Excretion — Practice

Question 1

The structural and functional unit of the human kidney is called

Accepted Answer

Nephron

Question 2

Which of the following is the correct path taken by urine in our body? (i) Kidneys (ii) Ureters (iii) Urethra (iv) Urinary bladder

Accepted Answer

i, ii, iv, iii

Question 3

Which of the following hormones has a direct impact on urination?

Accepted Answer

Vasopressin

Question 4

The amber colour of urine is due to

Accepted Answer

Urochrome

Question 5

The excretory organ of the earthworm is ______, the dark brown outer zone of the kidney is the ______, reabsorption of useful products takes place in the ______, and the alkaloid used to treat malaria is ______.

Accepted Answer

Nephridia; cortex; the renal tubule, where peritubular capillaries around Henle's loop take substances back; quinine

Question 6

Why is the diameter of the efferent arteriole smaller than that of the afferent arteriole?

Accepted Answer

So that pressure builds inside the glomerulus and drives filtration.

Question 7

Give reasons: urine is acidic in the beginning and becomes alkaline later, and urine is slightly thicker in summer than in winter.

Accepted Answer

Urea breaks down to ammonia, which makes standing urine alkaline. In summer more water leaves as sweat, so less is available for urine and it is more concentrated.

Question 8

What is meant by osmoregulation, and how is it maintained in the human body?

Accepted Answer

Osmoregulation is the maintenance of water balance and ion concentration within the organism. In humans it is done mainly by the kidneys, through reabsorption in the nephron and concentration of urine under vasopressin.

Question 9

Why do some people need dialysis, and what is the principle involved in it?

Accepted Answer

Because both kidneys have failed and wastes are accumulating in the blood. Dialysis works by diffusion across a thin membrane into a fluid that matches plasma except that it contains no nitrogenous wastes.

Question 10

Do you find any relationship between the circulatory system and the excretory system? What are they?

Accepted Answer

Yes. The excretory system works entirely on blood delivered by the circulatory system, and returns cleaned blood to it, so the two are connected at every stage of urine formation.

Practice — Excretion

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