Human excretory system Questions in English

(D) The Assertion $A$ is true because nephrons are classified into two types,cortical and juxtamedullary,based on their relative position in the cortex and medulla.
The Reason $R$ is false because juxtamedullary nephrons have a very long loop of Henle that extends deep into the medulla,which helps in concentrating the urine.
Conversely,cortical nephrons have a very short loop of Henle that extends only slightly into the medulla.
Therefore,the correct answer is that $A$ is true but $R$ is false.

(B) The correct answer is option $B$ because the loop of Henle of the juxta medullary nephron is significantly longer than that of the cortical nephron and extends deep into the renal medulla.
Option $A$ is incorrect because the renal corpuscle of the juxta medullary nephron is located in the inner cortical region,near the corticomedullary junction,not in the renal medulla.
Option $C$ is incorrect because juxta medullary nephrons are fewer in number compared to cortical nephrons,which constitute the majority of nephrons in the kidney.
Option $D$ is incorrect because the columns of Bertini are extensions of the renal cortex into the renal medulla,and nephrons are not specifically located within them.

(C) The given diagram represents the Malpighian body (Renal corpuscle) of a nephron.
$P$ represents the Afferent arteriole,which brings blood into the glomerulus.
$Q$ represents the Efferent arteriole,which carries blood away from the glomerulus.
$R$ represents Bowman's capsule,the cup-like structure surrounding the glomerulus.
$S$ represents the Proximal convoluted tubule $(PCT)$,which is the continuation of the Bowman's capsule.
Therefore,all options $A, B, C,$ and $D$ are technically correct labels for the structures shown in the diagram. However,in the context of standard multiple-choice questions where one must be selected,$C$ is a primary identification of the structure $R$ (Bowman's capsule).

(C) The nephron is the functional unit of the kidney. Its structure consists of various types of epithelial tissues:
$1$. The Bowman's capsule is lined by simple squamous epithelium.
$2$. The Proximal Convoluted Tubule $(PCT)$ is lined by brush-bordered cuboidal epithelium.
$3$. The Loop of Henle and distal parts contain cuboidal epithelium.
$4$. Ciliated columnar epithelium is typically found in the lining of the respiratory tract,fallopian tubes,and ventricles of the brain,but it is $NOT$ present in the nephron.

(B) $1$. In humans,approximately $25-30 \, gm$ of urea is excreted per day,so statement $A$ is correct.
$2$. The renal cortex extends in between the renal pyramids as renal columns called Columns of Bertini. Therefore,the statement that they are extensions of medulla into the cortex is incorrect; they are extensions of the cortex into the medulla.
$3$. The Proximal Convoluted Tubule $(PCT)$ is the major site of reabsorption,where $70-80 \%$ of electrolytes and water are reabsorbed,so statement $C$ is correct.
$4$. The Glomerular Filtration Rate $(GFR)$ in a healthy individual is approximately $125 \, mL/min$,which amounts to $180 \, L$ per day,so statement $D$ is correct.
Thus,statement $B$ is the incorrect statement.

(C) Statement $(A)$ is correct: The medulla of the kidney is divided into a few conical masses called medullary pyramids projecting into the calyces.
Statement $(B)$ is correct: The cortex extends in between the medullary pyramids as renal columns called columns of Bertini.
Statement $(C)$ is incorrect: Kidneys are situated close to the dorsal inner wall of the abdominal cavity,not the ventral part of the thoracic region.
Statement $(D)$ is correct: The dimensions and weight provided for an adult human kidney are accurate ($10-12 \ cm$ length,$5-7 \ cm$ width,$2-3 \ cm$ thickness,$120-170 \ gm$ weight).
Therefore,statements $(A), (B),$ and $(D)$ are correct.

(A) The analogy is based on the anatomical continuity within the kidney structure.
$1$. The $Renal \text{ } pelvis$ is the funnel-shaped structure that collects urine from the kidney and leads directly into the $ureter$.
$2$. Similarly, the $Renal \text{ } cortex$ extends into the $Renal \text{ } medulla$ as projections between the renal pyramids, which are known as the $columns \text{ } of \text{ } Bertini$ (or renal columns).
$3$. Therefore, the relationship represents the structural extension or continuity within the kidney.

(C) In the human kidney,the renal medulla is divided into several conical masses called renal pyramids.
Each renal pyramid projects into a minor calyx.
Therefore,the number of minor calyces corresponds directly to the number of renal pyramids present in the kidney.
Typically,there are about $8$ to $18$ renal pyramids,and thus an equal number of minor calyces.

(B) The wall of the urinary bladder consists of three layers of smooth muscle collectively known as the detrusor muscle.
These layers are arranged as follows:
$1$. Outer layer: Longitudinal muscle fibers.
$2$. Middle layer: Circular muscle fibers.
$3$. Inner layer: Longitudinal muscle fibers.
Therefore,the correct arrangement from outer to inner is Longitudinal,Circular,and Longitudinal.

(C) Statement $I$ is correct: The trigone is a smooth,inverted triangular region located at the base of the urinary bladder,formed by the two ureteral orifices and the internal urethral orifice.
Statement $II$ is incorrect: The wall of the urinary bladder consists of three layers: the outer serosa (peritoneum),the middle muscular layer known as the detrusor muscle (which consists of three layers of smooth muscle fibers),and the inner mucosa (transitional epithelium). The term 'dartos tunic' refers to the smooth muscle layer found in the scrotum,not the urinary bladder.

(B) Statement $(i)$ is correct: The renal papilla is the apex or narrow tip of the medullary pyramid that projects into the minor calyx.
Statement (ii) is incorrect: The renal cortex is a reddish-brown granular layer,not striated. The medulla is the region that appears striated due to the presence of loops of Henle and collecting ducts.
Statement (iii) is correct: The wall of the renal pelvis contains smooth muscles arranged in longitudinal,circular,and longitudinal layers to facilitate the movement of urine.
Statement (iv) is incorrect: The ureter is a muscular tube,not non-muscular. It is responsible for transporting urine from the renal pelvis to the urinary bladder via peristaltic contractions.

(B) The correct statement is that the efferent arteriole forms a peritubular capillary network around the renal tubule.
$1$. $ADH$ (Antidiuretic Hormone) acts primarily on the collecting duct and distal convoluted tubule $(DCT)$,not the $PCT$,to increase water reabsorption.
$2$. The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillary network.
$3$. Podocytes are specialized cells found in the Bowman's capsule,not in the loop of Henle.
$4$. The descending limb of the loop of Henle is permeable to water but nearly impermeable to electrolytes,whereas the ascending limb is impermeable to water.

(B) The wall of the urinary bladder is composed of three layers: the mucosa,the submucosa,and the muscularis layer.
The muscularis layer consists of smooth muscle fibers arranged in longitudinal and circular patterns,collectively known as the $Detrusor$ muscle.
This muscle is responsible for the contraction of the bladder during micturition (urination) to expel urine.

(D) The peritoneum is a serous membrane that lines the abdominal cavity and covers most of the abdominal organs.
Organs that are located behind the peritoneum are known as retroperitoneal organs.
The kidneys are situated in the abdominal cavity between the levels of the last thoracic and third lumbar vertebra,close to the dorsal inner wall of the abdominal cavity.
Because they are positioned behind the parietal peritoneum,they are classified as retroperitoneal organs.