Renal function Flashcards
what makes up the renal system
paired kidneys
paired utterers
bladder
urethra
What is the primary role of the renal system in homeostasis?
regulates body fluid balance, acid-base balance, blood pressure
How does the renal system regulate blood volume and pressure?
By adjusting the amount of water reabsorbed or excreted, the kidneys control blood volume, which directly affects blood pressure.
RAAS responds to low blood pressure
How does the renal system contribute to acid-base balance?
excreting hydrogen ions (H⁺) and reabsorbing bicarbonate (HCO₃⁻
How do the kidneys respond to dehydration?
increase water reabsorption by concentrating urine. This is mediated by antidiuretic hormone (ADH)
How does the renal system contribute to erythropoiesis?
The kidneys release erythropoietin (EPO) in response to low oxygen levels, stimulating red blood cell production in bone marrow, which helps maintain oxygen delivery throughout the body
What waste products does the renal system eliminate to maintain homeostasis?
urea creatinine and excess ions to prevent toxin build up
How do the kidneys help regulate calcium and phosphate balance?
They convert vitamin D to its active form, calcitriol, which promotes calcium absorption in the gut
How do the kidneys contribute to glucose homeostasis?
filter glucose from the blood, reabsorb it in the proximal tubules, and engage in gluconeogenesis, especially during fasting
Where in the kidney does glucose reabsorption primarily occur?
Glucose reabsorption primarily occurs in the proximal tubule. Here, glucose transporters (SGLT2 and SGLT1) reabsorb glucose from the filtrate back into the blood, preventing glucose loss in urine
What is SGLT2 , and what roles does it play in glucose reabsorption?
sodium glucose transporter 2
is responsible for reabsorbing about 90% of filtered glucose in the early proximal tubule, 1Na:1glucose ratio
What is SGLT1 , and what roles does it play in glucose reabsorption?
sodium glucose transporter 1
reabsorbs the remaining 10% in the later proximal tubule at a 2Na:1 glucose ratio
What happens if blood glucose levels exceed the renal threshold?
glucose is excreted in the urine (glucosuria) occurs in uncontrolled type 1 diabetes
How do the kidneys participate in gluconeogenesis?
The kidneys perform gluconeogenesis, particularly in the renal cortex, producing glucose from non-carbohydrate sources (e.g., lactate, glutamine) during prolonged fasting or metabolic stress. This process is regulated by hormones like cortisol and glucagon
How does diabetes affect glucose handling in the kidneys?
can increase SGLT2
can worsen hyperglycemia by promoting excessive glucose reabsorption instead of allowing excretion
How do SGLT2 inhibitors affect glucose handling in the kidneys?
SGLT2 inhibitors block glucose reabsorption in the proximal tubule, increasing urinary glucose excretion. This helps lower blood glucose levels in people with type 2 diabetes, also leading to a mild diuretic effect that can aid in blood pressure reduction
What hormones regulate renal glucose handling?
insulin and glucagon
What role does the GLUT2 transporter play in kidney glucose handling and where is it located?
located on the basolateral membrane of proximal tubule cells, facilitates passive diffusion of reabsorbed glucose into the bloodstream after it has been transported from the filtrate via SGLT2 and SGLT1
what is the glomerular filtration rate
125 ml/min-1
renal glucose handling is intrinsic/extrinsic?
intrinsic
what mediate gluconeogenesis and where does it mostly occur
glucose 6 phosphate
liver
higher plasma glucose = _____________ glucose filtration rate
higher
uncontrolled diabetes leads to
glucose in urine = glucosuria
increase volume of urine = polyuria
increased thirst = polydipsia
What is the renal threshold for glucose, and how does it relate to glucose reabsorption?
10mM
Above this threshold, the glucose transporters in the proximal tubule become saturated, and any excess glucose cannot be reabsorbed and is instead excreted.
site of SGLT1
Intestine and kidney
site of SGLT2
kidney
renal location of SGLT1
Late proximal tubule
renal location of SGLT2
early proximal tubule
which SGLT has a high affinity for glucose and which one has a low affinity
SGLT1 has high
SGLT2 has low as plenty glucose available
treatment for type 2 diabetes
inhibition of SGLT2
eg canagliflozin, dapagliflozin, empagliflozin, ertugliflozin
