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99 Cards in this Set

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4 main functions of kidney/nephron
1. Reabsorb
2. Secretion
3. Eliminate/conserve H20 from body
4. Adjust pH of plasma
Reabsorb
what you digest from glucose/sm prot/AA get filtered into tubular fluid
Where does secretion occur
-in the renal tubular cells
Tubular cells have what mechanism that "sucks" drugs/toxins out of peritubular cap and interstitium and secrete them into tubular fluid
-active secretory/transport mechanism
why are many drugs and toxins not readily filtered into tubular fluid by glomeruli
-they are bound to plasma proteins (usually albumin)
Eliminating/conserving H20 from body does what...
-it adjusts the urine osmolality
when body is water deprived, it will create what...
-body will create a very concentrated urine (1200 milliosmoles/liter)
when have too much water....
body gets rid of dilute urine (low osmolality)
how does body adjust the pH of the plasma
-by secreting H+ ions and making and conserving bicarbonate ions
Aldosterone increases ___ reabsorption int he renal tubules and increases ____ & ______ secretion into tubular fluid.
-Na
-K & H
if there's too much aldosterone, what increases and what does that cause?
-Plasma Na
-causes water retention
At the same time that Na increases, you have what being secreted?
-K+ and H+ are being secreted and dumped, so hypokalemia and increased plasma pH occur
Kidney takes 25 OH Vit D and converts it to 1.25 (OH)2 Vit D (active form), it increases what?
-increases Ca++ absorption from GI tract into blood for distribution to bone and other tissues
ADH gets released from wher in response to what?
-released from posterior pituitary
-in response to dehydration
diuresis means what
-increased Na and water excretion by the kidneys
PTH released in response to what?
-in response to the plasma not having enough Ca++
what does PTH do?
-causes bone osteoclast activity, removes Ca++ from bone and releases it into the plasma
blood flowing into kidney is what % plasma and what % cells
-55% plasma
-45% cells
what is the flow of blood through the kidney
-in through the afferent arteriole, to flomerular capillaries, to bowman's capsule, proximal tubule, collecting duct, renal pelvis, ureters
What is the first step of urine production?
-filtration
what occurs during filtration?
-fluid and substances filtered into proximal tubule are quickly reabsorbed by proximal tubule cells and carried back into circulation by peritubular cap.
the capillaries are composed of a single layer of endothelial cells that permit what?
-they permit leakage of fluid out of the blood into Bowman's capsule and then the proximal tubule
what are fenestrae?
holes that allow greater fluid movement
Mesangial cells
contractile, phagocytic, and respond to inflammatory complement cascade by secreting chemical junk
what is the filtration barrier?
-a triple layer of negatively charged membranes:
-flomerular capillary endothelial cells
-basement membrane
-visceral epithelial cells (podocytes)
when does the filtration barrier charge disappear?
-disappears due to glomerulitis
-(filtration barrier becomes excessively leaky to RBC and plasma prot)
Minimal Change Disease
-typically a childhood disease in which the negative charge of the filtration barrier goes away
massive proteinuria
lose protein/albumin into the urine and bad things happen
GFR
-how much plasma is filtered out of the capillaries into Bowman's capsule and therefore into the proximal tubule
Equation for amt plasma filtered
amt excreted (urinated) = amt filtered + amt secreted - amt reabsorbed
ERPF
-Effective Renal Plasma Flow - the total amt of plasma going through all the glomeruli per minute
PAH
-Para-aminohippuric acid - freely filtered into the tubular fluid and none of it is reabsorbed
GFR equation
GFR = [U] i.n. x V/Pi.n.
ERPF equation
[U]pah x V/[P]pah
what is the value of ERPF?
585 ml/min
What is Total Renal Plasma Flow?
the amount of plasma delivered to the whole kidney
What's the value of Total RPF?
650 ml/min
What is hemocrit?
-the fraction of whole blood volume comjposed of RBC's
what is the value of hemocrit?
45%
What is the fraction of whole blood?
1-45% = 55%
Calculation for Total renal blood flow
TRBF = TRPF/(1-Hct) = 650 ml/min/0.55 = 1200ml BLOOD/min
How much of the total blood volume is filtered each time around?
20%
macula densa
-part of the thick ascending limb of the tubule that passes between the branches of the afferent/efferent arterioles
the ________ cells in the afferent artiole detect changes in BP in the afferent arteriole
-granular
If BP decreased, granular cells secrete what?
-they secrete more renin
If BP is increased, granular cells secrete what?
-they secrete less renin
Renal flow through the kidney
-afferent arteriole - to glomerular capillaries - which release fluid called glomerular filtrate - enters Bowman's capsule - into proximal tubule - to descending loop - to Loop of Henle - to ascending loop - to distal convoluted tubule - to collecting duct
H20 is passively reabsorbed from the fluid of the ____________
- from the thin descending Loop of Henle
Na+ is passively reabsorbed from the fluid of the ____________
-from the thin ascending limb
Counter-current multiplier
-cyclic mechanism that creates a very high interstitial osmolality (1200mOsm) at the bottom of Henle's loop.
In dehydration, what horomone is released and from where
-ADH from the posterior pituitary
What does ADH do in dehydration?
-it creates new pores in the collecting duct through which water can move by osmosis. The osmotic "suction" that pulls water out of collecting duct is created by high osmolality of the interstitium above.
Even though water is being drawn into the interstitium, high osmolality is not diluted b/c.....
-the peritubular capillaries take it away, AND
-b/c the counter-current multiplier mechanism works to maintain the high osmolality.
Renal clearance
-used to determine how fast your kidneys excrete a substance/drug
definition of clearance
-the "virtual" volume of plasma from which the substance of interest has been entirely removed
(how many individual ml of blood are cleared of solute they are carrying)
equation for Clearance
Cx = Ux x V/Px
-expressed in ml/min
What is the breakdown product of P-Cr?
-Creatinine
T/F
low creatinine clearance means that the person has a renal problem (azotemia)
-T
Creatinine is ideal b/c...
-it's freely filtered and not reabsorbed
T/F
a patient's creatinine clearance is approximately = that patient's GFR
-T
T/F
pt's plasma concentration of creatinine should be constant if their clearance of creatinine is constant and in the correct range
-T
Renal Artery Stenosis
-Blood flow to kdiney is inadequate
-kidney tries to overcome pressure problems by producing renin, angiotensin, angiotensin 2, aldosterone, ADH
Causes of renal artery stenosis
1. atherosclerosis in renal artery vessels
2. fibromuscular dysplasia
4 things to look for in Renal artery stenosis
1. refractory HTN as Sx and HTN medication doesn't work
2. new onset of HTN in older pt with h/o norm BP
3. ARF upon starting ACE inhibitor
4. bruit
ARF upon starting ACE inhibitor has 3 effects:
-low renal blood flow causes low glomerular filtration press (GFP)
-efferent arteriole constricts to try to raise GFP, which causes HTN
-given ACE inhibitor, efferent arterioles are forced to dilate, which lowers GFP, resulting in RF
Fibromuscular Dysphagia
-primarily in young women 25-45
-unexplained HTN
-idiopathic
-fibromuscular structure crowds lumen of arteriole leading to HTN
-"Beads on a string" appearance
Rx: angioplasty
Primary hydronephrosis
-urine backs up into kidney and press causes damage to glomeruli, nephron, etc
-blockage occurs at uretero-pelvic jct
Secondary hydronephrosis
-blockage anywhere in urinary tract
Rx: remove blockage
Polycystic Kidney Disease
-it's a cause of adult CRF
-simple cysts: few fluid filled cysts, but no Sx
-polycystic: genetic autosomal dom disorder, chrom 16
-cysts take over renal tissue
-polycystin involved
Sx of poylcystic kidney disease (6)
1. enlarged kidneys
2. multiple fluid filled cysts
3. pt approx 40 y/o when Sx start appearing
4. hematuria, HTN in 70-75%
5. Increased risk of UTI
6. occasionally cysts in liver are present
Rx for Polycystic kidney disease
-dialysis until new kidney for transplant
CRF
-permanent injury to kidney
-scar tissue replaces regular tissue; irreversible
-if ARF isn't controlled, will lead to CRF
-increased BUN and creatinine due to increased GFR
Azotemia
-increased BUN and Bcre without signs or Sx
Uremia
-Any RF with signs and Sx
-urea buildup in blood
ESRD
-stage of RF requiring dialysis/kidney transplant
Causes of CRF: (6)
1. Diabetes
2. HTN
3. Glomerulonephritis (prim or secondary)
4. interstitial nephritis
5. polycystic kidney disease
6. other (injury to any part of nephron, interstitium, etc)
Diabetes (after 10 or more yrs)
-diabetes mellitus
-type 1: insulin deficiency
-type 2: insulin resistance in tissue; sx: microalbuminuria - >3.5g prot/day
HTN
-causes nephrosclerosis, thickening of arterioles, renal blood flow decreases
-low grade proteinuria
-can cause kidney disease but also works other way
interstitial nephritis
-heavy metals, etc
CRF drug of choice
-ACE inhibitor (in hope of saving the nephrons that are still alive)
Consequences of RF (7)
1. Na+ handling
2. water handling
3. K+ handling
4. Acid/base problems
5. Mineral metabolism decreases
6. drug secretion decreases
7. erythropoietin production decreases
Na+ handling: decreased ability to secrete or excrete Na+
-if increase Na+, Na+ retention, circulating fluid vol increases, leads to HTN and edema
-if decrease Na+, hypotension (?)
water handling
-if increase water, body fluid will be dilute, leading to hyponatremia
-if decrease water, hypernatremia, leads to confusion, convulsions, coma
K+ handling (distal tubule in charge)
-become hyperkalemic, display heart dysrhythmias
-pt advised to restrict K+ intake
A/B problems: Acidemia created
- Increased H+ concentration leads to decrease in enzymatic rxn
-HCO3- not being formed by kidneys, further incrase in H+
-not enough ammonia produced due to high H+ gradient
mineral metabolism decreases
-vit D deficient b/c not converted to final form
-Ca++ not absorbed as well so get hypocalcemia
-loss of bone mass
drug secretion decreases
-doses become larger b/c not clearing as fast
-increased action, worse side effects
erythropoietin production decreases
-anemia develops
CRF Sx:
general consequences
-N/V
-Fatigue
-Anorexia
-disrupted sleep
CRF Sx:
neurological conseq
-decreased seizure threshold
-peripheral neuropathy: parasthesias
CRF Sx:
hemotolgic conseq
-HTN (renin release) - kills heart by overworking LV
-Acute pericarditis due to uremia irritating pericardium - chest pain, chest rub
CRF Sx:
skeletal conseq
-bone pain
-susceptible to pathologic fx
-soft tissue calcification
CRF Sx:
other conseq
-GI bleeding
CRF Tx
-treat sx.
Proteinuria
-points to glomerulopathy
-glomeruli are leaking
Filters in glomeruli: (2)
1. size selective filter
2. charge selective filter
Size selective filter
-glucose, water, urea can filter through
-anything with radius > 4nm won't filter
Charge selective filter
-albumin neg charge, so blocked by filter
Protein in urine
-40% albumin
-40% Tamm-Hursfall prot