Questions and Answers
What is the primary functional unit of the kidney?
Which of the following hormones is produced by the kidney to regulate erythrocyte production?
What is NOT a function of the kidney?
Which component of the nephron is responsible for filtering blood?
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Which of the following substances do kidneys help to excrete?
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What structures comprise the renal corpuscle of a nephron?
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Which type of nephron is primarily located in the renal cortex?
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What is the function of the thick ascending limb of the loop of Henle?
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Which nephron type has loops of Henle that extend deep into the renal pyramids?
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What are the primary components of the nephron's tubule?
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What is the primary function of the juxtamedullary nephron?
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Where are juxtamedullary nephrons located?
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What characterizes the glomerulus of a cortical nephron?
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What type of nerve innervation is rich in cortical nephrons?
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Which nephron type is responsible for the secretion of renin?
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What is a significant feature of the loop of Henle in a juxtamedullary nephron?
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What is the typical ratio of cortical nephrons to juxtamedullary nephrons in the kidney?
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What role does the macula densa have in the juxtaglomerular apparatus?
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What triggers the micturition reflex to occur?
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Which of the following describes the main function of the ureters?
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What happens to the external sphincter during the micturition reflex?
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What volume range can the bladder typically hold before initiating the micturition reflex?
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What occurs when the bladder walls are stretched by greater volumes of urine?
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Study Notes
Kidney Function
- Regulates water and inorganic ion balance in the body.
- Excretes metabolic waste products and foreign chemicals through urine for internal homeostasis.
- Secretes hormones like:
- Erythropoietin: Controls erythrocyte production.
- Renin: Produced by juxtaglomerular cells, regulates formation of angiotensin.
- 1,25-dihydroxyvitamin D3: Influences calcium balance.
Anatomical Characteristics of the Kidney
- Composed of renal cortex, renal medulla, and renal pelvis.
- Functional unit is the nephron, with about 1 million nephrons per kidney.
- Each nephron consists of:
-
Renal Corpuscle:
- Glomerulus: Tuft of capillaries.
- Bowman’s Capsule: Surrounds glomerulus.
-
Renal Tubule:
- Proximal Convoluted Tubule
- Loop of Henle: Thick and thin limbs.
- Distal Convoluted Tubule.
-
Renal Corpuscle:
Types of Nephrons
-
Cortical Nephrons:
- ~85% of all nephrons.
- Located in the outer cortex.
- Short loops of Henle.
- Rich sympathetic innervation.
- Function primarily in reabsorption and secretion.
-
Juxtamedullary Nephrons:
- ~15% of all nephrons.
- Located closer to renal medulla, with long loops of Henle extending deeply.
- Forms vasa recta for blood supply.
- Function in concentrating and diluting urine.
Juxtaglomerular Apparatus (JGA)
- Composed of macula densa, mesangial cells, and juxtaglomerular cells.
- Macula Densa: Senses changes in NaCl concentration and volume of tubular fluid; informs glomerulus.
- Juxtaglomerular Cells: Secrete renin to regulate blood pressure.
- Functions in Tubulo-glomerular Feedback to regulate glomerular filtration rate.
Renal Circulation
- Blood flow is approximately 1200 ml/min, making up 20-25% of cardiac output.
- Blood distribution:
- Cortex: 94%
- Outer medulla: 5-6%
- Inner medulla: minor.
Micturition (Urination)
- Urine flows through the ureters to the bladder due to smooth muscle contractions in the ureter walls.
- The bladder stores urine and facilitates intermittent ejection during urination.
- Micturition involves:
- Filling the bladder until pressure exceeds 400-500 ml.
- Activation of the micturition reflex to empty the bladder.
Micturition Reflex
- Bladder capacity ranges from 250 to 400 ml.
- Increased volume stretches the bladder walls, initiating the reflex:
- Parasympathetic stimulation causes bladder contraction.
- Internal sphincter opens, and external sphincter relaxes, leading to urination.
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Description
Explore the essential functions of the kidneys in maintaining water balance, excreting waste, and regulating hormonal secretion. This quiz covers the mechanisms involved in urine production and the crucial roles of hormones such as erythropoietin and renin. Test your knowledge on how these processes contribute to the body's homeostasis.
