ANSC 3080 Lecture Notes - Lecture 11: Osmoreceptor, Aquaporin, Posterior Pituitary
27 Mar 2018
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Dilutes or concentrates urine in accordance with hydration state. Sheep (65kg) produces 180l glomerular filtrate per day, only 1-2l of urine with osmolality of ~500mosmol/l. If deprived of water, low urine volume, much higher osmolality (up to 3500 mosmol/l) If )water loaded), excrete larger volumes of urine with low osmolality (~100mosmol/l) Water movement occurs by osmosis through pores. Dilution/concentration depends on osmolarity of interstitial and tubular fluids in the kidney. If osmolarity in interstitial tissue was constant in the kidney (300 mosmol/l) urine could not be formed at a higher osmolarity. Handling of ions, urea and water creates increasing osmolarity from the medulla to the pelvis in the kidney. This enables urine to be secreted at a higher osmolarity than plasma. Dilution of the tubule fluid in the thick ascending limb and the distal convoluted tubule. Variability in water permeability of collecting duct in response to vasopressin (antidiuretic hormone, adh)
