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The URINARY System Excretion is the body’s removal of waste products from cellular metabolism. Whole-body examples: - lungs excrete CO2 - skin excretes salts Main excretory pathway is the urinary system Food Type Cellular Breakdown Products Carbohydrates ‐‐‐‐‐‐‐‐‐ > CO2 + H20 Harmless Lipids ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ > CO2 + H20 Proteins ‐‐‐‐‐> Amino Acids ‐‐‐‐‐‐‐ > NH2 Conversion in all cells NH2 ‐‐‐‐‐‐‐‐> Urea Harmless Toxic Does urea = urine ?? NO “Average” Urine: 95% Water …………… 5% Solids Solids in 1 day of Urine (~ 1500 mL) Urea Salts Creatine Ammonia Uric Acid 30 grams 20 g 1‐2 g 1‐2 g 1 g Urine is sterile until the urethra Bacteria live on epithelial lining of the urethra Muscles in the Urinary System ?? Bladder filling and emptying are muscular events !! Urine movement is unrelated to gravity. Ureter walls contain smooth muscle Wavelike contractions known as peristalsis Once every 10‐15 sec a contraction shoots urine into the bladder Possible to fill your bladder upside down. Urine Formation “Source” of urine ?? BLOOD Blood flow to organs of a 70 kg man at rest Blood Flow Organ (L/kg/min) Skin Brain Heart Liver Kidneys 0.08 0.5 0.8 0.9 4.0 Filters blood … modifies filtrate … creates urine Modifies final water content Directional Terms Proximal & Distal Afferent & Efferent Ascending & Descending Pre‐Urine Next Slide Blood filtrate passes through holes in capillary wall Filtration of molecules in the Glomerulus Pass into Substance Weight Pre‐urine? Water Urea Sucrose Small Protein Large Protein Blood Cells 18 60 342 15,000 70,000 ‐ Yes Yes Yes Some No No Conclusion: Anything smallish enters pre‐urine Problem: Nutrients & Building Blocks are small Solution: Re‐claim valuable molecules Pre‐Urine Final Urine Diuresis Anti‐diuresis Bladder Fills Urge to Urinate 200‐400 mL … walls stretch … brain awareness Toddlers? Urinary Bladder tolerates STRETCHING 600-800 mL storage QUESTION: Type of lining epithelium?? STRETCHable Epithelium (Bladder Empty Stretched Transitional Epithelium (Bladder Full) F E T U S Back into Blood Daily BALANCE ……. Why? CONSUMING SEAWATER: WHALE vs HUMAN Sea Water Urine Consumed Produced mL mM mL mM ___________________________________ Human 1000 535 1350 400 Whale 1000 535 650 820 ___________________________________
