Each human kidney contains nearly how many nephrons?
A
One million
B
Ten thousand
C
One hundred thousand
D
One billion
Show the answer
The answer is A.
Inside each kidney there are nearly one million complex tubular structures called nephrons. The nephrons are the functional units of the kidney.
B.
Far fewer than the number present in a kidney.
C.
Ten times fewer than the number present in a kidney.
D.
A thousand times more than the number present in a kidney.
NCERT: Class 11 Biology, Chapter 16 (Excretory Products and their Elimination), Human Excretory System
Sample 2Medium
A figure shows a nephron. A is a double-walled cup enclosing a tuft of capillaries. B is a highly coiled tubule leading from A, lined by simple cuboidal brush-border epithelium. C is a hairpin-shaped loop with a descending and an ascending limb. D is a second coiled tubule that opens into a collecting duct. In which labelled part are nearly all essential nutrients and 70–80 per cent of electrolytes and water reabsorbed?
A
B, the proximal convoluted tubule
B
A, Bowman's capsule with the glomerulus
C
C, Henle's loop
D
D, the distal convoluted tubule
Show the answer
The answer is A.
The proximal convoluted tubule, with its brush-border epithelium that increases surface area, reabsorbs nearly all essential nutrients and 70–80 per cent of electrolytes and water. It follows Bowman's capsule directly.
B.
Filtration, not reabsorption, takes place at the glomerulus and Bowman's capsule.
C.
Henle's loop reabsorbs little. It mainly keeps the medullary interstitial fluid concentrated.
D.
The distal convoluted tubule reabsorbs some Na+ and water under certain conditions, but most reabsorption has already happened in the PCT.
NCERT: Class 11 Biology, Chapter 16
Sample 3NEET level
Assertion (A): The filtrate gets diluted as it moves up the ascending limb of the loop of Henle. Reason (R): The ascending limb is impermeable to water but allows transport of electrolytes, actively or passively. Choose the correct answer from the options given below.
A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is not the correct explanation of A
C
A is true but R is false
D
A is false but R is true
Show the answer
The answer is A.
The ascending limb is impermeable to water but lets electrolytes out, actively or passively. Solutes leave while water stays, so the filtrate becomes diluted as it moves up; R explains A.
B.
Loss of electrolytes without water is exactly why the filtrate becomes dilute.
C.
R is true: the ascending limb is impermeable to water and moves electrolytes.
D.
A is true: the filtrate is diluted in the ascending limb.
NCERT: Class 11 Biology, Chapter 16 (Excretory Products and their Elimination), Function of the Tubules
Practise Excretory products and their elimination
Practice at the level you choose, with the answer after every question; timed tests with the answers when you submit. Every question is verified against NCERT first.