Urinary System
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Questions and Answers

What is the function of the filtration slit diaphragms in the glomerular filtration barrier?

  • To regulate the pressure of the blood flow
  • To produce the filtrate in the corpuscle
  • To filter small proteins from the blood plasma
  • To separate the podocyte pedicels from the capillary endothelium (correct)

    • What is the primary function of the podocytes in the renal corpuscle?

  • To filter blood in the glomerular capillaries (correct)
  • To reabsorb nutrients from the filtrate
  • To regulate blood pressure through vasodilation
  • To secrete substances into the proximal convoluted tubule

    • What is the major component of the glomerular filter formed by?

  • The GBM
  • The podocyte pedicels
  • The fenestrated capillary endothelium
  • Fusion of the basal laminae of a podocyte and a capillary endothelial cell (correct)

    • What is the structure that drains into an efferent arteriole?

    <p>Mass of capillary loops</p> Signup and view all the answers

    What is the mechanism of filtrate production in the corpuscle?

    <p>Blood plasma is forced under pressure through the capillary fenestrations</p> Signup and view all the answers

    What is the term for the secondary processes of the podocytes?

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

    What is the shape of the cells that form the simple squamous layer of Bowman's capsule?

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

    What is the function of the capsular space in the glomerulus?

    <p>To receive the filtrate</p> Signup and view all the answers

    What is the type of epithelium that forms the proximal convoluted tubule?

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

    What is the structure that surrounds the glomerular capillaries?

    <p>Bowman's capsule</p> Signup and view all the answers

    What is the region of the renal corpuscle where the afferent arteriole enters and the efferent arteriole leaves?

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

    What is the type of microscopy used to show the distinctive appearance of podocytes and their pedicel processes?

    <p>Scanning electron microscopy</p> Signup and view all the answers

    What is the function of the peritubular capillaries?

    <p>To reabsorb nutrients from the filtrate</p> Signup and view all the answers

    What is the type of epithelium that supports the basal lamina in the outer parietal layer of the glomerular capsule?

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

    What is the term for the process of producing filtrate in the corpuscle?

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

    What is the structure that branches from the arcuate arteries and radiates out through the cortex?

    <p>Small interlobular artery</p> Signup and view all the answers

    What is a common cause of inflammation in the urinary tract, besides urinary tract infections?

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

    What is the term for the unique stratified epithelium lining the ureter?

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

    What is the function of the muscularis in the ureter?

    <p>To move urine through the ureter by regular waves of peristalsis</p> Signup and view all the answers

    What is the term for the benign changes that can occur in the urothelium as a result of chronic cystitis?

    <p>Both A and B</p> Signup and view all the answers

    What is the type of carcinoma that usually arises from unstable urothelium?

    <p>Transitional cell carcinoma</p> Signup and view all the answers

    What is the function of the urethra?

    <p>To carry urine from the bladder to the exterior</p> Signup and view all the answers

    What is the characteristic appearance of the urethral mucosa in cross section?

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

    In men, where do the ducts for sperm transport during ejaculation join the urethra?

    <p>Prostate gland</p> Signup and view all the answers

    What is the primary function of the slit diaphragms in the glomerular filtration barrier?

    <p>To maintain the integrity of the filtration slit pores</p> Signup and view all the answers

    What is the width of the filtration slit pores between the interdigitating pedicels?

    <p>25-30 nm</p> Signup and view all the answers

    What type of proteins are involved in the formation of the slit diaphragms?

    <p>Nephrins, proteoglycans, and glycoproteins</p> Signup and view all the answers

    What is the primary component of the glomerular basement membrane?

    <p>Fused basal laminae from capillary and podocyte</p> Signup and view all the answers

    What is the approximate thickness of the glomerular basement membrane?

    <p>300-360 nm</p> Signup and view all the answers

    What is the function of the glomerular basement membrane in the filtration barrier?

    <p>To restrict the passage of proteins larger than 70 kDa</p> Signup and view all the answers

    What is the net charge of the surface of the slit diaphragm?

    <p>Negatively charged</p> Signup and view all the answers

    What is the fate of smaller proteins that are filtered from plasma?

    <p>They are degraded and reabsorbed in the proximal tubule</p> Signup and view all the answers

    What is the main function of the collecting system in the nephron?

    <p>To reabsorb more water if needed by the body</p> Signup and view all the answers

    What type of epithelium is found in the collecting ducts in the cortical medullary rays?

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

    What is the average diameter of the collecting ducts in the cortical medullary rays?

    <p>40 μm</p> Signup and view all the answers

    What happens to the collecting ducts as they approach the apex of each renal pyramid?

    <p>They merge to form larger collecting ducts</p> Signup and view all the answers

    What is the function of the JG cells in the nephron?

    <p>To regulate blood pressure by secreting renin</p> Signup and view all the answers

    What is the shape of the epithelial cells in the collecting ducts of the medulla?

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

    What is the diameter of the collecting ducts in the medulla?

    <p>200 μm</p> Signup and view all the answers

    What is the function of the connecting tubule in the nephron?

    <p>To carry the filtrate into a collecting system</p> Signup and view all the answers

    What is the location of the proximal convoluted tubule in the kidney?

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

    What is the structure that connects the proximal straight tubule to the thin descending limb of the loop of Henle?

    <p>Loop of Henle</p> Signup and view all the answers

    What is the blood vessel that converges into small stellate veins in the kidney?

    <p>Peritubular capillary</p> Signup and view all the answers

    What is the number of functional units called nephrons in each kidney?

    <p>1-4 million</p> Signup and view all the answers

    What is the location of the thin ascending limb of the loop of Henle in the kidney?

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

    What is the structure that originates in the cortex of the kidney?

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

    What is the fate of the blood that leaves the kidney?

    <p>It enters the veins</p> Signup and view all the answers

    What is the term for the diseases involving the renal corpuscles?

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

    What is the region where the connecting tubules converge?

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

    Where does the afferent arteriole enter and the efferent arteriole leave?

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

    What is the characteristic of juxtamedullary nephrons?

    <p>Lie close to the medulla</p> Signup and view all the answers

    What is the primary function of the podocytes and capillary endothelial cells?

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

    What is the result of polycystic kidney disease?

    <p>Loss of renal function and gross kidney enlargement</p> Signup and view all the answers

    What is the type of epithelium that continues and forms the proximal convoluted tubule?

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

    What is the structure that drains into an efferent arteriole?

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

    What is the structure that covers the cortex and hilum?

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

    What is the term for the extensions of the podocyte cell body that curve around the glomerular capillary?

    <p>Primary processes</p> Signup and view all the answers

    What is the characteristic of the kidney vasculature?

    <p>Large and well-organized</p> Signup and view all the answers

    How do the segmental arteries arise?

    <p>From the renal artery</p> Signup and view all the answers

    What is the structure that forms a large, diffuse network throughout the cortex?

    <p>Peritubular capillary</p> Signup and view all the answers

    What is the shape of the epithelial cells that form the visceral layer of the glomerular capsule?

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

    What is the structure that drains into a minor calyx?

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

    What is the location of the cortical nephrons?

    <p>Almost completely in the cortex</p> Signup and view all the answers

    What is the term for the small extensions of the primary processes that interdigitate with each other?

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

    What is the primary function of the microvilli in the proximal convoluted tubule?

    <p>To facilitate reabsorption of nutrients and ions</p> Signup and view all the answers

    What is the characteristic appearance of the lumen in the proximal convoluted tubule in routine histologic preparations?

    <p>A fuzzy, filled appearance</p> Signup and view all the answers

    What is the purpose of the vesicles in the apical cytoplasm of proximal tubular cells?

    <p>To contain reabsorbed proteins for degradation</p> Signup and view all the answers

    What is the function of the mitochondria concentrated along the basal invaginations in proximal tubular cells?

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

    What is the significance of the interdigitations of the lateral membranes in proximal tubular cells?

    <p>To make the discrete limits between cells difficult to see</p> Signup and view all the answers

    What is the function of the peritubular capillaries in the proximal convoluted tubule?

    <p>To remove reabsorbed proteins from the circulation</p> Signup and view all the answers

    What is the characteristic structure of the proximal convoluted tubule in the cortex?

    <p>A sparse, surrounding connective tissue</p> Signup and view all the answers

    What is the function of the transmembrane proteins in the proximal convoluted tubule?

    <p>To mediate tubular reabsorption and secretion</p> Signup and view all the answers

    What is the primary role of the urinary system?

    <p>To ensure optimal properties of the blood</p> Signup and view all the answers

    What is the function of the kidneys in regards to blood pressure regulation?

    <p>To regulate blood pressure through the secretion of renin</p> Signup and view all the answers

    What is the role of the kidneys in regards to erythrocyte production?

    <p>To stimulate erythrocyte production through the production of erythropoietin</p> Signup and view all the answers

    What is the role of the kidneys in regards to vitamin D?

    <p>To convert vitamin D to its active form</p> Signup and view all the answers

    What is the role of the kidneys during starvation or periods of prolonged fasting?

    <p>To produce glucose through gluconeogenesis from amino acids</p> Signup and view all the answers

    What is the primary function of the kidneys in regards to electrolyte balance?

    <p>To regulate electrolyte balance through the excretion of excess electrolytes</p> Signup and view all the answers

    What is the role of the kidneys in regards to bioactive substances?

    <p>To regulate bioactive substances through the excretion of excess bioactive substances</p> Signup and view all the answers

    What is the primary function of the kidneys in regards to acid-base balance?

    <p>To regulate acid-base balance through the excretion of excess hydrogen ions</p> Signup and view all the answers

    What is the mechanism by which polyanionic GAGs in the glomerular membrane restrict filtration?

    <p>Electrostatic repulsion</p> Signup and view all the answers

    What is the approximate percentage of blood plasma that is filtered into the capsular space in a normal glomerulus?

    <p>20%</p> Signup and view all the answers

    What is the function of the internal or visceral layer of the glomerular capsule?

    <p>To envelop the glomerular capillaries</p> Signup and view all the answers

    What is the composition of the initial glomerular filtrate similar to?

    <p>Blood plasma</p> Signup and view all the answers

    What is the function of the fenestrations in the capillary endothelium?

    <p>To block blood cells and platelets</p> Signup and view all the answers

    What is the location of the capsular space?

    <p>Between the two capsular layers</p> Signup and view all the answers

    What is the function of the thick, combined basal laminae?

    <p>To restrict large proteins and some organic anions</p> Signup and view all the answers

    What is the structure that receives the fluid filtered through the capillary wall?

    <p>Capsular space</p> Signup and view all the answers

    What is the type of epithelium that lines the membranous urethra?

    <p>Stratified columnar and pseudostratified columnar epithelium</p> Signup and view all the answers

    What is the length of the spongy urethra in males?

    <p>15 cm</p> Signup and view all the answers

    What is the function of the external striated muscle sphincter in both sexes?

    <p>To regulate urine flow through the urethra</p> Signup and view all the answers

    What is the characteristic feature of the female urethra?

    <p>It is exclusively a urinary organ</p> Signup and view all the answers

    What is the typical symptom of urethritis?

    <p>Pain or difficulty during urination</p> Signup and view all the answers

    What is the type of epithelium that lines the distal part of the spongy urethra?

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

    What is the primary cause of urinary tract infections?

    <p>Both coliform bacteria and Chlamydia</p> Signup and view all the answers

    What is the characteristic feature of the epithelium lining the female urethra?

    <p>It is nonkeratinized stratified squamous epithelium</p> Signup and view all the answers

    What is the shape of the corpuscles found in the renal cortex?

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

    What is the function of the renal columns?

    <p>To separate the renal pyramids</p> Signup and view all the answers

    Where do the minor calyces arise from?

    <p>From the renal pelvis</p> Signup and view all the answers

    What is the approximate length of each kidney in adults?

    <p>12 cm</p> Signup and view all the answers

    What is the structure that covers the cortex and hilum?

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

    How many conical structures are found in the renal medulla in humans?

    <p>8-15</p> Signup and view all the answers

    What is the purpose of the adipose tissue surrounding the renal pelvis and calyces?

    <p>To support the structure</p> Signup and view all the answers

    What is the structure formed by each pyramid plus the cortical tissue at its base and extending along its sides?

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

    What is the primary function of the podocytes in the renal corpuscle?

    <p>To filter blood through the filtration slits</p> Signup and view all the answers

    What is the structure that connects the proximal convoluted tubule to the distal convoluted tubule?

    <p>Loop of Henle</p> Signup and view all the answers

    What is the primary function of the glomerular capillary endothelium?

    <p>To allow for the exchange of substances between the blood and the filtrate</p> Signup and view all the answers

    What is the term for the process of producing filtrate in the renal corpuscle?

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

    What is the structure that drains into the minor calyx?

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

    What is the primary function of the macula densa?

    <p>To detect changes in NaCl concentration in the tubular fluid</p> Signup and view all the answers

    What is the location of the juxtaglomerular apparatus?

    <p>At the vascular pole of the renal corpuscle</p> Signup and view all the answers

    What is the primary function of the pedicels?

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

    What is the characteristic of the interstitium as seen in the TEM?

    <p>It has a slightly fibrous nature</p> Signup and view all the answers

    What is the primary function of the collecting ducts in the nephron?

    <p>To reabsorb water and ions if needed by the body</p> Signup and view all the answers

    What is the shape of the epithelial cells in the collecting ducts of the medulla?

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

    What is the diameter of the collecting ducts in the cortical medullary rays?

    <p>40 μm</p> Signup and view all the answers

    What is the location of the JG cells that secrete renin?

    <p>In the juxtaglomerular apparatus</p> Signup and view all the answers

    What is the result of the return of normal blood pressure on the secretion of renin?

    <p>It turns off the secretion of renin</p> Signup and view all the answers

    What is the structure that forms the last part of each nephron?

    <p>Connecting tubule</p> Signup and view all the answers

    What is the characteristic of the collecting ducts in the medulla compared to those in the cortical medullary rays?

    <p>They are larger and have columnar cells</p> Signup and view all the answers

    Study Notes

    Renal Vasculature and Filtration

    • Small interlobular arteries branch from arcuate arteries to supply afferent arterioles to glomerular capillaries.
    • Each glomerulus contains capillary loops that drain into efferent arterioles, leading to a network of peritubular capillaries throughout the renal cortex.
    • The renal corpuscle features a vascular pole (afferent and efferent arterioles) and a tubular pole (beginning of proximal convoluted tubule, PCT).
    • The outer parietal layer of glomerular capsules consists of simple squamous epithelium supported by a basal lamina, transitioning to cuboidal epithelium in the PCT.

    Podocytes and Filtration Membrane

    • Podocytes are stellate epithelial cells forming the visceral layer of the renal corpuscle, crucial for kidney filtration.
    • Podocytes have primary processes that extend around glomerular capillaries, leading to numerous interdigitating secondary processes called pedicels.
    • Filtration slits between pedicels, around 25-30 nm wide, are covered by specialized slit diaphragms composed of proteins important for renal function.

    Glomerular Filtration Barrier

    • Composed of three layers: fenestrated capillary endothelium, glomerular basement membrane (GBM), and filtration slit diaphragms.
    • Fenestrated endothelium blocks blood cells and platelets, while GBM restricts entry of large proteins over 70 kDa.
    • Negatively charged surfaces of the slit diaphragm and GBM enhance the restriction of organic anions.

    Urinary System Functions

    • The urinary system regulates water and electrolyte balance, blood pressure, and acid-base balance while excreting metabolic waste through urine.
    • Kidneys secrete renin, erythropoietin, and convert vitamin D into its active form during various physiological states.
    • Major filtration occurs when approximately 20% of blood plasma entering the glomerulus gets filtered into the capsular space.

    Renal Tubules and Collecting Ducts

    • Proximal convoluted tubule is the main site for reabsorption and features a brush border for increased surface area.
    • The loop of Henle comprises thin descending and ascending limbs, critical for urine concentration.
    • Connecting tubules from nephrons converge to form larger collecting ducts before emptying into minor calyces.
    • Collecting ducts vary in diameter, ranging up to 200 µm in the medulla, adapting epithelium from cuboidal to columnar cells.

    Nephrons and Kidney Structure

    • Each kidney houses 1-4 million nephrons, the functional units of urine formation.
    • Cortical nephrons reside primarily in the cortex; juxtamedullary nephrons have longer loops reaching into the medulla.
    • The kidney is approximately 12 cm long and enclosed by a fibrous capsule, with specific structures like the hilum for blood vessels and the ureter.

    Pathologies and Medical Applications

    • Polycystic kidney disease leads to the formation of fluid-filled cysts affecting renal function and structure.
    • Urinary tract infections commonly produce symptoms like dysuria and frequent urges due to bacterium-induced inflammatory responses.
    • Cystitis and bladder cancer often arise from chronic inflammation of the urinary tract.

    Microscopic and Histological Features

    • The renal corpuscle features a glomerulus surrounded by a capsular space and includes distinctive podocytes that surround glomerular capillaries.
    • Histological sections show complex podocyte structures with interdigitating processes, enhancing filtration efficiency.### Renal Histology
    • Mallory trichrome staining technique helps visualize renal structures.
    • Transmission Electron Microscopy (TEM) reveals slightly fibrous interstitium.
    • The simple squamous epithelium of thin limbs is thicker than that of the nearby vasa recta capillaries.

    Renal Function

    • Essential functions of the urinary system: filtration, secretion, and reabsorption.
    • Juxtaglomerular (JG) cells secrete renin; secretion stops with the return of normal blood pressure.

    Collecting Ducts Structure

    • The connecting tubule is the final segment of each nephron, transporting filtrate to a collecting system.
    • Collecting ducts consist of simple cuboidal epithelium, with an average diameter of 40 μm.
    • In the medulla, collecting ducts become larger and straighter, with increasing diameters up to 200 μm and more columnar cell structure.
    • Medullary collecting ducts converge to form papillary ducts near the apex of renal pyramids.

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