L6 Urinary System Slide 1 The Urinary System Slide 2 Functions of the Urinary System Regulate aspects of homeostasis o Water balance with Antidiuretic Hormone ADH o Acid base balance in the blood by regulating plasma pH o Regulate plasma ionic composition electrolytes with aldosterone o Regulate blood pressure and blood volume by regulating plasma volume and plasma osmolarity o Red blood cell production secrete erythropoietins stimulates RBC production when low oxygen levels are detected and rennin aka angiotesinogenase released in low blood pressure o Activated vitamin D3 calcitriol Elimination of waste products metabolic wastes o Nitrogenous wastes o Toxins o Drugs Slide 3 Developmental Aspects of the Urinary System Functional kidneys are developed by the third month Urinary system of a newborn o Bladder is small o Urine cannot be concentrated for first 2 months Therefore urinating a lot o Void 5 40 times per day Slide 4 Developmental Aspects of the Urinary System Control of the voluntary urethral sphincter does not start until the age of 18 months Complete nighttime control may not occur until the child is 4 years old o Cultural tropical climates o Circadian Rhythm Different hromones change during different times of night ADH increases at night conserves water so you urinate less Alcohol inhibits ADH Urinary infections are the most common problems before old age Escherichia coli E coli a type of bacteria accounts for 80 of UTI uninary tract infections Slide 5 Structures of the Urinary System Kidneys form urine Ureters transport urine from kidneys to bladder Bladder stores urine Urethra excretes urine from bladder to outside of body Slide 6 Urinary Bladder Smooth collapsible muscular sac o Stretch and recoil o storage Temporarily stores urine a moderately full bladder is about 5 inches long and holds about 500 m L of urine Trigone is a triangular region of the bladder base o Three openings Two from ureters One to the urethra o In males the prostate gland surrounds the neck of the bladder Slide 7 Position and shape of a distended and an empty urinary bladder in an adult male See Diagram Enlarge prostate pushes on bladder and pinches urethra Slide 8 Urinary Bladder Wall Three layers of smooth muscle collectively called the detrusor muscle Mucosa made of transitional epithelium o Stretch and recoil Walls are thick and folded in an empty bladder Bladder can expand significantly without increasing internal pressure Slide 9 Kidney Features The right kidney is slightly lower than the left due to position of liver Renal hilum is a medial indentation where several structures enter or exit the kidney ureters renal blood vessels and nerves An adrenal gland sits atop each kidney o Donating kidney AND adrenal gland Slide 10 Blood Supply Specialized for filtration One quarter of total blood supply of the body passes through the kidneys each minute Renal artery provides each nidney with arterial blood supply Renal artery divides into segmental arteries interlobar arteries arcuate arteries cortical radiate arteries Venous blood flow cortical radiate veins arcuate veins interlobal veins renal veins Slide 11 Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Slide 22 Slide 23 Slide 24 Slide 25 Slide 26 Slide 27 Slide 28 Slide 29 Slide 30 Slide 31 Slide 32 Slide 33 Slide 34 Slide 35 Slide 36 Slide 37 Slide 38 Maintaining Water Balance Diluted urine is produced if water intake is excessive Less urine concentrated is produced if large amounts of water are list sweating dehydration Proper concentration of various electrolytes must be present osmolarity Slide 39 Counter Current Multiplier in the Loop of Henle Osmotic gradient established by counter current multiplier Dependent on Loop of Henle Descending Limb o Permeable to water o No transport of Na Cl or K Ascending Limb o Impermeable to water o Transport of Na Cl and K Constantly being maintained Two things moving in the opposite directions to increase Deeper in medulla 1400 o Most concentrated urine o Function increase concentrated urine Animals that live in dry areas more intense max concentration Water leaves descending filtrate concentration goes up Ascending ion permeable o Ions leave o Concentrations of filtrate goes down Slide 40 Counter Current Multiplier Urine concentration and dilution mechanisms o The countercurrent exchanger mechanism The capillaries of the vasa recta function as countercurrent exchangers because the direction of blood flow around the loop of Henle is opposite to the direction of filtrate flow around the loop Vasa recta counter current than loop of Henle The extra ions omitted by the loop of Henle remain in the medulla Slide 41 Result of Counter Current Multiplier Fluid in proximal tubule 300 mOsm liter Fluid filtrate in descending limp osmolarity increases as it descends Fluid in ascending limb osmolarity decreases as it ascends Prevents dissipations of concentration gradient in medulla because eit collects the water from the descending loop Slide 42 Vasa Recta Prevents dissipation of osmotic gradient while supplying nutrients and removing wastes Special important function Slide 43 Regulation of Water and Electrolyze Reabsorption Osmoreceptors o Cells in the hypothalamus o React to changes in blood composition by becoming more active as osmolarity increases o Osmolarity actually works with compositions o Works with baroreceptors Slide 44 Water Reabsorption in Distal Tubules and Collecting Ducts ADH Dependent on osmotic gradient established by counter current multiplier Dependent on epithelium permeability to water Water permeability dependent on water channels o Aquaporin 3 present in basolateral membrane always o Aquaporin 2 present in apical membrane only when ADH is present in blood ADH conserves water o Not going into it accept that it is a G protein Binds to G protein cascade Kinase phosphoralates changes shape activates o Aquaporin 3 is always open o But water is not always permeable in collecting duct this is where aquaporin 2 comes in Slide 45 Permeable Membrane in Presence of ADH ADH stimulates insertion of water channels aquaporin 2 into apical membrane water can permeate membrane and be reabsorbed by osmosis Max osmolarity urine 1400 mOsm Water will freely go out because the concentration is greater outside Counter current multiplier does 2 things o 1 Creates diluted urine o 2 Concentration Slide 46 Regulation of ADH Release ADH posterior pituitary hormone Released
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