Excretory system MCQ Quiz - Objective Question with Answer for Excretory system - Download Free PDF

The correct answer is Decrease in the serum and glucocorticoid-regulated kinase 1 (Sgk1) levels

Explanation:

Aldosterone is a steroid hormone secreted by the adrenal cortex, which plays a crucial role in regulating sodium (Na+), potassium (K+), and water balance in the body. It exerts its effects mainly on the principal cells of the distal tubule and the collecting duct in the nephron of the kidney, enhancing Na+ reabsorption and K+ secretion. Aldosterone achieves this by influencing the expression and activity of proteins involved in Na+ transport, such as epithelial sodium channels (ENaC), Na+, K+-ATPase pumps, and other mediators.

• Decrease in the serum and glucocorticoid-regulated kinase 1 (Sgk1) levels
  • ​Serum and glucocorticoid-regulated kinase 1 (Sgk1) is a key mediator of aldosterone action in the kidney.
  • Aldosterone increases the levels of Sgk1, which in turn promotes the activity and expression of ENaC (epithelial sodium channels) on the apical membrane of principal cells.
  • Sgk1 also helps stabilize ENaC channels, preventing their degradation and ensuring efficient Na+ reabsorption.
  • A decrease in Sgk1 levels would counteract aldosterone's effects, making this option incorrect in the context of aldosterone's physiological action.

Other Options:

• Stimulation of CAP1 levels: CAP1 (Channel-activating protease 1) is involved in activating ENaC channels on the apical membrane. Aldosterone stimulates CAP1 levels, which enhances the activity of ENaC, facilitating Na+ reabsorption.
• Increase in the expression of ENaC in the apical membrane: Aldosterone increases the transcription and translation of ENaC, resulting in a higher density of these channels in the apical membrane of principal cells. 
• Increase in the amount of Na+, K+-ATPase in the basolateral membrane: Aldosterone upregulates the expression of Na+, K+-ATPase pumps on the basolateral membrane. These pumps actively transport Na+ out of the cell into the bloodstream, maintaining a low intracellular Na+ concentration, which drives further Na+ reabsorption.

The correct answer is A and D

Concept:

Osmotic diuresis refers to an increase in urine output caused by the presence of certain substances (such as mannitol) in the renal tubule that prevent water from being reabsorbed. Mannitol, an osmotic agent, is filtered at the glomerulus but not reabsorbed in the renal tubules. This leads to alterations in water and solute reabsorption across different segments of the nephron, thereby increasing urine production.

• Mannitol creates an osmotic gradient in the tubules, reducing water reabsorption.
• It affects the medullary concentration gradient, which is critical for water reabsorption in the collecting ducts.
• Osmotic diuresis leads to changes in both water and electrolyte handling in different parts of the nephron.

Explanation:

A. In the proximal tubule, water reabsorption falls due to the presence of mannitol in tubular fluid, and the concentration of Na+ is decreased in this fluid: This statement is correct. Mannitol in the proximal tubule increases the osmolarity of the tubular fluid, which reduces the reabsorption of water. As a result, the concentration of Na+ in the tubular fluid decreases because water reabsorption is not proportional to solute reabsorption.

B. In the descending loop of Henle, reabsorption of water is increased as medullary hypertonicity is decreased in osmotic diuresis: This statement is incorrect. In osmotic diuresis, the medullary hypertonicity is reduced due to the dilution of the interstitial fluid. This reduction in hypertonicity decreases the driving force for water reabsorption in the descending loop of Henle.

C. In the thin ascending loop of Henle, reabsorption of Na+ is increased as the concentration gradient for Na+ is decreased: This statement is incorrect. Sodium reabsorption in the thin ascending loop of Henle is passive and depends on the concentration gradient. In osmotic diuresis, the concentration gradient for sodium is reduced, which decreases sodium reabsorption in this segment.

D. In the collecting duct, reabsorption of water is less because of a decrease in the osmotic gradient along the medullary pyramid in osmotic diuresis: This statement is correct. Osmotic diuresis decreases the medullary interstitial osmotic gradient, which reduces the reabsorption of water in the collecting ducts, even in the presence of antidiuretic hormone (ADH).

The correct answer is a - iv, b - i, c - ii, d - iii.

Concept:

Different parts of the nephron (renal tubule) have specific sodium transport mechanisms depending on their location and function.

• Proximal Tubule: The Na⁺-amino acid co-transporter is active here. This part of the nephron is responsible for the bulk reabsorption of sodium along with glucose, amino acids, and other solutes. Sodium is reabsorbed together with these molecules via specific co-transporters.
• Thick Ascending Limb of the Loop of Henle: The Na⁺-K⁺-2Cl^- co-transporter is active here. This segment is vital for reabsorbing sodium, potassium, and chloride ions. It plays an essential role in concentrating urine by reabsorbing solutes without water, which is why it’s known as the "diluting segment."
• Distal Convoluted Tubule: The Na⁺-Cl^- co-transporter works here. Sodium and chloride are reabsorbed together, and this part of the nephron is under hormonal control, specifically by aldosterone, which fine-tunes sodium reabsorption.
• Collecting Duct: The Na⁺ channel (ENaC) is predominant here. Sodium reabsorption in the collecting duct is crucial for controlling the body's overall sodium balance. It is regulated by aldosterone, which increases the activity of ENaC channels, allowing more sodium to be reabsorbed.

Explanation:

Proximal Tubule (Column X: a)

• The primary transporters in the proximal tubule include Na⁺-amino acid co-transporters and Na⁺-glucose co-transporters.

Collecting Duct (Column X: b)

• The primary sodium transporter in the collecting duct is the Epithelial sodium channel (ENaC), which regulates sodium reabsorption.

Thick Ascending Limb (Column X: c)

• The main sodium transporter in the thick ascending limb is the Na⁺-K⁺-2Cl^- co-transporter

Distal Convoluted Tubule (Column X: d)

• In the distal convoluted tubule, the main sodium transporter is the Na⁺-Cl^- co-transporter.

Concept:

• The renin-angiotensin-aldosterone system (RAAS) is an important regulator that regulates blood volume, electrolyte balance, and systemic vascular resistance. 
• It is responsible for chronic as well as acute alterations. 
• It comprises three main components - renin, angiotensin II, and aldosterone
• It is a complicated system that involved multiple organs such as kidneys, lungs, systemic vasculature, adrenal cortex, and brain.

Mechanism of RAAS - 

1. When JG cells in the kidney get activated pre-renin is converted to renin. 
2. Renin cleaves the N-terminal of angiotensinogen and produces Angiotensin I. 
3. Angiotensin I do not have any biological role. It is further processed by the enzyme Angiotensin-converting enzyme (ACE).
4. ACE removes two amino acids from the C-terminal of angiotensin I to form angiotensin II polypeptide.
5. Angiotensin II is the main regulator of the RAAS. 
6. It regulates blood pressure, blood volume, and aldosterone secretion. 
7. Aldosterone is the final regular, its synthesis is regulated by angiotensin II, ACTH, and extracellular potassium concentration. 

Important Points

Option 1: INCORRECT

• Calcitonin is a straight-chain peptide with 32 amino acids.
• Parafollicular cells of thyroid gland secrete calcitonin hormone. 
• The function of calcitonin is to reduce the level of calcium in the blood and not in the bones. 
• It blocks the activity of osteoclasts, which are responsible for the breakdown of bone, hence, by prevents calcium from entering the blood. 

Option 2: INCORRECT

• Angiotensin is a main player in the RAS system. It helps to regulate blood pressure by activating water and salt (sodium) uptake and constricting blood vessels.

Option 3: CORRECT

• The parathyroid gland secretes the parathyroid hormone.
• This hormone is secreted in response to low blood calcium.
• It stimulates the release of calcium into the blood and also increases the excretion of phosphate through urine. 

Option 4: INCORRECT

• Vasopressin also called ADH is the important hormone involved in maintaining water balance in the body.
• Its function is to regulate water reabsorption. When it is secreted in larger amounts it increases water reabsorption in the collecting ducts. 

Hence, the correct answer is option 3.

The correct answer is 21-hydroxylase

Explanation:

Cortisol is a glucocorticoid hormone produced by the zona fasciculata of the adrenal cortex under the regulation of ACTH (adrenocorticotropic hormone) which is released by the pituitary gland. The synthesis of cortisol from cholesterol involves several enzymatic steps, with each step being crucial for the conversion of precursors to cortisol.

• 17 α-hydroxylase: This enzyme is involved early in the cortisol synthesis pathway. It converts pregnenolone into 17α-hydroxypregnenolone and progesterone into 17α-hydroxyprogesterone. While it is necessary for the production of cortisol, it is not the enzyme responsible for converting 17α-hydroxyprogesterone directly into 11-deoxycortisol.
• 21-hydroxylase: This enzyme acts on 17α-hydroxyprogesterone, converting it into 11-deoxycortisol. 21-hydroxylase is indeed critical in cortisol synthesis, the direct step referenced involves 11-deoxycortisol, not its conversion to cortisol.
• 11 β-hydroxylase: It converts 11-deoxycortisol to cortisol, the final step in the synthesis of cortisol. This enzyme is essential for the production of active cortisol from its immediate precursor, making it critical in the cortisol synthesis pathway within the adrenal gland's zona fasciculata.
• 18-hydroxylase: This enzyme is involved in the synthesis of aldosterone in the zona glomerulosa of the adrenal gland and is not directly involved in the cortisol synthesis pathway.

Conclusion:

In summary, 21-hydroxylase is the key enzyme responsible for the conversion of 17-Hydroxyprogestrone  to 11-deoxycortisol, making it the correct answer to the question. This enzyme's activity ensures the production of cortisol, a hormone vital for regulating various physiological processes, including metabolism, immune response, and stress response.

The correct answer is Option 2 i.e. Paxillin.

Concept:​

• The slit-diaphragm, a cell-cell connection between the foot processes of renal podocytes, controls the kidney's ability to filter blood,
• It is essential for mammalian survival.
• It is believed that the slit diaphragm serves as the kidney's last line of defence or a molecular sensor of renal filtration.

​Explanation:

• A considered specialised adherens junctions, slit diaphragms include both distinctive membrane proteins such as nephrin, podocin, and Neph1 and common adherens junction proteins e.g., P-cadherin, FAT, and catenins.
• NEPH2 belongs to the NEPH family of proteins, which are highly conserved within mammalian and submammalian species.
• NEPH2 has been shown to interact with cytoplasmatic proteins of the slit diaphragm.

Important Points

Option 1: NEPH1

• Consider the explanation above thus this option is true, as NEPH1 belongs to membrane proteins of slit diaphragms.

Option 2: Paxillin

• Consider the explanation above thus this option is not true.

Option 3: Nephrin

• Consider the explanation above thus this option is true, as Nephrin belongs to membrane proteins of slit diaphragms.

Option 4: NEPH2

• Consider the explanation above thus this option is true, as NEPH2 has been shown to interact with cytoplasmatic proteins of the slit diaphragm.

Concept:

• The renin-angiotensin-aldosterone system (RAAS) is an important regulator that regulates blood volume, electrolyte balance, and systemic vascular resistance. 
• It is responsible for chronic as well as acute alterations. 
• It comprises three main components - renin, angiotensin II, and aldosterone
• It is a complicated system that involved multiple organs such as kidneys, lungs, systemic vasculature, adrenal cortex, and brain.

Mechanism of RAAS - 

1. When JG cells in the kidney get activated pre-renin is converted to renin. 
2. Renin cleaves the N-terminal of angiotensinogen and produces Angiotensin I. 
3. Angiotensin I do not have any biological role. It is further processed by the enzyme Angiotensin-converting enzyme (ACE).
4. ACE removes two amino acids from the C-terminal of angiotensin I to form angiotensin II polypeptide.
5. Angiotensin II is the main regulator of the RAAS. 
6. It regulates blood pressure, blood volume, and aldosterone secretion. 
7. Aldosterone is the final regular, its synthesis is regulated by angiotensin II, ACTH, and extracellular potassium concentration. 

Important Points

Option 1: INCORRECT

• Calcitonin is a straight-chain peptide with 32 amino acids.
• Parafollicular cells of thyroid gland secrete calcitonin hormone. 
• The function of calcitonin is to reduce the level of calcium in the blood and not in the bones. 
• It blocks the activity of osteoclasts, which are responsible for the breakdown of bone, hence, by prevents calcium from entering the blood. 

Option 2: INCORRECT

• Angiotensin is a main player in the RAS system. It helps to regulate blood pressure by activating water and salt (sodium) uptake and constricting blood vessels.

Option 3: CORRECT

• The parathyroid gland secretes the parathyroid hormone.
• This hormone is secreted in response to low blood calcium.
• It stimulates the release of calcium into the blood and also increases the excretion of phosphate through urine. 

Option 4: INCORRECT

• Vasopressin also called ADH is the important hormone involved in maintaining water balance in the body.
• Its function is to regulate water reabsorption. When it is secreted in larger amounts it increases water reabsorption in the collecting ducts. 

Hence, the correct answer is option 3.

The correct answer is Option 4 i.e. H+ secretion

Key Points

• Selective reabsorption is the process where useful substances are reabsorbed from the glomerulus filtrate and transferred to the blood capillaries.
• Selective reabsorption occurs throughout the renal tubules through active as well as passive reabsorption.
• Important substances are reabsorbed actively while water is reabsorbed passively.

1. Reabsorption in PCT:
   • PCT is lined by columnar cells that have multiple finger-like projections called microvilli to increase the surface area of reabsorption.
   • here active reabsorption of amino acids, glucose and vitamins takes place.
   • It also reabsorbs most of Ca²⁺, it also reabsorb K⁺, Na⁺, Cl^-.
   • 75% of water reabsorb is absorbed passively and the filtrate becomes hypertonic.
2. Reabsorption in descending limb of Henle's loop: 
   • About 5% of the water is reabsorbed.
   • Na+, other salts and urea is reabsorbed actively.
3. Reabsorption in ascending limb of Henle's loop:
   • Reabsorption of K⁺ and Na⁺ takes place actively 
   • Cl^- is reabsorbed passively or by diffusion
   • This region is impermeable to water and filtrate becomes hypotonic.
4. Reabsorption of DCT and collecting duct
   • In DCT and collection duct, Na+ is absorbed actively while Cl^- is absorbed passively.
   • Na+ is reabsorbed in exchange for some K⁺ ions.
   • Reabsorption of water is dependent on the secretion and concentration of ADH. 
   • It maintains the pH and homeostasis. 
   • At the end of this hypertonic urine is secreted.

Explanation:

• Principle cells or P-cells are present in the collecting duct of the kidney. 
• They play a central role in the salt and water transport through their three main transporters - epithelial Na+ channel (ENaC), the renal outer medullary K+ channel(ROMK), and the aquaporin 2 (AQP2) water channel. 
• Reabsorption of Na⁺ by ENaC is balanced by the secretion of K⁺ by ROMK.
• Here, the secretion or absorption of H⁺ does not occur. 

Hence, the correct answer is Option 4.

Concept:

• The process of urination, or micturition, is a complex physiological process that involves the coordination of multiple nerve centers in the nervous system.
• These nerve centers are responsible for regulating the contraction and relaxation of the muscles in the bladder and urethra, as well as the opening and closing of the internal and external urethral sphincters.
• The micturition reflex center is located in the spinal cord and is responsible for coordinating the reflexive process of urination.
• When the bladder fills with urine, sensory nerves in the bladder wall send signals to the micturition reflex center in the spinal cord.
• This center then coordinates the contraction of the detrusor muscle, which is responsible for emptying the bladder, and the relaxation of the internal urethral sphincter, which allows urine to flow from the bladder into the urethra.
• The pontine micturition center, located in the brain stem, receives information from the bladder and coordinates
• The relaxation of the internal urethral sphincter and the contraction of the detrusor muscle to empty the bladder. It also coordinates with other regions of the brain to regulate voluntary control over urination.
• The cerebral cortex is involved in voluntary control over micturition, which is important for bladder control in humans.
• For example, a person can consciously delay urination until an appropriate time or location or can initiate urination when it is socially acceptable to do so.
• This voluntary control involves the communication between the cerebral cortex and the pontine micturition center, as well as the internal and external urethral sphincters.

Explanation:

• The dura mater is a tough membrane that surrounds and protects the brain and spinal cord, but it is not directly involved in the regulation of micturition.
• The other options are all involved in the regulation of micturition:
• Spinal cord: The spinal cord contains the micturition reflex center, which coordinates the process of urination.
• Brain stem: The brain stem contains the pontine micturition center, which receives information from the bladder and coordinates the relaxation of the internal urethral sphincter and the contraction of the detrusor muscle to empty the bladder.
• Cerebral cortex: The cerebral cortex can inhibit or facilitate micturition through voluntary control, which is important for bladder control in humans.

The correct answer is Option 4 i.e. D,E and F

Concept:​

• Acid-base balance is an important physiological process in the body that involves the regulation of hydrogen ion (H⁺) concentration in the extracellular fluid.
• The kidneys play a crucial role in the regulation of acid-base balance by selectively excreting or reabsorbing H⁺ and bicarbonate ions (HCO₃^-) in the urine.
• In acidosis, where the blood pH is lower than normal, the kidneys increase the secretion of H⁺ ions and reabsorption of HCO3- ions to help restore the normal pH.
• The mechanisms of regulation of H+ secretion by the kidneys in acidosis involve hormonal and molecular regulation of transporters in the proximal tubule of the nephron.
• The Na⁺ - H⁺ antiporter and Na⁺ - HCO₃^- symporter are two important transporters involved in this process.
• Cortisol, a hormone secreted by the adrenal cortex, can stimulate the transcription of the Na⁺ - H⁺ antiporter gene, leading to increased H⁺ secretion.
• Endothelin-1, a peptide hormone secreted by the proximal tubule, stimulates the phosphorylation and insertion of the Na⁺ - H⁺ antiporter into the apical membrane of proximal tubular cells, as well as the insertion of the Na⁺ - HCO₃^- symporter into the basolateral membrane of proximal tubular cells, leading to increased H⁺ secretion and HCO₃^- reabsorption.

• In fact, acidosis stimulates the secretion of cortisol by the adrenal cortex as a part of the body's response to acid-base disturbances.

• This is partially correct. Cortisol can modulate the transcription of the Na⁺ - H⁺ antiporter gene, but the effect is to increase the transcription, not decrease it.

• Cortisol does not have a significant effect on the translation of mRNA of the Na⁺ - HCO₃^- symporter gene.

• Acidosis stimulates the secretion of endothelin-1 from the proximal tubule.

• Endothelin-1 stimulates the phosphorylation and insertion of the Na⁺ - H⁺ antiporter into the apical membrane of proximal tubular cells, leading to increased H+ secretion.

• Endothelin-1 also stimulates the insertion of the Na⁺ - HCO₃^- symporter into the basolateral membrane of proximal tubular cells, leading to increased HCO₃^- reabsorption.

Key Points

•  Excretion is the process of eliminating metabolic wastes from an organism.
• Invertebrates are animals that lack a backbone and are found in a diverse range of habitats such as marine, freshwater, and terrestrial environments.
• Invertebrates have evolved different mechanisms for excreting waste products based on their environment and metabolic requirements.
• Some invertebrates, such as sponges and cnidarians, lack specialized excretory organs and rely on simple diffusion to excrete metabolic wastes.
• The diffusion process helps in excreting waste products such as ammonia, urea, and uric acid.
• In contrast, other invertebrates, such as annelids and mollusks, have specialized excretory organs known as nephridia and nephrons, respectively.
• Nephridia are excretory tubules present in annelids that help in removing nitrogenous wastes.
• Nephrons are tubular structures present in mollusks that play a role in excreting nitrogenous wastes.
• Arthropods, the largest group of invertebrates, have specialized excretory organs known as Malpighian tubules.
• These tubules help in removing nitrogenous wastes such as uric acid, which are produced during the breakdown of proteins.
• Malpighian tubules are an important adaptation for arthropods living in terrestrial habitats because they help in conserving water.
• In conclusion, invertebrates have evolved different mechanisms for excreting metabolic wastes based on their habitat and metabolic requirements.
• These mechanisms include simple diffusion, nephridia, nephrons, and Malpighian tubules.

Explanation:

• P. Flame cells are found in mollusks and jellyfish. INCORRECT
  • This statement is partially correct.
  • Flame cells, also known as protonephridia, are excretory structures found in certain invertebrates, including some mollusks and flatworms.
  • However, they are not present in jellyfish.
  • Flame cells are responsible for removing metabolic waste from the body and maintaining osmotic balance.
• Q. Nephridia and Malpighian tubules convert ammonia to urea for water conservation. CORRECT
  • This statement is correct.
  • Nephridia and Malpighian tubules are both excretory structures found in different groups of invertebrates.
  • Nephridia are present in segmented worms (such as earthworms) and some mollusks, while Malpighian tubules are found in insects and other arthropods.
  • Both structures help in the removal of metabolic waste, but they do not convert ammonia to urea. Instead, they assist in the elimination of nitrogenous waste (mostly in the form of uric acid) and help conserve water by excreting waste in a concentrated form.
• R. Green glands are found in flatworms and help in excreta elimination. INCORRECT
  • This statement is incorrect.
  • Green glands, also known as antennal glands, are excretory organs found in crustaceans such as crabs, lobsters, and crayfish.
  • They are not present in flatworms.
  • Green glands play a role in excretion by filtering waste products from the blood and eliminating them through a pore located at the base of the antennae.
• S. Excretory canals in nematodes carry waste materials to excretory pores in the body wall. INCORRECT
  • This statement is incorrect.
  • Nematodes, also known as roundworms, possess a specialized excretory system called the excretory pore or excretory duct. However, waste materials are not transported through excretory canals to excretory pores in the body wall.
  • Instead, nematodes excrete waste through a single excretory pore located at the posterior end of the body.
  • This pore serves as the endpoint for the excretory system, collecting waste products and eliminating them from the body.

The correct answer is A and D

Concept:

Osmotic diuresis refers to an increase in urine output caused by the presence of certain substances (such as mannitol) in the renal tubule that prevent water from being reabsorbed. Mannitol, an osmotic agent, is filtered at the glomerulus but not reabsorbed in the renal tubules. This leads to alterations in water and solute reabsorption across different segments of the nephron, thereby increasing urine production.

• Mannitol creates an osmotic gradient in the tubules, reducing water reabsorption.
• It affects the medullary concentration gradient, which is critical for water reabsorption in the collecting ducts.
• Osmotic diuresis leads to changes in both water and electrolyte handling in different parts of the nephron.

Explanation:

A. In the proximal tubule, water reabsorption falls due to the presence of mannitol in tubular fluid, and the concentration of Na+ is decreased in this fluid: This statement is correct. Mannitol in the proximal tubule increases the osmolarity of the tubular fluid, which reduces the reabsorption of water. As a result, the concentration of Na+ in the tubular fluid decreases because water reabsorption is not proportional to solute reabsorption.

B. In the descending loop of Henle, reabsorption of water is increased as medullary hypertonicity is decreased in osmotic diuresis: This statement is incorrect. In osmotic diuresis, the medullary hypertonicity is reduced due to the dilution of the interstitial fluid. This reduction in hypertonicity decreases the driving force for water reabsorption in the descending loop of Henle.

C. In the thin ascending loop of Henle, reabsorption of Na+ is increased as the concentration gradient for Na+ is decreased: This statement is incorrect. Sodium reabsorption in the thin ascending loop of Henle is passive and depends on the concentration gradient. In osmotic diuresis, the concentration gradient for sodium is reduced, which decreases sodium reabsorption in this segment.

D. In the collecting duct, reabsorption of water is less because of a decrease in the osmotic gradient along the medullary pyramid in osmotic diuresis: This statement is correct. Osmotic diuresis decreases the medullary interstitial osmotic gradient, which reduces the reabsorption of water in the collecting ducts, even in the presence of antidiuretic hormone (ADH).

Concept:

• Medical imaging of the urinary bladder is used to obtain images of the bladder in order to diagnose and monitor conditions that affect this organ.
• Imaging techniques that are commonly used for this purpose include X-ray, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound.
• These techniques can provide detailed information about the size, shape, and location of the bladder, as well as any abnormalities such as growths, tumors, or inflammation.
• For example, X-ray imaging of the bladder can be used to detect bladder stones or tumors, while CT and MRI can provide more detailed images of the bladder and surrounding tissues.
• Ultrasound can also be used to obtain real-time images of the bladder, as well as to guide certain procedures such as biopsies or catheterizations.
• Medical imaging of the urinary bladder is typically performed by a radiology technician or radiologist, who will use specialized equipment to obtain the images.
• The images will then be analyzed by a medical professional to determine the presence and extent of any abnormalities or conditions affecting the bladder.

Explanation:

• The correct region that needs to be observed for x-raying a growth on the urinary bladder is the hypogastric region.
• The hypogastric region is located in the lower part of the abdomen, just above the pubic bone, and it contains the bladder, among other structures. X-raying this region can provide information about the size, shape, and location of the bladder, as well as any abnormalities such as growths or tumors.
• The left inguinal region, right inguinal region, and umbilical region are not relevant for this specific imaging procedure.
• The urinary bladder is located in the hypogastric region, which is the lower part of the abdomen, just above the pubic bone. This is the region where a radiology technician would direct an X-ray machine to produce images of the bladder.
• The urinary bladder is a hollow, muscular organ that stores urine until it is eliminated from the body.
• It is located in the hypogastric region of the pelvis, which is the lower part of the abdomen, just above the pubic bone.​
• The hypogastric region is bounded by the inguinal regions on either side, and the umbilical region above.
• It contains the urinary bladder, as well as other structures such as the uterus (in females), rectum, and prostate gland (in males).
• The bladder is situated in the midline of the hypogastric region, between the pubic bones.
• During an X-ray procedure of the urinary bladder, the radiology technician will direct the X-ray machine to the hypogastric region to obtain images of the bladder. This is typically done in order to detect abnormalities such as bladder stones, tumors, or inflammation.
• The left inguinal region and right inguinal region are located in the lower part of the abdomen, near the groin area.
• They contain structures such as the femoral artery, femoral vein, and lymph nodes.
• The umbilical region is located in the center of the abdomen, around the navel, and it contains structures such as the small intestine and the umbilicus (belly button).

Therefore, the correct option 1.

Concept:

• The glomerulus is a network of tiny blood vessels located within Bowman's capsule.
• As blood flows through the glomerulus, small molecules such as water, electrolytes, and glucose are filtered out of the blood and into Bowman's capsule, forming a fluid called the filtrate.
• Larger molecules such as proteins and blood cells are retained in the blood.
• The filtrate then flows into the proximal tubule, where more reabsorption and secretion occur.
• In this process, some of the filtered substances are reabsorbed back into the bloodstream, while others are secreted into the tubule to be eliminated from the body.
• The remaining fluid then flows into the loop of Henle, where water and electrolytes are further reabsorbed or excreted.
• Finally, the filtrate flows into the distal tubule and collecting ducts, where more reabsorption and secretion occurs before the final urine is formed and excreted from the body.
• In summary, the process of urine formation involves the filtration of blood in the glomerulus, followed by reabsorption and secretion of various substances in the nephron.
• The composition of urine reflects the body's metabolic and physiologic state, and abnormalities in urine composition can be indicative of various kidney and systemic diseases.
• Therefore, monitoring urine output and composition is an important part of evaluating kidney function and overall health.

• Bowman's capsule is a part of the nephron, which is the functional unit of the kidney responsible for filtering blood and producing urine.
• In a normal kidney, blood is filtered in the glomerulus, which is a network of capillaries within Bowman's capsule.
• During filtration, water, electrolytes, and small molecules such as glucose are filtered out of the blood and into the Bowman's capsule, while larger molecules such as proteins and blood cells are retained in the blood.

Therefore, the correct answer is 2.

Concept:

• The renin-angiotensin-aldosterone system (RAAS) is an important regulator that regulates blood volume, electrolyte balance, and systemic vascular resistance. 
• It is responsible for chronic as well as acute alterations. 
• It comprises three main components - renin, angiotensin II, and aldosterone
• It is a complicated system that involved multiple organs such as kidneys, lungs, systemic vasculature, adrenal cortex, and brain.

Mechanism of RAAS - 

1. When JG cells in the kidney get activated pre-renin is converted to renin. 
2. Renin cleaves the N-terminal of angiotensinogen and produces Angiotensin I. 
3. Angiotensin I do not have any biological role. It is further processed by the enzyme Angiotensin-converting enzyme (ACE).
4. ACE removes two amino acids from the C-terminal of angiotensin I to form angiotensin II polypeptide.
5. Angiotensin II is the main regulator of the RAAS. 
6. It regulates blood pressure, blood volume, and aldosterone secretion. 
7. Aldosterone is the final regular, its synthesis is regulated by angiotensin II, ACTH, and extracellular potassium concentration. 

Important Points

Option 1: INCORRECT

• Calcitonin is a straight-chain peptide with 32 amino acids.
• Parafollicular cells of thyroid gland secrete calcitonin hormone. 
• The function of calcitonin is to reduce the level of calcium in the blood and not in the bones. 
• It blocks the activity of osteoclasts, which are responsible for the breakdown of bone, hence, by prevents calcium from entering the blood. 

Option 2: INCORRECT

• Angiotensin is a main player in the RAS system. It helps to regulate blood pressure by activating water and salt (sodium) uptake and constricting blood vessels.

Option 3: CORRECT

• The parathyroid gland secretes the parathyroid hormone.
• This hormone is secreted in response to low blood calcium.
• It stimulates the release of calcium into the blood and also increases the excretion of phosphate through urine. 

Option 4: INCORRECT

• Vasopressin also called ADH is the important hormone involved in maintaining water balance in the body.
• Its function is to regulate water reabsorption. When it is secreted in larger amounts it increases water reabsorption in the collecting ducts. 

Hence, the correct answer is option 3.