Test your understanding of excretory products, human excretory system, and kidney function with these multiple-choice questions.
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1. Hyperosmolarity of interstitial fluid in renal medulla is maintained by retaining high concentration of
The interstitial fluid of the medulla region has a higher osmotic concentration, stated to be equal to 1200 mosm/lt, primarily due to higher quantities of two solutes: NaCl and urea. This concentration gradient is critical for the kidney's ability to concentrate urine.
2. How much amount of blood passes through the kidneys per minute in a healthy person?
Approximately 1100-1200 ml of blood is filtered by the two kidneys every minute. This constitutes roughly one-fifth (1/5th) of the blood pumped out by each ventricle of the heart in a minute.
3. Chemically glomerular filtrate is similar to blood plasma, except
Nephric filtrate, also known as glomerular filtrate, consists of various small-sized molecules like water, electrolytes (Na+, K+, Ca2+, etc.), glucose, amino acids, hormones, vitamins, urea, creatinine, and uric acid. However, it specifically excludes large-sized particles and structures like fats, proteins, platelets, leucocytes, and erythrocytes. Therefore, it is similar to blood plasma, but without the proteins and blood cells.
4. A fall in GFR can activate the JG cells to release, which can stimulate the glomerular blood flow and thereby the GFR back to normal
The Juxtaglomerular Apparatus (JGA) located in the kidney responds to a decrease in blood pressure or blood volume in the afferent arteriole of the glomerulus. In response, it releases an enzyme called renin into the bloodstream. Renin then initiates a cascade of chemical reactions (Renin-Angiotensin-Aldosterone System, RAAS) that ultimately work to increase blood pressure and restore Glomerular Filtration Rate (GFR).
5. Substances like glucose, amino acids, Na+-etc. in the filtrate are reabsorbed by
The absorption of useful essential substances from glomerular filtrate, such as glucose and amino acids, occurs through both active and passive processes. Active reabsorption, which includes secondary active transport for substances like glucose and amino acids, occurs against the concentration gradient and requires energy. Kidneys consume a significant amount of oxygen for these active processes, even more than the heart.
6. Osmotic concentration of glomerular filtrate is the highest at the bottom of the U-shaped Henle's loop. It is about mOsmL–1
As the filtrate moves down the descending limb of the Loop of Henle, from the cortex towards the inner medulla, its osmolarity progressively increases. This increase is due to water passing out of the filtrate into the hypertonic interstitial fluid of the medulla. At the bottom of the U-shaped Henle's loop, the osmolarity can reach up to approximately 1200 m osm L–1.
7. Which part of nephron is impermeable to Hp but allows transport of electrolytes actively or passively?
The ascending limb of the Loop of Henle is distinctly impermeable to water (H₂O, or 'Hp' as assumed from context). However, its thin segment allows NaCl to diffuse out into the interstitial fluid, while its thick segment actively transports NaCl (and some Mg²+, Ca²+, K+) out of the filtrate, contributing to the high osmolarity of the inner medulla.
8. Counter current mechanism helps in concentrating urine in animals and mainly operates on
The Loop of Henle and the vasa recta (the network of capillaries surrounding the loop) both form a counter-current system. This special arrangement of blood flow and filtrate movement is significantly involved in maintaining a concentration gradient in the medullary interstitium, which in turn facilitates the reabsorption of water from the collecting duct, thereby concentrating the urine.
9. Diuretic substances like tea, coffee, alcohol etc. increases urine output by inhibiting release of hormone _______________
The volume of urine produced is significantly influenced by the hormone Vasopressin, also known as ADH (Antidiuretic Hormone). In the presence of ADH, more water is reabsorbed, leading to concentrated urine; conversely, in its absence, dilute urine is passed out. Therefore, diuretic substances increase urine output by inhibiting the release of ADH, which reduces water reabsorption.
10. Mark the inappropriate term w.r.t. the glomerular filtration
Glomerular filtration, also called ultrafiltration, is a nonselective process, meaning it filters small molecules irrespective of whether they are useful or waste products. It is a passive process that occurs due to a net higher hydrostatic pressure (glomerular filtration pressure of approximately 10 mm Hg) in the glomerular capillaries compared to Bowman's capsule. Therefore, describing it as an 'active process' is inappropriate.
11. Dialysis fluid contain all the constituents as in plasma, except ____
During haemodialysis, the patient's blood flows through a dialyzer filled with dialysis fluid. This dialysis fluid is specifically formulated to contain the same quantities of electrolytes and nutrients (like glucose, NaCl, amino acids) as normal blood plasma, but it critically contains no waste products. This difference in concentration gradient allows waste substances from the blood, such as urea, ammonia, and creatinine, to diffuse out of the blood and into the dialysis fluid.
12. Reabsorption of Hp from distal parts of the tubules is facilitated by hormone ____
Reabsorption of water (Hp, assumed to mean H₂O) from the distal parts of the nephron, specifically the distal convoluted tubule and collecting ducts, is primarily controlled by the hormone Vasopressin, which is also known as ADH (Antidiuretic Hormone). In the presence of this hormone, the walls of these tubules become permeable to water, allowing its reabsorption and leading to more concentrated urine.
13. Mark the incorrect statement
Let's analyze each statement: * Micturition, the voiding of urine, is indeed carried out by an autonomic reflex. * ADH (Antidiuretic Hormone) helps in water reabsorption, primarily in the distal convoluted tubule and collecting ducts, making the urine more concentrated (hypertonic), not hypotonic, to conserve body water. This statement is incorrect. * During glomerular filtration, a protein-free fluid (glomerular filtrate) is indeed filtered from blood plasma into the Bowman's capsule. * Glucose is completely reabsorbed from the glomerular filtrate in the Proximal Convoluted Tubule (PCT) through active transport. Therefore, the incorrect statement is that ADH helps in H₂O elimination (it helps in reabsorption) or makes urine hypotonic (it makes it hypertonic).
14. Which of the following organs, other than kidneys, also help in the elimination of excretory wastes?
Several organs in the human body, in addition to the kidneys, contribute to the elimination of excretory wastes: * Lungs eliminate carbon dioxide (CO₂) and a significant amount of water vapor (around 400 ml/day in normal resting conditions). * The skin, through sweat glands, excretes sweat, which contains water and some salts. Sebaceous glands in the skin eliminate sebum, containing waxes, sterols, hydrocarbons, and fatty acids. * The liver produces bile pigments (bilirubin, biliverdin) from the breakdown of hemoglobin, and also eliminates cholesterol, inactivated steroid hormones, vitamins, and drugs. Therefore, all listed organs (lungs, liver, skin, and sebaceous glands) play a role in excretion.
15. Find out the incorrectly matching pair w.r.t. the accessory excretory organs and the excretory wastes eliminated by them
Let's evaluate each pair: * Liver - Bilirubin, biliverdin and cholesterol: The liver produces bile pigments (bilirubin, biliverdin) as metabolic wastes of hemoglobin, and also eliminates cholesterol. This is a correct match. * Lungs - CO₂ and Hp (water): The lungs help in removing CO₂ and water. This is a correct match. * Salivary gland - Heavy metals and drugs: While salivary glands can excrete some substances, the provided source does not explicitly list them as major accessory excretory organs for heavy metals and drugs. This information is not directly in the source, but the general concept of other organs aiding excretion is. * Sudorific gland - Sebum containing waxes, sterols and fatty acids: Sudorific glands are sweat glands, which excrete sweat (water and salts). Sebaceous glands are responsible for eliminating sebum (waxes, sterols, hydrocarbons, and fatty acids). Therefore, this pair is incorrectly matched.
16. Presence of glucose (glycosuria) and ketone bodies (ketonuria) in urine are indicative of __
Glycosuria, the presence of glucose in urine, is a characteristic symptom of Diabetes mellitus. Ketonuria, the presence of ketone bodies in urine, is also a common finding in uncontrolled diabetes, as the body begins to break down fats for energy, producing ketones.
17. In case of dehydration, secretion of all hormones increases except one, mark this except one
In a state of dehydration, the body's primary response is to conserve water and maintain blood volume. This triggers the release of: * Renin (from JGA due to decreased blood pressure/volume). * Angiotensin II (activated by renin), which stimulates the release of Aldosterone (from adrenal gland). Both promote Na+ and water reabsorption. * Vasopressin (ADH) (from pituitary gland, triggered by increased blood osmolarity detected by osmoreceptors) to enhance water reabsorption. Atrial Natriuretic Factor (ANF), however, is released by the heart atria in response to *increased* blood volume and pressure. ANF acts to inhibit renin release and reduce aldosterone, thereby promoting Na+ and water excretion. Therefore, in dehydration (which involves decreased blood volume), the secretion of ANF would typically decrease, not increase.
18. Which of the following is a powerful vasoconstrictor that increases the glomerular blood pressure and thereby the GFR?
Angiotensin II is described as a powerful constrictor of arterioles and one of the most potent vasopressor substances known. It increases blood pressure by causing efferent arterioles to constrict. This constriction downstream of the glomerulus raises the blood pressure within the glomerulus, thereby increasing the Glomerular Filtration Rate (GFR).
19. Which part of brain sends voluntary motor signals to smooth muscles of urinary bladder when the bladder get filled with urine?
Micturition (urination) is initially an autonomic reflex, triggered by stretch receptors in the urinary bladder as it fills. However, this process can be voluntarily controlled in adults. The cerebral cortex directs the external sphincter to relax, allowing a person to consciously initiate or inhibit urination. It enables voluntary control over the micturition reflex.
20. Which of the following is not metabolised in human body and therefore, used in determining glomerular filtration rate?
Inulin is a fructan storage polysaccharide that is not metabolized in the human body. It is readily filtered through the kidneys and neither reabsorbed nor secreted significantly by the renal tubules. Due to these properties, inulin is widely used as a standard substance for testing kidney function, particularly for accurately determining the glomerular filtration rate (GFR).