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Questions and Answers
What is primarily responsible for the high osmolarity found in the medulla?
What is primarily responsible for the high osmolarity found in the medulla?
What causes the relaxation of the urethral sphincter during micturition?
What causes the relaxation of the urethral sphincter during micturition?
Which substance is converted by renin to angiotensin II, a potent vasoconstrictor?
Which substance is converted by renin to angiotensin II, a potent vasoconstrictor?
What is the main reason for kidney transplant being considered the ultimate remedy for kidney failure?
What is the main reason for kidney transplant being considered the ultimate remedy for kidney failure?
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What does the presence of glucose in urine indicate?
What does the presence of glucose in urine indicate?
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Which group of organisms eliminates ammonia as their primary nitrogenous waste product?
Which group of organisms eliminates ammonia as their primary nitrogenous waste product?
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What is the main function of the Juxta-Glomerular Apparatus (JGA) in relation to the glomerular filtration rate (GFR)?
What is the main function of the Juxta-Glomerular Apparatus (JGA) in relation to the glomerular filtration rate (GFR)?
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Which structure in the kidney is primarily responsible for the ultra-filtration of blood?
Which structure in the kidney is primarily responsible for the ultra-filtration of blood?
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What process occurs predominantly in the Proximal Convoluted Tubule (PCT)?
What process occurs predominantly in the Proximal Convoluted Tubule (PCT)?
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Which part of the nephron is impermeable to water, contributing to the dilution of the filtrate?
Which part of the nephron is impermeable to water, contributing to the dilution of the filtrate?
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Which structure collects urine from the nephrons before it is sent to the renal pelvis?
Which structure collects urine from the nephrons before it is sent to the renal pelvis?
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Which nitrogenous waste product is less toxic and allows for water conservation during excretion?
Which nitrogenous waste product is less toxic and allows for water conservation during excretion?
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What feature of urine formation is primarily aided by the counter-current mechanism in the nephron?
What feature of urine formation is primarily aided by the counter-current mechanism in the nephron?
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Study Notes
Kidney Function and Structure
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Kidney Structure: Bean-shaped, located between the last thoracic and third lumbar vertebrae. Averages 10-12 cm in length, 5-7 cm in width, and 2-3 cm in thickness. Each kidney contains approximately 1 million nephrons.
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Toxicity: Ammonia is the most toxic waste product, followed by urea and uric acid.
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Excretion Types: Ammonotelic animals (aquatic fish, insects) excrete ammonia, while ureotelic animals (terrestrial amphibians, marine fish) excrete urea, and uricotelic animals (reptiles, birds, land snails) excrete uric acid. Mammals do not excret through the kidneys.
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Excretory Structures: Kidneys process metabolic waste and maintain water and electrolyte balance.
Excretory Products
- Protonephridia/Flame Cells: Platyhelminthes, Rotifers, and some annelids use these structures for excretion.
- Nephridia: Excretory structures in annelids, some cephalochordates.
- Malpighian Tubules: Found in insects, used for excretion.
- Antennal/Green Glands: Excretory structures in crustaceans and some other arthropods.
Urine Formation
- Glomerular Filtration Rate (GFR): 125 ml/min, or approximately 180 liters per day, involves filtration of blood in the glomerulus.
- Proximal Convoluted Tubule (PCT): Absorbs about 70-80% of electrolytes and nutrients from the filtrate.
- Henle's Loop: Concentrates the filtrate by decreasing permeability to ions.
- Distal Convoluted Tubule (DCT): Further regulates electrolyte and water balance and secretes waste products like hydrogen ions.
- Collecting Duct: Reabsorbs water, creating a concentrated urine.
Urine Regulation
- Hormonal Control: ADH (antidiuretic hormone) and aldosterone regulate water reabsorption and electrolyte balance.
- Juxtamedullary Apparatus (JGA): Plays a crucial role in regulating GFR, via the release of renin.
- Atrial Natriuretic Factor (ANF): Involved in lowering blood pressure.
- Countercurrent Mechanism: Creates a concentration gradient in the kidney medulla to reabsorb water.
Disorders
- Uremia: Urea accumulation in the blood, often leading to kidney failure.
- Renal Calculi: Stones formed from crystallized salts in the kidney.
- Glomerulonephritis: Inflammation of the glomeruli in the kidney.
- Diabetes Mellitus: Impacted by urine pH, glucose, and ketonuria levels.
Hemodialysis
- Process: Cleanses the blood of waste products when the kidneys fail.
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Description
Test your knowledge on the structure and function of kidneys, including excretory mechanisms in various organisms. Explore the differences in waste excretion between ammonia, urea, and uric acid. This quiz covers key concepts in comparative physiology.
