Human excretory system Questions in English

(B) The nephron is the structural and functional unit of the kidney.
Each nephron consists of two major parts: the $Glomerulus$ and the $Renal \text{ } tubule$.
The $Glomerulus$ is a tuft of capillaries formed by the afferent arteriole.
The $Renal \text{ } tubule$ begins with a double-walled cup-like structure called $Bowman's \text{ } capsule$, which further continues into a highly coiled network consisting of the $Proximal \text{ } Convoluted \text{ } Tubule$ $(PCT)$, $Henle's \text{ } loop$, and $Distal \text{ } Convoluted \text{ } Tubule$ $(DCT)$.

(B) The collecting duct is a long duct that extends from the cortex of the kidney to the inner parts of the medulla.
$(i)$ It plays a crucial role in the reabsorption of a large amount of water.
$(ii)$ It is responsible for the production of concentrated urine.
$(iii)$ Therefore,the correct extension of the collecting duct is into the inner part of the medulla.

(D) The outer layer of the kidney is a tough capsule.
Inside the kidney,there are two zones: the cortex and the medulla.
The medulla is divided into a few conical masses called medullary pyramids.
The cortex extends in between the medullary pyramids as renal columns,which are known as the columns of Bertini.
Since all four statements $(I, II, III, IV)$ are correct,the correct option is $D$.

(B) The flow of filtrate through the nephron follows a specific anatomical sequence:
$1$. The process begins at the $I.$ Glomerulus,where blood is filtered.
$2$. The filtrate enters the $II.$ Bowman's capsule.
$3$. From there,it moves into the $IV.$ Proximal convoluted tubule $(PCT)$.
$4$. The filtrate then travels down into the $III.$ Henle's loop.
$5$. It subsequently passes through the $VI.$ Distal convoluted tubule $(DCT)$.
$6$. Finally,it reaches the $V.$ Collecting duct.
Thus,the correct sequence is $I \rightarrow II \rightarrow IV \rightarrow III \rightarrow VI \rightarrow V$.

(D) Podocytes are specialized cells found in the visceral layer of Bowman's capsule in the kidney.
These cells 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,option $D$ is the correct explanation.

(D) The human excretory system consists of a pair of kidneys,ureters,urinary bladder,and urethra.
Kidneys are reddish-brown,bean-shaped structures situated between the levels of the last thoracic and third lumbar vertebrae,close to the dorsal inner wall of the abdominal cavity.
Each kidney of an adult human measures $10-12 \, cm$ in length,$5-7 \, cm$ in width,and $2-3 \, cm$ in thickness,with an average weight of $120-170 \, g$.
Since all the given statements ($I, II,$ and $III$) are factually correct,there are no wrong statements.

(D) The urine is formed in the nephrons and collected in the calyces.
From the calyces,it moves into the renal pelvis.
From the renal pelvis,it travels through the ureter to reach the urinary bladder.
Finally,it is expelled from the body through the urethra.
The correct sequence is: $III \rightarrow II \rightarrow I \rightarrow IV \rightarrow V$.

(A) The nephron consists of two main parts: the glomerulus and the renal tubule.
The Malpighian corpuscle (glomerulus + Bowman's capsule),the Proximal Convoluted Tubule $(PCT)$,and the Distal Convoluted Tubule $(DCT)$ are located in the cortical region of the kidney.
The Loop of Henle extends into the medullary region of the kidney.
The collecting duct starts in the cortex but extends deep into the medulla.
Therefore,the structures situated in the cortical region are the Malpighian corpuscle,$PCT$,and $DCT$ ($I, II,$ and $III$).

(D) Juxta-medullary nephrons have the following characteristics:
$(i)$ The $Vasa$ $recta$ is prominent.
$(ii)$ The $Loop$ $of$ $Henle$ is long.
$(iii)$ The $Loop$ $of$ $Henle$ extends deep into the medulla.
$(iv)$ These are typically found in animals adapted to arid environments,such as camels,kangaroo rats,and desert rodents,to facilitate water conservation through the counter-current mechanism.

(D) The ascending limb of Henle's loop continues as another highly coiled tubular region called the Distal Convoluted Tubule $(DCT)$.
Juxtamedullary nephrons have long Henle's loops that extend deep into the medulla.
Vasa recta is absent or highly reduced in cortical nephrons.
The Malpighian corpuscles,Proximal Convoluted Tubule $(PCT)$,and Distal Convoluted Tubule $(DCT)$ are situated in the cortical region of the kidney,whereas the Henle's loop is primarily located in the medulla.

(C) The Malpighian body,also known as the renal corpuscle,is the filtration unit of the nephron.
It consists of two main structures: the glomerulus (a tuft of capillaries) and the Bowman's capsule (a double-walled cup-like structure that surrounds the glomerulus).
Therefore,Malpighian body = Glomerulus + Bowman's capsule.

(A) The kidney has a notch on its inner concave margin called the hilum (or hilus).
Through this hilum,the renal artery,renal vein,and ureter enter or leave the kidney.
Therefore,the correct answer is Hilus.

(C) The Bowman's capsule is a double-walled cup-like structure that surrounds the glomerulus.
It consists of two layers: an outer parietal layer and an inner visceral layer.
The inner visceral layer 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,podocyte cells are present in the inner wall of the Bowman's capsule.

(B) The kidneys are reddish-brown,bean-shaped structures located in the abdominal cavity.
They are situated between the levels of the $12^{th}$ thoracic and $3^{rd}$ lumbar vertebrae.
They are covered by the peritoneum only on the ventral side,meaning they are fused with the posterior body wall.
This specific anatomical arrangement is known as the retroperitoneal arrangement.

(D) The kidney is divided into an outer cortex and an inner medulla.
In the cortex,the following parts of the nephron are located: $PCT$ (Proximal Convoluted Tubule),$DCT$ (Distal Convoluted Tubule),and the Malpighian corpuscle (Glomerulus + Bowman's capsule).
The Loop of Henle primarily extends into the medulla.

(B) The statement in option $B$ is incorrect. Inside the kidney,the cortical region extends in between the medullary pyramids as renal columns,which are known as the columns of Bertini. The renal pelvis is a funnel-shaped space located towards the inner concave side of the kidney,not the extension of the cortex between pyramids.

(C) The loop of Henle is a specialized structure in the nephron responsible for the concentration of urine,allowing animals to excrete hypertonic urine to conserve water.
It is a characteristic feature of mammals and birds (to some extent).
Frogs (amphibians) possess mesonephric kidneys and primarily excrete dilute (hypotonic) urine as they live in aquatic or moist environments where water conservation is not as critical as in terrestrial mammals.
Therefore,the loop of Henle is absent in frogs.

(C) The afferent arteriole brings blood into the glomerulus,while the efferent arteriole carries it away.
The diameter of the afferent arteriole is larger than that of the efferent arteriole.
This difference in diameter creates a high hydrostatic pressure within the glomerulus,which is essential for the process of ultrafiltration.

(C) The inner wall of the Bowman's capsule is indeed lined with specialized cells known as podocytes,which are arranged in an intricate manner so as to leave some minute spaces called filtration slits or slit pores.
These podocytes are involved in the process of ultrafiltration,where they act as a sieve to filter blood.
The projections (foot processes) of podocytes do not increase the surface area for absorption; rather,they help in creating filtration slits that allow the passage of water and small solutes while preventing the passage of large molecules like proteins.
Therefore,the Assertion is correct,but the Reason is incorrect.

(A) The kidneys are located outside the peritoneal cavity,attached to the dorsal abdominal wall.
Because they are fused to the dorsal wall,the peritoneum covers only their ventral (anterior) surface.
This specific anatomical arrangement is known as the retroperitoneal position.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(A) The $L.s.$ (longitudinal section) of the kidney reveals a notch on its concave surface,which is known as the hilum. Through this hilum,the ureter,blood vessels,and nerves enter the kidney.

(C) Each human kidney contains approximately $1,000,000$ (one million) nephrons.
Nephrons are the structural and functional units of the kidney,responsible for the filtration of blood and the formation of urine.

(B) The glomerulus is a tuft of capillaries formed by the afferent arteriole,which is a fine branch of the renal artery.
These capillaries then reunite to form the efferent arteriole,which carries blood away from the glomerulus.

(N/A) Location: Podocytes are specialized epithelial cells located in the inner (visceral) layer of the Bowman's capsule in the kidney.
Function: They are arranged in an intricate manner so as to leave some minute spaces called filtration slits or slit pores. These pores allow the filtration of blood from the glomerular capillaries into the Bowman's space,ensuring that proteins and blood cells are retained in the blood while water and small solutes pass through.

(B) The human kidney is a bean-shaped organ located in the abdominal cavity.
Its color is characteristically described as reddish brown due to the high vascularity and the presence of numerous blood vessels involved in the filtration of blood.

(A) In an adult human,each kidney is a bean-shaped organ.
The average weight of a human kidney typically ranges between $120$ grams and $170$ grams.
Therefore,the correct option is $A$.

(A) In the provided diagram of the human excretory system:
$1$. $P$ represents the large blood vessel running centrally,which is the Dorsal aorta (carrying oxygenated blood to the kidneys).
$2$. $Q$ represents the tube emerging from the kidney and leading to the urinary bladder,which is the Ureter.
Therefore,$P$ is the Dorsal aorta and $Q$ is the Ureter.

(C) The human kidneys are bean-shaped structures located in the abdominal cavity.
According to the $NCERT$ textbook,the dimensions of a healthy adult human kidney are:
Length: $10-12 \,cm$
Width: $5-7 \,cm$
Thickness: $2-3 \,cm$
Therefore,option $C$ is the correct choice.

(D) The human kidneys are reddish-brown,bean-shaped structures situated between the levels of the last thoracic and third lumbar vertebra close to the dorsal inner wall of the abdominal cavity.

(A) The kidneys are reddish-brown,bean-shaped structures situated between the levels of the last thoracic $(T_{12})$ and third lumbar $(L_3)$ vertebra,close to the dorsal inner wall of the abdominal cavity.

(D) The hilum is a notch on the concave medial border of the kidney.
Through this notch,the ureter,blood vessels,and nerves enter the kidney.
Therefore,all the listed structures enter the kidney through the hilum.

(C) The kidney has an inner concave margin called the hilum,which serves as the entry and exit point for blood vessels,nerves,and the ureter.
Inside the hilum,there is a broad,funnel-shaped space known as the renal pelvis.
The renal pelvis further branches into projections called calyces.
Therefore,the correct answer is the renal pelvis.

(B) The human kidney is divided into two main zones: an outer $Renal \text{ cortex}$ and an inner $Renal \text{ medulla}$.
Inside the $Renal \text{ medulla}$, there are several conical projections called $Renal \text{ pyramids}$.
These pyramids project into the $Calyces$ and are separated by the $Renal \text{ columns}$ of $Bertini$.
Therefore, the renal pyramids are part of the renal medulla.

(A) The renal cortex extends in between the renal pyramids as renal columns called columns of Bertin. These columns project into the renal medulla,separating the renal pyramids from each other. Therefore,the renal columns are extensions of the renal cortex.

(A) In the longitudinal section of the human kidney:
$P$ represents the renal column (also known as the column of Bertini),which is an extension of the renal cortex between the renal pyramids.
$Q$ represents the renal pyramid (medullary pyramid).
$R$ represents the renal pelvis.
$S$ represents the renal cortex.
Therefore,the correct option is $P$.

(B) Each kidney in the human body contains approximately $1$ million nephrons. Since there are two kidneys, the total number of nephrons in the human body is approximately $2$ million. Therefore, the correct option is $B$.

(C) The kidney is the primary excretory organ in humans. Each kidney contains approximately $1$ million complex tubular structures called nephrons. The nephron is considered the structural and functional unit of the kidney because it is responsible for the filtration of blood,reabsorption of essential nutrients,and the formation of urine. Therefore,the correct option is $C$.

(A) The blood flow in the nephron follows a specific pathway:
$1$. The $Renal artery$ brings oxygenated blood to the kidney.
$2$. This branches into the $Afferent arteriole$, which enters the Bowman's capsule.
$3$. The $Afferent arteriole$ forms a network of capillaries called the $Glomerulus$, where filtration occurs.
$4$. Blood leaves the $Glomerulus$ through the $Efferent arteriole$.
$5$. Finally, the blood is collected and drained out of the kidney through the $Renal vein$.
Therefore, the correct sequence is: $Renal artery \rightarrow Afferent arteriole \rightarrow Glomerulus \rightarrow Efferent arteriole \rightarrow Renal vein$.

(C) The nephron consists of a glomerulus and a renal tubule. The renal tubule begins with a double-walled Bowman's capsule,followed by the Proximal Convoluted Tubule $(PCT)$. The next part is the Loop of Henle,which is a hairpin-shaped structure that extends into the renal medulla. Finally,the tubule continues as the Distal Convoluted Tubule $(DCT)$ and the Collecting Duct. Therefore,the correct answer is the Loop of Henle.

(B) The renal cortex contains the Malpighian corpuscle, Proximal Convoluted Tubule $(PCT)$, and Distal Convoluted Tubule $(DCT)$. The afferent and efferent arterioles are also associated with the glomerulus located in the cortex.
The renal medulla contains the Loop of Henle (descending and ascending limbs), the collecting duct, and the ducts of Bellini.
Therefore, structures in the renal cortex $(P)$ are: $II$ $(PCT)$, $III$ $(DCT)$, $VII$ (Afferent arteriole), and $VIII$ (Efferent arteriole).
Structures in the renal medulla $(Q)$ are: $I$ (Descending limb of Henle), $IV$ (Ascending limb of Henle), $V$ (Collecting duct), and $VI$ (Duct of Bellini).
Thus, the correct match is $(P - II, III, VII, VIII)$ and $(Q - I, IV, V, VI)$.

(A) The renal corpuscle,also known as the Malpighian body,is the filtration unit of the nephron.
It consists of two main parts: the glomerulus and Bowman's capsule.
In the provided diagram:
$Q$ represents the glomerulus (a tuft of capillaries).
$R$ represents the Bowman's capsule (the cup-shaped structure surrounding the glomerulus).
Together,$Q$ and $R$ form the renal corpuscle.
Therefore,the correct option is $A$.

(A) The Malpighian body,also known as the renal corpuscle,is the filtration unit of the nephron.
It consists of two main structures: the Glomerulus and the Bowman's capsule.
The Glomerulus is a tuft of capillaries formed by the afferent arteriole,and the Bowman's capsule is a double-walled cup-like structure that surrounds the glomerulus.
Therefore,Malpighian body = Glomerulus $+$ Bowman's capsule.

(A) Nephrons are of two types based on the position of the glomerulus and the length of the loop of Henle:
$1$. $\text{Cortical}$ $\text{nephrons}$: In these, the glomerulus is located in the outer cortex and the loop of Henle is very short, extending only a little into the medulla.
$2$. $\text{Juxtamedullary}$ $\text{nephrons}$: In these, the glomerulus is located near the corticomedullary junction and the loop of Henle is very long, running deep into the medulla.
Therefore, $P$ is $\text{Cortical}$ $\text{nephron}$ and $Q$ is $\text{Juxtamedullary}$ $\text{nephron}$.

(D) The duct of Bellini,also known as the papillary duct,is the final portion of the collecting duct system in the kidney.
These ducts collect urine from the distal convoluted tubules and collecting ducts.
The ducts of Bellini open into the minor calyx at the renal papilla,which is the apex of the renal pyramid.
Therefore,the correct option is $D$.

(C) The $Bellini$ ducts,also known as the papillary ducts,are the final segments of the renal collecting ducts.
They open into the renal calyces at the renal papillae.
Since the fluid passing through the collecting ducts has undergone final modifications and concentration,it is referred to as urine.
Therefore,the $Bellini$ ducts transport urine into the renal pelvis.

(B) The volume of blood pumped by each ventricle of the heart per minute is known as Cardiac Output,which is approximately $5000 \ mL$ $(5 \ L)$.
On average,the kidneys receive about $1100-1200 \ mL$ of blood per minute,which constitutes the Renal Blood Flow $(RBF)$.
To find the fraction,we calculate the ratio of Renal Blood Flow to Cardiac Output:
$\text{Fraction} = \frac{1100-1200 \ mL}{5000 \ mL} \approx 0.2-0.24$.
This value is approximately equal to $1/5$ of the total cardiac output.
Therefore,the correct option is $B$.

(B) Podocytes are specialized epithelial cells found in the inner (visceral) layer of Bowman's capsule in the kidney. These cells 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,the correct option is $B$.

(C) The $pH$ of human urine typically ranges from $4.5$ to $8.0$,but it is generally slightly acidic,with an average value of approximately $6.0$. This acidity helps in the excretion of metabolic waste products and plays a role in maintaining the body's acid-base balance.

(A) The color of human urine is typically light yellow. This coloration is primarily due to the presence of a pigment called $Urochrome$ (also known as $Urobilin$),which is a breakdown product of hemoglobin.

(A) The wall of the urinary bladder is composed of smooth muscles,specifically known as the $detrusor$ muscle.
These muscles are involuntary in nature,allowing the bladder to expand as it fills with urine and contract during the process of micturition to expel urine from the body.
Striated muscles are typically found in skeletal muscles,and cardiac muscles are exclusive to the heart.