Renal: intro lecture Flashcards
renal capsule
tight capsule embedded in fat
renal fascia
-role
fibrous tissue
-attaches kidney to posterior abdominal wall
hilum
renal blood vessels, nerves, lymphatics and ureter enter/exit kidneys
renal cortex
outer layer with glomeruli and convoluted tubules
renal medulla
inner section with tubules and collecting duct
-consists of pyramids
renal columns
from cortex through renal pyramids
minor calyx
pyramid apexes project into cavity–forms minor calyx
-recieves urine from collecting ducts through renal papilla
major calyx
joins to form the renal pelvis
renal pelvis
joins proximal end of ureter
which artery supplies blood to kidneys
renal arteries
which arteries supplies renal columns and pyramids
interlobar arteries
what feeds into the efferent arteriole
glomerular capillaries
what conveys blood to 2nd capillary bed
efferent arteriole
what subdivides into 4-8 glomerular capillaries
afferent arterioles
functional unit of the kidney
nephron
role of neprhon
- FILTERS plasma at the glomerulus
- REABSORBS and SECRETES substances at different tubular structures
-forms filtrate of protein-free plasma–>ultrafiltration
how many nephrones does each kidney have
about 1.2 million
-most in superficial cortical nephrons
juxtamedullary nephrons
close/deep in the medulla
-imp for concentrating urine and secreting renin
define filtration
movement of protein-free plasma across the glomerular membrane (hydrostatic pressure)
define tubular reabsoprtion
movement of fluid and solutes from tubular lumen to the peritubular capillaries
define tubular secretion
transfer of substances from peritubular capillaries to tubular lumen
define excretion
elimination of a substance in the final urine
bowen’s glomerular capsule
circular space b/w visceral and parietal epithelium
double layer cup
-contains PODOCYTES
Podocyte
- foot like processes–form network of intercellular clefts called FILTRATION SLITS —which modulate filtration
- part of the bowmans capsules inner membrane
- filtration is most imp function of podocytes***
renal corpuscule consists of
glomerulus + bowmens capsule
describe direction of blood for:
-efferent and afferent arteriole
afferent goes into the glomerulus—to the glom caps
efferent goes OUT of glomerulus aka kidney
glomerulus blood supply
afferent arteriole
-drained by efferent arteriole
juxtaglomerular cells
specialized cells located around afferent arteriole where the arteriole enters the glomerulus
**secrete renin when BP in arteriole falls
juxtaglomerular apparatus role
controls renal blood flow (aka BP), glomerular filtration, and renin secretions occurs here***
formed by distal convoluted tubule and glomerular afferent arteriole
macula densa
specalized epithelial cells in distal convoluted tubule that detects [na] of fluid in tubule
—>so in response to high sodium— it can trigger contraction of the afferent arteriole–>reducing BF to glomerulus and reducing GFR
synth nitric oxide
vasodilator
glomerular endothelial cell
synth endothelin-1
vasoconstrictor
- glomerular endothelial cell
- regulates glomerular blood flow
direction of filtrate as it enters glomerulus
plsma filtrats from glomerulus–>glomerular basement membrane–>bowman space–>forming primary urine
mesangial cells
secrete mesangial matrix and lie b/w glomerular capillaries (also provides support)
-phagocytic properties–>rel inflamm cytokines and GF
If a person’s glomerular filtration membrane (visceral epithelium) has been injured, which structure would be affected?
podocytes
- **these are the cells that make up the inner layer of glomerular filtration membrane
- cells have foot like processes that adhere to basement membrane
- covers glomerular capillaries
what is juxtaglomerular apparatus made of
-role?
juxtaglomerular cells and macula densa
–senses pressure and solute concentration
what are macula densa cells and where are they located
in the JGA
detect solute concentration
what is the vasa recta
network of capillaries that follows and surrounds the loop of henle
filtration rate
/day? and /min?
glomeruli filter 180L/day or 120ml/min (this is when we are born and healthy)
*slows down as we age
filtration rate directly related to?
renal blood flow
what is the primary force driving filtering
outward pressure
***BP entering the glomerulus aka renal blood flor
what counteracts the outward pressure in filtration
inwards pressure 2nd to hydrostatic pressure of fluid within the urinary space
AND
pressure from proteins left in capillaries—-bc they try to pull water back into circulation—–called colloidal osmotic pressure
net flitration pressure =?
outward - inward pressure
glomerulus is freely permeable to _____ and relatively impermeable to ____
perm to water and imperm to large colloids (plasma proteins)
where is 99% of filtrate reabsorbed
into peritubular capillaries and returned to the blood
favoring forces to filrtration
capillary hydrostatic pressure
opposing forces to filtration
oncotic pressure in capillary and hydrostatic pressure in Bowman capsule
kidneys get ______ ml blood/min
-how much of that is plasma?
1000-2000 ml
**600-700 ml=plasma aka renal plasma flow
peritubular capillaries
surround the PCT and DCT and loop of henle
vasa recta
network of capillaries for the juxtamedullary nephrons—- imp for formation of a concentrated urine
GFR
filtration of plasma into Bowman’s space
20% of the renal plasma flow (120-140 ml/min)
-directly related to perfusion pressure in glomerular capillaries
relationship b/w renal blood flow and MAP/vasc resistance
if MAP decreases= decrease in renal blood flow
if vasc resistance incrs=decrs in renal blood flow
afferent arterioles remain open by?
prostaglandins
efferent arteriole is kept slightly constricted by?
ACEI
capillary hydrostatic pressure
- define
- relationship to glom filtration
primary force favoring filtration of water and solutes
-glomerular filtration is favored by this and opposed by oncotic pressure in capillary and hydrostatic pressure in the bowman capsule
capillary oncotic pressure relationship to filtration
force opposing filtration
bowmans capsule hydrostatic pressure relationship with filtration
opposing force of filtration
interstitial hydrostatic pressure relationship to filtration
none
opposing forces to filtratioin
capillary oncotic pressure
bowmans capsule hydrostatic pressure
opposing forces to filtration
capillary hydrostatic pressure
list the roles of kidneys
A WET BED
A–acid base balance
W–water balance– thru reabsorbtion and elimination
E—electrolyte balance
T—toxin removal
B—blood pressure control via hormonal effects—AGII, aldosterone and fluid balance
E—effects hormone production–>erythropoetin (stim RBC prod), renin and activation of vit d
D—detached bone? its for bone metabolism—Ca and Phosphorus metabolism
renin
regulation of BP
erythropoetin
prod of RBCs
1,25 dihydroxyvitamin D3
metabolism of Ca
aldosterone
regulator of BP
-too much= lose K+ and retain Na+—>retain water–>incr BP
ADH
secretion makes DCT and collecting duct more permeable to water—so it goes back into the body
if there is reduced salt intake or reduced volume—what happens
RAAS
- enzyme Renin converts Angiotension I—> II–>incrs BP by stimulation vasoconstriction
- ATII stimulates Aldosterone–>causes Na+ resorption (reabsorbed)
where is ADH made
posterior pituitary
whats required to convert ATI—> ATII
renin
kidneys role with vit D?
kidneys hydroxylate 25 hydroxy Vit D3 to the active form of Vit D–> 25 hydroxy vit D3 aka Calcitriol
what is the active form of vit D
25 hydroxy vit d3 or Calcitriol
we use what to get a rough estimate of kidney functino
GFR
- tells us how much is filtered over time
- estimates % functioning nephrons
- dependent on sex, age, body size, creatinine
- cannot be measured directly tho—-we use creatinine/creatining clearance
avg GFR
men
women
200 ml/day
men= 130ml/min
women=120ml/min
GFR for kidney failure
<15
**dialysis is needed*
what would be GFR be for kidney dz with normal GFR
> 90
chronic conditions most commonly assoc with decr GFR?
htn (2nd mc)
dm (mcc)
difference b/w severely impaired GFR (stage 4) and Kidney failure (stage 5)
stage 5–>actively ON dialysis and your GFR <15
stage 4–> preparation for dialysis or transplant but not dialysis yet…… and GFR 15-29
renal autoregulation
- what is it
- what happens when systemic bp incrs
- **regulation of renal blood flow and GFR
- ->kidneys adjust dilation/constriction of afferent arterioles to counter changes in BP
- ->intrinsic mechanism works over large range of BP—but can malfunction if you have kidney dz !!!!
- as systemic BP increaes–afferent arterioles CONSTRICT—preventing an INCR in filtration pressure
- ->prevents wide fluctuations in systemic arterial presure from being transmitted to glomerular capillaries
- ->solutes and water excretion is constantly maintained—despite arterial pressure changes
what happns when arterial pressure declines
glomerular perfusion increases
- HOW?
- ***** autoregulation Myogenic Mechanism (stretching)
- ->stretch on the afferent arteriolar smooth muscle decreases—-arterioles relax
- –>incr in arteriolar pressure decreases glomerular perfusion–>causes arteriole smooth muscles to contract
what happens when Na filtration increases
GFR decreases
HOW??? Autoregulation: tubulo-glomerular Feedback
- –>macula densa cells stimulate afferent arteriole vasoconstriction
- –>when NA filtration decrs–>opposite occurs—>GFR increases
neural regulation of kidneys
sympathetic NS–vasocontricts—>lowers GFR
Baroreceptor reflex–>vasoconstriction of afferent arterioles with activation of alpha 1 adrenoreceptors–>decrs GFR and glom perfusion
changes in body position and/or exercise–affect on GFT
exercise or change in position–>activates renal sympathetic neurons–>causes mild vasoconstriction
severe hypoxia affect on kidneys
hypoxia stimulates chemoreceptors—>decreases GFR by means of sympathetic stimulation
RAAS
- function
- breakdown
- when is renin released
renin-angiotensin-aldosterone-system
*incrs systemic arterial pressure and incrs NA reabsoprtion
RENIN–>enzyme formed and stored in afferent arterioles of Juxtaglomerulus apparatus
Renin released when theres decr BP in afferent arterioles, decr NACL [ ] in DCT, symp nerve stimulation or B-adrenergic receptors and release of prostaglandins–>forms angiotensin I (it is physiologically inactive without renin)
Angiotensin-converting-enzyme (ACE) helps convert AGI–>AGII
AGII–>stimualtes secretion of aldosterone by adrenal cortex–>AGII= POTENT VASOCONSTRICTOR!!!!!!!—>aldosterone stimulates ADH secretion and thirst
most potent vasoconstrictor
AGII
Natriuretic Peptides
Atrial Natriuertic peptides (ANP) and Brain Natriuertic peptides (BNP)
ANP–>secreted from myocardial cells in atria
BNP–>secreted from myocardial cells in ventricles
BOTH
- inhibit Na and water absoprtion by renal tubules
- inhibit secretion of renin and aldosterone
- promote VASODILATION of afferent arterioles and CONSTRICTION of efferent arterioles
- incrs urine formation–>leading to decr blood volume and BP—>promotes NA and water loss
what can override renal autoregulation
extrinsic mechanisims—> neuronal and hormonal
NEURONAL
-large drop in BP–>sympathetic stimuation–>contraction of afferent arteriole–>reducing urine production–>activating RAAS–>to regulate BP and fluid balance
HORMONAL
-ANP can incr GFR–>ANP secreted if plasma volume increases–>which increaes urine output
C-type natriuretic peptide
secreted from vascular endothelium and in the neprhon
causes vasodilation
Urodilatin
secreted by DCT and collecting ducts
causes vasodilation, natriuetic and diruetic effects
A patient has hypovolemic hyponatremia. Which of the following is involved in the reaction/response to this ?
RAAS
what happens when bladder gets 250-300 ml of urine
- bladder contracts
2. internal urethral spinchter relaxes through activation of spinal reflex arc— aka the micturition reflex
three major things urine formation required and define all three
- glomerular filtration –>movement of substances from the blood within the glomerulus into the capsular space
- tubular reabsorption–>movement of substances from tubular fluid back into the blood
- tubular secretion–>movement of substances from the blood into the tubular fluid
renin release is triggered by
decrease in BP in afferent arterioles
how many ML of urine does the bladder need to contract
250-300 ml
Golmerular Filtration
blood moves from afferent arteriole–>into capillaries of glomerulus–>pressure INCRS–>this forces water and small molecules through glomeruluar wall and pores–>into the tubules–>where resoprtion and secretion occur
**simple diffusion of solutes from H–L concentration + osmosis
how many ML of urine does the bladder need to contract
250-300 ml
Golmerular Filtration what happens here
blood moves from afferent arteriole–>into capillaries of glomerulus–>pressure INCRS–>this forces water and small molecules through glomeruluar wall and pores–>into the tubules–>where resoprtion and secretion occur
**simple diffusion of solutes from H–L concentration + osmosis
tubular resoprtion–what happens here
water, glucose, amino acids and ions needed are transported out of filtrate into tubule cell and then they enter the blood (capillaries)
tubular secretion–what happens here
H+ K+ creatinine drugs are removed from pertibular blood and secreted by tubule cells into the filtrate
how much glucose is usually retained
180 mg/dl
what happens to creatinine in the tubules
since it is a waste producte– it is excreted
Proximal convoluted tubule
-what happens here—- what is reabsorbed from filtrate and what is secreted into filtrate
REABSORBED FROM FILTRATE
- NA (majority)
- CL
- K
- water (ADH NOT required)
- amino acids
- glucose
SECRETED INTO FILTRATE
- urea
- H+
- creatinine
- *PH is adjusted here
- *only surface covered with microvili for reabsoprtion
what part of the nephron is the ONLY surface that contains microvili for reabsorption
PCT
loop of henle
-what happens here (each loop)
- osmotic gradient is created
- countercurrent mechanism
DESCENDING LOOP
-allows water to pass from filtate into interstitial fluid—making a very concentrated filtrate
ASCENDING LOOP
- reabsorbs NA and CL from filtrate into the interstitial fluid–>active transport
- water is retained
**filtrate becomes more and more dilute as it enters the DCT
distal convoluted tubule what happens here
reabsorbs: NACL, water (ADH is required here) , bicarb,
secretes/stays in filtrate: K and H
- maintain blood PH and electrolyte balance
- secretes drugs and toxins
**thiazide diuretics works here!!!
collecting duct–what happens here
determines final urine volume by reabsorbing water (ADH REQUIRED) and secreting NA K H HCO3 from Filtrate
what does the convoluted portion of DCT do?
helps dilute tubulr fluid
what does the straight segment of DCT do
its permeable to water—– and is controlled by ADH
what cells are in the CD
principal cells
- they reabsorb water and sodium
- secrete K+
the primary function of the LOH is
establish a hyperosmotic state within the medullary instersitial fluid
what part of nephron regulated acid-base balance and how does it do this
DCT
-excretes H+ and forms new bicarb
what part of nephron maintains ph of filtrate
it is established in the DCT
what part of the nephron is highly permeable to NA K and CL and less permeable to water and urea
thick ascending portion of the LOH
ADH
- controls?
- roles in the nephron
- if present, what hapens with urine
controls concentration of final urine
increases WATER permeability in last segement of DCT and along CD
-causes high amount of water reabsorption—>less urine volume
% of urea excreted in urine and % relecyed in kidneys
50% urine
50% kidneys
- urea=end product of protein metabolism
- major constituent of urine
role of catecholamines on the afferent arteriole
norepi and epi cause afferent arteriole to constrict–>decrs GFR and RBF
what is renalase
horme made in kidney
-degrades catecholamines and regulates BP
best blood test to monitor chronic not acute dz
plasma creatinine [ ]
plasma cystatin C [ ] measures
progressive renal dysfunctin
-its a plasma protein that is freely filtered at glomerulus
BUN levels– what happens during dehydreation
BUN incrs
when do BUN levels rise
dehydration
kidney failure
normal urine ph
5-6.5
norma sp for urine
1.010
define the following
- diuresis
- antidiruetics
- anuria
- oliguria
- nocturia
- polyuria
diuresis=incr production of urine
antidiurietcs=dim urine production
anuria=no urine production
oliguria = <400 cc/day aka decr urine output
nocturia= at least 3x urinating at night
polyuria= prod of more than 3L/day
