Anatomy of the Kidney
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Questions and Answers

What is the primary function of the microvilli in the Proximal Convoluted Tubule (PCT) cells?

  • To enhance the folding of the basolateral membrane
  • To facilitate the exocytosis of waste molecules
  • To regulate the tight junctions between adjacent cells
  • To increase the surface area for passive transport (correct)

    • What is the role of the filtration slits in the glomerulus?

  • To store waste molecules before excretion
  • To facilitate the passage of substances into the capsular space (correct)
  • To filter out large molecules from the bloodstream
  • To regulate the pressure of the glomerulus

    • What is the main function of the basement membrane in the glomerulus?

  • To facilitate the passage of substances through the filtration slits (correct)
  • To provide mechanical support to the podocytes
  • To regulate the flow of substances into the capsular space
  • To filter out small molecules from the bloodstream

    • What is the primary function of the mitochondria in the PCT cells?

    <p>To generate ATP for active transport processes</p> Signup and view all the answers

    What is the main function of the tight junctions between adjacent PCT cells?

    <p>To limit the escape of large molecules from the tubular lumen into the interstitial space</p> Signup and view all the answers

    What is the main characteristic of the PCT cells in terms of permeability?

    <p>They are highly permeable to water and many solutes</p> Signup and view all the answers

    What is the function of the podocytes in the glomerulus?

    <p>To form the filtration membrane along with the capillary endothelium and basement membrane</p> Signup and view all the answers

    What is the primary function of the fenestrations in the glomerulus?

    <p>To allow the passage of substances through the filtration membrane</p> Signup and view all the answers

    Which structure is responsible for collecting urine from the renal pyramids before it is conveyed to the ureter?

    <p>Renal pelvis</p> Signup and view all the answers

    What is the primary role of the peritubular capillaries in the kidney?

    <p>Absorbing water and solutes from tubule cells</p> Signup and view all the answers

    Which structure carries blood away from the glomerulus?

    <p>Efferent arteriole</p> Signup and view all the answers

    Which pathway does blood follow after leaving the vasa recta?

    <p>Interlobular veins → arcuate veins → interlobar veins → renal vein</p> Signup and view all the answers

    What is the function of the renal columns?

    <p>Providing a route for blood vessels and nerves to and from the cortex</p> Signup and view all the answers

    Why do the renal pyramids appear striated?

    <p>Because they contain parallel bundles of ducts carrying urine</p> Signup and view all the answers

    Which blood vessels directly feed into the glomerulus?

    <p>Afferent arterioles</p> Signup and view all the answers

    What is the sequence of urine flow from the renal pyramids to the bladder?

    <p>Minor calyx → major calyx → renal pelvis</p> Signup and view all the answers

    Which cells of the Juxtaglomerular Apparatus serve as baroreceptors sensitive to blood pressure?

    <p>Granular cells</p> Signup and view all the answers

    What structures deliver urine through papillae into minor calyces?

    <p>Collecting ducts</p> Signup and view all the answers

    Which cells in the JGA possess secretory granules containing renin?

    <p>Granular cells</p> Signup and view all the answers

    What is the primary function of macula densa cells in the JGA?

    <p>Monitor and respond to changes in NaCl concentration</p> Signup and view all the answers

    What is the main characteristic of principal cells in the late distal convoluted tubule and cortical collecting duct?

    <p>Have few microvilli and basolateral folds</p> Signup and view all the answers

    Which cell type in the JGA acts as mechanoreceptors sensing blood pressure in the afferent arterioles?

    <p>Granular cells</p> Signup and view all the answers

    Which cells are interconnected by gap junctions in the JGA?

    <p>Extraglomerular mesangial cells</p> Signup and view all the answers

    Where is the juxtaglomerular apparatus located in relation to the afferent and efferent arterioles?

    <p>Between the thick ascending loop of Henle and the afferent and efferent arterioles</p> Signup and view all the answers

    Which is a function of intercalated cells in the kidneys?

    <p>Secretion of hydrogen ions</p> Signup and view all the answers

    What is the primary role of the myogenic mechanism in renal autoregulation?

    <p>Modifying the contraction of vascular smooth muscle cells in response to changes in blood pressure</p> Signup and view all the answers

    What is a key characteristic of principal cells in the medullary collecting duct?

    <p>Relatively smooth membranes</p> Signup and view all the answers

    What happens to the afferent arteriole when blood pressure decreases?

    <p>It dilates to increase blood flow</p> Signup and view all the answers

    What primarily regulates the permeability of principal cells to water and solutes?

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

    Which of the following best describes the effect of high blood pressure on the afferent arteriole?

    <p>The vessel constricts to reduce blood flow</p> Signup and view all the answers

    In urine formation, what remains in the blood plasma after filtration?

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

    What is the main factor that the tubuloglomerular mechanism responds to?

    <p>The osmolarity and/or the rate of filtrate flow in the terminal portion of the ascending loop of Henle</p> Signup and view all the answers

    Which of the following statements about urine formation is correct?

    <p>It involves filtration, reabsorption, and secretion.</p> Signup and view all the answers

    Which cells are sensitive to filtrate NaCl osmolarity in the tubuloglomerular mechanism?

    <p>Macula densa cells</p> Signup and view all the answers

    Where do large quantities of water and solutes initially pass into during urine formation?

    <p>Glomerular capsule</p> Signup and view all the answers

    How does the myogenic mechanism help to regulate glomerular blood flow?

    <p>By causing reflexive vasoconstriction or dilation of the afferent arteriole in response to blood pressure changes</p> Signup and view all the answers

    Which structural feature is NOT common between principal cells and intercalated cells?

    <p>Smooth luminal membrane</p> Signup and view all the answers

    What percentage of the filtrate ultimately becomes urine?

    <p>Less than 1%</p> Signup and view all the answers

    Study Notes

    The Juxtaglomerular Apparatus (JGA)

    • Located at the initial portion of the distal tubule where it passes between the afferent and efferent arterioles.
    • Forms a monitoring structure that includes cells from arterioles and the thick ascending loop of Henle.

    Cell Populations of the JGA

    • Juxtaglomerular (JG) Cells: Modified smooth muscle cells in the afferent arteriole.
      • Act as baroreceptors for blood pressure detection.
      • Contain secretory granules with renin.
    • Macula Densa Cells: Located in the thick ascending loop.
      • Function as chemoreceptors monitoring NaCl levels in the filtrate.
    • Extraglomerular Mesangial Cells: Interconnected and may relay signals between the macula densa and granular cells.

    Late Distal Convoluted Tubule (DCT) and Cortical Collecting Duct

    • Collecting ducts merge to deliver urine into minor calyces.
    • Two cell types:
      • Principal Cells: Fewer microvilli, respond to hormones regulating water and solute permeability.
      • Intercalated Cells: Secrete hydrogen ions for acid-base balance during increased body acidity.

    Regulation of Glomerular Filtration Rate (GFR)

    • Myogenic Mechanism: Smooth muscle cells in the afferent arterioles contract or relax in response to blood pressure changes.

      • High blood pressure results in vasoconstriction; low blood pressure causes dilation.

    • Tubuloglomerular Feedback: Involves sensitivity of macula densa cells to filtrate NaCl osmolarity and flow rates.

    Filtration Mechanism

    • Filtration membrane consists of capillary endothelium, basement membrane, and podocytes.
    • Filtration occurs through fenestrations, basement membranes, and filtration slits, allowing selective passage of substances into the capsular space.

    Proximal Convoluted Tubule (PCT)

    • Composed of brush border cells with numerous microvilli for increased reabsorption surface area.
    • Tight junctions allow water passage but restrict large molecules.
    • Basolateral membrane features integral proteins for transport, supported by abundant mitochondria for ATP generation.

    Renal Medulla

    • Contains renal pyramids that drain into minor calyces.
    • Renal columns are extensions of the cortex allowing for blood vessels and nerve passage.

    Renal Pelvis

    • Funnel-shaped structure within the renal sinus collecting urine from pyramids and transporting it to the ureter.

    Nephron Structure

    • Comprised of specialized tubular structures along with associated blood vessels.
      • Blood flow: Renal artery → segmental arteries → lobar arteries → interlobar arteries → arcuate arteries → interlobular arteries → afferent arterioles → glomerulus.
      • Efferent arterioles drain the glomeruli into peritubular capillaries and vasa recta.

    Urine Formation Mechanisms

    • Kidneys filter the body’s plasma volume approximately 60 times daily.
    • Filtrate: Comprises everything in blood plasma minus proteins.
    • Urine: Less than 1% of total filtrate, primarily containing metabolic wastes and surplus substances.
    • Three key processes in urine formation:
      • Filtration
      • Reabsorption
      • Secretion

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    Description

    This quiz covers the structure and function of the kidney, including the renal medulla, pyramids, and calyxes.

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