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84 Cards in this Set
- Front
- Back
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What are the major functions of your kidneys?
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1. Water Balance
2. Electrolyte Balance 3. Elimination of Organic Waste 4. Acid-Base Balance 5. Removal of toxic waste substances 6. Degrades some hormones 7. Endocrine Function |
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Describe how the kidney contributes to water balance.
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It can save water by excreting a hyperosmotic urine or eliminate water by excreting hypoosmotic urine. It can regulate the volume of the ECF by excreting or reabsorbing Na and or water.
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Describe how the kidney contributes to electrolyte balance.
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It regulates ECF concentrations of Na, K, Ca, Mg, phosphates, sulfates, HCO3-
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Describe how the kidney contributes to elimination of organic waste.
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Gets rid of Urea, Uric Acid,Creatinine. These are break down products
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Describe how the kidney contributes to acid-base balance/
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Excretes H in urine when ECF acidity is high. Excretes HCO3 in urine when ECF is basic. It synthesizes ammonia which aids in the excretion of acid.
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Describe how kidneys contribute to removing toxic waste substances.
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It breaks down products of drug metabolism
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What is the endocrine function of kidneys?
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It synthesizes and secretes hormones and local chemical messenger. It secretes renin - which catalyzes conversion of angiotensinogen to angiotensin I. This is converted to Angiotensin II and has effects of vasoconstriction and synthesis of aldosterone which regulates Na absorption and K secretion in kidney tubules. Kidney also secretes erythropoietin which regulates genesis of RBCs. It also secretes Vitamin D3 in active form which regulates calcium absorption in intestine.
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What is renal cortex?
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It is outermost layer with initial filtering segment
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What is renal medulla?
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contains 8-18 renal pyramids where you find blood vessels and tubules
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What does ureter do?
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It takes urine to bladder.
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What are the renal artery and vein?
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Renal artery brings arterial input and vein brings out renal output. Urine output is equal to urine concentration * rate. Arterial input is plasma concentration of substance * RPV.
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What is renal pelvis?
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In kidney urine flows and collects in renal pelvis
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What is the functional unit of the kidney? Describe its function and structure.
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Nephron is the functional unit of kidney. There are about 1 million nephrons per kidney whose job is to process plasma portion of the blood. Each nephron contains renal corpuscle and renal tubule.
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How do you calculate kidney input?
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Concentration of substance [X]artery * RPFa (Blood Flow)
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Describe output of kidney.
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[X]urine * V (rate of urine formation in mL/min)
This is stuff you want to get rid of. |
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How do you calculate output to renal vein?
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[X]vein * RPFv (Blood Flow) This is stuff you want to keep.
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About ____% of urea is eliminated in urine.
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50
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Why do we not want proteins and amino acids in urine?
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Because we want 100% reabsorptions of these
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What is the number of substances under endocrine control equal too?
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The number of substances coming into kidney through artery.
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What is the function of aldosterone?
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It causes Na reabsorption and K secretion
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What is the function of ADH?
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It causes water reabsorption
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What does ANP do?
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Atrionitricpeptide causes Na excretion
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What does PTH do?
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Caues Ca reabsorption and PO4 SECRETION -> Excretion
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How does kidney regulate water balance?
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It regulates volume by regulating Na. Total body Na determines Total Body H2O
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How does kidney eliminate organic acids?
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It does so by obligatory H2O loss. Obligatory water loss is about .44L/day in order to excrete organic waste products.
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How is renal function measured sometimes?
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Plasma levels of creatimkine
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What does the number of nephrons per kidney correlate with?
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Health
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Describe flow of kidney input starting with Renal artery.
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1. Renal Artery -> afferent arterial vessel -> Bowman's Capsule Filtrate -> loop of capillaries called glomureli capillaries -> efferent arterial -> tubule -> veins
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What controls glomeruli capillary flow?
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Afferent arterial dilated or constricted
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What happens if efferent arterial constricts?
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There is back up in glomeruli?
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How can we increase filtrate rate?
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Dilating the afferent or constricting efferent
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What is Bowman's Capsule Filtrate?
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It is the first part of renal tubule that is lined with epithelial cells and where the filtrate forms. This 1st capillary bed is where filtrate forms and the 2nd capillary bed is where we communicate with rest of renal tubule and have secretion or absorption
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What is the renal corpuscle?
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It is composed of the glomerular capillaries and is the initial portion of the renal tubule called bowman's capsule
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Describe process in tubular portion of nephron.
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Bowman's Capsule-> Proximal Convoluted Tubule-> Descending limb loop of henle -> Ascending limb loop of henle -> distal convoluted tubule -> cortical collecting duct -> medullary collecting duct. Filtrate leaving collecting duct drains into renal pelvis where urine is collected and moves to ureter.
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Describe the vascular component of the nephron?
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Afferent arteriole -> glomerular capillaries -> efferent arteriole -> peritubular capillaries and in some nephrons long capillary loops called the vasa recta. Blood in the vasa recta and peritubular capillaries empties into renal veins .
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What is the juxtaglomerular apparatus?
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It is the specialized area of nephron that contains granular cells which synthesis and secret erenin and macula densa cells which detect flow rate of filtrate
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What specifically d ogranular cells and macula densa cells do?
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Granular cells - synthesize and secrete renin and function as intrarenal baroreceptors. Macula densa cells detect flow rate of filtrate
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What are the three basic renal processes?
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Filtration, secretion, and reabsorption
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What does the combination of the three basic renal processes ultimately determine.
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The composition of the urine.
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How can one calculate the amount excreted?
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Filtered - Reabsorbed + Secreted
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What do filtration and secretion do and what does reabsorption do?
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Filtration and secretion add things to tubule while reabsorption removes them
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What things are freely filtered and what are not?
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Freely filtered - small H20, amino acids, glucose
Not - RBC, WBC , proteins |
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What is the definition of filtration?
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It is the flux of plasma water and low molecular plasma substances from the glomerular capillaries into bowman's space and this forms ultrafiltrate.
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What is size barrier of filtration?
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Fenestratiosn in the glomerular capillaries and foot processes of the podocytes (epithelial cells of Bowman's capsule)
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What is the charge barrier in the filtration of kidne?
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Negative charges are associated with glycoproteins in the capillary endothelial cells and negative charges of proteins in the basement membrane
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What is the compositiom of the ultrafiltrate?
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It contains all lower molecular weight substances in the same concentration as found in the plasma. Large molecules and cells are not filtered in a normal healthy kidney. Therefore urine should be protein free and free of cells
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What is GFR?
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Glomeruli Filtration Rate -It is the sum of the Starling forces that exist across glomerular capillaries. (Pgc - Pbs) - (Oncotic gc - Oncotic bs) = Net Filtration Pressure
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What is the major force driving filtration?
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Hydrostatic pressure in the glomerular capillaries. This force is greatest at the afferent end of the glomerular capillary and is diminished at the efferent end fo the capillary due to flux of fluid out of the capillaries
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How can we alter GFR?
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- Disease can affect filtration membrane and change size and charge barrier for filtration.
- Afferent arteriole vasodilation: Increases Pgc and GFR - Constriction of afferent arteriole: decreases Pgc and GFR - Efferent Arteriole vasodilation: decreases Pgc and GFR - Constriction of Efferent Arteriole: Increases Pgc and GFR |
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How does blood pressure affect GFR?
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Increasing blood pressure can lead to atrionaturitic factor which can dilate afferent and constrict efferent and results in increase Pgc and GFR. but it depends on amounts
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What is normal GFR/day?
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180/day This is important that your plasma volume gets filtered by kidnesy 60X/per day
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How long is average weight for donor kidney on dialysis?
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7 years
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What is filtration fraction?
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GFR/Renal Plasma Flow = .15 - .20. This means that 15% - 20% of plasma that enters the glomerulus is filtered and the remaining amount enters the peritubular capillaries
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How do you calculate filtered load?
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GFR * Plasma concentration of substances
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Why can we use insulin to measure GFR?
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We use insulin because it is a substance that can freely filtered and cannot be reabsorped. It is a plant extract that must be injected and gives exact measurement of GFR.
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Why can we use creatinine to measure GFR?
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It is a breakdown product of muscle creatine and using creatinine gives an estimate of GFR because a little is secreted
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What characteristics can be used to determine GFR?
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Freely Filtered, not secreted, not reabsorbed
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If criteria for the substances used to measure GFR are met then what does the filtered load equal?
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Excreted load.
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For insulin, how do we measure GFR?
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GFR = (U insulin * V mL/min)/ P insulin
7 |
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What is renal clearance?
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It represents the volume of plasma that is completely cleared of a substance. The unites are Volume/Time
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How do you calculate the clearance of substance X?
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(Ux * V)/Px
Ux = Urine concentration of X in mg/L V= rate of urine formation in mL/min, Px = Plasma concentration of X in mg/L |
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What is the definition of reabsorption?
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The movement of a substance from tubule lume ninto peritubular capillaries
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What does it mean if the clearance of a substance Q is less than the clearance of creatinine?
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It indicates decrease in kidney function
*** not sure about this note |
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What processes does reabsorption entail?
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Diffusion and active transport.
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Describe the process of water reabsorption.
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It occurs via osmosis also active transport of salts creates the osmotic gradient for reabsorption of water. Also, the medullary interstitial space has an osmotic gradient from the cortex into the medulla that is important in the final adjustment of water reabsorption. The osmotic gradient was largely developed by active co transport of Na K 2Cl in the thick ascending limb of loop of henle.
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What helps pump sodium into renal interstitial space and keeps concentration of sodium low in the renal tubule cell?
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Na/K ATP ase on basolateral membrane
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What are the mechanisms to increase sodium inside cell?
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Sodium Diffusion into renal tubule cells. Luminal boarder - Sodium co transport with glucose or with amino acids, or counter transport with H+
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What does the diffusion of sodium into interstitial space do ?
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It creates concentration gradient for movement of sodium to peritubular capillaries
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What is Transport Max?
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This represnts the maximum transport rate for a substance. As the filtered load of a substance increases, rabsorption increases until max transport rate is reached. At Tmax, additional increases in filtered loas will result in excretion of substance in the urine.
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How does diabetes cause hyperglycemia?
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Since glucose is freely filtered at glomerulus, the filtered load will exceed Tmax and glucose will appear in urine. In an individual with normal glucose, Tmax is never reached so urine is free of lgucose.
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What is the normal reabsorption rate of glucose?
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100%
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What is secretion?
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The movement of substance from the peritubular capillary or a substance metabolically produced in the renal tubule cell into the tubular lumen.
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How does secretion occur?
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dIFFUSION OR TRANSPORT MECHANISMS
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What happens when substance is excreted?
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It is eliminated from the body.
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What is the renal process when the amount of Q filtered is greater than the excreted load of Q?
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Absorption
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What is the renal process when Net filtered Q < than excreted load?
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Secretion
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Describe the Proximal tubule?
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Tubular cells have a brush boarder and many mitochondria. 67% of ultrafiltrate water and electrolytes are reabsorbed and 100% reabsorption of glucose, amino acids, and small proteins
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Describe loop of henle.
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There is no active transport here. It is permeable to water and electrolytes.
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What ensures that hyperosmotic filtrate is delivered to thick portion of ascending limb?
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Counter current mechanism of flow in loop
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Describe the thick ascending limb?
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It is impermeable to water. Co transports Na K 2CL. Filtrate becomes diluted as it courses through this ascending limb and enters distal tubule hypotonic
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Describe the Distal Tubule.
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Impermeable to water, active transport of salts. Aldosterone increases sodium reabsorption here
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Describe collecting duct.
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Active transport of salts, permeable to water. Aldosterone increases sodium reabsorption and ANF increases potassium reabsorption, ADH increases water reabsorption by increasing the number of water channels in the collecting duct.
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Where does the final adjustment of urine osmolality occur?
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Collecting Tubule
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How do diarrhetics work?
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They block salt transport and if they block thick ascendign limb these are the most powerful
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