Podcast
Questions and Answers
Which of the following are functions of the kidney? (Select all that apply)
Which of the following are functions of the kidney? (Select all that apply)
What is the functional unit of the kidney?
What is the functional unit of the kidney?
Nephron
What percentage of nephrons are cortical nephrons?
What percentage of nephrons are cortical nephrons?
Juxtamedullary nephrons have shorter loops of Henle compared to cortical nephrons.
Juxtamedullary nephrons have shorter loops of Henle compared to cortical nephrons.
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The juxtaglomerular apparatus consists of _____, mesangial cells, and macula densa.
The juxtaglomerular apparatus consists of _____, mesangial cells, and macula densa.
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What hormone is produced by juxtaglomerular cells?
What hormone is produced by juxtaglomerular cells?
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What happens during the micturition reflex?
What happens during the micturition reflex?
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The bladder can hold approximately _____ ml of urine before the micturition reflex is triggered.
The bladder can hold approximately _____ ml of urine before the micturition reflex is triggered.
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Study Notes
Kidney Function
- Regulates water and inorganic ion balance, maintaining homeostasis.
- Excretes metabolic waste products through urine production.
- Eliminates foreign chemicals, supporting the body's internal balance.
- Secretes hormones including:
- Erythropoietin: Stimulates red blood cell production.
- Renin: Controls angiotensin formation, impacting blood pressure.
- 1,25-dihydroxyvitamin D3: Influences calcium homeostasis.
Anatomical Characteristics of the Kidney
- Comprised of the renal cortex, renal medulla, and renal pelvis.
- Nephrons are the functional units, with approximately 1 million per kidney.
- Each nephron includes:
- Renal corpuscle (Bowman’s capsule and glomerulus).
- Renal tubule with segments including proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
Two Types of Nephrons
- Cortical Nephrons:
- Make up ~85% of all nephrons.
- Located in the outer cortex.
- Feature small glomeruli and short loops of Henle.
- High sympathetic nerve innervation and focused on reabsorption and secretion.
- Juxtamedullary Nephrons:
- Located nearer to the medulla.
- Have larger glomeruli and longer loops of Henle extending deep into renal pyramids.
- Form vasa recta and are less innervated, specialized for urine concentration and dilution.
Differences between Cortical and Juxtamedullary Nephrons
- Cortical Nephron:
- Found in outer cortex, features small glomeruli, and short loops.
- High renin concentration and accounts for 90% nephron ratio.
- Juxtamedullary Nephron:
- Located in the inner cortex, has larger glomeruli and long loops.
- Minimal renin and comprises 10% of total nephron ratio.
Juxtaglomerular Apparatus (JGA)
- Composed of macula densa, mesangial cells, and juxtaglomerular cells (JGC).
- Macula densa: Senses tubular NaCl concentration, helping to regulate renin release and glomerular filtration rate (GFR).
- JGC: Located in afferent arterioles; responsible for renin secretion.
Renal Circulation
- Renal blood flow: ~1200 ml/min, constituting 20% of cardiac output.
- Blood distribution: Mostly to the cortex (94%), with outer medulla receiving 5-6%.
- Abnormal urine output can lead to water and electrolyte loss.
Functions of Ureters and Bladder
- Urine is propelled to the bladder via smooth muscle contractions in the ureter walls.
- Micturition (urination) involves:
- Bladder filling until pressure exceeds 400-500 ml.
- A reflex action that leads to bladder emptying.
- The bladder capacity ranges from 250-400 ml; stretching of its walls initiates the micturition reflex.
Micturition Reflex
- Involves spinal reflex pathways, leading to:
- Parasympathetic stimulation causing bladder contractions.
- Opening of the internal sphincter, with conscious control over the external sphincter.
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Description
This quiz explores the essential functions of the kidneys, including water and ion regulation, waste excretion, and hormone secretion. Understand how these processes contribute to internal homeostasis and overall bodily health. Test your knowledge on critical renal physiology concepts.
