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27 Cards in this Set
- Front
- Back
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Excretion
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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 |
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Functions of Urinary System
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-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 |
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Overview of How Urinary System Works
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1. Blood is filtered-remove excess H2O & some small molecules
2. Some nutrients are reabsorbed from filtrate 3. Remainging H20 and wastes are excreted |
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Urea
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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 |
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Ammonia
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(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 |
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Urine
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fluid produced and excreted by urinary system
-contains H20 and dissolved wastes such as urea |
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kidneys
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-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 |
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renal artery
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carries blood with dissolved cellular wastes into the kidney
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renal vein
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filtered blood leaves kidney through this vessel
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ureter
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(2) muscular tubes, urine exits kidney through it
-urine goes to bladder |
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bladder
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-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 |
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urethra
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narrow tube through which the urine exits
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renal cortex
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outer laye of kidneys
contains nephrons |
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renal medulla
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inner layer of kidneys
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renal pelvis
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subdivided inner chamber that collects urine
-sends urine to ureter |
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nephrons
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tiny filters
about 1 million per kidney |
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glomerulus
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bundle of thin-walled capillaries in the Bowman's capsule
BP forces some H2O & nutrients through capillary walls for filtration |
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Bowman's capsule
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cup-shaped part of nephron that collects blood filtrate from glomerulus
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tubule
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small tube in nephron, urine forms in this tubule from blood filtrate as it passes through
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proximal tubule
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exits Bowman's capsule
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loop of Henle
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at bottom of nephron
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distal tubule
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bring fluid to collecting ducts
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collecting ducts
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receive fluid from nephron-send it into renal pelvis
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Urine Formation:
1. FILTRATION |
-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 |
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Urine Formation:
2. TUBULAR REABSORBTION |
-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 |
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Urine Formation:
3. TUBULAR SECRETION |
-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 |
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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) |
