Excretory Products and Their Elimination MCQs for NEET — Zoology Questions with Answers

The text notes: 'The filtrate gets concentrated as it moves down the descending limb but is diluted by the ascending limb.' The dilution occurs because the ascending limb is impermeable to water, but allows electrolytes to be transported out (passively in the thin part, actively in the thick part), thus reducing the solute concentration of the filtrate without water following it.

The NCERT text explicitly states: 'Mammals have the ability to produce a concentrated urine. The Henle’s loop and vasa recta play a significant role in this.'

The text clearly states: 'Collecting Duct: This segment allows passage of small amounts of urea into the medullary interstitium to keep up the osmolarity.'

The descending limb is permeable to water, allowing water to exit and the filtrate to become concentrated. If it became impermeable to water, water would be retained in the filtrate, and thus, the osmolarity of the filtrate reaching the ascending limb would be significantly lower (more dilute) than normal.

The NCERT text states: 'Each kidney has over a million tubular structures called nephrons. Nephron is the functional unit of kidney and has two portions – glomerulus and renal tubule.'

According to the NCERT text: 'Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle.'

The NCERT text states: 'Proximal Convoluted Tubule (PCT): ... Nearly all of the essential nutrients, and 70-80 per cent of electrolytes and water are reabsorbed by this segment.'

The NCERT text mentions: 'Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure.'

The NCERT text states: 'GFR in a healthy individual is approximately 125 ml/minute, i.e., 180 litres per day!'

The NCERT text explicitly states: 'For example, substances like glucose, amino acids, Na$^+$, etc., in the filtrate are reabsorbed actively whereas the nitrogenous wastes are absorbed by passive transport.'