Renal Lab

urinary system

consists of kidneys, ureters, urinary bladder, and urethra

waste products eliminated by kidneys

urea, uric acid, and creatine

regulating plasma composition through elimination of metabolic wastes, toxins, excess ions, and water

how kidneys contribute to homeostasis

upper abdominal quadrant of retroperitoneal space

where kidneys are located

urea

formed in breakdown of amino acid

uric acid

formed in breakdown of nucleic acid

creatine

formed in breakdown of creatine phosphate

- regulation of volume, composition, and pH of body fluids
- regulation of acid-base homeostasis
- regulation of energy metabolism
- regulation of plasma osmolarity
- detoxification of metabolic wastes
- conversion of vitamin D3 into active form
- synthesis and conversion of hormones such as erythropoietin and renin

Functions of kidney

production of ammonia

how kidneys regulate acid-base homeostasis

gluconeogenesis during fasting conditions

how kidneys regulate energy metabolism

control of aquaporin receptors within collecting duct

how kidneys regulate plasma osmolarity

excretory mechanisms

how kidneys detox metabolic wastes

nephron

smallest function unit of kidney; helps produce urine

renal a, segmental a, interlobar a, arcuate a, afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa recta, interlobular v, arcuate v, interlobar v, segmental v, renal v

renal blood flow

glomerular capsule, PCT, loop of Henle, DCT, collecting duct, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, urethra

urinary flow

vasa recta

capillaries surrounding nephron loop

efferent arteriole

conducts blood from glomerulus to peritubular capillaries

peritubular capillaries

capillaries surrounding distal and proximal convoluted tubules

cortical nephron

- found in renal cortex
- major role in waste reabsorption
- produces diluted urine
- shorter loops of Henle
- 80-85% of nephrons in humans

juxtamedullary nephron

- next to medulla
- produce more concentrated urine
- longer loops of Henle that extend down the renal medulla
- only 15-20% of nephrons in humans

renal corpuscle

bowman's capsule + glomerulus

renal corpuscle and renal tubule

nephron is composed of

3 parts of renal tubule

- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule

filtration

- filtrate of blood leaves the kidney capillaries and enter the renal tubule
- movement of water and plasma solutes through the glomerular capillary walls into the urinary space of the Bowman's capsule

Reabsorption

- most of the nutrients, water, and essential ions are recovered from the filtrate and returned to the blood
- when a substance is transported from the filtrate, through the tubular cell membrane walls, and eventually into system circulation

secretion

- certain substances are secreted from the blood into the filtrate product to be eliminated
- substance is transported from peritubular blood vessels into the filtrate product, which will ultimately form urine

excretion

process of eliminating or expelling waste matter through the final excretory product, urine

filtrate

- composed of water, electrolytes, and organic matter
- stuff that is squeezed out of blood into capsule

water, glucose, amino acids, sodium, potassium, calcium, chloride, phosphate, and bicarbonate

Absorbed in PCT

water

reabsorbed in descending limb of nephron loop

sodium, chloride, and potassium

reabsorbed in ascending limb of nephron loop

water, calcium, sodium, and chloride

reabsorbed in DCT

hydrogen ions, ammonium, creatinine, toxins, and drugs

secreted in PCT

hydrogen ions and potassium

secreted in DCT

glomerular filtration

initial stage for urine formation

porous

endothelium of glomerular capillaries are ____

fluid, waste products, ions, glucose, and amino acids

capillaries of glomerular filtration allow _____ to pass from blood into the capsule

blood cells and proteins

blocked out of glomerular filtration so they stay in the blood and exit through the vasa recta

glomerular filtration rate (GFR)

- volume of filtrate produced by both kidneys per minute
- physiological indicator of renal function
- determined by starling's pressures

Starling's pressures

capillary hydrostatic pressure, interstitial fluid hydrostatic pressure, capillary blood oncotic pressure, and interstitial fluid oncontic pressure

cuboidal epithelial cells

in the proximal convoluted tubule contain ______ cells

mitochondria

PCT cell walls contain _____ to power pumps that pull sodium ions from the filtrate using active transport

microvilli

increase surface area of PCT to allow reabsorption of large amounts of "good stuff"

proximal convoluted tubule (PCT)

where majority of renal reabsorption occurs in the proximal convoluted tubule

100% reabsorption

in healthy individual will absorb ____ of glucose

200mg/dL

renal threshold for glucose

350mg/dL

absolute threshold of glucose reabsorption, where no more glucose can be absorbed

loop of Henle

starts in cortex, dips into medulla, and comes back into cortex

reabsorption of water

loop of henle drives _____ by creating a salt concentration gradient in the tissue of the medulla

ascending

portion of loop of henle that actively pumps out salt and is impermeable to water

descending portion

high concentration of salt in interstitial fluid of medulla causes water to passively flow in the _____ via osmosis

hypertonic

interstitial fluid is _____ to filtrate

descending limb

passively permeable to water

thick ascending limb

impermeable to water; active transport of Na+, Cl- follows passively

distal convoluted tubule

responsible for reabsorption of sodium, bicarbonate, and secretion of ammonium; impermeable to water

Parathyroid hormone

what acts of DCT to stimulate calcium reabsorption

collecting duct

where does DCT empty

Collecting duct

- contains aquaporins
- involved in sodium reabsorption and potassium excretion

aquaporins

aid in reabsorption of water into blood; located in collecting duct

Renin-angiotensin-aldosterone system (RAAS)

low blood volume activates juxtaglomerular apparatus to secrete renin

Renin > angiotensin I > angiotensin converting enzyme (ACE) > angiotensin II

process of renin to angiotensin II

Angiotensin II

variety of function including causing release of aldosterone from adrenal cortex

aldosterone

- promotes sodium reabsorption in DCT and collecting duct
- promotes retention of water and sodium
- stimulates thirst
- increases blood volume thus increases blood pressure

high ADH

renal mechanism produce hyperosmotic (concentrated) urine

absence of ADH

renal mechanisms produce hyposmotic (diluted) urine

ADH

- increases permeability of water of DCT and collecting duct, which are normally impermeable
- causes increased water reabsorption and retention and decreases volume of urine

micturation

medical term for urination

urinary sphincters

2 sphincters that must open before urine can flow into urethra

internal sphincter

under involuntary control

external sphincter

under voluntary control

full feeling bladder

150-200 mL of urine

urgent feeling in bladder

300-400 mL of urine

involuntary urination

>600 mL of urine

Urinary tract infections

- most often occurs in sexually active women
- symptoms include burning sensation while urinating, increased urgency and frequency of urination, fever, and sometimes cloudy or blood-tinged urine

urinary tract infections in elderly

- susceptible due to weakness of bladder, incontinence, poor bladder emptying, and retention of urine
- symptoms include mental changes and confusion

renal calculi (kidney stones)

- 4 different types
- calcium oxalate is most common
- experience severe pain

Risk factors for kidney stones

family history, chronic dehydration, obesity, certain diets (high protein or salt)

lithotripsy

shock waves used to break up kidney stones
used when stones >5 mm become lodged in ureter