Excretion

Excretion

• 1.
  Excretion Brianna & Keonna
• 2.
  Overview  The balanceof water in the body depends on the rate of exchange of solute between internal body fluids and the external environment.  Excretory Systems are key to homeostasis because the dispose of metabolic wastes, and control body fluid composition.
• 3.
  Nitrogenous Wastes  Animalsexcrete nitrogenous wastes as ammonia, urea or uric acid  Animals that excrete ammonia need access to lots of water because ammonia can only be tolerated in low concentrations  Urea combines ammonia with carbon dioxide, and it has a very low toxicity ◦ Excreted by vertebrate mammals, turtles, amphibians, sharks, etc .
• 4.
   Insects, birds,snails, and many reptiles uric acid which is essentially non toxic.  Its non toxicity makes it hydrophobic, thus it can be excreted without much water loss.  Requires more ATP to the synthesize from ammonia.
• 5.
  Excretory Processes  Most animals produce fluid waste known as Urine ◦ Body fluid (i.e. Blood) comes in contact with a selectively permeable membrane of the transport epithelium ◦ Filtration is driven by hydrostatic pressure (blood pressure)  Water, small salts, sugars, nitrogenous wastes, and amino acids are removed from body fluids to create filtrate
• 6.
   Filtrate isconverted into fluid waste when reabsorption places useful materials from the filtrate back into the blood stream by active tranport.  Selective Secretion pumps nonessential solutes and wastes into the filtrate by active transport.
• 7.
  Excretory Systems  Excretory systems vary widely among animal groups ◦ Flatworms that lack a coelom or body cavity have protonephridia which form network of dead end tubules connected to external openings ◦ Annelids (ex: earthworms) have metanephridia, excretory organs that open internally to the coelom
• 8.
   Insects andterrestrial anthropods have Malpighian tubules which extend from dead end tips to the digestive tract  Kidneys are present in vertebrates and chordates ◦ Consist of highly organized tubules associated with a network of capillaries ◦ Ducts and other structures carry urine from the tubules and out of the body
• 9.
  Structure of MammalianExcretory System  The average kidney is about 10 cm long  Blood is supplied to the kidney through the renal artery and drained by the renal vein ◦ take up less than 1% of the body’s mass but receive ¼ of the blood that leaves the heart
• 10.
   Urine exitsthe kidney through two ducts called ureters  Ureters drain into the urinary bladder  Urine is expelled through a tube called the urethra  The sphincter muscles regulate urination near urethra and bladder