Question

Uriniferous tubules are mainly concerned with
A. Concentration of urine
B. Passage of urine
C. Reabsorption of useful substances from glomerular filtrate
D. Removal of urea from blood

Answer 1

Hint: Blood filtration, which is performed by the glomerulus and is termed glomerular filtration, is the first step of urinary production.

Complete Answer:
There are about a million complex tubular structures in each kidney, called nephrons, which are functional units.
There are two sections of a nephron-the glomerulus and the renal tubule.
1) Glomerulus is an afferent arteriole formed by a group of capillaries.
2) The renal tubule begins with a double walled Bowman's capsule and is further divided into a proximal convoluted tubule (PCT), a loop of Henle (HL) and a convoluted distal tubule (DCT).
- On average, the kidneys process about 1100-1200 ml of blood per minute, which is nearly one-fifth of the blood pumped out per minute from each ventricle of the heart.
- The glomerular capillary blood pressure induces blood filtration through three layers. These are the endothelium of the glomerular blood vessels, the epithelium of the Bowman capsule and the basement membrane between these two layers.
- On average, an adult person excretes about 1 to 1.5 litres of urine a day. The urine produced is a watery fluid with a light yellow colour that is strongly acidic (pH-6.0) and has a distinctive odour. On average, 25-30 gm of urea is removed per day.

Therefore, the correct answer is option D i.e., Removal of urea from blood.

Note: The epithelial cells or podocytes of the Bowman capsule are organised in a complex way to leave certain tiny gaps or filtration slits. Through these membranes, blood is filtered so precisely that nearly all the plasma constituents except the proteins migrate into the lumen of theBowman’s capsule. Therefore, it is regarded as an ultra-filtration process.