Renal Flashcards
what is the urinary system composed of?
paired kidneys
ureters
bladder
urethra
where is urine produced?
the kidneys
where does urine drain through?
ureters into urinary bladder
where is urine stroed?
bladder
what is urine elimainted through?
urethra
what are the major blood vessels connceting the urinary system with the rest of the body?
abdominal/thoracic aorta
inferior veina cava
kidneys need ____ blood in _______ time
max blood
min time
where are the kidneys loacted in the body?
T12 to L3
retro-peritoneally (outside the cavity)
what is the approximate size of the kidney?
12 cm tall
6 cm wide
3 cm thick
why is the location of the kidney’s strategic?
the kidney’s are located centrally near major vessels, tissues, arteries etc…
its close proximation to the heart allows for max blood in min time
kidneys clean the body of _________ and ___________
metabolic waste and foreign substances
kidneys regulate _______and __________
fluid volume and blood pressure
although kidneys mostly deal with urine, they help to regulate ___ and ____of ECF and blood
osmolarity
essential ion concentration
why are the kidneys important to endocrine functions?
they produce erythropoietin which stimulates RBC production
and produce renin which activates angiotensin and aldosterone
what are nephrons and where are they located in the kidney?
nephrons are microscopic tubular structures
they are located in both the cortex and medulla
what represents the outer region of the kidney?
cortex
what represents the inner region of the kidney?
medulla
what does the medulla form?
pyramids or lobes which are prolonged by large cavities connected with the renal pelvis
what is the renal pelvis?
the central receptacle collecting the urine
where is urine made?
the nephrons
where is urine collected?
pelvis
as you go from the head of the nephron tubule to the end, name the parts;
bowman’s capsule
proximal tubule
descending loop of henle
ascending loop of henle
distal tubule
renal pelvis
what does the bowman’s capsule contain?
a set of micro vessels called the glomerulus
the bowmans capsule AND the glomerulus form ______
the renal corpuscle
when the renal tubule folds back on itself so that the distal tubule contacts the renal corpuscle, it is called _________
juxtaglomerular apparatus
blood enters the nephrons via ______
afferent arteriole
describe the path of blood after entering the afferent arteriole;
glomerular capillaries
efferent arteriole
peritubular capillaries
renal micro circulation is a ______-
portal circulation
why is renal microcirculation a portal?
interconnecting
capillary mixing
facilitates a large change in blood compositiion
what are the 2 types of nephrons?
cortical and juxtamedullary
what is the location of a cortical nephron?
most of the loop of henle is in the cortx or outer layer
what is the location of the juxtamedullary nephron?
most of the loop of henle is loacted in the medulla or the inner portion
cortical nephrons make up the larger portion of nephrons they have _____ loops and make ______ of filtrate
short loops
90%
juxtamedullary nephrons are larger and contain the ________ capillaries and a _________ loop
vasa recta
long loop
what is the vasa recta?
a long, narrow capillary set that follows down the loop of henle
what is the path of blood flow into a kidney?
reneal artery
segmental artery
interlobar artery
arcuate artery
cortical radiate artery
arterioles (nephron)
which artery interacts directly with the glomerulus?
cortical radiate artery
are the arteries within the medulla of the kidney?
no they are within the spaces around the medulla
renal microcirculation is located _________
in the nephron
describe the path of blood out of the kidney;
vasa recta and peritubular capillaries (naphron)
cortical radiate vein
arcuate vein
ionterlobar vein
renal vein
what are the 3 different processes involved in the renal blood treatment and urine formation?
filtration
reabsorption
secretion
where does filtration occur?
renal corpuscle
where does reabsorption and secretion occur?
peritubular capillaries
what results in the formation of urine?
from the adjustment of bloof composition and volume by the nephron
urine is produced by the progressive transformation of the initial blood filtrate through the renal tubule
what are the 3 processes involved in urine formation?
glomerular filtration
tubular reabsorption
tubular secretion
what is glomerular filtration?
nondiscriminant filtration of a protein-free plasma from the glomerulus into the bowmans capsule
what is tubular reabsorption?
selective movement of the filtered substances from the tubular lumen into the peritubular capillaries
what is tubular secretion?
selective movement of nonfiltered substances from the peritubular capillaries into the tubular lumen
what percentage of plasma that enters the glomerulus is filtered?
20%
what percentage of plasma that enters the glomerulus is not filtered and leaves through the effernet arteriole?
80%
where does blood filtration occur?
renal corpuscle aka the filter
the internal wall of the renal corpuscle is made of 2 cell types of different origins, what are they?
cells from vessels
cells from the primitive tubule
what is the layer of cells in contacy with the glomerulus called?
visceral
what is the layer of cells not in contact with the glomerulus on the renal corpuscle called?
parietal
the cells from the primitive tube differentiate into __________
podocytes
what do podocytes form?
a layer that surrounds the glomerular capillaries
they form the visceral layer of the bowman’s capsule
what are pedicels?
extensions from podocytes
they form filtration slits
what are the components that form the glomerular filtration barrier?
the visceral layer and capillary wall
what is filtered into the bowman’s capsule? (aka ultrafiltrate of plasma)
water
small solutes (Na, Cl, HCO3, glucose, amino acids)
what is not filtered into the bowman’s capsule and gets left in the blood stream?
large particles such as proteins (albumins, antibodies, hormones, enzymes)
blood cells
what is the numeric value of the normal filtration fraction?
0.2
what measures the intensity of filtration?
glomerular filtration rate
what is the glomerular filtration rate?
the rate at whcih ultrafiltrate of plasma moves from the glomerulaar capillaries into the bowmans capsule
what is GFR under normal conditions?
125ml/min
what determines the GFR?
filtration coefficient (properties of the filtration barrier, surface area, permeability)
net filtration pressure (starling forces)
what are starling forces?
forces that determine the net movement of fluid across membranes of capillaries
fluid movememnt across the wall of a capillary results from the balance between hydrostatic pressure gradient and osmotic pressure gradient
what are the hydrostatic forces?
intra-capillaary pressure
external pressure
what are the osmotic forces?
intra capillary osmotic pressure
external osmotic pressure
what does the net hydrostatic force/pressure result from?
blood pressure in the glomerulus
(capillary pressure = 55)
pressure of fluid in the bowmans capsule
(external pressure = 15)
how do you calculate net hydrostatic pressure?
net = P(cap) + P(ext)
what does net hydrostatic pressure actually mean?
it pushes the fluid from glomerular capillary into the bowman’s capsule
what does net osmotic pressure result from?
osmotic pressure in the bowman’s capsule
(=0)
osmotic pressure in the glomerular capillaries
(=30)
how do you calculate net osmotic pressure?
Pos = P(bow) + P(glo cap)
what does net osmotic pressure actually do?
pulls back the fluid from the bowman’s capsule into the glomerular capillary
in the renal corpuscle, hydrostatic pressure is __________
opposed by osmotic pressure
greater than osmotic pressure
how do you calculate net glomerular filtration pressure?
GFP = [net hydro] - [net osmo]
what does net pressure cause?
movement of fluid from blood to filtrate (glomerulus to bowman’s capsule)
because GFR depends on blood pressure, does GFR rise when the arterial blood pressure increases?
yes when the blood pressure is outside normal range
no when it is inside normal range
what does autoregulation do?
maintains a nearly constant GFR when the mean arterial blood pressure is between 80 and 180
what are the mechanisms of autoregulation?
reducing BP in glomeruli which result in reduced GFR
1: myogenic response of afferent arterioles
2: tubulo-glomerular feedback
what are the regulation by hormones and autonomic neurons?
1: change in the resistance of the arterioles
2: alteration of the filtration coefficient
what is the myogenic response?
inherent property of smooth muscle that surroind all blood vessels EXCEPT capillaries and mesenteric artery
increased stretch of the blood vessel walls causes _________
contraction if smooth muscle
constriction of vessel
this decreases flow and pressure
the myogenuc responses always tends to _________ excessive BP in the glomerulus
limit
what is the tubulo-glomerular feedback?
a local control pathway in which the flow rate of filtrate inside the renal tubule influences the GFR
any increase in GFR enhances the flow of filtrate
increased flow in the renal tubule is detected by?
macula densa cells
what do macula densa cells do?
secrete a vaso constrictive substance reducing the blood flow to afferent arteriole and glomerulus
describe the tubulo-glomerular feedback steps;
1&2: in response to increased GFR due to elevated BP, urine flow increases through the renal tubule
3: the resulting larger amount of NaCl in the distal tube is sensed by the cells of the macula densa
4: increase of production of a vasoconstrictor (adenosine)
5: constriction of afferent arterole
6: decrease of intraglomerular BP (hydrostatic pressure) and reduction of GFR
what is hormonal control/barostatic control of renin secretion?
the granular cells behave like baroreceptors and respond to drops in BP by secreting renin
what does renin do?
activates the synthesis of angiotensin 2 which contributes to increase in the total peripheral resistance (TPR) and restores normal BP and GFR
if GFR increases, what works to lower it?
macula densa cells
myogenic response
if GFR decreases, what works to increase it?
granular cells
what percentage of the fluid that enters the renal tubule, how much is reabsorbed?
about 19%
reabsorption takes place in all regions of the renal tubule EXCEPT?
the renal corpuscle
what does reabsorption do?
moves fluids and solutes from the renal tubule to the peritubular capillary
what seperates the renal tubule and capillaries?
the ISF
what are the 2 steps in the reabsorption process?
1: from renal tubule to ISF
2: from ISF to peritubular capillary
the epithelial cells of the proximal tubule are designed to _________
facillitate exchanges
what are the epithelial cells on the large surface areas designed for exchange?
microvili on apical membrane
infoldings of basal membrane
what are the epithelial cells on the polarized epithelium designed for excahnge?
apical and basal membranes have different transporters and permeabilities
describe the general mechanism of reabsorption steps;
1: sodium is reabsorbed by active transport. ISF becomes more positive
2: electrochemical gradient drives anion reabsorption. attractive of negative charges in the ISF
3: water moves by osmosis, following solute reabsorption. ISF becomes more concentrated. H2O moves to ISF
4: concentrations of other solutes increase as fluid volume in lumen decreases. permeable solutes afre reabsorbed by diffusion
what is the first element absorbed in the proximal tubule?
sodium
what is active transport?
uses energy to move substances againts their concentration gradients
what is secondary active transport?
uses energy of sodium transport
what is passive diffusion?
substances moves down their concentration gradients
what is endocytosis?
transport by membrane vesicles of some large molecuels remaining in the filtrate
describe the active transport in the kidneys;
sodium reabsorption
sodium in the cell is low
1: Na is pumped out the baasolateral side of the cell by the NaK ATPase
2: Na enters the cell through membrane proteins, moving down its concentration gradient
what is the secondary active transport in the kidney?
glucose reabsorption
High glucose in the cell
1: Na moving down its gradient using the SGLT protein pulls glucose into the cell against its gradient
2: glucose diffuses out of the basolateral side using the GLUT protein
3: Na is puymped out by NaK ATPase
what is transport maxiumum?
rate of transport that occurs when all carriers are occupied
what happens when the concentration of a substance in the filtrate exceeds the transport maximum?
some remains in the filtrate and appears in the urine
what is the renal threshold?
the plasma concentration at which the substance appears in the urine
the resistence increases as the size of the vessel ________
decreases
high resistence vesseuls = ________ output pressure
lower
_____ blood pressure in peritubular capillaries facilitates the reabsorption
low
what is the direction of secretion?
from peritubular capillaries to renal tubule
where does secretion occur?
in the proximal and distal convolute tubules and collecting duct
most secretion is perfromed by ____ transport
active
what is clearance?
disapperance rate of substance in the body due to excretion or metabolism
what is renal clearance used for?
evaluating the renal function via
GFR and RBF
what does clearance compare?
filtration rate with excretion rate
if X is filtered but not reabsored/secreted
C = GFR
if X is filtered and secreted
C = RPF
C > GFR
if X is filtered and reabsorbed
C < GFR
if X is reabsorbed
C = 0
how do you calculated renal clearance?
C = urine * rate of production / plasma
what is para-aminohippurate?
freely filtered from glomerular blood and secreted from peritubular blood
NONE in renal venous blood
C = RPF
how do you switch from RPF to RBF?
using hematocrit
divide the value by the hematocrit AS A DECIMAL
what is inulin?
used by researchers
not filtered
not secreted
C = GFR
creatinine is ______ absorbed and _______ secreted
not, not
what are body fluids?
refers to the water in the body and all substances dissolved in it
water determines the body fluid _____
volume
solutes determine the ________ and _________ of the body fluid
composition and osmolarity
what are the functions of water in the body?
tempterature regulation
cushioning
lubrication
reactant
solvent
transportation
what percentage of total body weight is fluid?
60%
where are fluids absorbed in the body?
into the plasma in intestine
where does fluids circulate in the body?
within plasma and around cells
where is fluids removed from the body?
kidneys through urine
what are the 2 compartments body fluids are distributed into?
ICF and ECF
the ECF contains
ISF and plasma
what percentage of the total weight of body fluids is ICF?
40%
what percentage of total weight of body fluids is ISF?
15%
what percentage of total weight of body fluids is plasma?
5%
what are electrolytes?
charged particles that are dissolved in fluids
what are the major positive electrolytes?
Na
K
Ca
Mg
what are the major negative electrolytes?
Cl
HCO3
HPO4
H2PO4
SO4
proteins
organic acids
in each compartment, positive and negative charges must balance _________
electro-neutrality
what type of membrane seperates the ECF and ISF?
semi permeable membrane
plasma and ISF have _____ osmolatiry
the same
what are membranes responsible for?
controling the fluxes of ions in and out of cells
membrane active transports maintain?
the difference of some iion concentrations between ICf and ECF
is the ECF is hyperosmolar, what happens to the cells?
cells would shrink because water is rushing into the ECF
if the ECf is hypoosmolar, what happens to the cells?
cells would swell because water us rushing into them from the ECF
controlling water is the most effiecient and easy way to compensate for changes in _________
ECF
the average adult body contains ________ L of water
40
water is maintained in a steady state called ______
water homeostasis
what type of feedback mechanisms maintain water homeostasis?
negative
what is water homeostasis?
a balace between water intake and output
what is hypervolemia?
too much water and solute taken in at the same time
volume increases BUT osmolarity remains the same
what is hypovolemia?
water and solute are lost at the same time, usually a loss of plasma volume
Volume decreases BUT osmolarity remains the same
what is overhydration?
too much water is taken in WITHOUT solute
volume increases and osmolarity decreases
what is dehydration?
when water is lost but not solute
volume decreases and osmolarity increases
what is the name of the model for which represents the kidney’s ability to regulate water loss?
the mug model
what is diuresis?
loss of water in urine
how is diuresis measure?
from the concentration or osmolarity of urine
if the body needs water elimination, the kidneys will produce _____- urine and diuresis is _____
diluted
large
is the body needs water conservation, the kidneys will produce _____ urine and diuresis is __________
concentrated
low
ISF of the cortex is _____ to plasma and renal filtrate
isosomtic
ISF of the medulla is ______ to the plasma and renal filtrate
hyperosmotic
what part of the renal tubule is impermeable to water?
loop of henle
because the loop of henle is impermeable to water, is it also impermeable to solutes?
no
describe what happens in the descending limb of the loop of henle for osmolarity;
increasing concentration of the medulla progressively remove water from the filtrate
osmolarity increases
describe what happens in the ascending limb of the loop of henle for osmolarity?
the salts are progressively extruded from the filtrate with no water loss
osmolarity decreases and the filtrate becomes hypoosmotic
what is meant by renal concurrent?
the blood in the vasa recta and filtrate circulate in opposite directions in the loop of henle
describe what happens in the blood in the loop of henle?
the concentration of the blood entering the Vasa Recta progressively increases as the osmolarity in themedulla increases ( the blood loses water and captures solutes from the ascccending limb)
all the water is then reabsorbed in the hyperosmotic blood which is progressively diluted along the descending limb
which part of the loop of henle does water reabsorption operate?
descending
where is water loss partially controlled?
distal part of the renal tubule and in teh collecting duct
where is anti diuretic hormone secreted?
hypothalamus
where is anti diuretic hormone released from?
posterior pituitary
what controls anti diuretic hormone secretion?
hypothalamic osmoreceptors
describe the hormonal control of water loss;
1: normal - low water permeability in collecting duct. there is low ADH, diluted urine, high diuresis
2: increased water permeability in the collecting duct. there is hugh ADH with concentrated urine and low diuresis
describe the feedback loop of ADH:
1: vasopressin binds to membrane receptor
2: receptor activates cAMP second messenger system
3: cell inserts AQP2 water pores into apical membrane
4: water is absorbed by osmosis into the blood
what initiates the ADH secretion?
increased osmolarity of ECF
decreased blood volume]decreased arterial blood pressure
how does ECF stimulate ADH?
when ECf osmolarity rises, water shifts out of the intracellular compartment and the cells shrink
the shrinking hypothalamic osmoreceptors signal for ADH release
veins and atria contain ______ receptors which detect changes in wall ______
stretch
decreased stretch (low blood volume ) signals for ______
ADH secretion
walls of largge arteries (aorta and carotid) contain _________
baroreceptors
what are baroreceptors?
neurons that monitor BP
decrease in BP signals _______
ADH secretion
gain and loss of ___ affects the ECF volume via control of ADH secretion
Na
what is natriuresis?
excretion of sodium in urine
what is pressure natriuresis?
increases renal Na excretion when arterial blood pressure increases
what is the hypothesis of pressure natriuresis?
when BP increases, the hydrostatic pressure within peritubular capillaries increases
this reduces net starling force for reabsorption from renal ISF to capillaries
with reduced peritubular capillary reabsorption, more water and salt stay in the renal tubule and sodium elimination in the urine increases
Na excretion and BP goes hand in hand. true or false
true
what is the feedback loop for Na and BP known as?
renal body-fluid feedback mechanism
if BP is too low, what happens to salt?
the renal elimination of salt and water decreases.
The ECF volume expands until BP is restored
if BP is too high, what happens to salt?
the renal excretion of salt and water leads to reduction of ECF volume until BP is restored
further reabsorption can take place in the distal tubule and collecting duct when the hormone __ is present
aldosterone
what percentage of filtered Na is dependent on aldosterone?
8%
increasing aldosterone, _______ Na reabsorption
increases
what tubules express aldosterone receptors?
distal and collecting tubule
describe the mechanism of control for aldosterone on Na reabsorption;
1: aldosterone combines with a cytoplasmic receptor
2: hormone-receptor complex initiates transcription in the nucleus
3: new protein channels and pumps are made
4: aldosterone-induced proteins modify existing proteins
5 result is increased Na reabsorption
where is atrial natriuretic peptide secreted?
atrial monocytes
ANP synthesis and release depends on ______
cardiac filling pressures
increased blood volume _______ ANP synthesis
activated
what does ANP do to salt?
limits the normal Na reabsorption by the nephrons and inhibits the aldosterone effect
where is renin released from?
juxtaglomerulaar cells around afferent arterioles
when is angiotensin 2 produced?
when the kidneys release renin
describe the feedback mechanism for angiotensin 2:
liver makes angiotensinogen
kidney makes renin
renin and angiotensinogen make angiotensin 2
angiotensin 2 activates thrist, vasopressin, vasoconstriction
this in turn causes H2O reabsorption and fluid intake to conserve H2O
how does a drop in BP mediate the secretion of renin and activate the RAAS?
1: direct effect of BP on graqnular cells (decreased vasoconstriction)
2: due to decreased GFR, macula densa stimulates granular cells
3: increase sympathetic activity stimukates granular cells
what is the RAAS?
renin-angiotensin-aldosterone
what are the activators of the RAAS?
mecula densa: low GFR, low salt intake
renal BP: low BP, Low ECF volume
increased sympathetic activity
what are the mediators of RAAS?
renin
angiotensin 2
aldosterone
what are the actions of RAAS?
descreased salt and water excretion
increased ADH
increased sympathtic activity
thirst
describe the cardiopulmonary sympathetic reflec steps:
renal sympathetic activity activates;
renin
sodium reabsorption
vasoconstriction
which cause renal salt and water retention
this increases plasma volume which decreases cardio-pulmonary volume/stretch
ANP is produced in the atria in respomse to?
increased BP or increased plasma volume
what does ANP inhibit?
Na reabsorption
RAAS
smooth muscle of afferent arterioles
sympathetic nervous system
ANP inhibiting the RAAS and Na reabsorption causes?
an increases in natriuresis and diuresis
and a decrease in ECF osmolarity/volume
ANP inhibiting smooth muscle of afferent arterioles causes?
vasodilation
increased GFR
increased Na and H2O filtered
ANP inhibiting the sympathetic nervous system causes?
decreased cardiac output
decreased TPR
decreased BP
which situations would required increased ECF?
salt loading
transfusion
heart failure
which situations would required decreased ECF?
dehydration
hemorrhage
