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Questions and Answers
Which of the following best describes the primary role of the kidneys in maintaining homeostasis?
Which of the following best describes the primary role of the kidneys in maintaining homeostasis?
- Regulating blood sugar levels by secreting insulin
- Stabilizing the volume and ion concentrations of the extracellular fluid (correct)
- Controlling the body’s immune response to infections
- Producing hormones that regulate muscle contractions
List the urinary system components.
List the urinary system components.
Urinary system components include the kidneys, ureters, urinary bladder and the urethra
Out of the urinary system components, which one is physiologically relevant?
Out of the urinary system components, which one is physiologically relevant?
- Urethra
- Urinary bladder
- Kidney (correct)
- Ureters
List the important functions of the kidney (hint 7)
List the important functions of the kidney (hint 7)
Which of the following is not a function of the kidneys in the body?
Which of the following is not a function of the kidneys in the body?
What does “endocrine functions of the kidney” refer to?
What does “endocrine functions of the kidney” refer to?
What are the three important hormones produced by the kidney?
What are the three important hormones produced by the kidney?
What is the primary role of calcitriol in response to Hypocalcemia?
What is the primary role of calcitriol in response to Hypocalcemia?
Which organ is primarily responsible for Vitamin D3 into its active form, calcitriol??
Which organ is primarily responsible for Vitamin D3 into its active form, calcitriol??
What’s the function of the liver in the synthesis of calcitriol?
What’s the function of the liver in the synthesis of calcitriol?
What is the primary function of erythropoietin in the body?
What is the primary function of erythropoietin in the body?
Where are erythropoietin receptors primarily expressed?
Where are erythropoietin receptors primarily expressed?
What are the two types of nephrons in the kidney?
What are the two types of nephrons in the kidney?
Which of the following statements accurately describes a key difference between cortical and juxtamedullary nephrons?
Which of the following statements accurately describes a key difference between cortical and juxtamedullary nephrons?
The glomerulus of the juxtamedullary nephron aer closer to the renal capsule, whereas the glomerulus of the cortical nephrons aer located near the cortex/medulla junction
The glomerulus of the juxtamedullary nephron aer closer to the renal capsule, whereas the glomerulus of the cortical nephrons aer located near the cortex/medulla junction
What are the five structures of the nephron?
What are the five structures of the nephron?
Nephrons can’t be replaces, and are partially regenerated
Nephrons can’t be replaces, and are partially regenerated
The (juxtamedullary/cortical) nephron’s blood supply is through the PERITUBULAR CAPILLARIES
The (juxtamedullary/cortical) nephron’s blood supply is through the PERITUBULAR CAPILLARIES
The (juxtamedullary/cortical) nephrons blood supply is from the efferent arterioles giving rise to the vasa recta.
The (juxtamedullary/cortical) nephrons blood supply is from the efferent arterioles giving rise to the vasa recta.
What is the primary function of the glomerulus in the nephron?
What is the primary function of the glomerulus in the nephron?
Which of the following is the main function of the proximal tubule?
Which of the following is the main function of the proximal tubule?
What is the primary role of the thin limbs of Henle's loop in the nephron?
What is the primary role of the thin limbs of Henle's loop in the nephron?
Which of the following best describes the function of the thick ascending limb of Henle’s loop?
Which of the following best describes the function of the thick ascending limb of Henle’s loop?
What is the main function of the distal convoluted tubule?
What is the main function of the distal convoluted tubule?
Which of the following is a key function of the collecting duct in the nephron?
Which of the following is a key function of the collecting duct in the nephron?
What percent of the cardiac output goes to the kidney?
What percent of the cardiac output goes to the kidney?
Describe the flow of the cardiac output to the kidney.
Describe the flow of the cardiac output to the kidney.
What is ischemia?
What is ischemia?
What is reperfusion?
What is reperfusion?
Which of the following medical scenarios is least likely to involve ischemia-reperfusion injury?
Which of the following medical scenarios is least likely to involve ischemia-reperfusion injury?
What’s a common outcome of both ischemia and reperfusion at the cellular level?
What’s a common outcome of both ischemia and reperfusion at the cellular level?
Why is renal ischemia-reperfusion injury particularly concerning compared to other tissues?
Why is renal ischemia-reperfusion injury particularly concerning compared to other tissues?
What is the maximum volume of urine that adult dogs can produce in a day, considering the upper end of the glomerular filtration rate?
What is the maximum volume of urine that adult dogs can produce in a day, considering the upper end of the glomerular filtration rate?
Which component is primarily retained during the filtration process in the glomerulus?
Which component is primarily retained during the filtration process in the glomerulus?
Which statement correctly describes glomerular filtrate?
Which statement correctly describes glomerular filtrate?
What is a critical feature of the glomerulus functioning in the filtration process?
What is a critical feature of the glomerulus functioning in the filtration process?
What is the primary reason that the glomerular filtration barrier is relatively impermeable to large proteins?
What is the primary reason that the glomerular filtration barrier is relatively impermeable to large proteins?
Which layer of the glomerular basement membrane is especially rich in glycoproteins?
Which layer of the glomerular basement membrane is especially rich in glycoproteins?
How does glomerular filtration rate (GFR) relate to renal blood flow (RPF)?
How does glomerular filtration rate (GFR) relate to renal blood flow (RPF)?
What molecular property is NOT a factor influencing glomerular filterability?
What molecular property is NOT a factor influencing glomerular filterability?
Which statement accurately describes the glomerular filtration barrier?
Which statement accurately describes the glomerular filtration barrier?
Which part of the kidney's filtration system is primarily responsible for the formation of the filtrate?
Which part of the kidney's filtration system is primarily responsible for the formation of the filtrate?
What component of the filtration barrier helps provide the overall net negative charge?
What component of the filtration barrier helps provide the overall net negative charge?
In the context of glomerular filtration, which type of molecules are filtered most freely?
In the context of glomerular filtration, which type of molecules are filtered most freely?
What criteria must indicator substances meet to be used for calculating GFR?
What criteria must indicator substances meet to be used for calculating GFR?
Why is it important for indicator substances not to be metabolized in the kidney?
Why is it important for indicator substances not to be metabolized in the kidney?
Explain one reason why indicator substances must not alter renal function.
Explain one reason why indicator substances must not alter renal function.
Identify one consequence of using a substance that does not meet the criteria for GFR calculation.
Identify one consequence of using a substance that does not meet the criteria for GFR calculation.
What characterizes an ideal indicator substance for GFR measurement?
What characterizes an ideal indicator substance for GFR measurement?
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Study Notes
Urine Formation: Glomerular Filtration
- Urine formation begins with fluid filtration from glomerular capillaries into Bowman's capsule.
- The glomerulus, a capillary network, acts as a semipermeable membrane.
- It retains cells and large proteins, preventing their passage.
- Glomerular filtrate, initially large in volume (99%+ reabsorbed), is mostly reabsorbed, leaving <1 liter for excretion. The exact amount is highly variable.
- Adult dogs: urine production is approximately 20-40 ml/kg body weight/24 hours (1.0-2.0 ml/kg/hour).
- Adult cats: average urine production is 28 ml/kg body weight/24 hours (~1.2 ml/kg/hr).
- Glomerular Filtration Rate (GFR):
- Dogs: 2.4 – 3.7 mL/min/kg (up to 5,328 mL/kg/day).
- Glomerular filtrate is similar to plasma.
- GFR depends on renal blood (plasma) flow (RPF); about 20% of renal plasma is filtered.
- Example: If RPF = 625 mL/min, then GFR ≈ 125 mL/min (20% of RPF).
Glomerular Structure and Filtration Barrier
- Glomerulus: branching, anastomosing capillaries covered by podocytes (epithelial cells) and encased in Bowman's capsule.
- Bowman's capsule: lined with parietal epithelium; Bowman's space lies between capillaries and capsule.
- Filtration barrier components:
- Capillary endothelial cells (fenestrated).
- Glomerular basement membrane (GBM): primarily glycoproteins, not cells; functions as a filter.
- Visceral epithelium (podocytes).
Glomerular Basement Membrane (GBM) Details
- GBM (sometimes incorrectly called basal lamina): three layers (visible via electron microscopy).
- Lamina rara interna
- Lamina densa (electron-dense; contributes to GBM's net negative charge).
- Lamina rara externa
- All three layers contain proteins (lamina densa rich in glycoproteins like lamins, type IV collagens, proteoglycans).
- The "mesh-like" structure makes the glomerular capillaries relatively impermeable to large proteins; glomerular filtrate is essentially protein-free.
Glomerular Filterability
- The glomerular filtration barrier is highly selective. Filterability depends on:
- Size (inversely related to radius and molecular weight).
- Electrical charge.
- Plasma protein binding.
- Electrolytes (e.g., sodium) and small organic compounds (e.g., glucose) filter as freely as water.
Glomeruler Filtration Rate (GFR)
- GFR can be calculated using indicator substances.
- These substances must be freely filterable.
- The filtered amount of the substance must not change due to reabsorption or secretion in the tubule.
- These test substances must not be metabolized in the kidney.
- The indicator substances must not alter renal function.
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