Urine Formation Questions in English

(B) An adult human typically excretes approximately $1$ to $1.5$ liters of urine per day.
This volume can vary depending on the individual's water intake,physical activity,and environmental conditions.
The kidneys filter the blood and regulate the water balance in the body,resulting in the production of urine as a waste product.

(C) The amount of the filtrate formed by the kidneys per minute is known as the Glomerular Filtration Rate $(\text{GFR})$.
In a healthy individual, the $\text{GFR}$ is approximately $125\ ml/\text{minute}$, which totals about $180\ \text{liters}$ per day.
The value given in the reason $(25\ ml/\text{minute})$ is incorrect.
Therefore, the Assertion is True, but the Reason is False.

(C) Statement $i$ is incorrect because the diameter of the afferent arteriole is larger than that of the efferent arteriole,which creates high hydrostatic pressure in the glomerulus.
Statement $ii$ is correct; the colloidal osmotic pressure (exerted by plasma proteins) is approximately $30 \ mmHg$,which acts against the filtration pressure.
Statement $iii$ is correct; podocytes are arranged in an intricate manner to leave some spaces called filtration slits or slit pores,which facilitate the process of ultrafiltration.
Therefore,statements $ii$ and $iii$ are correct.

(C) Statement $i$ is correct: Glomerular capillaries are formed by the branching of the afferent arteriole and have extremely thin walls to facilitate filtration.
Statement $ii$ is correct: The diameter of the afferent arteriole is wider than the efferent arteriole,which creates high hydrostatic pressure in the glomerulus.
Statement $iii$ is incorrect: Glomerular filtrate is deproteinised plasma,but it is isotonic to blood plasma,not acidic.
Statement $iv$ is incorrect: $PCT$ (Proximal Convoluted Tubule) cells reabsorb high threshold substances (like glucose and amino acids) actively. Low threshold substances like sulphates and nitrates are reabsorbed to a very limited extent and are generally not actively reabsorbed against a gradient in the $PCT$ in the same manner as high threshold substances.
Therefore,statements $iii$ and $iv$ are incorrect.

(A) Ultrafiltration is the first step of urine formation occurring in the Malpighian body (glomerulus + Bowman's capsule).
During this process,blood is filtered under high hydrostatic pressure in the glomerulus.
The glomerular filtrate formed is similar to blood plasma in composition,but it lacks large proteins and blood cells.
Therefore,the statement that the filtrate is similar to urine is incorrect,as urine is much more concentrated and contains metabolic wastes like urea,which are modified during tubular reabsorption and secretion.
The effective filtration pressure $(EFP)$ is indeed approximately $10 \text{ mm Hg}$.

(B) The visceral layer of Bowman's capsule is composed of specialized cells called $podocytes$.
These $podocytes$ are arranged in an intricate manner so as to leave some minute spaces called $filtration$ $slits$ or $slit$ $pores$.
Blood is filtered so finely through these membranes that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman's capsule.
Therefore,filtration slits are the fine gaps between the foot-like processes (pedicels) of the podocytes.

(A) Urine formation involves three main processes:
$1$. Glomerular filtration (Ultrafiltration): This is the first step where blood is filtered through the glomerulus into the Bowman's capsule.
$2$. Reabsorption: Essential substances like glucose,amino acids,and water are reabsorbed from the filtrate back into the blood.
$3$. Tubular secretion: Additional waste products like $H^+$,$K^+$,and ammonia are secreted into the filtrate.
Therefore,the first step is Ultrafiltration.

(B) The kidneys produce approximately $180$ liters of glomerular filtrate per day.
This is calculated based on the Glomerular Filtration Rate $(GFR)$, which is about $125 \ mL$ per minute in a healthy individual.
Calculation: $125 \ mL/min \times 60 \ min/hr \times 24 \ hr/day = 180,000 \ mL/day = 180 \ liters/day$.

(A) The process of formation of urine begins with the filtration of blood,which occurs in the glomerulus. This process is called glomerular filtration.
During this process,blood is filtered so finely through the membranes of the glomerular capillary and the Bowman's capsule that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman's capsule.
Therefore,the glomerular filtrate is essentially blood plasma from which proteins have been removed,and it is commonly referred to as deproteinized plasma.

(C) The correct option is $C$.
During the process of urine formation,the first step is the filtration of blood.
This process occurs in the $Glomerulus$,a network of capillaries located within the $Bowman's$ capsule.
This specific process is known as glomerular filtration,where blood is filtered under high pressure.

(B) The correct answer is $B$.
Plasma proteins are large molecules that cannot pass through the glomerular filtration membrane during the process of ultrafiltration.
As a result,they are retained in the blood capillaries of the glomerulus.
In contrast,substances like urea,water,and glucose are small enough to pass through the filtration slits of the podocytes and the basement membrane,meaning their concentrations in the glomerular filtrate are initially similar to their concentrations in the blood plasma.