L4 Renal tubular reabsorption and secretion (P1 Hard)
35 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What limits the reabsorption of phosphate in the body?

  • The availability of sodium
  • The normal plasma concentration of phosphate (correct)
  • The activity of parathyroid hormone
  • The function of the distal convoluted tubule

    • What is the primary mechanism of phosphate reabsorption in the kidneys?

  • Passive diffusion in the nephron
  • Active transport coupled with calcium reabsorption
  • Co-transport with sodium in the proximal convoluted tubules (correct)
  • Facilitated diffusion through aquaporins

    • How does parathyroid hormone (PTH) affect calcium reabsorption?

  • It inhibits calcium transport in the distal convoluted tubule
  • It has no effect on calcium reabsorption
  • It reduces calcium reabsorption in the proximal convoluted tubule
  • It stimulates calcium reabsorption in the proximal convoluted tubule (correct)

    • In which part of the nephron does active phosphate reabsorption primarily occur?

    <p>Proximal convoluted tubule</p> Signup and view all the answers

    What is a true statement about calcium reabsorption in the kidneys?

    <p>It can occur through both 2nd active transport and passive mechanisms</p> Signup and view all the answers

    Which mechanism of tubular reabsorption involves the movement of water between cells?

    <p>Paracellular transport</p> Signup and view all the answers

    What is the primary role of tubular reabsorption in the kidneys?

    <p>To maintain the composition of plasma</p> Signup and view all the answers

    Which substance is typically involved in primary active transport during tubular reabsorption?

    <p>Sodium ions</p> Signup and view all the answers

    Which component does NOT need to be crossed during transepithelium transport in tubular reabsorption?

    <p>Capillary wall</p> Signup and view all the answers

    What type of transport is described as 'highly selective' and regulates substances in the renal tubules?

    <p>Reabsorption</p> Signup and view all the answers

    Which of the following statements about tubular secretion is incorrect?

    <p>It is passive in nature.</p> Signup and view all the answers

    The tight junctions in renal epithelial cells serve primarily to:

    <p>Prevent leakage of substances between cells</p> Signup and view all the answers

    During tubular reabsorption, what is the role of the basolateral membrane?

    <p>It is the site of primary active transport.</p> Signup and view all the answers

    What is the primary method of glucose reabsorption in the early portion of the proximal convoluted tubule (PCT)?

    <p>Simultaneous transport with sodium using SGLT</p> Signup and view all the answers

    At what plasma glucose concentration does glucose begin to appear in urine?

    <p>180 mg%</p> Signup and view all the answers

    What percentage of sodium is reabsorbed in the proximal convoluted tubule (PCT)?

    <p>65%</p> Signup and view all the answers

    Which transport mechanism is primarily responsible for potassium reabsorption in the Loop of Henle?

    <p>Both primary and secondary active transport</p> Signup and view all the answers

    What is the role of the Na+-K+ ATPase in renal sodium reabsorption?

    <p>To create a sodium gradient for reabsorption</p> Signup and view all the answers

    What is the primary characteristic of glucose reabsorption in the nephron?

    <p>All filtered glucose is reabsorbed</p> Signup and view all the answers

    What regulates the plasma levels of phosphate and calcium in the kidneys?

    <p>Renal thresholds for normal plasma concentrations</p> Signup and view all the answers

    Which statement about sodium reabsorption is true?

    <p>It requires both active transport and diffusion processes</p> Signup and view all the answers

    What is the primary mechanism for passive chloride reabsorption in the proximal convoluted tubule (PCT)?

    <p>Passive diffusion through tight junctions</p> Signup and view all the answers

    Which of the following percentages represents the obligatory reabsorption of water in the proximal convoluted tubule?

    <p>65%</p> Signup and view all the answers

    What primarily stimulates potassium ion secretion in the distal convoluted tubule?

    <p>Hormonal regulation by aldosterone</p> Signup and view all the answers

    Which substance is primarily reabsorbed through osmosis in the descending loop of Henle?

    <p>Water</p> Signup and view all the answers

    What condition is caused by a decline in glomerular filtration rate (GFR) leading to increased blood urea nitrogen levels?

    <p>Uremia</p> Signup and view all the answers

    Which mechanism primarily drives hydrogen ion secretion in the proximal convoluted tubule?

    <p>Counter-transport with bicarbonate</p> Signup and view all the answers

    Which of the following compounds undergoes secretion via tubular secretion mechanisms?

    <p>Potassium</p> Signup and view all the answers

    What is the primary driver for water reabsorption in the collecting duct?

    <p>Hormonal influence from antidiuretic hormone (ADH)</p> Signup and view all the answers

    What is the fate of hydrogen ions that are filtered but not reabsorbed by the renal tubules?

    <p>Excreted via urine</p> Signup and view all the answers

    Which ions are primarily secreted in the distal convoluted tubule?

    <p>Potassium and hydrogen</p> Signup and view all the answers

    How much of the filtered load of urea is typically reabsorbed in the proximal convoluted tubule?

    <p>50%</p> Signup and view all the answers

    Which statement best describes the concentration mechanism of urea in the renal tubule?

    <p>Urea concentration increases as water is reabsorbed</p> Signup and view all the answers

    What factor is NOT a contributor to the secretion of hydrogen ions in renal tubules?

    <p>Hydrostatic pressure in capillaries</p> Signup and view all the answers

    Which process is primarily responsible for the facultative reabsorption of water in the nephron?

    <p>Antidiuretic hormone action</p> Signup and view all the answers

    Study Notes

    Renal Module Information

    • Course code: IMP-07-20318
    • Phase: I
    • Year/semester: 2nd year/Semester 3
    • Credit hours: Not specified
    • Course duration: 5 weeks

    Lecture 4: Renal Tubular Reabsorption and Secretion

    • Intended learning outcomes (ILOs):
      • Describe the function of various parts of renal tubules (tubular reabsorption and secretion).
      • Identify tubular reabsorption and secretion and its significance.

    Tubular Functions

    • Reabsorption: The process of reclaiming materials from the filtrate and returning them to the blood.
    • Secretion: The process of removing substances from the blood and adding them to the filtrate.

    Tubular Reabsorption

    • Goal: To maintain proper composition and volume of internal fluid environment and its concentration in plasma.
    • Mechanisms:
      • Paracellular: Occurs between cells (water).
      • Transcellular: Takes place through cells (most substances).
        • Substance must cross five barriers: luminal, cytosol, basolateral cell membrane, interstitial fluid, and capillary wall.
    • Mechanisms of Tubular Reabsorption:
      • Passive diffusion: For H2O, Cl, urea
      • Active transport: For various substances, including:
        • Primary Active transport: Na+, K+, Ca2+, H+
        • Secondary Active transport: Glucose, amino acids

    Sodium Reabsorption

    • Mechanism:
      • Na+ diffuses into the cell
      • Na+-K+ ATPase pumps Na+ out of the cell into the interstitial fluid.
      • This creates a concentration gradient allowing entry of Na+, glucose, and amino acids.

    Glucose Reabsorption

    • Entire filtered glucose is reabsorbed
    • Reabsorption is via sodium-dependent secondary active transport
    • Threshold glucose level for excretion in urine: 180 mg/dL

    K Transport

    • PCT reabsorbs 65% of K (obligatory)
    • Loop of Henle reabsorbs 25-30% of K (obligatory)
    • Mechanism of K+ transport: Active transport (both primary and secondary)
      • Primary active transport in PCT
      • Secondary active transport in the Loop

    Phosphate and Calcium Reabsorption

    • Kidneys regulate plasma levels of phosphate and calcium.
    • Renal threshold = normal plasma concentration
    • Phosphate Reabsorption:
      • Active reabsorption through co-transport with Na+
      • Controlled by PTH, which inhibits phosphate reabsorption in the PCT.
    • Calcium Reabsorption:
      • Secondary active transport or passive reabsorption
      • Both PCT and DCT reabsorb calcium
      • Controlled by PTH, which stimulates calcium reabsorption in the PCT.

    Passive Reabsorption

    • Substances passively reabsorbed and dependent on active Na+ reabsorption include: Cl−, H2O, urea.
    • Cl- Reabsorption:
      • Passive through tight junctions in the PCT.
      • In other parts of the tubule, secondary active transport.
      • Mechanism includes electrical and concentration gradients.
    • H2O Reabsorption:
      • Passive, by osmosis, throughout the nephron.
      • 80% obligatory (in PCT and Loop of Henle).
      • 20% facultative (variable).
    • Urea Reabsorption:
      • Passive, linked to Na+ reabsorption and H2O removal.
      • 65% of H2O removal in the PCT increases urea concentration.
      • Only about 50% of filtered urea is reabsorbed.

    Tubular Secretion

    • Removal of substances from the blood and addition to filtrate
    • Substances include:
      • Hydrogen ions (H+)
      • Potassium (K+)
      • Organic compounds

    H+ Secretion

    • All H+ excreted in urine is through secretion.
    • Mechanism: active transport using primary and secondary transport mechanisms.
    • PCT: actively secreted through counter transport mechanisms with sodium
    • DCT and collecting ducts: active transport (pump mechanism).
    • Rate is directly proportional to plasma [H+].

    Control of H+ Secretion

    • H+ secretion is directly proportional to plasma [H+](or PCO2).

    K+ Transport

    • Both reabsorption and secretion occur via different transport systems.
    • K+ secretion is in the distal and collecting tubules, accomplished via primary active transport.

    Summary of Tubular Reabsorption (excluding sodium)

    • Proximal tubule: Active: Glucose, amino acids, K+, phosphate, calcium; Passive: Cl-, H2O, urea.
    • Loop of Henle: Active: Cl−, K+; Passive: H2O.
    • Distal and collecting tubules: Active: Variable; Passive: Variable.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Renal Tubular Reabsorption and Secretion PDF

    Description

    This quiz covers key concepts related to tubular reabsorption in renal physiology, including mechanisms of phosphate and calcium reabsorption, the role of hormones, and specifics of tubular transport. Test your understanding of how the kidneys manage substances in the body through the nephron.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser