The Urinary System Functions
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Questions and Answers

What is the primary function of the kidney in regulating blood ionic composition?

  • Elimination of ions when found in excess
  • Reabsorption of ions when the body needs them (correct)
  • Secretion of ions when the body needs them
  • Regulation of blood pH via secretion of H+

    • How does the kidney regulate blood pH?

  • Via regulation of electrolyte concentrations
  • Via secretion of H+ and reabsorption of HCO3- (correct)
  • Via conserving water when there is low blood volume
  • Via secretion of HCO3- and reabsorption of H+

    • What is the primary mechanism of calcium reabsorption in the kidney?

  • Release of calcitriol (active form of Vit.D) (correct)
  • Regulation of blood osmolarity
  • Reabsorption of ions when the body needs them
  • Regulation of blood volume

    • What is the role of the kidney in regulating blood potassium levels?

    <p>Reabsorption of potassium ions when the body needs them</p> Signup and view all the answers

    How does the kidney regulate blood volume?

    <p>All of the above</p> Signup and view all the answers

    What is the primary function of Na+/K+ ATPase pumps in the renal tubular cells?

    <p>To maintain the low intracellular sodium levels in the tubular cells</p> Signup and view all the answers

    Which of the following transport mechanisms is responsible for the reabsorption of water in the renal tubules?

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

    What is the primary function of the renal handling of potassium?

    <p>To regulate the extracellular potassium levels</p> Signup and view all the answers

    Which segment of the renal tubule is primarily responsible for the reabsorption of calcium?

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

    What is the primary mechanism by which the kidneys regulate the acid-base balance of the body?

    <p>Regulation of bicarbonate reabsorption and hydrogen ion secretion</p> Signup and view all the answers

    Study Notes

    Components of the Urinary System

    • The urinary system consists of 2 kidneys (right and left), 2 ureters (right and left), urinary bladder, and urethra.

    Kidney Functions

    • Regulate blood ionic composition by:
      • Reabsorbing Na+, K+, Ca+2, Cl-, and phosphate ions when needed
      • Eliminating excess ions through secretion
    • Regulate blood pH by:
      • Secreting H+ ions
      • Reabsorbing HCO3-
    • Regulate blood osmolarity by controlling electrolyte concentrations
    • Regulate blood glucose levels
    • Regulate blood volume by:
      • Conserving water when blood volume is low
      • Eliminating water when blood volume is high
    • Regulate blood pressure by:
      • Secreting renin to activate the Renin-Angiotensin-Aldosterone System (RAAS)
      • Adjusting renal resistance
    • Produce erythropoietin for red blood cell synthesis and calcitriol for calcium absorption
    • Remove wastes and foreign substances from the body### Internal Anatomy of the Kidney
    • The renal cortex and renal pyramids form the functional portion of the kidney
    • The nephron is the functional unit of the kidney, located in the renal cortex and renal pyramids, and consists of a vascular component and a tubular component
    • Each kidney contains approximately 1 million nephrons

    Blood and Nerve Supply of the Kidney

    • The renal artery supplies the kidney with oxygen and nutrients, and filters blood
    • The renal vein carries filtered blood back to the circulation
    • At rest, the kidneys receive 25% of cardiac output (1250 ml/min) via the renal arteries
    • The nerve supply to the kidney is derived from the renal plexus (sympathetic division of the autonomic nervous system), which regulates blood flow and renal resistance

    Components of the Nephron

    • Vascular component:
      • Afferent arteriole: carries blood to the glomerulus and controls blood flow
      • Glomerulus: a ball-like tuft of capillaries that filters water and solutes from the blood
      • Efferent arteriole: transports blood from the glomerulus and controls the amount of blood leaving the glomerulus
      • Peritubular capillaries: surround the tubular part of the nephron and are involved in tubular changes
      • Vasa recta: surrounds the loop of Henle
    • Tubular component:
      • Bowman's/glomerular capsule: collects glomerular filtrate
      • Proximal convoluted tubule (PCT): filters fluid from the Bowman's capsule, and is the site of most reabsorption
      • Loop of Henle: a U-shaped structure that reabsorbs and secretes solutes
      • Distal convoluted tubule (DCT): continues reabsorption and secretion of solutes
      • Collecting ducts: drain urine to the renal pelvis and then to the ureter

    Types of Nephrons

    • Cortical nephrons: 80-85% of nephrons, with a short extension of the loop of Henle
    • Juxtamedullary nephrons: 15-20% of nephrons, with a long extension of the loop of Henle, important for maintaining osmolarity of the urine

    Juxtaglomerular Apparatus (JGA)

    • Structure formed where the afferent arteriole makes contact with the ascending limb of the loop of Henle
    • Helps regulate blood pressure and the rate of blood filtration by the kidneys
    • Two types of contacted cells:
      • Macula densa: senses Na+ concentration in the filtrate and provides feedback to the afferent and efferent arterioles
      • Juxtaglomerular cells: modified smooth muscle cells that secrete renin

    Glomerular Filtration

    • The first step in the formation of urine
    • Filtration of a protein-free plasma from the glomerulus into the Bowman's capsule
    • Glomerular filtrate is produced at a rate of 125 ml/min
    • Structure of the renal corpuscle:
      • Glomerular capsule: consists of visceral and parietal layers
      • Filtration membrane: consists of fenestrated endothelium, basal lamina, and slit membrane
    • Glomerular filtration occurs by the interaction of forces:
      • Glomerular capillary pressure (favoring filtration)
      • Glomerular capillary oncotic pressure (opposing filtration)
      • Bowman's capsule hydrostatic pressure (opposing filtration)
      • Net filtration pressure (favoring filtration)

    Regulation of Glomerular Filtration Rate (GFR)

    • Three principal mechanisms:
      • Renal autoregulation: kidneys regulate GFR through factors within the organs
      • Neural regulation: sympathetic nerve fibers supply the afferent and efferent arterioles
      • Hormonal regulation: two hormones regulate GFR, atrial natriuretic peptide (ANP) and angiotensin II

    Tubular Reabsorption and Secretion

    • The second and third processes in the formation of urine
    • Filtered substances are transferred from the tubular lumen to the peritubular capillaries
    • Highly selective and variable process
    • Reabsorption rates are high, with 124 of 125 ml of filtered fluid per minute being reabsorbed
    • Routes:
      • Paracellular reabsorption
      • Transcellular reabsorption

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    Description

    This quiz covers the components of the urinary system, including the kidneys, ureters, bladder, and urethra. It also explores the functions of the kidneys, including regulating blood ionic composition, blood pH, and blood osmolarity.

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