fluid from the blood into the Bowman's capsule .

The barrier between the blood in the capillary and the…

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F214 Module 2: Excretion
Water Reabsorption:
The role of the loop of Henle is to create a low (very negative) water
potential in the tissue of the medulla . This ensures that even more
water can be reabsorbed from the fluid in the collecting duct.

As the fluid in the…

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F214 Module 2: Excretion
Common causes of kidney failure are:
hypertension high blood pressure can damage the small blood vessels in your kidneys and stop them
working properly.
diabetes mellitus blocks the small blood vessels of your kidney and makes them leaky so you kidneys
work less efficiently.
Infection .…

Page 8

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F214 Module 2: Excretion
Haemodialysi 4dialysisfree days a week. Have to plan your life around the dialysis
s sessions , e.g. holidays.
Your diet and the amount of fluid you
drink needs to be restricted ­ avoid foods
high in potassium (e.g. bananas,
chocolate, crisps) and advised not to drink…

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