Podcast Beta
Questions and Answers
What is the formula for urinary excretion rate?
What is the assumed condition for the filtration calculation of a substance?
What is the main difference between GFR and tubular reabsorption?
What is required for a substance to be reabsorbed?
Signup and view all the answers
What type of transport is involved in reabsorption?
Signup and view all the answers
What percentage of the filtered load of sodium and water is normally reabsorbed?
Signup and view all the answers
Which substances are reabsorbed in the proximal tubule?
Signup and view all the answers
What is the characteristic of reabsorption in the proximal tubule?
Signup and view all the answers
What is the main function of the paracellular pathway in the proximal tubule?
Signup and view all the answers
What is the purpose of secretion of H+ in the proximal tubule?
Signup and view all the answers
What determines the transport maximum (Tm) for substances in the proximal tubule?
Signup and view all the answers
What is the significance of the threshold for glucose in the proximal tubule?
Signup and view all the answers
In which part of the nephron do the epithelial cells have much tighter junctions?
Signup and view all the answers
What is the characteristic of the thin descending segment of the loop of Henle?
Signup and view all the answers
What is the function of the aldosterone hormone in the nephron?
Signup and view all the answers
What is the main difference between the transport of glucose and sodium in the proximal tubule?
Signup and view all the answers
What is the primary function of reabsorption in the kidney?
Signup and view all the answers
What determines the amount of a substance filtered by the kidneys?
Signup and view all the answers
What is the main difference between glomerular filtration and tubular reabsorption?
Signup and view all the answers
What is the primary mechanism of reabsorption in the proximal tubule?
Signup and view all the answers
What is the main function of the proximal tubule?
Signup and view all the answers
What is the effect of a small change in glomerular filtration or tubular reabsorption?
Signup and view all the answers
What is the significance of the coordinated regulation of glomerular filtration and tubular reabsorption?
Signup and view all the answers
What is the characteristic of tubular reabsorption in the proximal tubule?
Signup and view all the answers
What is the primary function of the paracellular pathway in the proximal tubule?
Signup and view all the answers
Which substances are reabsorbed in the first half of the proximal tubule?
Signup and view all the answers
What is the purpose of the secretion of H+ in the proximal tubule?
Signup and view all the answers
What determines the transport maximum for substances in the proximal tubule?
Signup and view all the answers
What is the characteristic of the transport of glucose in the proximal tubule?
Signup and view all the answers
What is the function of the thin descending segment of the loop of Henle?
Signup and view all the answers
What is the effect of aldosterone on sodium reabsorption in the distal parts of the nephron?
Signup and view all the answers
What is the significance of the threshold for glucose in the proximal tubule?
Signup and view all the answers
Study Notes
Kidney Function and Reabsorption
- Urinary excretion rate is calculated as Filtration rate - Reabsorption rate + Secretion rate
- Filtration of a substance is calculated as GFR × plasma concentration (e.g., Filtration of Glucose = 180 L/day × 1 g/L = 180 gr/day)
Importance of Reabsorption
- Small changes in glomerular filtration or tubular reabsorption can cause large changes in urinary excretion
- Changes in tubular reabsorption and glomerular filtration are closely coordinated to avoid large fluctuations in urinary excretion
Types of Transport
- Active transport: primary active, secondary active
- Passive transport: diffusion (simple, facilitated), osmosis, pinocytosis
Reabsorption and Secretion in Proximal Tubule (PT)
- Normally, 65% of filtered load of sodium and water, and a slightly lower percentage of filtered chloride are reabsorbed
- Reabsorbs all filtered glucose and amino acids
- High capacity for active and passive reabsorption through transcellular and paracellular pathways
- Reabsorption of glucose and amino acid especially in the first half of PT
- Reabsorption of Na in 3 steps
- Reabsorption of Cl especially in the 2nd half of PT
- Secretion of organic acids and bases, including bile salts, oxalate, catecholamines, and hydrogen
Transport Maximum (Tm)
- Tm for substances that are actively reabsorbed or secreted
- Example: Glucose transport system in the proximal tubule (GFR × plasma glucose = 125 ml/min × 1 mg/ml = 125 mg/min)
- Threshold for Glucose: ~ 250 mg/min
- Tm for glucose: ~ 375 mg/min
- Substances that are passively transported do not exhibit a Tm
- Substances that are actively transported but do not exhibit a Tm, such as reabsorption of Na in PT
Kidney Function and Reabsorption
- Urinary excretion rate is calculated as Filtration rate - Reabsorption rate + Secretion rate
- Filtration of a substance is calculated as GFR × plasma concentration (e.g., Filtration of Glucose = 180 L/day × 1 g/L = 180 gr/day)
Importance of Reabsorption
- Small changes in glomerular filtration or tubular reabsorption can cause large changes in urinary excretion
- Changes in tubular reabsorption and glomerular filtration are closely coordinated to avoid large fluctuations in urinary excretion
Types of Transport
- Active transport: primary active, secondary active
- Passive transport: diffusion (simple, facilitated), osmosis, pinocytosis
Reabsorption and Secretion in Proximal Tubule (PT)
- Normally, 65% of filtered load of sodium and water, and a slightly lower percentage of filtered chloride are reabsorbed
- Reabsorbs all filtered glucose and amino acids
- High capacity for active and passive reabsorption through transcellular and paracellular pathways
- Reabsorption of glucose and amino acid especially in the first half of PT
- Reabsorption of Na in 3 steps
- Reabsorption of Cl especially in the 2nd half of PT
- Secretion of organic acids and bases, including bile salts, oxalate, catecholamines, and hydrogen
Transport Maximum (Tm)
- Tm for substances that are actively reabsorbed or secreted
- Example: Glucose transport system in the proximal tubule (GFR × plasma glucose = 125 ml/min × 1 mg/ml = 125 mg/min)
- Threshold for Glucose: ~ 250 mg/min
- Tm for glucose: ~ 375 mg/min
- Substances that are passively transported do not exhibit a Tm
- Substances that are actively transported but do not exhibit a Tm, such as reabsorption of Na in PT
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the processes of glomerular filtration, tubular reabsorption, and secretion in the kidney, including the importance of reabsorption and how to calculate filtration rates.