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27 Cards in this Set

  • Front
  • Back
elimination of substances from body (Urinary system sometimes reffered to as excretory system)
ex. CO2 eliminated by respiratory system
Undigested solids eliminated by digestive system
Non-gaseous waste products of cellular metabolism (such as urea, extra vitamins, H2O, & drugs) eliminated by urinary system
Functions of Urinary System
-removal of wastes such as urea (excretion)
-maintenance of Homeostasis-pH, BP, water balance-too dilute or too concentrated
-Regulates blood levels of sodium, potassium, chlorine, calcium
-Retains nutrients such as glucose & amino acids
Overview of How Urinary System Works
1. Blood is filtered-remove excess H2O & some small molecules
2. Some nutrients are reabsorbed from filtrate
3. Remainging H20 and wastes are excreted
a water-soluble, nitrogen containing waste product of amino acid breakdown (from protein). A component of urine
-some amino acids have their amino groups(-NH2) removed in liver for energy, of for use in synthesis
(NH3) is a highly toxic waste product of amino acid breakdown
-it is converted to urea(less toxic) in liver
-urea can be easily removed by kidneys
fluid produced and excreted by urinary system
-contains H20 and dissolved wastes such as urea
-paired organs on either side of spinal column
-"bean-shaped", above waist
-they collect the fluid portion of the blood
-H20 and nutrients are reabsorbed back into blood
renal artery
carries blood with dissolved cellular wastes into the kidney
renal vein
filtered blood leaves kidney through this vessel
(2) muscular tubes, urine exits kidney through it
-urine goes to bladder
-muscular chamber that collects and stores urine
-smooth muscle walls that can expand
-500 ml capacity
-internal sphincter muscle-involuntary
-external sphincter muscle-voluntary(brain can control ext. muscle)
*stretch receptors trigger bladder to contract
narrow tube through which the urine exits
renal cortex
outer laye of kidneys

contains nephrons
renal medulla
inner layer of kidneys
renal pelvis
subdivided inner chamber that collects urine
-sends urine to ureter
tiny filters
about 1 million per kidney
bundle of thin-walled capillaries in the Bowman's capsule

BP forces some H2O & nutrients through capillary walls for filtration
Bowman's capsule
cup-shaped part of nephron that collects blood filtrate from glomerulus
small tube in nephron, urine forms in this tubule from blood filtrate as it passes through
proximal tubule
exits Bowman's capsule
loop of Henle
at bottom of nephron
distal tubule
bring fluid to collecting ducts
collecting ducts
receive fluid from nephron-send it into renal pelvis
Urine Formation:
-kidneys receive about 1 liter of blood/min.
-nephron receives blood from arteriole(small artieries)
-capillaries in glomerulus of Bowman's capsule are permeable to H2O and small dissolved solids
-H2O and small molecules are pushed out into Bowman's capsule
-fluid is now called filtrate
-filtrate travels through the nephron
Urine Formation:
-occures primarily in proximal tubule
-tubule cells use active transport to remove salts, amino acids, glucose, and vitamins from filtrate-substances go out of tubule to surrounding fluid (extra cellular) then back to blood
-some nutrients diffuse back into nearby capillaries
-H2O moves out of tubules and back into capillaries by osmosis about 99% of filtered H2O reabsobed
Urine Formation:
-occurs mainly in distal tubule
-wastes and extra substances from the blood are secreted into distal tubule
-these wastes(H+,K+,NH3,drugs) are added to the filtrate and become part of the urine
Urine Formation:
4. CONCENTRATION (of urine)
-there is an osmotic concentration gradient of salts and urea in the interstitial fluid around the loop of Henle and the collecting ducts
-most concentrated fluid at the bottom of the loop
-the longer the loop, the higher the concentration gradient
-urine in collecting duct also passes through this concentration gradient on teh way to the renal perlvis
-additional H2O may leave filtrate by osmosis & go back to capillaries
-wastes are left behind in collecting ducts
-filtrate is now called urine
-urine passes from renal pelvis to bladder(stored), by way of the ureters
-it is then excreted from bladder through the urethra (when bladder is full)