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Chapter 13: Urinary System Written Assignment KEY
Written Section ( 20 Marks)
1. Explain how ADH and Aldosterone affects the concentration of ions in the blood
(4 Marks)
ADH causes an increase in water in the blood due to water reabsorption at the collecting
duct therefore; blood will have more water and an overall less concentration of solutes.
Aldosterone causes in increased sodium reabsorption followed by osmosis of water
therefore, the blood will have a higher sodium ion concentration and water concentration.
2. Explain how the conditions in the renal medulla result in the production of urine which
is hypertonic to blood. (urine which is concentrated) (3 Marks)
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___Since there is sodium ion (salt/NaCl) reabsorption along the ascending limb of the
loop of the nephron, this causes that area (the renal medulla) to become hypertonic and
have a higher salt concentration. This causes water reapbsorption along the descending
limb of the loop and the collecting duct since they both pass through the medulla. As a
result, the extra water reabsorption along the collecting duct concentrates the urine and
makes it hypertonic to blood.
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