Regulation of Kidney Function Questions in English

(A) Renin is an enzyme secreted by the $Juxtaglomerular$ $(JG)$ cells of the kidneys.
These cells are located in the afferent arteriole of the nephron.
Renin is released in response to a decrease in blood pressure or blood flow to the kidneys.
It initiates the Renin-Angiotensin-Aldosterone System $(RAAS)$,which helps in increasing blood pressure and the reabsorption of sodium and water.

(C) Juxtaglomerular cells of the kidney secrete an enzyme called renin.
This enzyme converts angiotensinogen produced by the liver into angiotensin-$I$.
Subsequently,angiotensin-$I$ is converted into angiotensin-$II$.
The renin-angiotensin pathway stimulates the adrenal cortex to produce aldosterone.
Aldosterone helps in maintaining $Na^{+}$ and water concentration in the body,thereby regulating blood pressure.

(C) The reabsorption of water in the distal convoluted tubule $(DCT)$ and collecting tubule $(CT)$ of the nephron is regulated by the hormone Vasopressin,also known as Antidiuretic Hormone $(ADH)$.
Vasopressin is released from the posterior pituitary gland.
It increases the permeability of the $DCT$ and $CT$ to water,allowing for greater water reabsorption back into the blood,thereby concentrating the urine and preventing dehydration.

(B) $ADH$ (Antidiuretic hormone),also known as vasopressin,is produced in the hypothalamus and released into the bloodstream from the posterior pituitary gland.
It enhances fluid retention by stimulating the kidneys to reabsorb more water from the distal convoluted tubules and collecting ducts.
When there is a decrease in the secretion of vasopressin (hyposecretion),the permeability of the collecting ducts to water decreases.
This leads to reduced water reabsorption,resulting in the excretion of large amounts of dilute urine.

(C) The $ANF$ (Atrial Natriuretic Factor) is released by the atrial wall of the heart in response to increased blood flow to the atria.
$ANF$ causes vasodilation (dilation of blood vessels),which leads to a decrease in blood pressure.
This mechanism acts as a check on the renin-angiotensin mechanism,which is responsible for increasing blood pressure and glomerular filtration rate $(GFR)$.
Therefore,$ANF$ counteracts the effects of the renin-angiotensin system.

(A) The kidneys have built-in mechanisms for the regulation of the Glomerular Filtration Rate $(GFR)$.
One such efficient mechanism is carried out by the Juxtaglomerular Apparatus $(JGA)$.
$JGA$ is a special sensitive region formed by cellular modifications in the Distal Convoluted Tubule $(DCT)$ and the afferent arteriole at the location of their contact.
$A$ fall in $GFR$ activates the $JG$ cells to release renin,which stimulates the glomerular blood flow and thereby brings the $GFR$ back to normal levels.

(D) The functioning of the kidneys is regulated by three main hormonal feedback mechanisms:
$(i)$ The $Hypothalamus$ regulates water balance through the release of $ADH$ (Antidiuretic Hormone) or vasopressin.
$(ii)$ The $JGA$ (Juxtaglomerular Apparatus) regulates blood pressure and glomerular filtration rate through the renin-angiotensin-aldosterone mechanism.
$(iii)$ The $Heart$ regulates blood volume and pressure by releasing $ANF$ (Atrial Natriuretic Factor),which acts as a vasodilator and inhibits renin secretion.
Therefore,all these organs are involved in the hormonal regulation of kidney function.

(A) The Juxtaglomerular apparatus $(JGA)$ activates the Renin-Angiotensin-Aldosterone System $(RAAS)$.
$JGA$ releases the enzyme renin into the blood,which triggers a cascade of chemical reactions leading to the production of Angiotensin-$II$.
Angiotensin-$II$ acts as a potent stimulator for the adrenal cortex to release aldosterone,which is a mineralocorticoid.
Aldosterone helps in the reabsorption of $Na^+$ and water from the distal parts of the tubule,thereby increasing blood pressure and blood volume.

(D) The juxtaglomerular $(JG)$ cells are specialized cells in the kidney that act as baroreceptors.
They are activated by a decrease in Glomerular Blood Pressure $(GBP)$,a decrease in Glomerular Blood Flow $(GBF)$,or a decrease in the Glomerular Filtration Rate $(GFR)$.
When these values fall,the $JG$ cells release the enzyme renin,which initiates the Renin-Angiotensin-Aldosterone System $(RAAS)$ to restore blood pressure and filtration rates.
Therefore,all three conditions ($I, II,$ and $III$) lead to the activation of $JG$ cells.

(D) The correct answer is $D$ (All of these).
Osmoreceptors in the body are specialized sensory neurons that are activated by changes in blood volume,body fluid volume,and ionic concentration (osmolarity).
An excessive loss of fluid from the body leads to an increase in blood osmolarity and a decrease in blood volume,which activates these receptors.
Once activated,these osmoreceptors stimulate the hypothalamus to release $ADH$ (Antidiuretic Hormone),also known as vasopressin,from the neurohypophysis (posterior lobe of the pituitary gland).
$ADH$ facilitates the reabsorption of water from the distal convoluted tubule and collecting duct of the nephron,thereby preventing further water loss and maintaining fluid balance in the body.

(C) The kidneys have built-in mechanisms for the regulation of the glomerular filtration rate $(GFR)$.
One such efficient mechanism is carried out by the juxta glomerular apparatus $(JGA)$.
$JGA$ is a special sensitive region formed by cellular modifications in the distal convoluted tubule $(DCT)$ and the afferent arteriole at the location of their contact.
$A$ fall in $GFR$ can activate the $JG$ cells to release renin,which can stimulate the glomerular blood flow and thereby bring $GFR$ back to normal.

(C) The Renin-Angiotensin-Aldosterone System $(RAAS)$ functions as follows:
$1$. The liver produces and secretes the inactive plasma protein Angiotensinogen $(A)$.
$2$. Renin (secreted by the juxtaglomerular cells of the kidney) converts Angiotensinogen into Angiotensin $I$.
$3$. Angiotensin-Converting Enzyme $(ACE)$,which is primarily produced in the lungs $(B)$,converts Angiotensin $I$ into the active hormone Angiotensin $II$.
$4$. Angiotensin $II$ stimulates the adrenal cortex $(C)$ to release the hormone Aldosterone,which increases sodium and water reabsorption in the kidneys.
Therefore,$A$ is Liver,$B$ is Lung,and $C$ is Adrenal cortex.

(B) An increase in blood flow to the atria of the heart causes the release of Atrial Natriuretic Factor $(ANF)$.
$ANF$ causes vasodilation (dilation of blood vessels), which reduces blood pressure.
This mechanism acts as a check on the Renin-Angiotensin mechanism, which is responsible for increasing blood pressure.
Therefore, $A = ANF$, $B = \text{vasodilation}$, and $C = \text{renin-angiotensin mechanism}$.

(C) Vasoconstrictors are substances that narrow blood vessels,increasing blood pressure. $Angiotensin-II$ is a potent vasoconstrictor.
$ANF$ (Atrial Natriuretic Factor) and histamine act as vasodilators,which widen blood vessels.
$Renin$ is an enzyme secreted by the juxtaglomerular cells that initiates the conversion of angiotensinogen to $Angiotensin-I$,which is subsequently converted to $Angiotensin-II$.

(A) Aldosterone is a steroid hormone secreted by the adrenal cortex. It acts on the distal convoluted tubules and collecting ducts of the nephrons to stimulate the reabsorption of $Na^+$ ions and water,while promoting the excretion of $K^+$ ions and phosphate ions. This process helps in maintaining blood pressure and electrolyte balance.

(C) $ANF$ (Atrial Natriuretic Factor) is secreted by the atrial wall of the heart in response to increased blood flow or blood pressure. It acts as an antagonist to the Renin-Angiotensin mechanism. $ANF$ causes vasodilation (dilation of blood vessels) and promotes the excretion of $Na^+$ (sodium) and water in urine,thereby decreasing blood pressure. Therefore,the statement that $ANF$ enhances sodium reabsorption is incorrect.

(C) The activity of the kidney is regulated by hormonal feedback mechanisms involving the hypothalamus, $JGA$ (Juxtaglomerular apparatus), and the heart.
$1$. $Vasopressin$ (also known as $ADH$ or Antidiuretic Hormone) is released from the neurohypophysis and facilitates water reabsorption from the later parts of the tubule, thereby preventing diuresis.
$2$. $Aldosterone$ is a mineralocorticoid released from the adrenal cortex. It acts on the distal convoluted tubule $(DCT)$ and collecting duct to increase the reabsorption of $Na^+$ and water, which helps in maintaining blood volume and blood pressure.
Therefore, both $Vasopressin$ and $Aldosterone$ play a crucial role in influencing kidney function.

(C) The kidneys perform the vital function of osmoregulation,which involves maintaining the constant composition and volume of the blood and extracellular fluids. Regardless of the intake of food or fluids,the kidneys regulate the concentration of electrolytes and water,ensuring that the internal environment remains stable. This process is essential for homeostasis.

(D) Angiotensin $II$ increases blood volume through multiple mechanisms:
$(i)$ It stimulates the adrenal cortex to release aldosterone,which promotes the reabsorption of $Na^+$ and water from the distal convoluted tubule $(DCT)$ and collecting duct.
$(ii)$ It acts directly on the proximal convoluted tubule $(PCT)$ to increase the reabsorption of $NaCl$ and water.
Since both options $(A)$ and $(B)$ are correct,the correct answer is $(D)$.

(B) When the volume of body fluid falls below normal,the osmoreceptors are stimulated,which causes the release of $ADH$ (Antidiuretic Hormone) from the neurohypophysis.
$ADH$ facilitates water reabsorption from the later parts of the tubule,specifically the distal convoluted tubule $(DCT)$ and the collecting duct.
This increases the permeability of these tubules to water,thereby preventing diuresis and conserving body water.

(A) The Atrial Natriuretic Factor $(ANF)$ is a peptide hormone released by the atrial walls of the heart in response to an increase in blood flow or blood pressure.
$ANF$ acts as a vasodilator and promotes the excretion of sodium and water,thereby reducing blood volume and pressure.
It functions as a check on the Renin-Angiotensin-Aldosterone System $(RAAS)$ by inhibiting the release of renin from the Juxtaglomerular $(JG)$ apparatus.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(B) Vasopressin or $ADH$ (Antidiuretic Hormone) is secreted by the posterior lobe of the pituitary gland.
It acts primarily on the collecting ducts and the distal convoluted tubules of the nephron.
It increases the permeability of these segments to water,facilitating the reabsorption of water back into the blood.
This process reduces the volume of water excreted in the urine,thereby preventing diuresis,which is why it is called an antidiuretic hormone.

(C) The conversion of Angiotensinogen to Angiotensin-$I$ is catalyzed by the enzyme Renin.
Renin is secreted by the juxtaglomerular cells of the kidney in response to a decrease in blood pressure or blood flow.
Rennin (with double 'n') is a proteolytic enzyme found in the stomach of infants that helps in the digestion of milk proteins.

(A) Ethanol acts as a diuretic agent because it suppresses the release of $ADH$ (Antidiuretic Hormone),also known as vasopressin,from the posterior pituitary gland.
Vasopressin is responsible for the reabsorption of water from the distal convoluted tubules and collecting ducts of the nephrons.
When ethanol inhibits the secretion of vasopressin,the permeability of the collecting ducts to water decreases,leading to increased urine production (diuresis).
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation for the Assertion.

(D) Erythropoietin is a glycoprotein hormone that plays a crucial role in erythropoiesis,which is the production of red blood cells $(R.B.C.)$.
This hormone is primarily synthesized and secreted by the juxtaglomerular cells (specifically the interstitial fibroblasts) of the kidney in response to hypoxia or low oxygen levels in the blood.
Once released into the bloodstream,it travels to the bone marrow,where it stimulates the differentiation and proliferation of erythroid progenitor cells into mature red blood cells.
Therefore,the correct answer is the juxtaglomerular cells of the kidney.

(A) $JGA$ stands for Juxtaglomerular apparatus.
It is a special sensitive region formed by cellular modifications in the distal convoluted tubule $(DCT)$ and the afferent arteriole at the location of their contact.
It plays a significant role in the regulation of the kidney function,specifically in the Renin-Angiotensin-Aldosterone System $(RAAS)$.

(A) $RAAS$ stands for Renin-Angiotensin-Aldosterone System.
When there is a drop in glomerular blood flow,glomerular blood pressure,or $GFR$,the juxtaglomerular $(JG)$ cells release renin.
Renin converts angiotensinogen in the blood to angiotensin $I$ and further to angiotensin $II$.
Angiotensin $II$ acts as a powerful vasoconstrictor,which increases glomerular blood pressure and thereby $GFR$.
Angiotensin $II$ also activates the adrenal cortex to release aldosterone.
Aldosterone causes the reabsorption of $Na^{+}$ and water from the distal parts of the renal tubule,which leads to an increase in blood pressure and $GFR$.

(B) The $JG$ apparatus is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact.
$A$ fall in $GFR$ (Glomerular Filtration Rate) can activate the $JG$ cells to release $Renin$,which converts angiotensinogen in blood to angiotensin $I$ and further to angiotensin $II$.
Angiotensin $II$ being a powerful vasoconstrictor increases the glomerular blood pressure and thereby $GFR$. It also activates the adrenal cortex to release aldosterone.
Therefore,when $GFR$ decreases,$JG$ cells release renin.

(A) The $JGA$ (Juxtaglomerular Apparatus) is a specialized sensitive region formed by cellular modifications in the distal convoluted tubule $(DCT)$ and the afferent arteriole at the location of their contact.
It plays a significant role in the regulation of the kidney function,specifically in the renin-angiotensin-aldosterone system.

(A) The correct answer is $ANF$ (Atrial Natriuretic Factor).
$ANF$ is released by the atrial wall of the heart in response to increased blood flow or blood pressure,and it acts as a vasodilator to decrease blood pressure.
In contrast,$ADH$ (Antidiuretic Hormone),Renin,and Aldosterone are part of the Renin-Angiotensin-Aldosterone System $(RAAS)$ which functions to increase blood pressure and blood volume.
Therefore,$ANF$ is the odd one out as it is the only factor among the options that decreases blood pressure.

(D) Osmoreceptors are specialized sensory neurons located in the hypothalamus that monitor the osmotic pressure of the blood.
They are activated by changes in blood volume,body fluid volume,and excessive ionic concentration (osmolarity).
Excessive loss of water from the body (e.g.,due to sweating or dehydration) leads to an increase in blood osmolarity and a decrease in blood volume.
Since all these factors trigger the osmoreceptors to stimulate the release of $ADH$ (Antidiuretic Hormone) from the neurohypophysis,the correct answer is $D$.

(A) Aldosterone is a steroid hormone secreted by the adrenal cortex.
It acts primarily on the distal convoluted tubule $(DCT)$ and the collecting duct of the nephron.
Its main function is to stimulate the reabsorption of sodium ions $(Na^+)$ and water from the renal filtrate back into the blood.
This process helps in maintaining blood pressure,body fluid volume,and electrolyte balance.
Therefore,the correct effect is the reabsorption of $Na^+$ and water in the distal parts of the renal tubules.

(B) When there is a loss of water from the body,the body fluid volume decreases,which stimulates osmoreceptors in the hypothalamus.
These osmoreceptors stimulate the neurohypophysis (posterior pituitary) to release $ADH$ (Antidiuretic Hormone or Vasopressin).
$ADH$ acts on the distal parts of the kidney tubules (distal convoluted tubule and collecting duct) to facilitate the reabsorption of water.
This reabsorption prevents diuresis and helps in increasing the blood volume and blood pressure,thereby maintaining homeostasis.

(B) $ADH$ (Antidiuretic Hormone),also known as vasopressin,is released from the posterior pituitary gland.
It is secreted in response to a decrease in blood volume or blood pressure,or an increase in blood osmolarity,not when blood pressure increases.
$ADH$ causes vasoconstriction of blood vessels,which increases blood pressure.
It facilitates water reabsorption from the distal convoluted tubule $(DCT)$ and collecting duct,thereby reducing urine volume.
It does not directly increase the $GFR$ (Glomerular Filtration Rate); in fact,its primary role is water conservation.

(B) The $Renin-Angiotensin-Aldosterone$ System $(RAAS)$ is a critical mechanism for regulating blood pressure and fluid balance.
When blood pressure or glomerular blood flow decreases,the juxtaglomerular $(JG)$ cells release the enzyme $Renin$ into the bloodstream.
$Renin$ acts on the plasma protein $Angiotensinogen$ (produced by the liver) and converts it into $Angiotensin-I$.
Subsequently,$Angiotensin-I$ is converted into $Angiotensin-II$ by the $Angiotensin-Converting$ $Enzyme$ $(ACE)$,which is primarily found in the lungs.

(C) The Renin-Angiotensin-Aldosterone System $(RAAS)$ is a critical mechanism for regulating blood pressure and fluid balance.
$1$. When blood pressure or blood flow to the kidneys decreases,the juxtaglomerular $(JG)$ cells release the enzyme Renin.
$2$. Renin converts the plasma protein Angiotensinogen (produced by the liver) into Angiotensin-$I$.
$3$. Angiotensin-$I$ is then converted into the active hormone Angiotensin-$II$ by the Angiotensin-Converting Enzyme $(ACE)$,which is primarily found in the capillaries of the lungs.
$4$. Angiotensin-$II$ acts as a potent vasoconstrictor and stimulates the release of Aldosterone from the adrenal cortex.

(C) Angiotensin-$II$ is a powerful vasoconstrictor that increases glomerular blood pressure and thereby $GFR$ (Glomerular Filtration Rate).
It activates the adrenal cortex (not the adrenal medulla) to release aldosterone.
Aldosterone causes reabsorption of $Na^+$ and water from the distal parts of the tubule,which leads to an increase in blood pressure and $GFR$.
Therefore,the statement that it stimulates the adrenal medulla to release aldosterone is incorrect.

(C) The $RAAS$ ($Renin-Angiotensin-Aldosterone$ System) is a hormone system that regulates blood pressure and fluid balance.
$1$. $Renin$ is released by the juxtaglomerular cells in response to low blood pressure.
$2$. $Renin$ converts $Angiotensinogen$ into $Angiotensin-I$,which is then converted to $Angiotensin-II$.
$3$. $Angiotensin-II$ stimulates the adrenal cortex to release $Aldosterone$.
$4$. $ADH$ ($Antidiuretic$ $Hormone$ or $Vasopressin$) is released by the posterior pituitary in response to high blood osmolarity,which acts independently of the $RAAS$ pathway to increase water reabsorption in the kidneys.

(A) $ADH$ (Antidiuretic Hormone),also known as vasopressin,is synthesized by the hypothalamus and released by the posterior pituitary gland.
Its primary function is to facilitate the reabsorption of water and electrolytes from the distal convoluted tubules $(DCT)$ and collecting ducts of the nephrons in the kidneys.
By increasing water reabsorption back into the blood,$ADH$ reduces the volume of urine produced.
Therefore,injecting $ADH$ leads to a decrease in urine output.

(D) $ADH$ (Antidiuretic Hormone),also known as vasopressin,is synthesized by the hypothalamus and released by the posterior pituitary gland.
It acts mainly at the kidney and stimulates the reabsorption of water and electrolytes by the distal tubules,thereby reducing water loss through urine (diuresis).
$A$ deficiency of $ADH$ leads to a condition called diabetes insipidus,which is characterized by the excretion of large amounts of dilute urine.
Diabetes mellitus is caused by a deficiency of insulin,not $ADH$.
Therefore,the statement that its deficiency causes diabetes mellitus is incorrect.

(A) Erythropoietin is a peptide hormone produced by the juxtaglomerular cells of the kidney.
It acts on the bone marrow to stimulate the process of erythropoiesis (the production of red blood cells).
Therefore,the correct secretion site is the juxtaglomerular cells and the target site (effect) is the bone marrow.

(A) The Atrial Natriuretic Factor $(ANF)$ is a peptide hormone secreted by the atrial wall of the heart.
When blood pressure increases,the atrial wall releases $ANF$ to counteract the effect.
$ANF$ causes vasodilation (dilation of blood vessels),which decreases blood pressure.
Since $ANF$ is a peptide hormone,it cannot pass through the lipid bilayer of the cell membrane and instead binds to cell-surface receptors.
Therefore,statement $(A)$ is incorrect because $ANF$ is secreted when blood pressure increases,not when it decreases.

(A) When blood pressure increases,the walls of the atria of the heart are stretched.
This stretching stimulates the cardiac wall to secrete a peptide hormone called Atrial Natriuretic Factor $(ANF)$.
$ANF$ acts as a vasodilator (dilates blood vessels) and promotes the excretion of sodium and water,thereby reducing blood pressure.
Conversely,$ADH$ (Antidiuretic Hormone) is released when blood pressure is low or blood osmolarity is high to conserve water and increase blood pressure.
Therefore,an increase in blood pressure specifically triggers the release of $ANF$.

(A) Angiotensin $II$ is a powerful vasoconstrictor that stimulates the adrenal cortex to release aldosterone. This statement is correct.
$(b)$ Aldosterone promotes the reabsorption of $Na^+$ and water from the distal parts of the kidney tubules,which increases blood volume and blood pressure. This statement is correct.
$(c)$ Atrial Natriuretic Factor $(ANF)$ is released by the heart in response to increased blood flow/pressure and acts as a check (antagonist) on the renin-angiotensin mechanism. This statement is correct.
$(d)$ $ADH$ (Antidiuretic Hormone) causes vasoconstriction,not vasodilation. This statement is incorrect.
$(e)$ Vasopressin $(ADH)$ is synthesized by the hypothalamus and released from the neurohypophysis (posterior pituitary),not the adenohypophysis. This statement is incorrect.
Therefore,statements $(a), (b),$ and $(c)$ are correct.

(C) Statement $A$ is incorrect because an excessive loss of body fluid switches $ON$ the osmoreceptors,not $OFF$.
Statement $B$ is correct because $ADH$ (Antidiuretic Hormone) facilitates water reabsorption from the distal parts of the tubule,thereby preventing diuresis.
Statement $C$ is correct because $ANF$ (Atrial Natriuretic Factor) is released by the atrial wall of the heart in response to increased blood flow and causes vasodilation (dilation of blood vessels) to decrease blood pressure.
Statement $D$ is correct because $ADH$ increases water reabsorption,which increases blood volume and consequently increases blood pressure.
Statement $E$ is incorrect because $ADH$ does not cause a decrease in $GFR$ (Glomerular Filtration Rate); rather,it helps in maintaining water balance.
Therefore,statements $B, C$ and $D$ are correct.

(B) Angiotensin-$II$ is a powerful vasoconstrictor that increases the glomerular blood pressure and thereby $GFR$.
$\text{ADH}$ (Antidiuretic Hormone),also known as vasopressin,primarily acts on the kidney to facilitate water reabsorption from the later parts of the tubule,but at high concentrations,it also causes constriction of blood vessels (vasoconstriction).
Therefore,both hormones share the physiological effect of causing vasoconstriction.

(B) When a person drinks excess water,the osmolarity of the blood decreases (blood becomes more dilute).
This change is detected by osmoreceptors in the hypothalamus.
In response,the hypothalamus signals the posterior pituitary gland to decrease the secretion of Antidiuretic Hormone $(\text{ADH})$,also known as vasopressin.
Reduced $\text{ADH}$ levels lead to decreased water reabsorption in the distal convoluted tubules and collecting ducts of the kidneys,resulting in the production of dilute urine to eliminate the excess water.
Therefore,$\text{ADH}$ release is suppressed.

(A) Let's analyze each statement:
$A.$ Incorrect. Osmoreceptors are activated by excess loss of fluid,but this leads to the stimulation (not inhibition) of $\text{ADH}$ secretion to conserve water.
$B.$ Correct. $A$ fall in Glomerular Filtration Rate $(\text{GFR})$ activates the juxtaglomerular cells to release renin.
$C.$ Incorrect. $\text{ANF}$ (Atrial Natriuretic Factor) is secreted in response to an increase in blood flow or pressure in the atria,not a decrease.
$D.$ Correct. $\text{ANF}$ acts as a check (antagonist) on the renin-angiotensin mechanism by causing vasodilation and decreasing blood pressure.
$E.$ Correct. $\text{ADH}$ (Vasopressin) causes constriction of blood vessels,which increases blood pressure and influences kidney function.
Therefore,statements $B, D,$ and $E$ are correct.

(B) $ADH$ stands for Antidiuretic Hormone,also known as Vasopressin.
It is synthesized by the hypothalamus and stored and released by the posterior pituitary gland (neurohypophysis).
Its primary function is to act on the kidney tubules (specifically the distal convoluted tubule and collecting duct) to promote the reabsorption of water from the glomerular filtrate back into the blood.
This process helps in reducing the loss of water through urine,thereby maintaining the body's water balance.

(D) Angiotensinogen is a plasma protein (globulin) produced and secreted into the blood by the liver cells,known as hepatocytes.
When blood pressure or blood volume decreases,the juxtaglomerular $(JG)$ apparatus of the kidneys releases an enzyme called renin.
Renin converts angiotensinogen into angiotensin-$I$,which is further converted into angiotensin-$II$ by angiotensin-converting enzyme $(ACE)$.
Angiotensin-$II$ acts as a powerful vasoconstrictor and stimulates the adrenal cortex to release aldosterone,thereby helping to regulate blood pressure and electrolyte balance.