Chemistry unit 2

what are the functions of the kidney?

waste removal, fluid/acid-base homeostasis, hormone secretion

what is the nephron?

the functional unit of the kidney

what is in the nephron?

glomerulus, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct

what are the 3 renal processes?

glomerular filtration, tubular reabsorption, tubular secretion

how does filtration work?

high pressure between afferent and efferent arterioles

-wider afferent → arriving into glomerulus

-narrower efferent → exiting glomerulus

_________ blocks large negatively charged proteins

glomerular basement membrane

what is the size cutoff of the glomerular basement membrane?

66,000 daltons (~albumin)

what are the components of the filtrate?

protein free and cell free

what does the PCT reabsorb 75% of?

water, sodium, chloride

what does the PCT reabsorb 100% of?

glucose (up to renal threshold), amino acids, vitamins

what does the PCT reabsorb most of?

urea, uric acid

what is the purpose of PCT reabsorption?

bulk, unregulated reabsorption of everything the body probably wants back

loop of henle _____ limb reabsorbs ~15% of water

descending

loop of henle _____ limb reabsorbs Na and Cl

ascending

what is the purpose of loop of henle?

specialized, gradient-building reabsorption

what is the purpose of DCT and collecting duct?

small, hormonally-adjustable reabsorption

what governs up to ~10% of water reabsorption

AVP (another name for ADH)

what does aldosterone govern?

Na+ reabsorption and K+/H+ secretion

where does passive diffusion happen?

in collecting duct

what does passive diffusion help maintain?

medullary hyperosmolality alongside the loop of henle

what does the collecting duct passively diffuse?

40-60% urea

what is secretion?

second chance to get rid of stuff that wasn’t already filtered out

what are the options of sectetion?

• PCT

  • DCT and collecting duct

what does PCT secrete?

H+, drugs, uric acid (first reabsorbed, then some secreted back out right away)

what does the DCT and collecting duct secrete?

ammonia and aldosterone governed by K+ and H+

what is arginine vasopressin (AVP)?

antiiuretic hormone (AD)

-posterior pituitary hormone

what does AVP / ADH released with?

increase osmolality or decrease in blood volume

what is the action of AVP?

increase of water permeability of distal tubule and collecting duct

what is the result when AVP is released?

concentrated urine, decrease in plasma osmolality

what is RAAS?

adrenal cortex hormone, renin-angiotensin driven

what is RAAS triggered by?

decrease in renal blood flow and decrease in plasma Na+

what does RAAS stimulate?

Na+ reabsorption and K+/H+ secretion

what is RAAS linked to?

renal, adrenal, and cardiovascular systems

what is dehydration?

maximally concentrated urine (~!200 mOsm/L)

what is water excess?

maximally dilute urine (~50 mOsm/L)

what shares AVP’s osmotic trigger?

thirst

-continuous fine-tuning maintains fluid balance

what are the 3 acid base systems?

kidney, lungs, & buffers

what does the kindey do for acid base balance?

regenerates bicarbonate, excretes metabolic acid

what are metabolic acids that are secreted by kidney?

lactic acid, ketoacids, other nonvolatile acids

-ammonia and phosphate buffer H+ excretion

what are hormones made by kidneys?

renin, EPO, 1,25-dihydroxyvitamin D3, prostaglandins

what is renin?

initiates the RAAS

what is eryhtopoeitin?

stimulates red cell production

what is 1,25-dihydroxyvitamin D?

increase in Ca/Phos absorption in gut; regulates calcification of bone

what is porstaglandin?

increase in renal blood glow, Na+/ water excretion, renin release

-helps activate RAAS systemically

what are the markers for kidney filtration rate?

serum BUN, serum creatinine, serum cystatin C

what is the filtration rate?

testing to see if GFR is keeping up

what is glomerular integrity?

test if the filter is leaking

what are the markers for glomerular integrity?

urine albumin (microalbumin, protein)

what is tubular integrity?

testing if the PCT reabsorbing/catabolizing normally

what are the markers for tubular integrity?

B2 microglobulin

what is creatinine?

byproduct of muscle creatine metabolism, production is constant and freely filtered

what is creatinine a standard marker for?

estimating GFR

what does creatinine clearance require?

24 hour urine, midpoint serum creatinine

-direct method of measuring glomerular filtration

what is the formular for creatinine clearance (mL/min)?

(Ucr x V) x 1.73

(Pcr x 1440) A

what is the estimated GFR (eGFR)?

calcuated with every serum creatinine result, no timed urine collection required

what was historically included as a coefficient in eGFR?

rade

what is the race neutral formula of eGFR?

2021 CKD-EPI equation

what is cystatin C?

less problematic alternative to creatinine eGFR; produced at a steady rate by nearly all tissue

what is cystatin C less affected by?

muscle mass, diet, or age

cystatin C is________ by the proximal tubule

filtered, reabsorbed, and catabolized

what rises before creatinine in acute kidney injury?

cystatin C

what is B2-microglobulin?

sheds from nucleated cell surfaces, freely filtered by glomerulus and then reabsorbed and catabolized by proximal tubule

what can cause an increase in serum B2-M?

increased production (multiple myeloma, inflammation, others), glomerular issue OR PCT issue

what can signal transplant rejection because rejection damages tubular tissue?

B2-microglobulin

what is myoglobin?

muscle injury marker

-overloads and damages tubules in rhabdomyolysis

what is an acute kidney injury (AKI) risk?

myoglobin overloads and damages tubules in rhabdomyolysis

what is albuminuria?

30-300mg/24 hr and albumin:creatinine ratio >30mg/g for random

what is albumin an early marker for?

diabetic nephropathy

what is the formula that is used for timed urine test?

mass excreted/ time period= urine conc. x total urine volume

what happens to glomerular permeability in albuminuria?

increase over 7-10 years

what are the types of timed urine test?

albumin, protein, calcium, sodium, potassium, creatinine, urea, hormones/metabolites

what is acute glomerulonephritis?

rapid onset; often follows group A strep infection

what is chronic glomerulonephritis?

gradual scarring, slow function loss

-may progress silently for years

what is seen in the urine of hlomerulonephritis?

hematuria, RBC casts

what is nephrotic syndrome?

massive proteinuria (>3.5 g/day)

hypoalbuminemia → generalized edme

hyperlipidemia and lipiduria

what is seen in the urine of someone with nephrotic syndrome?

oval fat bodies

what are tubuluar disorders?

renal tubular acidosis (RTA) and interstitial nephritis

what are the causes to interstitial nephritis?

drugs, infection, transplant rejection

what is proximal RTA?

causes decrease in bicarbonate reabsorption

what is distal RTA?

causes impaired H+ gradient

>10⁵ colonies/ mL is diagnostic for ____

infection

what is diagnostic for pyelophritis?

wbc casts

what can obstruction lead to?

increased pressure —> nephron necrosis

what is the most common kidney stone type?

calcium oxalate

what is uric acid stones linked to?

gout

what can cause cystine stones?

inherited cystinuria

what can kidney stones symptoms mirror?

other obstructive disease

what can cause prerenal acute kidney injury?

blood-supply defect (hypovolemia)

what can cause intrinsic acute kidney injury?

kidney itself (acute tubular necrosis)

what can cause postrenal acute kidney injury?

urinary tract obstruction

what is chronic kidney disease?

kidney damage or decrease in function for > 3 months

what is chronic kidney disease staged by?

staged 1-5 GFR

-albuminuria substaged A1-A3

what are the leading causes of chronic kidney disease?

diabetes, hypertension, age, obesity

what is renal hypertension?

ischemia activates renin-angiotensin aldosterone

-resulting in vasoconstriction —> persistent hypertension

how is renal hypertension by evaluated by?

serum aldosterone, Na+, and renin

-expect an increase in serum Na, decrease in K, and increase in urine K

what is hemodialysis?

• synthetic membrane outside the body

• blood and dialysate flow counter-current

• creatinine clearance ~150-160 mL/min

  • performed at dialysis center

what is peritoneal disalysis?

• peritoneal wall acts as the membrane

• gravity-driven exchange

• continuous, 24/7 process

• lower clearance of small solutes

what is transplantation?

• greatest chance of full functional recovery

• 80% cadaveric donors

• means cadaveric graft half-life of 7 years

what is an acid?

substance that can donate H+ when dissolved in water

what is base?

substance that can accept hydrogen ions