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The CORRECT ANSWER is (b) Adrenal cortex

Explanation: ALDOSTERONE is released from the zona glomerulosa of the adrenal cortex. It is a mineralocorticoid hormone that increases the reabsorption of sodium ions and WATER from the distal parts of the NEPHRON.

Correct CHOICE is (b) False

The best I can EXPLAIN: Kidney transplantation is the ULTIMATE method in the correction of acute renal failures or kidney failures. A FUNCTIONING kidney is used in the transplantation from a donor, preferably a close relative to avoid REJECTION by the immune system of the host.

The correct CHOICE is (a) Ornithine amino acid

The best I can explain: Ornithine amino acid is the starting point of the urea FORMATION in the Krebs-Hanseleit cycle or the urea cycle. Ornithine and CITRULLINE are the main amino acids of the urea formation.

The correct choice is (C) As BLOOD PRESSURE increases, efferent renal ARTERIOLE dilates

The best I can explain: Myogenic mechanism of the kidney is the main mechanism to regulate the glomerular filtration rate. As the blood pressure increases, the efferent renal arteriole gets dilated and hence reduces the blood pressure.

The correct option is (c) To maintain the ionic balance

Explanation: Tubular secretion is an important step of urine formation in our kidneys. Tubular secretion helps in the MAINTENANCE of the ionic balance of various ELECTROLYTES and IONS that are present in our body fluids.

The correct choice is (c) 4-5 MINUTES

To elaborate: As we know that our kidney filters approximately 1100-1200 ml of the blood PER minute and our cardiac output is 5 times this volume, therefore our kidneys TAKE approximately 4-5 minutes to FILTER the whole blood of the body.

The CORRECT CHOICE is (C) Starfish

To EXPLAIN I would say: Guanotelic organisms are those organisms whose main excretory PRODUCT is guanine in the urine. These include spiders, scorpions, and some marine birds like an arctic tern, etc.

Correct answer is (c) Ascending portion of the vasa recta

The best I can explain: NACL is returned to the interstitium by the ascending portion of the vasa recta. Just like NaCl, small amounts of urea are also transported BACK to the interstitial fluid by the collecting TUBULE.

Right option is (b) False

The explanation: If the loop of HENLE is removed, hypotonic urine will be produced as WATER will not be reabsorbed as in DESCENDING Henle’s loop, 5-10% of the water reabsorption takes PLACE.

Right choice is (b) False

Explanation: MACULA densa of DCT is sensitive to NACL. These are the cells of DCT epithelium which are in contact with the arteriolar wall and are DENSER than other EPITHELIAL cells.

The correct option is (c) PCT

For explanation: The tip of HENLE’s loop, interstitial FLUID, and collecting duct show maximum osmolarity i.e. 1200 mOsmol/L. All of these structures are present in the INNER medullary regions of the KIDNEY.

Right option is (a) ALBUMIN

For EXPLANATION I would say: The blood COLLOIDAL osmotic pressure or the BCOP of the GLOMERULUS is maintained by the protein albumin. It resists the filtration of fluid from the capillaries.

The correct OPTION is (c) Three

Best explanation: Three moles of ATP are required in the formation of urea by the ornithine CYCLE. 1 ATP is utilized in the cytoplasm while 2 moles of ATP are required in the mitochondria.

Correct option is (B) Spongilla

For explanation I would SAY: Osmoconformers are the animals that can change their body osmolarity ACCORDING to the external environment like hagfish, marine invertebrates, sharks, and skates.

Right OPTION is (B) Gills

Best EXPLANATION: Ammonia is generally excreted through the gills. It is generally excreted by the diffusion across the body surfaces or through the gill surfaces as it is readily soluble. Kidneys do not play a significant role in the ELIMINATION of ammonia.

Correct choice is (c) Eyes

Best explanation: The functioning of the kidneys is efficiently MONITORED and REGULATED by the hormonal FEEDBACK MECHANISMS involving the hypothalamus, JGA, and to a certain extent, the HEART.

Correct option is (c) PCT

Explanation: The NEPHRIC filtrate present in the PCT is isotonic to blood plasma i.e. 300 mOsmol/L. In PCT, there is obligatory reabsorption of WATER, i.e., ABSORPTION without the INFLUENCE of any HORMONE.

Correct CHOICE is (d) Helps in diluting the urine

Explanation: Countercurrent mechanism helps to maintain a concentration gradient in the medullary interstitium. The presence of such an interstitial gradient helps in EASY passage of water from the collecting TUBULE and THEREFORE helps in CONCENTRATING the urine.

The correct option is (b) False

For explanation I WOULD SAY: Urea formation TAKES place in the hepatocytes of the liver. The cycle of the formation of urea is called an ORNITHINE cycle of the urea cycle or the Krebs-Henseleit cycle.

Right answer is (d) Loop of HENLE

Easiest EXPLANATION: The loop of Henle is not situated in the CORTICAL regions of the kidney as it is that part of renal tubule which dips into the medulla. The Malpighian corpuscle, PCT, and DCT are some parts of the nephron which are situated in the cortical regions of the kidney.

Correct option is (a) Bony fishes

Explanation: Mammals, many terrestrial AMPHIBIANS, and marine fishes mainly excrete urea and are CALLED as ureotelic animals. Terrestrial ADAPTATIONS necessitated the production of lesser toxic NITROGENOUS WASTE like urea.

The correct option is (a) MAINTAINS osmolarity

Explanation: The proximity between the Henle’s loop and vasa recta, as WELL as the counter-current in them, help in maintaining an INCREASING osmolarity TOWARDS the inner medullary INTERSTITIUM.

Correct answer is (b) Stretching of the urinary bladder

The explanation: The signal given by CNS is INITIATED by the stretching of the urinary bladder as it GETS FILLED with the URINE. In response, the stretch RECEPTORS on the walls of the bladder send signals to the CNS.

The correct answer is (a) Increase in blood pressure

To EXPLAIN: More sodium IONS in the blood or fewer potassium ions in the blood lead to INCREASED blood pressure and blood VOLUME. This CONDITION can be a symptom of the hypersecretion of the salt retaining hormone, i.e., aldosterone.

Right ANSWER is (d) Ammonia and CO2

For explanation I would say: CO2 and ammonia are a pair of WASTE SUBSTANCES removed from the blood during the ornithine cycle. The most abundant, harmful, and universal waste product of metabolism is CO2.

The correct answer is (b) False

The EXPLANATION is: No, the PODOCYTES are not PRESENT in the epithelial lining of PCT. Instead, the epithelial cells of the BOWMAN’s capsule are called podocytes. These cells are arranged very CLOSED to each other but some minute spaces are left between these cells for the filtration to take place.

Correct choice is (a) True

Best explanation: The KIDNEY is RETROPERITONEAL because it is attached to peritoneum on the ventral side. The dorsal surface of the kidney is attached to the dorsal ABDOMINAL WALL, so only its ventral surface is COVERED by the peritoneum.

Correct OPTION is (c) 15-20%

Easy explanation: Juxta-medullary nephrons constitute about 15-20% of the total nephrons. These nephrons have LONG Henle’s loop. VASA recta are PRESENT. These nephrons work in stressful conditions.

Correct OPTION is (b) Two

Explanation: Each nephron is divided into two parts- the GLOMERULUS and the renal tubule. The glomerulus is a tuft of capillaries while the renal tubule begins with a double-walled cup-like STRUCTURE called Bowman’s CAPSULE.

The CORRECT option is (b) False

Explanation: The outer layer of the kidney is a tough CAPSULE. INSIDE the kidney, there are two zones, an outer cortex, and an inner medulla. Inner to the hilum, a BROAD funnel-shaped space is presently called the RENAL pelvis.

Right ANSWER is (d) Antennal glands

To elaborate: Antennal glands or green glands perform the excretory FUNCTION in crustaceans like prawns. Protonephridia are the excretory structures which are primarily concerned with ionic and FLUID volume REGULATION.

Right answer is (a) INSECTS

For explanation I would SAY: Malpighian tubules are the excretory structures of most of the insects INCLUDING COCKROACHES. Malpighian tubules help in the removal of nitrogenous wastes and OSMOREGULATION.

Correct option is (a) 300 mOsmol/L

Explanation: The osmolarity of the filtrate in the cortex is about 300 mOsmol/L while in the inner MEDULLA it is 1200 mOsmol/L. In the inner medulla, urine is four TIMES more CONCENTRATED than the initial filtrate.

Correct option is (a) Haematuria

Easiest explanation: When RBCS are present in the URINE then it is termed as haematuria. The presence of white blood CELLS, haemoglobin and proteins are termed as pyuria, haemoglobinuria, and PROTEINURIA respectively.

Correct CHOICE is (a) Absorption of the filtrate by the renal tubules

The explanation: The absorption of the filtrate by the renal tubules is termed as reabsorption. The tubular epithelial cells in DIFFERENT segments of the nephron perform this EITHER by active or PASSIVE mechanisms.

Correct OPTION is (B) DCT

To EXPLAIN: Juxtaglomerular apparatus is a special sensitive region formed by the cellular modifications in the DISTAL convoluted tubule and the afferent arteriole at the location of their CONTACT.

Correct answer is (c) Vasa recta

The explanation: A minute vessel of peritubular capillaries run PARALLEL to the HENLE’s loop forming a U shaped vasa recta. Vasa recta are absent or HIGHLY reduced in cortical nephrons.

The correct answer is (a) One MILLION

The BEST explanation: Each kidney has approximately one million complex tubular structures called NEPHRONS. These nephrons are the STRUCTURAL and functional units of the kidneys.

Right option is (a) Cloaca

For explanation I would say: In HUMANS, the excretory system consists of a pair of kidneys, one pair of ureters, a urinary BLADDER, and URETHRA. Kidneys are reddish-brown and bean-shaped STRUCTURES.

The correct option is (C) Uric ACID

The best I can explain: Excretion of uric acid is an adaptation for water CONSERVATION as uric acid is least SOLUBLE in water and is FORMED by nucleic acid metabolism.

Right option is (c) ANF

To explain I WOULD say: Angiotensin II, EPINEPHRINE and ADH or the ANTIDIURETIC hormone or VASOPRESSIN are vasoconstrictors. They can increase blood pressure. ANF or the Atrial Natriuretic Factor is a vasodilator and can decrease blood pressure.

Right option is (c) ANGIOTENSIN II

To explain: When the GFR decreases, the juxtaglomerular CELLS of the kidney RELEASE renin, which converts angiotensinogen to angiotensin I and further to angiotensin II. Angiotensin II activates the adrenal cortex to release aldosterone.

Right answer is (d) Vasoconstrictor

The best explanation: ADH AFFECTS the KIDNEY function by its constrictory effects on the blood VESSELS as it is a vasoconstrictor. This causes an increase in the blood pressure which further INCREASES the GFR.

Right answer is (C) 2%

The BEST explanation: The composition of URINE is as follows- 96% of water, 2% of urea, and the rest 2% comprise of uric acid, ammonia, hydrogen ions, potassium ions, hippuric acid, CREATININE, creatinine sulphate, DRUGS, and antibiotics.

Correct choice is (d) PROTEINS

The explanation: Proteins are not PASSED on to the lumen of Bowman’s capsule during glomerular filtration because the BLOOD is filtered so FINELY through the podocytes of the Bowman’s capsule that almost all the constituents of the plasma except the proteins pass onto the lumen of Bowman’s capsule. This process of filtration of blood is KNOWN as ultra-filtration.

Right choice is (a) Mammals

The EXPLANATION is: Those organisms which secrete uric acid as a nitrogenous waste are KNOWN as uricotelic organisms. Some uricotelic organisms are REPTILES, birds, land snails, and insects. They excrete uric acid in the form of a pellet or paste to conserve WATER and to reduce the weight of the BODY because removal of uric acid requires a minimum amount of water.