drink large volumes of water, produce large volume of hypotonic urine • Dehydration causes low urine output of hypertonic urine
Hormones Affecting Renal Function Hormones Affecting Renal Function Aldosterone – promotes Na + reabsorption and K + secretion, reduces urine output ADH – promotes water reabsorption, reduces urine output Angiotensin II – constricts vessels BP, promotes water reabsorption, stimulates aldosterone and ADH secretion ANP – inhibits NaCl and water reabsorption, dilates afferent and constrict efferent vessels, increases urine output Calcitonin/Calcitriol – promotes Ca 2+ reabsorption weakly Epinephrine/Norepinephrine – induces renin secretion and constricts afferent arteriole, reduces urine output PTH – promotes Ca 2+ reabsorption
3 Factors Affect Blood Pressure 3 Factors Affect Blood Pressure 1. Heart Rate NE binds beta-adrenergic receptor ↑heart rate ↑BP Hypertension treated with beta-blocker 2. Vessel Diameter Renin ACE Angiotenisin II vasoconstriction ↑BP Hypertension treated with renin inhibitor, ACE inhibitor, or angiotensin II receptor blocker 3. Blood Volume ↑ Na + ↑ blood volume ↑BP Hypertension treated with diuretics like Lasix Na + pump inhibitor
Urinalysis – Urine Composition
Urine Volume • Normal volume - 1 to 2 L/day • Polyuria > 2L/day • Oliguria < 500 mL/day • Anuria - 0 to 100 mL/day
Diabetes • Chronic polyuria of metabolic origin • With hyperglycemia and glycosuria – diabetes mellitus I and II , insulin hyposecretion/insensitivity – gestational diabetes , 1 to 3% of pregnancies • ADH hyposecretion – diabetes insipidus ; CD water reabsorption
Diuretics • Effects urine output blood volume • Uses – hypertension and congestive heart failure • Mechanisms of action GFR – high doses of caffeine tubular reabsorption • alcohol (inhibits ADH) • Lasix “loop diuretic” inhibit Na + , K + , Cl - thick segment
Renal Function Tests • Renal clearance : volume of plasma cleared of a waste in 1 minute • Determine renal clearance (C) by assessing blood and urine samples: C = UV/P – U (waste concentration in urine) – V (rate of urine output) – P (waste concentration in plasma) • Determine GFR: inulin is neither reabsorbed or secreted so its GFR = renal clearance GFR = UV/P • Clinical GFR estimated from creatinine excretion
Urine Storage and Elimination • Ureters ( about 25 cm long) – 3 layers • adventitia - CT • muscularis - 2 layers of smooth muscle – urine enters, it stretches and contracts in peristaltic wave • mucosa - transitional epithelium – lumen very narrow, easily obstructed – renal calculi (kidney stones) • Lithotripsy – ablation of stones
Urinary Bladder • 3 layers – parietal peritoneum , superiorly; fibrous adventitia rest – muscularis : detrusor muscle, 3 layers of smooth muscle – mucosa : transitional epithelium • trigone : openings of ureters and urethra, triangular • rugae : relaxed bladder wrinkled, highly distensible • capacity: moderately full - 500 ml, max. - 800 ml
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