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49 Cards in this Set
- Front
- Back
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What are at least six different functions of the kidney?
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-Regulation of : fluid volume, osmolarity, ion concentration, pH, production of hormones, excretion ofmetabolic wastes and foreign substances
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Why is the kidney considered an important homeostatic organ?
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-The kidney helps to tightly regulate the blood volume and osmolarity of the blood.
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Can a person survive with only one kidney?
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-yes
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Can a person survive without kidneys?
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- A person will die within 2 weeks (or less) of loss of both kidneys without dialysis.
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What is micturition?
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-Micturation is the clinical term for urination
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Approximately what volume of urine is produced/day?
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-The minimum "obligatory" production of urine is 400ml,but normally about 1-2L of urine per day are produced
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What type of neuron stimulates contraction of the urinary bladder?
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-Parasympathetic neurons activate the detrusor muscle of the bladder and relaxation of the internalurethral sphincter
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Is there a somatic neuron involved inthe release of urine?
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- A somatic neuron (under voluntary control) relaxes to opens the external urethralsphincter.
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About how many nephrons are found in each kidney?
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-about 1 million!
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What are the parts of a nephron?
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- The parts of a nephron include: Bowman's capsule, theproximal convoluted tubule, the descending limb of the Loop of Henle, the ascending limb of the Loop ofHenle, the distal convoluted tubules, and the collecting duct.
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Where does filtration occur?
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- Filtration occurs between the glomerulusand Bowman's capsule
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What portion of the blood is filtered by the nephrons?
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- About 20% of the blood directed to the kidney's is filtered by the nephrons.
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What is the composition of thefiltrate when it enters the proximal tubule?
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-The filtrate has the same composition as plasma without the proteins
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What is the average volume of filtrate formed/day?
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-About 180L of filtrate are formed each day
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What % of this is reabsorbed? (hint: compare withvolume of urine formed)
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- About 99% of this is reabsorbed.
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How is the glomerular filtration rate (GFR) regulated?
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-GFR can be regulated by vasoconstriction (sympathetic innervation) or vasodilation (absence ofsympathetic innervation) of the afferent arteriole. Also vasoconstriction or vasodilation of the efferent arteriole will affect GFR
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What is the effect of the sympathetic nervous system on the afferent arterioles of the glomeruli?
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- vasodilation (absence of sympathetic innervation) of the afferent arteriole or vasoconstricion (sympathetic stimulation)
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Sympathetic effect on the GFR?
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-With sympathetic innervation of the afferent arteriole, the blood flow to theglomeruli will decrease, this will decrease the hydrostatic pressure in the glomerulus and thereforedecrease the GFR.
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What two capillary networks are associated with each nephron. Where are they?
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-The two cappilary networks are the glomerulus, and the peritubular capillary bed (which includes thevasa recta).
-The glomerulus in surrounded by Bowman's capsule, and the peritubular capillary bedsurrounds the entire nephron. |
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At what portion(s) of the nephron is most of the filtrate reabsorbed?
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-Most of the reabsorption of filtrates occurs in the proximal convoluted tubule
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How does reabsorption occur in the PCT?
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-Active transport occurswith Na+, glucose, and amino acids (which requires ATP). Passive transport occurs with Cl- and Urea.And water moves via osmosis
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Is ATP needed for reabsorption?
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-with active transport of Na+, glucose and amino acids, yes
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What % of H2O reabsorption occurs before thedistal convoluted tubule?
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- 85% of H2O reabsorption occurs before the distal convoluted tubule.
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Is this amount of reabsorption b4 the distal convoluted tubule obligatory?
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- yes, this amount is always reabsorbed (is obligatory) regardless of the state of hydration of the body
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What is the Countercurrent Multiplier System?
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-It is the system produced by the nephrons (more specifically the Loop of Henle part of the nephrons)which, due the flow of ultrafiltrate in counter directions and differential movement of molecules andpermeabilities of molecules along the tubule, allows for the creation of a hyperosmotic interstitial fluidenvironment. This hyperosmotic interstitial fluid allows for almost complete recovery of water (~99%) by passive diffusion back into the body.
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Why is the CCMS unique?
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-It is unique because this is the only area of the body in whichosmolality is changed and tolerated by cells (the cells do not creanate due to the hyperosmotic condition).
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How does the CMS work?
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-The countercurrent flow and proximity of the descending and ascending limbs ofthe Loop of Henle interact to cause the osmolarity to build in the medulla. Salt pumped in the thickascending part raises osmolarity around the descending limb, causing more water to diffuse out of thefiltrate.
-Within the vasa recta, salt enters the vessels and again water follows, so that both salts and waterare continually moved from the tubules to the interstitial fluid and into the blood stream. All the fluidstransiently experience an increase in osmolarity within the depths of the medulla, but by the time theblood vessels exit the kidneys, the osmolarity is returned to normal (0.3 Osm or 300mosm). |
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Ureter
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-where urine flows from kidneys and empties into bladder
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Urethra
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-exit of the urine
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Nephron
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-a functional unit of kidney responsible for forming urine
>1 million nephrons/kidney -a long tube & has associated BVs |
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Bowman's (glomerular)capsule
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-surrounds glomerulus to form the renal corpuscle
-where glomerular filtration occurs -filtrate passes into PCT |
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Proximal convoluted tubule
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-where reabsorption of salt and water (33%) occur, returning to peritubular caps
-contains symporters for Na+ on apical side -contains Na+K+ ATPase pumps on basolateral side -reabsorption of all biomolecules occurs here! |
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Loop of Henle
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-after the proximal tubule, dips into the renal medulla
-contains the Countercurrent Multiplier System -allows us to multiple the effects of reabsorbing water and salts -by the end, 85% of filtered water and salts are reabsorbed |
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Distal convoluted tubule |
-after the loop of henle and the juxtaglomerular apparatus, lies entirely w/in the cortex -where hormonal regulation of electrolyte balance occurs -Aldosterone is released to reabsorb electrolytes |
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Collecting duct |
-follows the distal tubule, where its contents are emptied into. -each drains up to eight separate nephrons -plunges thru the medulla to empty its fluid contents (urine) into the renal pelvis -releases ADH to conserve water |
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Renal corpuscle
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-glomerulus + Bowman's Capsule
-where filtration occurs |
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Glomerular filtration AKAGlomerular ultrafiltration
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-the filtration of blood plasma thru the renal corpuscle
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GFR - glomerular filtrationrate
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-volume of filtrate produced by both kidneys/min
-ave. 115 ml/min in women; 125 ml/min in men -totals about 180 L/day (45 gallons) |
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Afferent arteriole
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-major control of GFR by changing its diameter
-vasoconstriction decreases blood flow into glomerulus -vasodilation increases blood flow into glomerulus |
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Efferent arteriole
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-where filtered blood exits after glomerulus
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Obligatory water loss
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-minimum of 400 ml/day urine necessary to excrete metabolic wastes
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Reabsorption
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-return of filtered molecules to the capillaries
-reabsorption of salt and water (water is never transported; it follows the other molecules by osmosis) |
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Decending Loop of Henle
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-plunges into the renal medulla
-only water reabsorption from high salt concentration outside of the limb |
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Ascending Loop of Henle
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-High conc. of cholesterol in the cells = no water absorption
-transporters allow transport of Na+, K+ and Cl- out of the limb -the salts create a gradient for water to follow it |
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Countercurrent MultiplierSystem
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-produces the concentration gradient in the kidneys
-a huge osmotic gradient to draw the water back into the blood |
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Urea
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-contributes to high osmolarity in medulla
-deep region of collecting duct is permeable to urea & transports it |
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Vasa recta
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-a series of straight caps in the medulla that lie parallel to the loop of henle
- has a hairpin turn in the medulla and carries blood at a very slow rate, two factors crucial in the maintenance of countercurrent exchange that prevent washout of the concentration gradients established in the renal medulla - |
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what occurs on the descending portion of the vasa recta?
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NaCl and urea are reabsorbed into the blood, while water is secreted.
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what occurs on the ascending portion of the vasa recta?
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NaCl and urea are secreted into the interstitium, while water is reabsorbed.
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