lecture 16 - urinary Flashcards
urinary system consists of
2 kidneys, 2 ureters, urinary bladder, and urethra
urinary system contributes to hemeostasis by:
excreting wastes
producign hormones
maintaining blood osmolarity
changing blood comp, vol, pressure and pH
function of the kidneys (general)
to filter blood
selective reabsorb substances needed to maintain the body
in depth kidney functions (8)
regulate blood ionic composition
- Na, K, Ca, CL
regulate blood osmolarity
- regulates water loss to keep blood at ~300mOsm/L
regulate blood pH
- excrete H into urine and conserve HCO3
regulate blood vol
- by conserving or eliminating water
regulate BP
- adjust blood vol
- secrete renin -> activate RAA -> increase BP
regulate blood glucose level
- gluconeogenesis - production of glucose
produce hormones
- calcitriol/erythropoietin
excretes waste
- forms urine and excretes it
hormones produced by hte kidneys
calcitriol
- active form of vit D involved in calcium homeostasis
erythropoietin
- stimulates RBC production
how does the kidney regulate blood osmolarity
by regulating water loss
how does the kidney regulate pH
by excreting H and conserving HCO3
how does the kidney regulate BP
by adjusting blood vol
by secreting renin to activate RAA pathway
how does the kidney regulate blood glucsoe level
by gluconeogenesis whihc uses the amino acid glutamine to make glucose
how does the kidney regulate excrete waste
by making and excreting urine
some small notes about kidneys
retroperitoneal
located between t12-L3
right is lower than left cause of liver
hilum of kidney
region through whihc the ureter leaves, and vessels/nerves enter
3 layers of tissue surroundng each kidney
fibrous capsule
perirenal fat capsule
renal fascia
from deep to super
fibrous layer of the kidneys
transparent, collagen rich tissue
- continuous with ureter coating
- barrier against injury
innermost
perirenal fat capsule of teh kidneys
mass of fatty tissue that surrounds fibrous capsule
- protects kidneys
- holds kidney within abdominal cavity
renal fascia of the kidney
collagenous and elastic dense irregular CT
- holds kidney to abdominal wall and surrounding structures
renal cortex
outermost part of the kidney
- lighter boarder
renal medulla
inner dark parts of kidney
- location of loop of henle
parenchyma
functional part of kidneys
aka, renal cortex and medulla
kidney lobe
renal pyramid, adjoining renal columns, renal cortex
parts of the renal medulla
renal papilla
renal pyramids
renal columns
nephrons
renal papillae
pyramid apex, points at kidney centre
renal pyramids
secreted apparatus of kidney
renal columns
extend between pyramids, anchors cortex
nephrons
functional cells of kidneys located within the parenchyma
pathway of urine in kidney
nephron, papillary ducts, minor/major calyces, renal pelvis
4 main blood vessels you need to know (plus renal artery/vein)
renal artery
afferent glomerular arterioles
glomerular capillaries
efferent glomerular arterioles
peritubular capillaries
renal vein
peritubular capillaries contain mixed blood, all before = o2 blood
3 capillary beds in the kidneys
glomerular (afferent/glomerulus/efferent)
peritubular
vasa recta
nerve supply to teh kideys
renal nerves
what do teh renal nerves do
cause vaso condtriction and dilation of renal arterioles
what regulates blood flow thru kidneys
sympathetic outflow
glomerular capillary bed function
filtration and urine formation
peritubular capillary bed function
carry away reabsrobed substanced from filtrate in cortex
vasa recta capillary bed function
carry away reabsorbed substances from the filtrate in medulla
nephron functions
filtration, reabsorption, secretion
renal corpuscle function
filters blood
renal tubule function
space where filtered fluid (glomerular filtrate) passes
parts of renal corpuscle
glomerulus and glomerular capsule
parts of renal tubule
proximal and distal convoluted tubules
nephron loop
site of plasma filtration
renal corpuscle
glomerulus
capillary network
glomerular capsule (bowmans capsule)
double walled epitehlial cup where filtration occurs
convoluted
tightly coiled
proximal convoluted tubule (PCT) attacehs to
attaches to corpuscle
nephorn loop
has descending and ascending limbs
dips down into the medulla
distal convoluted tubule
farther from corpuscle
empties into collecting duct, tehn papillary ducts, then minor calyces and so on
two types of nephrons
cortical nephrons
juxtamedullary nephrons
cortical nephrons
most common 80-85%
- renal corpuscle located in outer portion of cortex
- short nephron loop, only dips into outer medulla
- recieves blood form peritubular capillaries
- creates urine with similar osmolarity to blood
juxtemedullary nephrons
15-20%
- renal corpuscle deep in cotex
- long nephron loop deep into medulla
- receives blood from peritubular capilliaries and vasa recta
- ascending limb has thick and thin parts
- created very concentrated urine
glomerular capsule wall is made of
single layer of epi cells
visceral layer of glomerular capsule contains
modified simple sq epi cells called podocytes
parietal layer of glomerular capsule consists of
simple sq epi that forms outer wall
main epi cells in nephron
simple cuboidal
juxtaglomerular apparatus consists of
macula densa and juxtaglomerular cells
what cells in the kidney have receptors for ADH and aldosterone
principal cells
capsular space
where filtered fluid goes from glomerular capillaries
located between layers of corpuscle
macula densa
where the ascending limb of the nephorn loops contacts the afferent arteriole
juxtaglomerular cells
smooth muscle cells in teh wall of the afferent arteriole
juxtaglomerular apparatus functions
regulates BP in the kidney
full pathway of fluid in kidneys
glomerular capsule
proximal convoluted tubuler
descenind limb od loop
ascending limb of loop
distal convoluted tubules
collecting duct
papillary fuct
minor calyx
major calyx
renal pelvis
ureter
urinary bladder
urethra
3 basic processes of nephrons and collecting ducts
glomerular filtration
tubular reabsorption
tubular secretion
rate of excretion
filtration + secretion - reabsorbtion
glomerular filtration
a portion of blood plasma is filtered into glomerular capsule and then into renal tubuler
tubular reabsorption
water and useful substances are reabsorbed into the blood in renal tubules and collecting ducts
filtrate formed per day
150-180L
99% is returned to bloodstream vai reabsorption
why is the renal corpuscle able to filter so much fluid compared to other capillaries (3)
glomerular capillaries have lots of surface area for filtration
filtration membrane is thin and porous
glomerular pressure is high
filtration membrane is made of
glomerular capillaries and podocytes
endothelial capsular membrane and what it permits and prevents
nephrons filtering unit
it permits filtration of water and small solutes
prevents filtration of most plasma proteins, blood cells and platelets
3 barriers that filtered substances must cross in the glomerular capsule
glomerular endothelial cells
basement membrane
slit membrane formed by podocytes
fenestration of glomerular capsule prevents filtration of:
blood cells, but allows blood plasma to go thru
basement membrane of glomerulus prevents filtration of
larger proteins
slit membrane between pedicels of podocytes prevent filtration of
mediium sized porteins
glomerular endothelial cells (layer)
leaky due to fenestrations
permits solutes in plasma to exit
prevents filtration of blood cells/platelets
contains mesangial cells that increase glomerular filtration when relaxed
where are mesangial cells located
among glomerular capillaries and in cleft between afferent and efferent arterioles
basement membrane of glomerular filtration membrane is made of/functions
porous layer of acellular material between endothelial cells and podocytes
consists of collagen fibres and porteoglycans in negatively charges glycoprotein matrix
allows water and small solutes to pass
prevents filtration of larger proteins
basement membrane is teh second layer of the filtration membrane
slit membrane formed by podocytes contain (2)
pedicels - processes from podocytes that wrap around capillaries
filtration slits - spaces between pedicels
slit membrane
thin membrane that extends across teh filtration slit
- permits passage of small molecules (water, glucose, vitamins)
- prevents albumin
- is the last barrier of the glomerular filtration barrier
NFP
total of all pressures
net filtration pressure
GBHP
glomerular blood hydrostatic pressure
CHP
capsular hydrostatic pressure
BCOP
blood colloid osmotic pressure
formula of NFP in kidneys
GBHP - CHP - BCOP = NFP
Glomurular blood hydrostatic pressure
blood pressure in glomerular capillaries
- 55mmHg ~
what does GBHP promote
filtration by pushin water and solutes out of capillaries through the filtration membrane
capsular hydrostatic pressure
hydrostatic pressure exerted against the filtration membrane by fluid already in the capsular space
- 15mmHg~
what does CHP do
opposes filtration
acts as a back pressure against the glomerular filtration membrane
blood colloid osmotic pressure
due to pressence of proteins in blood plasma
- 30mmHg~
what does BCOP do
opposes filtration by pulling fluid back into teh blood
normal NFP
10mmHg~
GFR
glomerular filtration rate
glomerular filtration rate
amount of filtrate formed in all renal corpuscles of both kidneys each minute
avg = 105-135 ml / min
too high GFR =
useful substances pass too quickly through renal tubules and are not absorbed
too low GFR =
nearly all filtrate is reabsorbed and certain waster products may not be excreted
GFR and NFP are
directly related
any change to one will affect the other
how iwll severe blood loss affect GFP
everything will decrease (vol, NFP, pressure, GBHP)
how will an increase in BP affect GFR
everything (BP, vol, NFP) will increase, but not for long becausethe body will regulate it back down to normal
3 things that regulate GFR
renal autoregulation
neural regulation
hormonal regulation
how do the 3 mechanisms that control GFR actually do it (neural/hormonal/renal)
by changing the amount of SA available for filtration
by changin the rate of blood flow into or out of the glomerulus
when blood flow to the glomerulus increases, so does
GFR
Renal autoregulation
mechanism by the kidneys to regulate GFR
myogentic / tubular
hormonal regulation
mechanism that regulated GFR
angiotensin 2 - decreases GFR
ANP - increases GFR
neural regulation
mechanism that regulates GFR
synpathetic branch of ANS
myogenic mechanism
negative feedback loop that keeps GFR constant despite BP changes
myogenic mechaism response to increase in BP
increase in BP = stretch in afferent arteriole walls = increased GFR
smooth muscle contracts = reduced diameter of arteriole = decreased renal flow = GFR decreases until normal
myogenic mechanism response to decrease in BP
decrease in BP = smooth muscle fibres are less stretched
afferent glomerular arterioles dilate = increased renal blood flow = GFR increases
tubuloglomerular feedback
(loop, waht it results in)
increase in BP = GFR increases above normal = increase in flow of filtered fluid within renal tubules
this results in less absorption of Na, Cl, and water in PCT and nephron loop
macula densa cells detect this, and inhibit NO release from juxtaglomerular cells. this causes constriction of afferent glomerular arteriole, lowering blood flow and GFr
what do macula densa cells detect and inhibit
Na, Cl and water
they inhibit the release of nitric oxide from cells in juxtaglomerular apparatus which makes the afferent glomerular arteriole constrict, decreasing blood flow and GFR
which mechanism is slower
myogenic or tubuloglomerular
tubularglomerulas
what two hormones contribute to GFR regulation
angiotensin 2 and atrial natriuretic peptide
how does angiotensin 2 regulate GFR
decreases GFR
strong vasoconstrictor, which reduces renal blood flow
how does atrial natriuretic peptide regulate GFR
increases GFR
increase in blood volume stretches atria which stimulates ANP release.
ANP causes relaxation of glomerular mesangial cells, resulting in increase capillary surface area, increasing GFR
how is angiotensin 2 made
via teh RAA pathway (see previous notes)
which cells secrete ANP
cardiac muscle cells
neural regulation of GFR
kidney blood vessels are supplied by sympathetic ANS fibres that release NE
how does NE released by sympathetic ANS fibres regulate GFR
NE activated alpha1 receptors causing vasoconstriction
at rest, what is the neural regulation of the kidneys/GFR like
sympathetic activity is minimal, afferetn and efferent arterioles are dilated
renal autoregulation dominates
when would strong sympathetic ANS fibre stimulation happen, reducing GFR by a good bit
during hemorrhage or exercise
lowering of renal blood flow causes
redirection of blood to other tissues
lowered urine output, keeping blood volume high
what forms the walls of the entire nephron tube
a single layer of epithelial cells, varying across different parts
PCT epithelium
simple cuboidal with microvilli for increases SA
nephron loop (descending and thin ascending) epithelium
simple squamous
nephron loop thick ascending limb epithelium
simple cuboidal
most of distal convoluted tubule epithelium
simple cuboidal
last part of DCT and collecting duct epithelium
simple cuboidal with intercalated cells that regulate blood pH
where are principal cells located and what do tehy detect
located in last part of DCT and collecting duct
contain receptors for ADH and aldosterone
how much water should the body excrete after urine is produced
1.5-2L
how much Na should the body excrete after urine is produced
very little (4g)
how much Cl should the body excrete after urine is produced
very little (6g)
how much bicarbonate should the body excrete after urine is produced
extremely little (0.03g)
how much glucose should the body excrete after urine is produced
none
how much creatinine should the body excrete after urine is produced
all of it
reabsorption
returning most of the filtered water and solutes back to the bloodstream
biggest contributor to reabsorption
epithelial cells iwth microvilli in the PCT
how is 99% of filtered water reabsorbed
osmosis
how are most solutes (Na, k, Cl, Ca, glucose) reabsorbed
active and passive processes
how are proteins reabsorbed
pinocytosis
pathway of somethign being reabsorbed
released into ISF, the diffused into blood vessels
tubular fluid - tubular cells - ISF - peritubular capillary
reabsorption routes (2)
parecellular reabsorption
transcellular reabsorption
reabsorption destination
peritubular capillaries
paracellular reabsorption
reabsorbed material moves through leaky tight junctions between cells
transcellular reabsorption
material moves through both the apical and basal membranes of the tubule cell by active or passive transport
apical membrane of tubule faces
lumen
basolateral membrane of tubule faces
ISF
transport methods
active, facilitated diffusion, simple diffusion
reabsorption of Na is by _____, how does it work
primary active transport
Na diffuses into tubule cell, and sodium potassium pumps in basolateral membrane pump sodium from tubule cell to ISF, where is diffuses into capillaries
Na/K pumps are only located
in basolateral membrane because Na reabsorption is a one way process
symporters
move 2 or more solutes in the same direction
anitiporters
move 2 or moe solutes in opposite directions
transport maximum
all transport proteins have a speed limit in mg/min
water reabsorption is driven by
osmosis, water follows solutes (na , cl, glucose)
2 types of water reabsorption
obligatory
facultative
obligatory water reabsorption occurs in
PCT and descending limb
facultative water reabsorption occurs in
late DCT and collecting duct
obligatory water reabsorption
80% of water reabsorption
water is “obligated” to follow solutes that are being reabsorbed (Na, Cl, glucose)
PCT and descending limb loop have aquaporins to make them permeable to water
facultative water reabsorption
occurs under control of ADH
late DCT and collecting duct have ADH receptors (pricipal cells)
capable of adapting to need
tubular secretion
transfer of materails from blood and tubular cells into tubular fluid that will eventually become urine
functions of tubular secretion
control of blood pH via secretion of H
elimination of certain substances like drugs, creatinine, and H
