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Function 1.Remove nitrogenous wastes 2.Maintain electrolyte, acid-base, and fluid balance of blood 3.Homeostatic organ 4.Acts as blood filter 5.Release hormones: calcitriol & erythropoietin
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Kidneys as Filters Diuretic- lose water; coffee, alcohol Antidiuretic- retain water; ADH Aldosterone- sodium & water reabsorption, and K + excretion GFR= 180 liters (50 gal) of blood/day 178-179 liters are reabsorbed back into blood Excrete a protein free filtrate
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renal cortex renal medulla Each kidney contains over 1 million nephrons and thousands of collecting ducts Collecting duct Loop of Henle PCT DCT Glomerulus
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Nephron’s functions: 1.glomerular filtration 2.tubular reabsorption 3.tubular secretion
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Histology of a renal corpuscle
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Pressures that drive glomerular filtration
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The filtration membrane
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Nephron
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Composition of Glomerular Filtrate Water Small Soluble Organic Molecules Mineral Ions
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Proximal Convoluted Tubule Reabsorbs: water, glucose, amino acids, and sodium. 65% of Na + is reabsorbed 65% of H 2 O is reabsorbed 90% of filtered bicarbonate (HCO 3 - ) 50% of Cl - and K +
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Loop of Henle Creates a gradient of increasing sodium ion concentration towards the end of the loop within the interstitial fluid of the renal pyramid. 25% Na+ is reabsorbed in the loop 15% water is reabsorbed in the loop 40% K is reabsorbed in the loop
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Distal Convoluted Tubule Under the influence of the hormone aldosterone, reabsorbs sodium and secretes potassium. Also regulates pH by secreting hydrogen ion when pH of the plasma is low. only 10% of the filtered NaCl and 20% of water remains
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Collecting Duct Allows for the osmotic reabsorption of water. ADH (antidiuretic hormone)- makes collecting ducts more permeable to water-- produce concentrated urine
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From the original 1800 g NaCl, only 10 g appears in the urine Urine Water- 95% Nitrogenous waste: urea uric acid creatinine Ions: sodium potassium sulfate phosphate
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Nitrogenous Wastes ammonia urea uric acid
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Hormonal Control of Kidney Function
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Fig. 18.09
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Hormonal Control of Kidney Function hypothalamus posterior pituitary antidiuretic hormone collecting ducts
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aldosterone
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Fig. 18.16 Regulation of Aldosterone secretion by renin-angiotensin- aldosterone (RAA) pathway
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Hormonal Control of Kidney Function reduced blood pressure and glomerular filtrate juxtaglomerular apparatus renin
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Hormonal Control of Kidney Function renin angiotensinogen angiotensin I angiotensin II
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Hormonal Control of Kidney Function adrenal cortex aldosterone angiotensin II convoluted tubules
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Urinary Bladder ureters internal sphincters external sphincters urethra
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Bladder 1.Mucosa (transitional epithelium) 2.Muscular layer (detrusor muscle): 3 layers of smooth muscle 3.Fibrous adventia
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Internal urethral sphincter: Smooth muscle Involuntary control More superiorly located External Urethral sphincter: Skeletal muscle Voluntary control Posteriorly located Sphincter Muscles on Bladder
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When bladder fills with 200 ml of urine, stretch receptors transmit impulses to the CNS and produce a reflex contraction of the bladder (PNS) Diuresis (Micturition) When is incontinence normal?
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Why do doctors ask for a urine sample? Urinalysis characteristics: smell- ammonia-like pH- 4.5-8, ave 6.0 specific gravity– more than 1.0; ~1.001-1.030 color- affected by what we eat: salty foods, vitamins
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odor- normal is ammonia-like diabetes mellitus- smells fruity or acetone like due to elevated ketone levels diabetes insipidus- yucky asparagus--- Odor
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pH- range 4.5-8 ave 6.0 vegetarian diet- urine is alkaline protein rich and wheat diet- urine is acidic
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Color- pigment is urochrome Yellow color due to metabolic breakdown of hemoglobin (by bile or bile pigments) Beets or rhubarb- might give a urine pink or smoky color Vitamins- vitamin C- bright yellow Infection- cloudy Color
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Water: s.g. = 1g/liter; Urine: s.g. ~ 1.001 to 1.030 Pyelonephritus- urine has high s.g.; form kidney stones Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary Specific Gravity
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Glucose- when present in urine condition called glycosuria (nonpathological) [glucose not normally found in urine] Indicative of: Excessive carbohydrate intake Stress Diabetes mellitus Abnormal Constitutes of Urine
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Albumin-abnormal in urine; it’s a very large molecule, too large to pass through glomerular membrane > abnormal increase in permeability of membrane Albuminuria- nonpathological conditions- excessive exertion, pregnancy, overabundant protein intake-- leads to physiologic albuminuria Pathological condition- kidney trauma due to blows, heavy metals, bacterial toxin Abnormal Constitutes of Urine
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Ketone bodies- normal in urine but in small amts Ketonuria- find during starvation, using fat stores Ketonuria is couples w/a finding of glycosuria-- which is usually diagnosed as diabetes mellitus RBC-hematuria Hemoglobin- Hemoglobinuria- due to fragmentation or hemolysis of RBC; conditions: hemolytic anemia, transfusion reaction, burns or renal disease Abnormal Constitutes of Urine
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Bile pigments- Bilirubinuria (bile pigment in urine)- liver pathology such as hepatitis or cirrhosis WBC- Pyuria- urinary tract infection; indicates inflammation of urinary tract Casts- hardened cell fragments, cylindrical, flushed out of urinary tract WBC casts- pyelonephritus RBC casts- glomerulonephritus Fatty casts- renal damage Abnormal Constitutes of Urine
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INQUIRY 1.List several functions of the kidneys. 2.What does the glomerulus do? 3.What are several constitutes you should not find in urine? 4.What is specific gravity? 5.What two hormones effect fluid volume and sodium concentration in the urine? 6. Where are the pyramids located in the kidney? 7.What vessel directs blood into the glomerulus? 8.Where does most selective reabsorption occur in the nephron?
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Moment of Zen KIDNEY
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