Test: Excretory Products & their Elimination - 1 - NEET MCQ

The glomerulus is a tuft of capillaries

• Blood enters the glomerulus through the afferent arteriole, a fine branch of the renal artery.
• Blood from the glomerulus is carried away by an efferent arteriole.

Detailed Explanation:

Option A is wrong because blood enters through the afferent arteriole and not the efferent. 

Option B is wrong because there is no such radial arteriole present. And, The collecting duct system is the last part of the nephron and participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone). 

Option C is wrong because blood doesn't enter through distributing arteriole because no such arteriole is present. 

Option D is right because blood enters glomerular capillaries through the afferent arteriole and leaves through the efferent arteriole. 

Hence Option D is correct. 

Line in NCERT: "Afferent arteriole Efferent arteriole"

Uric acid is  less toxic than ammonia or urea. It contains four nitrogen atoms; only a small amount of water is needed for its excretion. Out of solute, it precipitates and forms crystals.

Detailed Explanation:

Option A is wrong because Urea moves to the blood and gets filtered and eliminated with water in urine via the kidneys.

Option B is correct Uric acid is insoluble in water as there are in solid form, thus, containing the least water.
In birds, uric acid mixes with undigested food to form the bird dropping.

Option C is wrong because Ammonia is very toxic and needs water for diffusion.

Option D is wrong because none of the above options has the same toxicity level. 

Hence Option B is correct.

Line in NCERT: "Ammonia is the most toxic form and requires large amount of water for its elimination, whereas uric acid, being the least toxic, can be removed with a minimum loss of water."

During micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. The external urethral sphincter (sphincter urethrae) is under somatic control and is consciously relaxed during micturition. 

Detailed Solution:

Option A is right because, during micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax.

Option B is wrong because the muscles of the urinary bladder contract and do not relax. 

Option C is wrong because during micturition, the muscles do not dialate.

Hence, the correct option is A. 

Line in NCERT: "the CNS passes on motor messages to initiate the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine."

Renal corpuscle, also called malpighian body, filtration unit of vertebrate nephrons, functional units of the kidney.
It consists of a knot of capillaries (glomerulus) surrounded by a double-walled capsule (Bowman’s capsule) that opens into a tubule.

Line in NCERT: "Glomerulus alongwith Bowman's capsule, is called the malpighian body or renal corpuscle."

the pH of Urine Under Healthy Conditions:

• The pH of urine under healthy conditions is slightly acidic.
• The normal pH range for human urine is between 4.5 and 8.0, with an average of around 6.0.
• The acidity of urine is mainly due to the presence of various acidic waste products and hydrogen ions (H+) that are excreted by the kidneys.

In summary, under healthy conditions, the pH of urine is slightly acidic, helping the body eliminate acidic waste products and maintain an overall balanced pH. However, this can vary depending on factors such as diet, hydration, and medical conditions.

• Analysis of urine helps in the clinical diagnosis of many metabolic disorders.
• The presence of glucose or Glycosuria and ketone bodies or Ketonuria in urine is indicative of diabetes mellitus.

Line in NCERT: Not Found

Malfunctioning of kidneys can lead to accumulation of urea in blood, a condition called uremia

• Globulins are not reabsorbed
• .Substances like glucose, amino acids, Na+, etc., in the filtrate are reabsorbed actively

Line in NCERT: "substances like glucose, amino acids, Na*, etc., in the filtrate are reabsorbed actively whereas the nitrogenous wastes are absorbed by passive transport."

JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact

Line in NCERT: "JGA, a specialised portion of the nephrons, plays a significant role in the regulation of GFR."

Oxygen is not accumulated by the body of living organisms as this is required by the cells to perform respiration. Also, it is not a waste product of the cells. Animals accumulate ammonia, urea, uric acid, carbon dioxide, water, and ions like Na⁺, K⁺, Cl^–, phosphate, sulphate, etc., by certain metabolic activities.

• The epithelial cells of Bowman’s capsule called podocytes, which 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, it is considered as a process of ultra filtration.

Line in NCERT: "The epithelial cells of Bowman's capsule called podocytes are arranged in an intricate manner so as to leave some minute spaces called filtration slits or slit pores."

• The heart is not involved in excretion. The heart is a muscular organ that pumps blood throughout the body, delivering oxygen and nutrients to the tissues and organs.
• Lungs help in excretion of carbon dioxide
• Liver helps in excretion of toxic substance
• Skin helps in removal of extra salts along with sweat.

Hence, option C is correct.

Line in NCERT: "Other than the kidneys, lungs, liver and skin also help in the elimination of excretory wastes."

• The ascending limb of the loop of Henle is not permeable to water (H₂O). 
• The loop of Henle is a U-shaped structure in the nephron of the kidney that plays a crucial role in the formation of urine. 
• The ascending limb of the loop of Henle is responsible for reabsorbing ions like sodium (Na⁺), potassium (K⁺), and chloride (Cl^-) from the filtrate, but it is impermeable to water.

Line in NCERT: "Ascending limb of Henle's loop is impermeable to water but allows transport of electrolytes actively or passively."

• Conditional reabsorption of sodium ions and water takes place in distal convoluted tubule (DCT).
• 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.

Fig: Reabsorption and secretion of major substances at different parts of the nephron (Arrows indicate direction of movement of materials.)

Line in NCERT: "Conditional reabsorption of Na+ and water takes place in this segment."

Osmoreceptors in the body are activated by changes in blood volume, body fluid volume, and ionic concentration.

• Osmoreceptors are specialized cells that detect changes in the osmotic pressure or concentration of solutes in the blood. They are primarily sensitive to changes in blood volume, body fluid volume, and ionic concentration.
• When there is a decrease in blood volume or an excessive loss of fluid from the body, the osmoreceptors are activated.
• These changes in blood volume trigger a response in the hypothalamus, which then releases antidiuretic hormone (ADH) or vasopressin. This hormone helps in water reabsorption from the latter parts of the tubules, preventing excessive urine formation and maintaining fluid balance in the body.

Therefore, changes in blood volume play a crucial role in activating osmoreceptors and regulating fluid levels in the body.

Line in NCERT: "Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration."

Reptiles, birds, land snails  excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.

Line in NCERT: "Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals."

Excessive fluid loss from the body can activate osmoreceptors, stimulating the hypothalamus to release antidiuretic hormone (ADH) or vasopressin, which facilitates water reabsorption in the tubules.

Line in NCERT: "Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis."

Antidiuretic hormone (ADH) is a chemical produced in the brain that causes the kidneys to release less water, decreasing the amount of urine produced. A high ADH level causes the body to produce less urine.

Line in NCERT: "ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis."

• When there is a decrease in glomerular blood flow, the JG (Juxtaglomerular) cells in the kidneys respond by releasing a hormone called renin.
• Renin plays a crucial role in the renin-angiotensin mechanism. It converts angiotensinogen, a protein present in the blood, into angiotensin I, which is further converted to angiotensin II.
• Angiotensin II acts as a potent vasoconstrictor, causing the blood vessels to narrow, which increases the glomerular blood pressure and subsequently the glomerular filtration rate (GFR).
• The release of renin is part of a complex regulatory system that helps regulate blood pressure and maintain renal function.

Line in NCERT: "The JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II."

• During urine formation, the tubular cells secrete substances like hydrogen ions, potassium ions and ammonia into the filtrate.
• Hydrogen ions (H⁺) are secreted into the filtrate by the tubular cells as a means of regulating the pH of the urine. 
• Potassium ions (K⁺) are also secreted into the filtrate, and their concentration is regulated to maintain a balance with sodium ions (Na⁺) in the body. 
• Ammonia (NH₃) is also secreted into the filtrate, and it plays a role in regulating the pH of the urine as well as serving as a buffer to help maintain acid-base balance in the body.

Line in NCERT: "During urine formation, the tubular cells secrete substances like H+, K* and ammonia into the filtrate."