Question

Refer to the given figure which shows part of the urinary system of mammals. Liquids pass through tubes X, Y, and Z in the directions shown by the arrows. The volume of liquid passing through Y in a day is-

A. Greater than that passing through X
B. Less than that passing through Z
C. Much less than that passing through X but slightly greater than that passing through Z
D. Slightly less than that passing through X but much greater than that passing through Z

Answer 1

Kidney is the key excretory organ in the excretory system of humans. The blood enters through the renal artery in the kidney to get purified. After purification, the blood leaves the kidney from the renal vein. Through the ureter, the urine formed is transported to the urinary bladder for temporary storage.

Complete answer:
The excretory system of human beings involves blood purification by a pair of bean-shaped organs called kidneys. The kidneys are complicated units enclosing the functional units called nephrons. The nephrons are the structures that filter the blood inside the kidney. For blood to get filtered, first it needs to enter the kidney. The blood enters the kidney through tube X or the renal artery.

Renal arteries transport the blood to the nephrons from where the blood is filtered. All the necessary ions are absorbed and the waste product is solubilized in water forming the urine. The purified blood leaves the kidney through tube Y or renal vein. The purified blood re-enters the circulatory system. The urine formed in nephron units is then transported through tube Z or ureter to the urinary bladder in the lower abdominal region for temporary storage. When blood enters the kidneys, most of the waste, excess molecules and ions are removed with the urine formation. About 180 liters of filtrate is produced each day in kidneys.

The proximal tubules further help in the reabsorption of inorganic ions, glucose, and amino acids into the blood. Most of the water also gets pumped out of the filtrate to draw back into the blood. This makes the volume of liquid less in the renal vein than in the renal artery. But the volume of liquid is more in tube Y than the ureter.

So, the correct answer is option C.

Note: Each kidney consists of about one million nephron units. Each of the nephrons further has its own internal set of structures that filters the blood and produces urine. After blood enters the nephron it first passes through the renal corpuscle where the glomerulus absorbs protein from the blood. The Bowman capsule passes the remaining fluid to renal tubules where proximal tubules reabsorb water, sodium, etc. back into the blood.