Excretion Questions in English

(N/A) Nephrons are the basic filtering units of kidneys. Each kidney possesses a large number of nephrons,approximately $1-1.5$ million. The main components of the nephron are the glomerulus,Bowman's capsule,and a long renal tubule.
Functioning of a nephron:
$1$. The blood enters the kidney through the renal artery,which branches into many capillaries associated with the glomerulus.
$2$. The water and solutes are transferred to the nephron at Bowman's capsule.
$3$. In the proximal tubule,some substances such as amino acids,glucose,and salts are selectively reabsorbed,and unwanted molecules are added to the urine.
$4$. The filtrate then moves down into the loop of Henle,where more water is absorbed.
$5$. From here,the filtrate moves upwards into the distal tubule and finally to the collecting duct. The collecting duct collects urine from many nephrons.
$6$. The urine formed in each kidney enters a long tube called the ureter. From the ureter,it is transported to the urinary bladder and then into the urethra.

(N/A) Plants utilize several methods to eliminate excretory products:
$1$. Transpiration: Plants remove excess water through the process of transpiration.
$2$. Storage in Vacuoles: Many waste products are stored within the cell vacuoles.
$3$. Secretion: Waste materials like gums and resins are stored in old xylem tissues.
$4$. Shedding: Some waste products are stored in leaves,which eventually fall off the plant.

(D) The amount of urine produced is regulated by several factors:
$1$. The amount of excess water present in the body: If the body has excess water,more urine is produced.
$2$. The amount of dissolved wastes: The kidneys need water to excrete these wastes.
$3$. Hormonal control: The Antidiuretic hormone $(ADH)$,also known as vasopressin,is secreted by the pituitary gland. It increases the reabsorption of water in the kidney tubules,thereby reducing the volume of urine produced.
$4$. Habitat: Organisms living in aquatic environments generally produce more dilute urine compared to those in terrestrial environments.

(B) In human beings,the kidneys are the primary organs of the excretory system. They function to filter the blood,remove nitrogenous waste products like urea,and regulate water and electrolyte balance,which is the process of excretion.

(B) The kidneys contain many filtration units known as $nephrons$.
Each $nephron$ consists of a filtering component called the $glomerulus$ and a tubule.
$Nephrons$ are responsible for filtering the blood,reabsorbing essential substances,and excreting waste products in the form of urine.
Therefore,the correct option is $B$.

(B) The process of urine formation and excretion in the human body follows a specific pathway:
$1$. Urine is produced in the kidneys by the filtration of blood.
$2$. It then travels through the ureters,which are tubes connecting the kidneys to the urinary bladder.
$3$. The urinary bladder stores the urine until it is ready to be excreted.
$4$. Finally,the urine is expelled from the body through the urethra.
Therefore,the correct sequence is: Kidney $\to$ Ureters $\to$ Urinary bladder $\to$ Urethra.

(N/A) Many plants store waste materials in the vacuoles of mesophyll cells and epidermal cells.
When old leaves fall,the waste materials are excreted along with the leaves.

(N/A) Urine formation in the kidneys occurs through three main processes:
$1$. Glomerular Filtration: Blood enters the glomerulus under high pressure,where water,glucose,amino acids,and nitrogenous wastes are filtered into the Bowman's capsule.
$2$. Tubular Reabsorption: As the filtrate passes through the renal tubule,essential substances like glucose,amino acids,salts,and a significant amount of water are reabsorbed back into the blood capillaries.
$3$. Tubular Secretion: Certain substances like potassium ions,hydrogen ions,and some drugs are actively secreted from the blood into the filtrate to maintain the ionic balance and $pH$ of the body fluids.

(B) The volume of glomerular filtrate produced is approximately $180 \, L$ per day.
However,the actual volume of urine excreted is only $1-2 \, L$ per day.
This significant difference occurs because the kidney tubules perform the process of selective reabsorption.
During this process,essential substances like water,glucose,amino acids,and salts are reabsorbed back into the blood capillaries surrounding the nephron tubules,leaving behind only the waste products to be excreted as urine.

(B) The kidneys are the primary excretory organs in the human body. They filter the blood to remove metabolic waste products. The main nitrogenous waste product filtered from the blood by the kidneys is $Urea$,which is produced in the liver during the breakdown of amino acids.

(N/A) In the nephron, as the filtrate moves along the tubule, substances like $glucose$, $amino \text{ } acids$, $salts$, and $water$ are selectively reabsorbed into the blood capillaries surrounding the nephron tubule. Any two of these can be mentioned, for example: $1$. $Glucose$ and $2$. $Amino \text{ } acids$.

(A) $(i)$ Filtration of blood occurs in the Glomerulus,which is a network of capillaries.
$(ii)$ Reabsorption of glucose and water primarily occurs in the Proximal Convoluted Tubule $(PCT)$ of the nephron.
$(iii)$ Secretion of salts and other substances to maintain the composition of the final filtrate occurs in the Distal Convoluted Tubule $(DCT)$.
$(iv)$ Collection of the final filtrate (urine) occurs in the Collecting Duct,which carries it to the renal pelvis.

(N/A) Renal artery: It carries oxygenated blood containing nitrogenous wastes from the aorta to the kidney for filtration.
$(b)$ Kidney: It is the primary excretory organ that filters the blood to remove metabolic wastes,excess water,and salts,thereby forming urine.
$(c)$ Ureter: It is a pair of thin muscular tubes that transport urine from the kidneys to the urinary bladder.
$(d)$ Urinary bladder: It is a muscular sac that stores urine temporarily until it is voided from the body through the urethra.

(N/A) $(i)$ Kidney
$(ii)$ Urinary bladder
$(iii)$ Ureter
$(iv)$ Urethra
$(b)$ The amount of water reabsorbed in the nephron depends on two main factors:
$1$. The amount of excess water present in the body.
$2$. The amount of dissolved nitrogenous wastes that need to be excreted.

(N/A) The structure of a nephron is shown in the figure. The key parts are the Glomerulus (a cluster of capillaries),Bowman's capsule (a cup-shaped structure surrounding the glomerulus),the Renal artery (which brings blood to the nephron),and the Collecting duct (which collects urine from various nephrons).
$(b)$ When blood is filtered through the glomerulus,substances like glucose,amino acids,salts,and water enter the Bowman's capsule as part of the filtrate. As this filtrate moves through the tubular part of the nephron,useful substances like glucose are selectively reabsorbed back into the blood capillaries surrounding the tubule.

(N/A) The human urinary system consists of a pair of kidneys,a pair of ureters,a urinary bladder,and a urethra. (Refer to the provided diagram for labeling).
$(b)$ The two major components of normal human urine are:
$1.$ Water (which constitutes about $95\%$ of urine).
$2.$ Nitrogenous waste products,primarily urea (which constitutes about $2\%$ of urine),along with other salts and minerals.

(N/A) The diagram of the human excretory system is provided in the image.
$(b)$ Two vital functions of the kidneys are:
$(i)$ They maintain the $pH$ and salt concentration of the body constant,and also regulate the water balance.
$(ii)$ They help in the removal of nitrogenous waste products (like urea) that are harmful to the human body.

(N/A) One nitrogenous waste present in urine is $Urea$.
The basic filtration unit of the kidney is called a $Nephron$.
The amount of urine produced is regulated by the quantity of excess water present in the body and the amount of dissolved nitrogenous wastes that need to be excreted. Additionally,hormones like $ADH$ (Antidiuretic Hormone) play a crucial role in reabsorbing water from the kidney tubules based on the body's hydration status.

(N/A) The structure of a nephron is shown in the provided diagram,with the renal artery,Bowman's capsule,glomerulus,and collecting duct clearly labeled.
$(b)$ As the initial filtrate flows along the nephron tubule,the following four substances are selectively reabsorbed into the blood:
$(i)$ Glucose
$(ii)$ Amino acids
$(iii)$ Salts (such as $Na^+$,$Cl^-$)
$(iv)$ Water

(B) The process of urine formation and excretion in the human body follows a specific pathway:
$1$. Urine is produced in the kidneys through the process of filtration.
$2$. From the kidneys,urine travels through the ureters,which are thin tubes that carry urine to the bladder.
$3$. The urinary bladder acts as a storage organ for urine until it is ready to be expelled.
$4$. Finally,urine is expelled from the body through the urethra.
Therefore,the correct sequence is: kidney $\rightarrow$ ureter $\rightarrow$ urinary bladder $\rightarrow$ urethra.

(B) The statement is $False$.
Excretion is defined as the biological process by which an organism eliminates metabolic waste products from its body.
While metabolic processes are chemical in nature,excretion itself is a physiological or biological process,not merely a chemical reaction.

(B) The statement is False.
While the liver is responsible for the formation of urea through the ornithine cycle (converting toxic ammonia into less toxic urea),the actual removal or filtration of nitrogenous wastes from the blood occurs in the kidneys.
The lungs are responsible for the exchange of gases ($CO_{2}$ and $O_{2}$),whereas the kidneys are the primary organs for the excretion of nitrogenous metabolic wastes.

(A) The statement is $True$. The urinary bladder is a muscular sac that stores urine produced by the kidneys. As the bladder fills with urine,its walls stretch,increasing the internal pressure. This expansion triggers stretch receptors in the bladder wall,which send nerve impulses to the central nervous system,creating the voluntary urge to micturate (urinate) through the urethra.

(B) The statement is $False$.
Kidneys are not located in the thoracic cavity.
They are located in the abdominal cavity, specifically in the retroperitoneal space, one on either side of the vertebral column (backbone).