Question

Refer to the given figure of a nephron and select the incorrect option regarding $P,Q,R$ and $S$?

• A. Blood enters PP through the afferent arteriole and leaves through the efferent arteriole.
• B. Filtrate coming from $P$ has glucose, proteins and som.e platelets also.
• C. Cuboidal cells lining $R$ actively excrete additional wastes from the blood into the filtrate.
• D. Anti-diuretic hormone alters the permeability of QQ, thereby increasing the reabsorption of water in them.

Answer 1

The correct option is D Anti-diuretic hormone alters the permeability of QQ, thereby increasing the reabsorption of water in them.

1. Blood enters P through the afferent arteriole and leaves through the efferent arteriole. This is important for the process of filtration, since efferent arterioles are thinner than afferent arterioles.

2. Glomerular filtrate contains the same content of blood except for RBCs and plasma proteins. The useful contents are later reabsorbed actively or passively.

3. Cuboidal cells lining R actively excrete additional waste in form of urea to maintain the desired osmotic gradient for water reabsorption.

4. ADH alters the permeability of DCT and the Collecting duct for water reabsorption. PCT marked as Q is not involved.

So, the correct option is 'Anti-diuretic hormone alters the permeability of Q and S, thereby increasing reabsorption of water in them'.