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

The correct answer is Option 2 

Explanation:

• The nephron is the structural and functional unit of the kidney. It is responsible for filtering blood, reabsorbing essential nutrients, and excreting waste as urine.
• The nephron consists of various parts:
  • Bowman's capsule
  • Proximal tubule
  • Loop of Henle
  • Distal tubule.
  • Collecting duct. 
• The proximal tubule (P) is closer to Bowman's capsule and is primarily involved in reabsorbing water, ions, glucose, and amino acids.
• The distal tubule (D) is farther along the nephron and plays a role in the selective reabsorption of ions and water, influenced by hormones like aldosterone and ADH (antidiuretic hormone).

PCT is lined by simple cuboidal brush border epithelium which increases the surface area for reabsorption.

• Nearly all of the essential nutrients, and 70-80 per cent of electrolytes and water are reabsorbed by this segment.
• PCT also helps to maintain the pH and ionic balance of the body fluids by selective secretion of hydrogen ions and ammonia into the filtrate and by absorption of HCO₃ ^– from it.

Distal Convoluted Tubule (DCT): Conditional reabsorption of Na+ and water takes place in this segment. DCT is also capable of reabsorption of HCO₃ ^– and selective secretion of hydrogen and potassium ions and NH₃ to maintain the pH and sodium-potassium balance in blood.

The correct answer is Both Statement I and Statement II are correct.

Concept:

• Diabetes mellitus is a chronic metabolic disorder characterized by prolonged hyperglycemia (high blood sugar levels). It occurs due to either insufficient production of insulin or the body's inability to use insulin effectively.
• Hyperglycemia can lead to various complications if not managed properly.

Explanation:

• Statement I: Presence of glucose and ketone bodies in urine are indicative of diabetes mellitus.
  • In diabetes mellitus, the body is unable to regulate blood glucose levels effectively.
  • Excess glucose is excreted in the urine, which is known as glucosuria.
  • When the body starts breaking down fat for energy due to lack of insulin, ketone bodies are produced and can be detected in urine, known as ketonuria.
• Statement II: Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus.
  • Prolonged high blood sugar levels can cause damage to various organs and systems in the body.
  • Chronic hyperglycemia is a hallmark of diabetes mellitus and is responsible for many complications like neuropathy, retinopathy, and cardiovascular diseases.

The correct answer is Aquatic insects - uricotelic

Concept:

Different organisms have evolved different methods of excretion based on their habitat and physiology. The primary forms of nitrogenous waste excreted by living organisms are ammonia, urea, and uric acid.

• Ammonotelic: Organisms that excrete nitrogenous waste as ammonia are called ammonotelic. Many bony fishes, aquatic amphibians, and aquatic insects are ammonotelic in nature.
• Ureotelic: Organisms that excrete nitrogenous waste primarily as urea are called ureotelic. Urea is less toxic than ammonia and requires less water for its excretion. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals.
• Uricotelic: Organisms that excrete nitrogenous waste as uric acid are called uricotelic. This method is seen in birds, reptiles, and some terrestrial arthropods. Uric acid is less toxic and requires less water to be excreted, which is advantageous for animals in arid environments

Explanation:

• Bony fishes - ammonotelic: Bony fishes primarily excrete ammonia, which is highly soluble in water. This is known as ammonotelic excretion.
• Aquatic insects - uricotelic: Aquatic insects do not generally excrete uric acid. Aquatic insects primarily excrete ammonia or urea.
• Mammals - ureotelic: Mammals, including humans, excrete urea as the primary nitrogenous waste product. This is termed ureotelic excretion.
• Reptiles - uricotelic: Reptiles primarily excrete uric acid, which is less toxic and conserves water. This is known as uricotelic excretion.

The correct answer is I → II → IV → III → V

Explanation:

• The nephron is the basic structural and functional unit of the kidney. It is responsible for filtering blood and forming urine.
• The nephron consists of several parts that work together to filter blood, reabsorb necessary substances, and excrete waste products.
  • Glomerulus: The glomerulus is a network of capillaries located at the beginning of the nephron. It is responsible for filtering blood and initiating urine formation.
  • Bowman's capsule: Bowman's capsule surrounds the glomerulus and collects the filtrate that comes out of the glomerulus. Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle
  • Proximal convoluted tubule: The proximal convoluted tubule is the first segment of the tubular part of the nephron. It reabsorbs essential nutrients, water, and ions from the filtrate back into the blood.
  • Henle's loop: Henle's loop, also known as the loop of Henle, dips into the medulla of the kidney and is responsible for concentrating the urine by reabsorbing water and salts.
  • Distal convoluted tubule: The distal convoluted tubule is the final segment of the nephron before the collecting duct. It further modifies the filtrate by reabsorbing more ions and water.

Fig:  A diagrammatic representation of a nephron showing blood vessels, duct and tubule

The correct answer is Heart

Explanation:

• Atrial Natriuretic Factor (ANF), also known as Atrial Natriuretic Peptide (ANP), is a hormone involved in the regulation of blood pressure and fluid balance.
• ANF is released by the atrial wall of the heart in response to the stretching of the atrial walls, which occurs due to an increase in blood volume or pressure.
• ANF acts on the kidneys to promote the excretion of sodium and water, leading to a decrease in blood volume and blood pressure.

The correct answer is osmosis.Key Points 

• Dialysis is a procedure to remove waste products and excess fluid from the blood when the kidneys stop working properly.
• Osmosis is the process by which solvent molecules pass from a solution of lower concentration to a solution of higher concentration through a semipermeable membrane.

Additional Information Kidney

• Kidneys are bean-shaped organs located on either side of the spine, below the ribs, and behind your belly.
• The left side kidney is placed a little higher than the right side kidney.
• Kidneys are the excretory organs. 
• Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm, and weighs around 120-170g.
• The function of the kidneys is to filter your blood.
• The kidney removes wastes, controls the body's fluid balance, and keeps the right levels of electrolytes.
• All of the blood in your body passes through them about 40 times a day.
• Renal Vein is the blood vessel which carries blood to the kidney.
• The cup-shaped part of the nephron is called the Bowman's Capsule.
• Uremia is a condition in which both kidneys fail to function.
• Kidney stones are generally calcium oxalate crystals.
• The volume of urine produced in an adult human being every 24 hours - 1.5 litres.
• The first organ transplant in the world - Kidney.
• The first kidney transplant in the world was conducted by - Dr. Joseph Murray.
• The functional unit of the kidney - Nephron.
• The study of kidneys is called Nephrology.

Important Points Diffusion

• Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration down the concentration gradient.

​Adsorption

• Adsorption is the process by which ions, atoms, or molecules adhere to the surface of a solid material.

Electrophoresis

• Electrophoresis is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field. 

Concept:

• Anticoagulant: It is a chemical substance commonly known as a blood thinner that prevents the blood from getting coagulated or clotted. These are primarily used for the analysis of blood cells & during dialysis.
• Some of the anticoagulants used are Sodium citrate, Sodium EDTA & Heparin.

​Explanation:

• Heparin is the most powerful anticoagulant. It activates the Antithrombin III present in the blood plasma
• The antithrombin binds and deactivates the serum clotting factors, this prevents the clotting of blood.
• Moreover, Heparin works in both in-vivo & in-vitro conditions, thus heparin is to be added to the blood sample drawn from the patient for analysis of
  blood corpuscles and plasma.

Concept-

• The nephron is the structural and functional unit of the kidney.

• A nephron is divided into the following regions-
  • Bowman's capsule- The first step of urine formation is filtration which is done by glomerulus present in bowman's capsule.
  • Proximal convoluted tubule (PCT)- Nearly all the essential nutrients and 70%-80% of electrolytes and water are reabsorbed by PCT.
  • Loop of Henle- This hairpin-like loop has a descending limb, followed by an ascending limb.
  • Distal convoluted tubule (DCT)- The DCT of different nephrons opens into a straight tube called a collecting duct.

Explanation-

• In the presence of aldosterone hormone in DCT salt (Na⁺) are reabsorbed actively.
• Due to the presence of ADH in DCT water is reabsorbed passively.

Thereby Conditional reabsorption of Na⁺ and water takes place in DCT.

Additional Information

• Reabsorption of HCO^-₃ occurs in DCT.
• Reabsorption of water occurs in descending limb of the loop of Henle.
• Reabsorption of electrolytes occurs in ascending limb of the loop of Henle.

Key Points

• The mammalian kidney consists of numerous tubular structures called nephrons.
• Each nephron has 2 parts:
  • Glomerulus - is a tuft of capillaries that takes part in the first step of urine formation, i.e. glomerular filtration.
  • Renal Tubule - starts with the Bowman's capsule, continues as proximal convoluted tubule(PCT), Henle's loop and the distal convoluted tubule(DCT). 
• The glomerulus together with Bowman's capsule is called malpighian or renal corpuscle.
• Glomerulus:
  • It helps in filtration of blood through 3 layers of cells - endothelium of glomerular blood vessels, epithelium of Bowman's capsule and the basement membrane between the two layers.
  • The epithelial cells of Bowman's capsule are called podocytes.
  • Podocytes are intricately arranged such that there are minute pores in between, which are called filtration slits or slit pores.
• Proximal Convoluted Tubule:
  • It helps in maintaining the pH and ionic balance of the body fluids.
• ​Loop of Henle:
  • The loop of Henle has two limbs - the descending limb and the ascending limb.
  • As the glomerular filtrate moves in opposite directions along the two limbs of Henle's Loop, it gives rise to a counter-current mechanism, which is responsible for concentrating the urine.
  • Minimum reabsorption takes place.
  • It plays important role in maintenance of high osmolarity of medullary interstitial fluid.
  • It helps in concentrating the urine so that water is conserved in the body.
• Distal Convoluted Tubule:
  • There is conditional reabsorption of water and Na+.
  • It helps in maintaining the pH and sodium-potassium balance in blood.

Important Points

Urine formation involves 3 major processes:

• Glomerular Filtration - The glomerular capillary blood pressure causes the filtration of blood through the 3 layers. It is also called ultrafiltration because blood is finely filtered through the podocytes such that all plasma contents except proteins pass onto the lumen of Bowman's capsule.
• Reabsorption - The GFR is about 4.5 times that of the urine output, suggesting that almost 99% of the filtrate is reabsorbed by the renal tubules by active or passive mechanisms.
  • PCT - actively reabsorbs all of glucose, 75% of amino acids & Vitamin C, 90% of bicarbonate (HCO₃^-), 70% of Na⁺, 75% of K⁺ and huge amount of Ca²⁺ from the glomerular filtrate. This makes for the reabsorption of almost 80% of the total glomerular filtrate.
  • Ascending Limb of Henle's Loop - actively reabsorbs about 25% of K⁺ and some Cl^-, while some Na⁺ is reabsorbed by diffusion.
  • DCT & Collecting Tubules - reabsorb some Na⁺ from filtrate in exchange of K⁺ from interstitial fluid.
• Secretion - The tubular cells secrete substances like H⁺, K⁺ and ammonia into the filtrate. It is an important step because it helps in maintaining ionic balance of body fluids.

Additional Information

• Renal plasma flow - is the amount of plasma (blood) that passes through the glomerulus of all the nephrons in both the kidneys per minute.
• Cardiac output - is the amount of blood pumped by the heart in a minute.

Cardiac output = Stroke volume (Blood pumped by each ventricle per minute) × Heart Rate

• About 1000-1200ml of blood or 650ml of blood plasma is the renal plasma flow, which is one-fifth of the cardiac output.
• Glomerular Filtration Rate (GFR) - is the amount of blood filtered out of the glomerulus and is clinically used to diagnose kidney diseases.
• The GFR for a healthy individual is about 125ml/min or 180L per day.
• Urine output - is the amount of urine excreted from the body per day and is about 1.5L on an average.

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

Explanation-

The urethra is not a structure of the kidney.

The urethra is a tubular structure that is part of the urinary system. Its main function is to transport urine from the bladder, where it is stored before micturition, to the outside of the body.

Anatomy:

The structure of the urethra varies between males and females, primarily due to its role in the male reproductive system.

• In males, the urethra is approximately 20 centimeters long and travels through the prostate gland and penis. 
• In females, the urethra is significantly shorter, averaging about 4 centimeters in length. It extends from the bladder neck to the external urethral orifice located above the vaginal opening and does not have distinct sections like the male urethra.

Function:

• The primary function of the urethra is to convey urine from the bladder to the outside of the body during the act of micturition (urination).
• In males, it also serves a reproductive function by enabling the passage of semen during ejaculation.

The other structures listed - cortex, medulla, and pelvis - are all parts of the kidney. 

• Cortex: This is the outer layer of the kidney, which contains many blood vessels and where the initial stages of urine filtration occur.
• Medulla: Located beneath the cortex, the medulla contains the renal pyramids and is where the majority of urine concentration takes place.
• Pelvis: The renal pelvis is a funnel-shaped space in the innermost part of the kidney. It collects urine output from the collecting ducts and funnels it into the ureters.

So, the urethra is the structure that does not belong to the kidney.

Important Points

• Nephron is the functional unit of kidney and it has two parts.
  • The glomerulus
  • The renal tubule
• Glomerulus is a tuft of capillaries formed by the Afferent and Efferent arteriole.
• Glomerulus is enclosed by a cup like structure called Bowman's capsule.
• Glomerulus and Bowman's capsule together form the malpighian body or renal corpuscle.
• This tubule continues to form the Proximal Convoluted tubule (PCT), then continues to the Henle's loop and lastly the Distal Convoluted Tubule (DCT).
• DCT further end up in the collecting ducts.
• Urine formation process takes place in three steps, that takes place in different parts of a nephron.
  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion.

Key PointsGlomerulus - 

• The filtration of the blood in the glomerulus occurs due to the the glomerular capillary blood pressure through 3 layers.
  • endothelium of glomerular blood vessels.
  • epithelium of Bowman's capsule
  • the basement membrane between two layers
• As a result the blood is filtered very finely through these membranes.
• Therefore fine filtration process of blood in Bowman's capsule is called Ultrafiltration of blood.

Proximal Convoluted tubule - 

• PCT is lined by brush bordered simple cuboidal epithelial cells.
• This helps in increasing the area of reabsorption.
• Around 70-80 % of the electrolytes and the essential nutrients are reabsorbed into the PCT.

Henle's Loop - 

• This the part which plays a major role in Maintenance of high osmolarity.
• The decending limb of henle's loop is impermeable to the electrolytes but is permeable to water and this concentrates the filtrate.
• The ascending limb is impermeable to water but is permeable to the electrolytes.
• Therefore concentrated filtrate gets diluted as it ascends through the loop due to the passage of the electrolytes.

Distal Convoluted tubule - 

• It plays the role in conditional reabsorption of water and Na²⁺.
• It is responsible for the reabsorption of HCO₃ ions and selective secretion of Hydrogen and potassium ions and ammonia to maintain the pH.
• It also helps in maintaining the sodium- potassium balance in the body.

From the above explanation we can understand that the correct answer is Option 4.

• Uremia refers to a condition where urea and other nitrogenous waste products accumulate in the blood due to the kidneys' inability to eliminate them. This can occur in cases of severe kidney dysfunction or failure.
• Urea is a waste product formed from the breakdown of proteins. Normally, it is filtered out of the blood by the kidneys and excreted in urine. When kidney function is impaired, urea builds up in the bloodstream, leading to symptoms such as fatigue, confusion, nausea, and fluid retention.

• Rationale: Angina is a condition characterized by chest pain or discomfort due to reduced blood flow to the heart muscle. It is not related to urea accumulation in the blood.

• Rationale: Gout is a form of arthritis caused by the accumulation of uric acid crystals in the joints. While it involves the accumulation of a waste product, it is not related to urea or kidney function directly.

• Rationale: Osteoporosis is a condition characterized by weakened bones that are more prone to fractures. It results from an imbalance between bone formation and bone resorption, and is unrelated to urea levels in the blood.

• Among the given options, uremia is the correct term for the accumulation of urea in the blood. This condition highlights the critical role of the kidneys in filtering waste products from the blood and maintaining overall metabolic balance in the body.

The correct answer is Option 2 i.e. Uriniferous tubule.

Explanation-

The uriniferous tubule is a term that covers the entirety of a nephron and its associated collecting duct in the kidney, both of which play an integral role in the production of urine.

Each uriniferous tubule is divided into two main parts:

1. The Nephron: This is the basic functional unit of the kidney and is responsible for the filtration, reabsorption, and secretion processes. Each nephron itself consists of two major parts:

• Glomerulus: A spherical structure consisting of tiny blood vessels, or capillaries. The filtration of the blood begins at glomerulus creating glomerular filtrate, which is similar to blood plasma but without proteins.
• Renal Tubule: Glomerular filtrate passes through the renal tubule. The renal tubule is comprised of three sections: the proximal convoluted tubule, loop of Henle, and distal convoluted tubule. In these sections, necessary substances (e.g., glucose, amino acids, and some salts) are reabsorbed back into the bloodstream, while wastes and excess substances are secreted into the tubular fluid.

2. The Collecting Duct: Each collecting duct takes the processed filtrate (now known as urine) from many nephrons towards the renal pelvis, from where it proceeds to the ureter and bladder for temporary storage before elimination from the body. The collecting duct also finalizes the processing of urine, primarily by determining its final concentration based on the body's hydration status.

 Additional Information

• Seminiferous Tubules: Seminiferous tubules are located within the testes, and they are the specific location where the spermatogenesis, the creation of sperm takes place.

  Each testis consists of numerous, tightly coiled seminiferous tubules where immature germ cells transform into spermatozoa over time, a process regulated by hormones and supporting cells. The seminiferous tubules are coiled and connected in a network to deliver sperm to the epididymis, where they mature and are stored.

• Bowman's Capsule: This is part of the renal corpuscle in the kidney, which also includes the glomerulus. The Bowman's capsule surrounds the glomerulus, functioning to collect the filtrate that is filtered from the blood through the walls of the glomerulus. The filtered fluid then goes through a series of tubules (proximal convoluted tubule, loop of Henle, and distal convoluted tubule), collectively called the renal tubule, which further processes the filtrate into urine.

• Nephrostomes are not found in human kidneys. They are part of the excretory system in some invertebrates, such as annelids (a group that includes earthworms), where they serve to connect coelomic cavities to tubular structures called nephridia for waste elimination

Conclusion-  The term 'Uriniferous tubule' refers to the entire path that the developing urine takes from the start of filtration in the nephron to the point where the urine leaves the nephron and flows into the collecting duct.

The correct answer is Option 2 

Explanation:

• The nephron is the structural and functional unit of the kidney. It is responsible for filtering blood, reabsorbing essential nutrients, and excreting waste as urine.
• The nephron consists of various parts:
  • Bowman's capsule
  • Proximal tubule
  • Loop of Henle
  • Distal tubule.
  • Collecting duct. 
• The proximal tubule (P) is closer to Bowman's capsule and is primarily involved in reabsorbing water, ions, glucose, and amino acids.
• The distal tubule (D) is farther along the nephron and plays a role in the selective reabsorption of ions and water, influenced by hormones like aldosterone and ADH (antidiuretic hormone).

PCT is lined by simple cuboidal brush border epithelium which increases the surface area for reabsorption.

• Nearly all of the essential nutrients, and 70-80 per cent of electrolytes and water are reabsorbed by this segment.
• PCT also helps to maintain the pH and ionic balance of the body fluids by selective secretion of hydrogen ions and ammonia into the filtrate and by absorption of HCO₃ ^– from it.

Distal Convoluted Tubule (DCT): Conditional reabsorption of Na+ and water takes place in this segment. DCT is also capable of reabsorption of HCO₃ ^– and selective secretion of hydrogen and potassium ions and NH₃ to maintain the pH and sodium-potassium balance in blood.

Concept:

• Excretion is a physiological process, which plays an important role in eliminating waste and other toxic materials from the body.
• The kidney is the principal excretory organ.
• The waste product of the body is mainly excreted in the form of urine.
• Urine formation involves three main processes, namely glomerular filtration, reabsorption, and tubular secretion.
• The first step in urine formation is the filtration of blood and it is carried out by the glomerulus.
• A comparison of the volume of the filtrate formed per day with that of the urine released and almost 99% of the filtrate is reabsorbed by the renal tubules. This process is called reabsorption.
• The last step of urine formation is tubular secretion.

Key Points

• The process of tubular secretion involves the movement of substances from the peritubular capillaries to the renal tubular lumen.
• It takes place in the proximal part of the nephron and the descending limb of the loop of Henle.
• Tubular secretion is mainly caused by active transport and passive diffusion.
• During urine formation, the tubular cells secrete substances like hydrogen ions, potassium ions, and ammonia into the filtrate.
• The products of metabolism are removed from the body through tubular secretion include, including creatinine, uric acid, ammonium ions, drugs, etc.
• Tubular secretion is also a significant event in urine formation as it helps in the maintenance of the ionic and acid-base balance of the body fluids.
• The released ions combine with the filtrate and form urine.
• The nephron tubule releases the urine into a collecting duct.

Hence, the correct answer is option (3).