Lecture 14 and 15 Renal Flashcards
kidney function redundant meaning
only 1 fully functioning kidney is needed - this is why you can donate your kidney
structure of kidney
- 1 renal artery and vein
- isoosmotic renal cortex
- hyperosmotic renal medulla made up of renal pyramids that are separated by renal columsn
arteries going through kidney
renal artery –> many small arterioles –> afferent arterioles –> glomerulus (ball of capillaries) –> efferent arterioles –> peritubular capillaries –> interlobular veins –> renal vein
nephron structure
PCT proximal convoluted tubule –> descending limb of loop of henle –> ascending limb of loop of Henle –> DCT distal convoluted tubule –> collecting duct
vasa recta
- parts of peritubular capillaries that are parallel to the nephron
structures that drain filtrate
collecting duct –> minor and major calyces –> renal pelvis –> bladder
2 types of nephron - location and function
- cortical, located mostly in cortex where it is isotonic to blood
- juxtamedullarly, goes very deep into medulla where it is concentrated and is thus good and making concentrated urine
renal corpuscle - list 3 barriers and characteristics
1) fenestrae, holes between endothelial cells that prevent RBC, WBC, and platelets from pass through
2) basement membrane - negatively charged to repel negatively charged proteins
3) slit diaphragms created by large podocyte cells which have primary processes and pedicels, also negatively charged
glomerular filtration rate and pressure
- about 120ml/min
- 45 gallons = 180 liters a day
- 10 mmHg net pressure
obligatory water loss and average urine production
- obligatory = 400mL
- average = 1-2L
intrinsic regulation aka renal autoregulation - goal, name the 2 mechanisms
- goal is to maintain 10mmHg filtration pressure regardless of blood volume adn pressure
- myogenic and tubuloglomerular feedback by the JGA
myogenic regulation
- hypertension –> smooth muscle contraction and afferent arteriole constriction so less blood flow
- hypotension –> smooth muscle relaxation and more blood to afferent arteriole and more pressure
JGA and tubuloglomerular feedback - 2 important cell types and their function
- macula densa: specialized cuboidal cells in DCT that sense sodium levels
- sodium level = water and filtrate amount because water and sodium travel together
- granular cells: between DCT and afferent arterioles, receive signals from macula densa and cause dilation/constriction of afferent arterioles
PCT - how are glucose, Na+, and proteins reabsorbed, what type of transport is. used
- Na+/K+ ATP ase pumps Na+ out of cell and into blood
- sodium glucose cotransporter and sodium amino acid cotransporter moves glucose and amino acid from filtrate and inito cell as Na+ follows down its concentration gradient - secondary active transport
- glucose enters blood following its concentration gradient by facilitated diffusion
Cl- reabsorption in PCT
- follows Na+ passively
electrolyte reabsorption
- as water is removed from filtrate (as it follows Na+) filtrate gets more concentrated
- this creates a concentration gradient which electrolytes can follow to go into blood
- only as much electrolytes as needed are reabsorbed
water reabsorption - percentages in each portion of renal tubule
- 65% in PCT 10% in descending henle, leftover 15% subjected to ADH and aldosterone in late DCT
ADH vs aldosterone effects
- ADH: water reabsorption only
- aldosterone: water and Na+ reabsorption
what happens in descending Henle
- aquaporins and concentration gradient causes what to be reabsorbed
what happens in ascending Henle - what important transporter
- Na+ gets pumped out by NKCC
descending VR function
- water released
- Na+ reabsorbed
ascending VR function
- absorbs water from the descending Henle and brings it back to the body
- Na+ also leaves to be recirculated
describe recirculation of salt
- pushed out of filtrate by NKCC in ascending Henle
- reabsorbed by descending Henle
- pushed back into medulla by ascending henle
explain positive feedback / counter current multiplier system between descending and ascending henle
- descending creates concentrated filtrate by water being reabsorbed through aquaporins
- ascending releases Na+ in to medulla making it salty so that more water can go down concentration gradient and be reabsorbed in the descending limb
- recall NKCC is driven by concentration gradient across filtrate and inside of the cell
NKCC - location, what is it driven by and what is transferred
- located in thick ascending henle on the apical side (between filtrate and inside of the cell)
- Na+/K+ ATPase moves Na+ into the medulla to decrease Na+ concentration in the cell
- NKCC is a cotransporter, secondary active transport of 1 Na 1 K and 2 Cl
- Na+ moves down concentration gradient and into cell
urea - what is it and what is the flow of recirculation
- waste product
- taken out of the colelcting duct –> into medulla –> brought back into filtrate by ascending and DCT
ADH mechanisms - what else is needed to drive water reabsorption
- ADH causes more aquaporins to be added to DCT by principal cells
- concentration gradient is needed for water to be reabsorbed
- hypertonicity created by NKCC
aldosterone - what mechanism
- lipophilic and genomic mechanism that causes Na+ and water that follows to be reabsorbed
renal plasma clearance definition and formual
- ability to remove substance from blood through urine
- volume of plasma rom which a substance is entirely removed
- RPC = (filtration + secretion) - reabsorption
RPC = 0 meaning and 2 ways
- no filtration, like for proteins and RBC
- filtered but 100% reabsorbed like glucose
RPC < GFR example
- means some of it is reabsorbed
- urea because it recirculates in the medulla
RPC = GFR example
- creatinine and inulin
- no secretion and reabsorption
RPC > GFR example
- xenobiotics aka dugs
- more is secreted
creatinine - origin, clinical usage
- comes from creatine proteins in muscle that are broken down
- high blood plasma creatinine levels = glomerular dysfunction
inulin
- similar to creatinine because RPC = GFR but inulin must be consumed orally
organic anion transporters and organic cation transporters - where are they located and what do they transport
- located in liver and kidney and secrete drugs into bile and urine
renal blood flow meaning and amount
- amount of blood flowing through the glomerulus
- only 20% of it is actually filtered
- 650 ml/min
renal plasma threshold aka transport maximum meaning
- maximum amount of a substance that can be reabsorbed by the transporters
- glucose = 180-200mg/dL
glomerular filtration rate meaning and amount
- 120ml/min
- 45 gallons = 180L a day
renal insufficiency vs renal failure glomerular filtration rate amount
- renal insufficiency <60ml/min aka less than half of normal kidney function
- 60ml/min is need for normal functioning
- renal failure = <20% of normal function
- main cause of renal failure and need for dialysis is diabetic neuropathy
fasting blood glucose - normal, prediabetes, and diabetes
- normal = 70-100
- prediabetes >125
- diabetes >145
random glucose test range
- always less than 200
aldosterone - what is reabsorbed/secreted and hw much
- 90% of Na+ and K+ are reabsorbed before DCT
- without aldosterone 80% of remaining 10% of Na+ is reabsorbed along with water
- with aldosterone 100% of remaining 10% is reabsorbed along with water that follows
what stimulates aldosterone production and how
- high K+ or low Na+
- recall aldosterone causes Na+ reabsorption and K+ secretion
- hyponatremia causes RAA system to be activated
- hypokalemia stimulates zona glomerulosa directly
K+ excretion (diagram)
- 100% reasborbed in PCt
- some is secreted by aldosterone
ANP - how produced, cause, mechanism of effect, and effect
- atrial natriuretic peptide
- stretch receptors in atrium sense high blood volume (opposite of dehydration)
- more salt and water get excreted
- mesengial cells between glomerular capillaries relax and increase blood flow and thus GFR
summarize 3 effectors on GFR
- autoregulation = no change in GFR
- ANP = increased GFR
- symapthetic = decreased GFR by constricting afferent arterioles
relationship between Na+, K+, and H+ reabsorption
- Na+ reabsorbed causing electrical gradient and K+ or H+ enters filtrate based on concentration
diabetic acidosis - why does it cause hyperkalemia then hypokalemia
- during acidosis H+ enters cells and K+ exits cells –> transient hyperkalemia causes body to excrete K+ through aldosterone –> hypokalemia
what 2 organs/systems regulate blood pH
- kidney and respiratory
what does the kidney excrete to regulate blood pH
- H+ and bicarbonate
3 urine buffers and where are they created
- ammonia made by cells lining the PCT which deamminate glutamic acid to produce ammonia
- bicarbonate that is filtered from blood
- phosphate ions
Na+/H+ antiporters, where are they located, what are they driven by, what do they do
- located on apical membrane of cells in the PCT
- move H+ into filtrate and Na+ into cell
describe how bicarbonate is reabsorbed
- converted by carbonic anhdyrase on cell surface to CO2 and H2O
- bicarbonate cannot travel directly into cell
- converted by CA in cell back into bicarbonate
- bicarbonate goes down concentration gradient into blood where more buffer is needed due to acidosis
diuretics - meaning and 2 main mechanisms
- increase urine production
- block Na+ reabsorption and water that follows
- block water reabsorption directly
carbonic anhydrase inhibitors - mechanism
- mild diuretic
- prevents CA from causing bicarbonate to be reabsorbed and as a result less water and CO2 are reabsorbed
- used to treat alkalosis
loop diuretics - mechanism and location
- most powerful diuretic
- blocks NKCC so that salt and water cannot be reabsorbed
- also affects countercurrent multiplier system - medulla is less concentrated so less water is reabsorbed in descending henle by diffusion down gradient through aquaporins
thiazide diuretics - mechanism and locaiton
- prevetns reabsorption of last 10% of Na+ in DCT
aldosterone antagonist - mechanism and location, why are they potassium sparing
- recall aldosterone causes Na+ reabsorption and K+ secretion so aldosterone antagonists spare K+
- DCT
osmotic diuretics - mechanism, 1 example, relation to diabetes
- increases osmotic activity of filtrate so that water is kept inside
- mannitol = sugar alcohol orally consumed, not metabolized
- mimics polyuria due to diabetes
