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BISC306 (101)
Cain William (101)
Lecture 33

BISC306 Lecture 33: Lecture 33
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Department
Biological Sciences
Course Code
BISC306
Professor
Cain William

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Lecture XXXIII I. Non-mammalian vertebrate kidneys a. The birds are the only other vertebrate that possess nephrons with loops of Henle b. Hagfish i. Glomeruli and collecting ducts, but no tubules ii. Carry out little to no osmoregulation; limited role of the kidney iii. Blood is basically sea water iv. A lot of regulation done by their gills v. Want to save water c. Some marine teleosts have no glomeruli, as they produce very little urine i. Want to save water d. Fresh water fish has to deal with water gain; fresh water teleosts have many large glomeruli, as they produce copious urine; want to get rid of water e. Amphibians i. Don’t have the ability to produce hyperosmotic urine II. Proximal tubule absorbs water and salt leaving to produce fluid isosmotic to plasma a. ADH controls relative water and salt reabsorption in distal tubule III. Diuresis (low ADH) a. Don’t reabsorb much water; produce very hypoosmotic urine IV. Antidiuresis (high ADH) V. Without the loop of Henle and countercurrent exchange, amphibians cannot make hyperosmotic urine VI. Osmoregulation in insects a. Doesn’t undergo filtration; secretes into tubule and empties into hindgut b. Malpighian tubules, anterior hindgut and rectum comprise the osmoregulatory system c. No filtration involved d. Open circulatory system so no way to develop the necessary pressure e. Malpighian tubules produce a fluid that is generally isosmotic to the hemolymph i. Support secretion of KCl (and/or NaCl) along with waste products like uric acid ii. And water follows by osmosis f. The hindgut reabsorbs water and salts i. Water loss is a huge problem, so really dry feces g. Urine may be 4Xs more concentrated than hemolymph in desert locus h. The mealworm can produce urine up to 10Xs more concentrated than the hemolymph using a different mechanism than is shown here VII. Nitrogenous waste a. Have to package nitrogen in some form b. Most is in urea c. Some as ammonia, a little as uric acid; very little as creatinine and others d. Ammonia is the easiest/cheapest to make; so why don’t all organisms use ammonia? e. Safety issue f. In order to safely excrete nitrogen in the form of ammonia, need to expend water g. There are minimum requirements for water to safely excrete compound h. Ammonia is easy for fish because expending wat
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