the urinary system Flashcards
what is the primary function of the kidneys?
cleanse the blood (filter it)
kidney maintain the body’s internal environment by:
- Regulating total water volume and total solute concentration in water
- Regulating ion concentrations in extracellular fluid (ECF)
- Ensuring long-term acid-base balance
- Excreting metabolic wastes, toxins, drugs
- Producing erythropoietin (regulates blood pressure and renin (regulates RBC production)
- Activating vitamin D
- Carrying out gluconeogenesis, if needed
upper parts of both kidneys are protected by what?
thoracic cage
perirenal fat provides what?
cushioning
lower parts of the kidneys are susceptible to what?
blunt trauma
(especially right kidney)
renal artery is especially vulnerable to injury from what?
rapid deceleration during car crashes, lead to laceration or thrombosis
what is hematuria and what is it an important sign of?
blood in urine and is an important sign of such trauma
internal kidney has three distinct regions, what are they?
- renal cortex
- renal medulla
- renal pelvis
where is the renal cortex?
granular-appearing superficial
where is the renal medulla?
deep to cortex, composed of cone-shaped medullary (renal) pyramids
what does the renal pelvis do?
urine flow
the order of urine flow:
renal pyramid
minor calyx
major calyx
renal pelvis
ureter
what is the major unit in the kidneys that produce urine?
nephrons
what are the 2 main parts of the nephrons?
renal corpuscle
renal tubule and collecting ducts
what is in the renal corpuscle?
glomerulus
glomerulus capsule (bowsman capsule)
what is the glomerulus?
tuft of capillaries composed of fenestrated endothelium
the renal tubule is about _____________ long
3 cm (1.2 in)
three major parts of the renal tubule:
- proximal convoluted tubule
- nephron loop
- distal convoluted tubule
where is the proximal convoluted tubule and what does it do?
proximal, closest to renal corpuscle
functions in reabsorption and secretion
the nephron loop was formerly called what?
loop of henle
what does the nephron loop look like? what two limbs does it have?
U-shaped structure
descending limb
ascending limb
where are the distal convoluted tubule? and what does it do?
distal, farthest from renal corpuscle
function more in secretion than reabsorption
distal convoluted tubule drains into a . . .
collecting duct
collecting ducts receive what?
filtrate from many nephrons
where does the collecting duct run through?
medullary pyramids
why do the ducts fuse together?
to deliver urine through papillae into minor calyces
2 major groups of nephrons:
- cortical nephrons
- juxtamedullary nephrons
cortical nephrons make up _____of nephrons and are almost entirely in _________.
85%
cortex
what are the juxtamedullary nephrons?
long nephron loops that deeply invade medulla
juxtamedullary nephrons ascending limbs have _______ and ______ segments
thick and thin
juxtamedullary nephrons are important in production of what?
concentrated urine
blood pressure is high where?
in glomerulus
blood pressure is low where?
peritubular capillaries
the 3 nephron capillary beds:
glomerulus
peritubular capillaries
vasa recta
the capillary beds in the renal tubule:
glomerulus
peritubular capillaries
glomerulus capillaries are specialized for what?
filtration
glomerulus are fed and drained by what?
arterioles
why is blood pressure high in glomerulus?
arterioles are high-resistance vessels
what are peritubular capillaries?
porous capillaries adapted for absorption of water and solutes
where do peritubular capillaries arise from?
efferent arterioles
peritubular capillaries empty into where?
venules
whart are vasa recta?
long, thin-walled vessels parallel to long nephron loops of juxtamedullary
where does vasa recta arise from?
efferent arterioles serving juxtamedullary nephrons
what does vasa recta function in?
formation of concentrated urine
each nephron has one what?
juxtaglomerular complex (JGC)
juxtaglomerular complex (JGC) involves modified portions of:
- distal portion of ascending limb of nephron loop
- afferent (sometimes efferent) arteriole
why is the juxtaglomerular complex important ?
important in regulating rate of filtrate formation and blood pressure
_______ of fluid processed daily, but only ______ of urine is formed.
180 L
1.5 L
kidneys filter body’s entire plasma volume ______ times each day
60
kidneys consume ______ of oxygen used by body at rest
20-25%
urine is produced from what?
filtrate
urine is _____ of original filtrate
<1%
urine contains what?
metabolic wastes and unneeded substances
three processes are involved in urine formation and adjustment of blood composition:
- glomerular filtration
- tubular reabsorption
- tubular secretion
what does glomerular filtration do?
produces cell and proteins free filtrate
what does tubular reabsorption do?
selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts
what does tubular secretion do?
selectively moves substances from blood to filtrate in renal tubules and collecting ducts
what is the first step in how the kidneys make urine?
glomerular filtration
glomerular is a . . .
passive process
no ____________ is required for glomerular filtration
metabolic energy
hydrostatic pressure forces fluids and solutes through the _________________ into the glomerular capsule
filtration membrane
where does the filtration membrane lie?
between the blood and the interior of the glomerular capsule
filtration membrane is a porous membrane that allows what?
free passage of water and solutes smaller than plasma proteins
plasma proteins remain in the blood to maintain what?
colloid osmotic pressure
by the plasma proteins remaining in blood it prevents what?
loss of all water to capsular space
proteins in filtrate indicate what?
membrane problem
blood is coming from the afferent arteriole and has to get into the glomerular capillaries through hydrostatic pressure; so where is the hydrostatic pressure in that equation?
hydrostatic pressure is in afferent
outward pressures are . . .?
forces that promote filtrate formation
hydrostatic pressure in ______________ is essentially glomerular blood pressure
glomerular capillaries (HP gc)
inward pressures are. . .?
forces inhibiting filtrate formation
what are 2 types of inward pressures?
hydrostatic pressure in capsular
colloid osmotic pressure in capillaries
what does hydrostatic pressure in capillaries do?
filtrate pressure in capsule (15 mmHg)
what does colloid osmotic pressure in capillaries do?
“pull” of proteins in blood (30 mmHg)
what is net filtration pressure (NFP):
sum of forces
NFP is the main controllable factor determining what?
glomerular filtration rate (GFR)
what is glomerular filtration rate (GFR)?
volume of filtrate formed per minute by both kidneys
GFR is directly proportional to:
- net filtration pressure
- total surface area available for filtration
- filtration membrane permeability
why is constant GFR important?
it allows kidneys to make filtrate & maintain extracellular homeostasis
what regulates glomerular filtration?
intrinsic control
extrinsic control
goal of intrinsic controls:
renal autoregulation
maintain GFR in kidney
goal of extrinsic controls:
maintain systemic blood pressure
_________ and ____________ are main extrinsic controls
nervous system
endocrine system
GFR effects . . .
systemic blood pressure
increased GFR causes increased __________, which lowers ___________ and vice versa
urine output
blood pressure
two types of renal autoregulation:
- myogenic mechanism
- tubuloglomerular feedback mechanism
what is myogenic mechanism?
local smooth muscle contracts when stretched
increased BP causes muscle to ___________, leading to constriction of ____________________________
stretch
afferent arterioles in glomerulus
decreased BP causes ___________ of afferent arterioles in the glomerulus
dilation
what is tubuloglomerular feedback mechanism?
Flow-dependent mechanism directed by macula densa cells in the juxtaglomerular complex
what does the tubulglomerular feedback mechanism respond to?
filtrate NaCl concentration
if GFR increases then . . .
filtrate flow rate increases leading to decreased reabsorption time causing high NaCl levels to filtrate
feedback mechanism causes . . .
constriction of afferent arterioles which lowers NFP and GRF allowing more time for NaCl reabsorption
extrinsic control involves:
- neural and hormonal mechanisms
- sympathetic nervous system
what is the purpose of extrinsic controls?
regulate GFR to maintain systemic blood pressure
extrinsic controls will override renal intrinsic controls if . . .
blood volume needs to be increased
___________________ is released by the ________________________ & ______________ is released by ____________________________
norepinephrine
sympathetic nervous system
epinephrine
adrenal medulla
releasing norepinephrine and epinephrine causes :
systemic vasoconstriction
constriction of afferent arterioles
blood volume & pressure increases
systemic vasoconstriction increases what?
blood pressure
constriction of afferent arterioles decreases what?
GFR
what is the main mechanism for increasing blood pressure?
renin-angiotensin-aldosterone mechanism
renin is released by . . .
granular cells
what raises blood pressure when it is low?
RAAS
any change in blood volume or pressure stimulates what?
distal convoluted tubule (DCT) and collecting duct to reverse the change
alter Na+ and H2O reabsorption is regulated by:
aldosterone
ADH
ANP
when there is LOW bp ________ and _________ absorb ______ water with the help of ______________ and ______ working together
DCT and collecting ducts
more
aldosterone & ADH
what does HIGH blood volume causes what?
a stretch in the atrium which triggers a release of ANP
ANP inhibits the release of what?
ADH and aldosterone
