Urinary System Overview
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Questions and Answers

What is the main function of the urinary system in regulating blood volume and pressure?

  • It increases blood pressure by removing excess nutrients
  • It regulates blood volume and pressure through the removal of excess fluids (correct)
  • It helps to regulate electrolytes and body pH
  • It promotes water retention by removing excess hormones

    • What is the role of erythropoietin in the body?

  • It helps to regulate blood volume and pressure
  • It regulates calcium absorption
  • It regulates electrolytes and body pH
  • It regulates erythropoiesis (correct)

    • What is the function of the glomeruli in the kidney?

  • Filtration (correct)
  • Selective re-absorption and excretion
  • Regulation of electrolytes and body pH
  • Calcium absorption

    • What is the function of the tubular system in the kidney?

    <p>Selective re-absorption and excretion</p> Signup and view all the answers

    What is the outer zone of the kidney that contains renal corpuscles and convoluted tubules?

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

    What is the structure that covers the cortex and is continuous at the hilum with supporting tissue?

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

    What is the result of dehydration on blood pressure?

    <p>It decreases blood pressure</p> Signup and view all the answers

    What is the effect of excessive oxygen on erythropoietin production?

    <p>It inhibits erythropoietin production</p> Signup and view all the answers

    Where does the afferent arteriole enter and the efferent arteriole leave in the renal corpuscle?

    <p>Vascular pole</p> Signup and view all the answers

    What type of epithelium supports the parietal layer of the glomerular capsule?

    <p>Simple squamous epithelium</p> Signup and view all the answers

    What is the function of the podocytes' pedicels?

    <p>To embrace a portion of one glomerular capillary</p> Signup and view all the answers

    What is the purpose of the slit diaphragms in the filtration slits?

    <p>To facilitate ultrafiltration</p> Signup and view all the answers

    What is characteristic of the epithelium lining the proximal convoluted tubule?

    <p>Simple cuboidal epithelium</p> Signup and view all the answers

    What is the function of the apical microvilli in the lining cells of the proximal convoluted tubule?

    <p>To increase the surface area for absorption</p> Signup and view all the answers

    What is the name of the protein important for the structure and function of the slit diaphragms?

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

    What is the name of the process that occurs in the filtration slits?

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

    What percentage of solutes and water in the initial filtrate are resorbed by the PCT under most conditions in humans?

    <p>80%</p> Signup and view all the answers

    Which type of epithelium lines the thin limb of the loop of Henle?

    <p>Simple squamous epithelium</p> Signup and view all the answers

    What is the primary function of the ascending thick limb of the loop of Henle?

    <p>Active transport of salt from apical to basal surfaces</p> Signup and view all the answers

    Which hormone regulates Na+ for K+ exchange in the DCT?

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

    What is the characteristic of the plasma membranes of the cells in the ascending thick limb of the loop of Henle?

    <p>Impermeable to water and small solutes</p> Signup and view all the answers

    What is the location of the hormonally regulated Na+ for K+ exchange?

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

    What is the characteristic of the cells in the DCT?

    <p>Do not stain as darkly as PCT cells in LM preparations</p> Signup and view all the answers

    What is the characteristic of the epithelium in the collecting tubules and ducts?

    <p>Gradually changes from simple cuboidal to simple columnar epithelium</p> Signup and view all the answers

    What is the composition of the muscular layer of the bladder wall?

    <p>Inner and outer longitudinal layers and a middle circular layer</p> Signup and view all the answers

    What is the approximate capacity of a moderately full bladder?

    <p>500 ml of urine</p> Signup and view all the answers

    What is the shape of the bladder when it is empty?

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

    What is the outermost layer of the bladder wall?

    <p>Fibrous adventitia</p> Signup and view all the answers

    What is the orientation of the smooth muscle cells in the middle layer of the muscularis externa?

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

    What happens to the rugae of the bladder as it expands?

    <p>They disappear</p> Signup and view all the answers

    What is the primary function of the peritubular capillaries?

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

    What is the effect of vasopressin on the epithelia of the collecting tubules and ducts in the medulla?

    <p>It increases their water permeability</p> Signup and view all the answers

    What is the location of the juxtaglomerular apparatus (JG apparatus)?

    <p>In the region of the nephron where the ascending limb of the loop of Henle and the adjacent afferent and efferent arterioles are positioned next to each other</p> Signup and view all the answers

    What is the function of the macula densa cells?

    <p>To monitor the osmotic concentration in the tubule contents</p> Signup and view all the answers

    What type of epithelium lines the mucosa of the ureters?

    <p>Transitional epithelium</p> Signup and view all the answers

    What is the function of the juxtaglomerular cells (JG cells)?

    <p>To secrete renin into the bloodstream</p> Signup and view all the answers

    What is the result of increased release of renin by the JG cells?

    <p>Conversion of angiotensinogen into angiotensin II</p> Signup and view all the answers

    What is the purpose of the peritubular capillaries clinging closely to adjacent renal tubules?

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

    Study Notes

    Overview of the Urinary System

    • The main components of the urinary system are: kidneys, ureters, urinary bladder, and urethra.
    • The urinary system has several functions, including:
      • Removal of metabolic wastes and toxins
      • Elimination of excess nutrients and hormones
      • Regulation of blood volume and pressure
      • Regulation of electrolytes and body pH
      • Regulation of erythropoiesis
      • Calcium absorption
      • Control of the concentration of most compounds in the extracellular fluid

    Kidney Structure

    • The kidney is formed of multiple lobes, each lobe made up of a renal pyramid.
    • The kidney has a fibrous capsule that covers the cortex and is continuous with the supporting tissue at the hilum.
    • The renal cortex extends between the medullary pyramids and contains renal corpuscles and convoluted tubules.
    • The renal medulla contains multiple medullary pyramids separated by regions of cortex.
    • Millions of nephrons are packed into each kidney.
    • The cortex consists of convoluted tubules (distal and proximal) and renal corpuscles (glomeruli).

    Nephron Structure

    • Each renal corpuscle has a vascular pole and a urinary or tubular pole.
    • The vascular pole is where the afferent arteriole enters and the efferent arteriole leaves.
    • The urinary or tubular pole is where the proximal convoluted tubule begins.
    • The parietal layer of the glomerular capsule consists of a simple squamous epithelium supported by a basal lamina and a thin layer of reticular fibers.
    • The cells of this layer, called podocytes, have a cell body and several primary processes that give rise to numerous secondary processes or pedicels.
    • The pedicels interdigitate, defining elongated spaces 30-40 nm wide, called filtration slits.
    • Spanning adjacent processes is a thin semipermeable diaphragm of uniform thickness.

    Proximal Convoluted Tubule (PCT)

    • The PCT is lined by simple cuboidal epithelium.
    • The lining cells have numerous long apical microvilli, basal infoldings, and lateral canaliculi.
    • The PCT is the site of most of the reabsorption of useful solutes and water from the filtrate.
    • Approximately 80% of solutes and water in the initial filtrate are resorbed by the PCT.

    Loop of Henle

    • The loop of Henle is composed of three parts: descending thick limb, thin limb, and ascending thick limb.
    • The descending thick limb is lined by simple cuboidal epithelium.
    • The thin limb is lined by simple squamous epithelium.
    • The ascending thick limb is lined by simple cuboidal epithelium.
    • The loop of Henle establishes and maintains a high salt concentration in the interstitial fluid of the deep medulla.

    Distal Convoluted Tubule (DCT)

    • The DCT is lined by simple cuboidal epithelium.
    • The DCT is the location of hormonally regulated (by aldosterone) Na+ for K+ exchange.
    • The DCT is responsible for further reabsorption of solutes and water.

    Collecting Tubules and Collecting Ducts

    • Collecting tubules and ducts are lined by simple epithelia that gradually change from flattened simple cuboidal epithelium to simple columnar epithelium.
    • The epithelia of the collecting tubules and ducts in the medulla increase their water permeability in response to vasopressin (antidiuretic hormone).

    Peritubular Capillaries

    • The peritubular capillaries arise from the efferent arterioles draining the glomeruli.
    • These capillaries cling closely to adjacent renal tubules and empty into nearby venules.
    • They are low-pressure, porous capillaries that readily absorb solutes and water from the tubule cells.

    Juxtaglomerular Apparatus (JG Apparatus)

    • The JG apparatus is located in the region of the nephron where the ascending limb of the loop of Henle and the adjacent afferent and efferent arterioles are positioned next to each other.
    • The macula densa consists of cells of the ascending thick limb of the loop of Henle (DCT type cells) that are next to the efferent arteriole and are much taller than adjacent DCT cells.
    • The JG cells are smooth muscle cells in the tunica media of the afferent arteriole that have become modified into secretory epithelial-like cells.

    Ureters

    • The ureters are muscular tubes that transport urine from the kidneys to the urinary bladder.
    • The mucosa consists of a transitional epithelium underlain by a lamina propria and a muscularis externa.
    • The muscularis externa consists of two or three layers of smooth muscle.

    Urinary Bladder

    • The bladder wall has three layers: a mucosa containing transitional epithelium, a thick muscular layer, and a fibrous adventitia.
    • The muscular layer, called the detrusor muscle, consists of intermingled smooth muscle fibers arranged in inner and outer longitudinal layers and a middle circular layer.
    • The bladder is very distensible and uniquely suited for its function of urine storage.

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    A quiz about the main components and functions of the urinary system, including kidney function, waste removal, and electrolyte regulation.

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