renal function Flashcards
What is the function of the renal system?
- excretion of waste products & urine
- regulation of BP
- RBC production (erythropoietin)
- breakdown of drugs
- metabolism of hormones
- regulation of electrolytes & acid-base balance
- synthesis of vitamin D
- fluid balance
- balance pH of blood stream
What is inactivates when kidneys are not functioning properly and why is this a problem?
vitamin D is inactivated; vitamin D plays a role with calcium absorption
How many lobes are in each kidney?
8 - 18 lobes
Where are the kidneys located?
located retroperitoneally on the posterior wall of the abdomen
What is each lobe of the kidneys composed of?
nephrons; functional unit of the kidney
What does the renal cortex contain?
contains glomeruli, convoluted tubules, & blood vessels
Which kidney is slightly lower than the other and why?
right kidney is slightly lower than the left; because of the liver
Where are the renal pyramids in the kidneys?
in the inner medulla
What shape are the kidneys?
bean shaped
Why is it hard for the kidneys to get injured?
they are semi protected by the ribs and other organs
What is the renal pelvis?
the collection system of the urine
the kidneys take how much of the body’s cardiac output?
20-25%
What does the renal artery divide into?
divides into 5 segmental arteries that enter the hilus
What do the segmental arteries branch into?
segmental arteries inside the kidney branch into lobular arteries then interlobular arteries
How much blood do the kidneys filter?
kidneys filter about 90-120ml of blood per minute
What do nephrons lack the ability to do?
regnerate; causes generalized decrease in functioning nephrons as we age
What do glomerulus work in?
filteration
What do peritubular capillaries work in?
reabsoprtion
List structures of the nephron (hint:4)
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct
What are the who categories of nephrons?
- cortical
- juxtamedullary
What nephrons are thin and penetrate the entire length of the medulla?
juxtamedullary nephrons
What nephrons are the primary site of urine concentration?
juxtamedullary nephrons
What percent of nephrons are cortical nephrons?
85%
What kind of nephrons have short, thick loops of henle that penetrate only a short distance into the medulla?
cortical nephrons
If you lose/ donate a kidney why are you able to live without that one kidney?
you are able to live because the other one will compensate for the missing one
what are capillaries enclosed in thin, double-walled capsules (bowman capsule)?
glomerulus capillaries
how does blood circulate through the glomerulus capilaries?
goes from the afferent arteriole → glomerular capillaries → efferent arteriole → peritubular capillaries
What are the three layers of the glomerular capillary membrane?
- capillary endothelial layer
- basement membrane
- single-celled capsular epithelial layer
What is the average glomerular filtration rate?
125 ml/min or 180L/day
What is filtration pressure & GFR regulated by?
constriction/ relaxation of the afferent & efferent arterioles
- arterioles innervated by SNS
- arterioles sensitive vasoactive hormones
When does renal function begin to decline?
around age 40
there is approximately at ____ loss of nephrons for each decade after 40
10%
By age 70 what is the average GFR?
down 30ml/ min; 95ml/min
If an individual is healthy decline in nephrons will have little impact until what age?
90
What will the GFR be in ESRD?
15ml/min or less
What indicates good renal function?
a high GFR; the higher the GFR the better
How does increased protein and glucose load effect the kidneys?
can cause renal damage
What are the who mechanisms that regulate renal blood flow?
- neural & humoral control mechanism
- autoregulatory mechanism
What happens in the naural & humoral control mechanism?
increase in SNS activity → constriction of arterioles → decrease in renal blood flow
What are the humoral substances released in the neural & humoral control mechanism?
- angiotensin II
- endothelin
- endothelial-derived nitric oxide
What do prostaglandins do in the neural & humoral control mechanism?
protect against vasoconstriction effects of sympathetic stimulation & angiotensin II
What humoral substance preferentially constricts efferent arterioles?
angiotensin II
What is endothelin and what does it act like in the neural & humoral control mechanism?
peptides released from damaged endothelial cells in the kidney & other tissues; vasoconstrictor
What class of medications inhibit prostagladin?
NSAIDS
Why should NSAIDS be avoided?
they inhibit prostaglandin synthesis; decrease renal blood flow & decrease the GFR
in what mechanism is the exact mechanism responsible for renal blood flow regulation unclear?
autoregulatory mechanism
What occurs in the proposed autoregulatory mechanism 1?
- direct effect on vascular smooth muscle
- increase in BP causes vessels to relax
- decrease in BP causes vessels to constrict
What is the second proposed autoregulatory mechanism?
juxtaglumerular complex; feedback control system that links RBF to GFR and composition of distal tubular fluid
What are macula densa cells?
specialized group of epithelial cells in distal tubule in close contact with afferent & efferent arterioles
How do macula densa cells work?
- monitor BP by sensing the stretch of the afferent arteriole (changes in volume delivery)
- monitors sodium concentration in filtrate as it flows through
What do juxtaglomerular cells contain?
granules of inactive renin
What is used to determine renin release?
information from macula densa cells
What happens when there is decreased renal perfusion?
RAAS will be triggered
where do about 65% of reabsorption & secretory processes occur?
proximal tubule
the _________ tubule is highly permeable to water
proximal
osmolality _________ and is maximum at the ______ _______ in the loop of henle
increases; loop elbow
What portion of the loop of henle is impermeable to water?
ascending loop
in the loop of henle, as filtrate ascends it becomes what?
more dilute
the distal convoluted tubule is ___________ ___________ to water
relatively impermeable
Where do thiazide diuretics work and how?
thiazide diuretics work at the distal convoluted tubule; by inhibiting NaCl reabsorption in this segment
Where do potassium sparing diuretics work?
late distal tubule
What 3 factors effect urine concentration?
- osmolarity of the interstitial fluids in the urine- concentrating part of the kidney
- antidiuretic hormone (ADH)
- action of ADH on the cells in the collecting tubules of the kidney
list the elimination functions of the kidneys
removal of
- water
- waste products
- excess electrolytes
- unwanted substances
list the endocrine functions of the kidneys
- assist with BP regulation through renin-angiotensin- aldosterone mechanism
- regulation of RBCs through synthesis of erythropoietin
- assist with calcium homeostasis by activating vitamin D
- glucose homeostasis
What do all age related changes in the GU system impact?
all impact the elimination of medications
list age-related changes to the GU system
- decrease blood flow to kidneys
- decreased number of functioning nephrons
- decreased GFR (most reliable indicator)
- decrease tubular secretion
Why is GFR a better indicator than BUN/Cr?
because it tells us about kidney function & the kidneys ability to excrete waste
