A&P: CH. 25 [Urinary System]

• maintains environment by

  • regulating water volume and solute concentration
  • regulate ion and extracellular fluid concentration
  • acid-base balance
  • waste disposal
  • erythropoietin and renin production (RBC and B.P.)
  • vitamin D to active form
  • gluconeogenesis during prolonged fasting
• ureters: transport urine from kidneys to urinary bladder
• urinary bladder: temporary storage reservoir for urine
• urethra: carries urine from bladder to be expelled
• renal fascia: outer layer dense fibrous connective anchoring kidney and adrenal gland to surrounding structures
• perirenal fat pad: cushion between renal capsule and perirenal fascia, protects kidney from trauma
• hilum: opening through which blood vessels, nerves, ureter enter/exit the kidney
• fibrous capsule: prevents infections in surrounding regions from spreading to kidneys
• internal kidney

  A) renal cortex

  B) renal medulla

  C) renal pelvis

  D) minor calyx

  E) ureter

  F) papilla of pyramid

  G) renal column

  H) fibrous capsule

  
• renal pyramids appeared striped due to bundles of microscopic urine collecting tubules and capillaries
• calyces collect urine which drain from papillae and empty into renal pelvis
• pyelitis: inflammation of the renal pelvis.
• pyelonephritis: inflammation affecting entire kidney
• nephron is functional unit of kidney, responsible for filtering blood and producing urine
• path of blood flow (renal vessels)

  1. aorta
  2. renal artery
  3. segmental artery
  4. interlobar artery
  5. arcuate artery
  6. cortical radiate artery
  7. afferent arteriole
  8. glomerulus
  9. efferent arteriole
  10. vasa recta
  11. cortical radiate vein
  12. arcuate vein
  13. interlobar vein
  14. segmental vein
  15. inferior vena cava
• sympathetic fibers regulate renal blood flow and influence urine formation by nephron
• all renal corpuscles located in renal cortex, renal tubules begin in cortex and pass into medulla
• renal corpuscle

  • glomerulus: porous capillaries that form filtrate
  • glomerular corpuscle: parietal and visceral layer; visceral layer has podocytes that form filtration slits
• filtrate from renal corpuscle passes through proximal convoluted tube then the distal convoluted tube to enhance filtrate processing
• PCT has microvilli to enhance reabsorption proterties
• DCT lacks microvilli
• cortical nephrons are 85% of nephrons found in the kidney
• juxtamedullary nephrons play an important role in kidneys ability to produce concentrated urine
• peritubular capillaries and vasa recta reclaim most of the filtrate
• peritubular capillaries experience low pressure
• vasa recta supply oxygen and nutrients to renal medulla
• macula densa are chemoreceptors in the ascending limb that monitor NaCl content of filtrate entering DCT
• granular cells are mechanoreceptors that sense BP in afferent arterioles and release renin
• extraglomerular mesangial cells pass regulatory signals between macula densa and granular cells
• 3 major renal processes

  1. glomerular filtration: makes cell and protein free filtrate (renal corpuscle)
  2. tubular reabsorption: moving substances from filtrate back to blood (tubule and collecting duct)
  3. tubular secretion: moving substances from blood into filtrate (tubule and collecting duct)
• filtrate has everything in plasma except for proteins
• urine contains excess salts and metabolic waste
• glomerular filtration is a passive process where hydrostatic pressure forces fluid and solutes through a membrane
• glomerular mesangial cells: engulf macromolecules that get stuck in filtration membrane
• keeping plasma proteins in capillaries maintains the colloid osmotic pressure of glomerular blood
• hydrostatic pressure in glomerular capillaries pushes water and solutes out of blood and across filtration membrane
• hydrostatic pressure in the capsular space is pressure exerted by filtrate in glomerular capsule
• colloid osmotic pressure in glomerular capillaries is pressure exerted by proteins in blood
• NFP=outward pressure - inward pressure

  = (HPgc) - (HPcs+OPgc)

  = (55) - (15+30)

  = 10mmHg
• GFR is directly proportional to net filtration pressure, total surface area available for filtration, filtration membrane permeability