Urinary SystemHonors Anatomy & Physiology

KidneysFilter 200L of fluid from blood

excreting waste as urineRegulate blood volume, balance

water & salts, pHSecretes renin (BP) &

erythropoeitin (EPO) Renal Cortex – superficial

(light)Renal Medulla – deeper (dark)

arranged in (8) pyramidsCalyces collect urine & empty

into renal pelvis

NephronsFunctional units of

kidney> 1 million per kidneyGlomerulus capillary bed

Fed & drained by arterioles

High pressure forces fluid & soluted out of blood

Peritubular capillariesFrom efferent arterioles

of glomerulusLow pressure reclaims

solutes & water

UrineColor

Yellow due to urochrome (pigment from Hb)

Transparent –cloudy indicator of UTI

Odor If left out smells of ammonia from

bacteria metabolizing urea (diabetics urine smells fruity)

Average pH6 vary (4.5-8) dependent on diet

Composition95% waterUrea (from breakdown of amino acids)Uric acid (from breakdown of nucleic

acids)Creatinine (from creatine phosphate)Na+, K+, PO43-, SO42-, Ca2+ Mg+2 ,HCO3-

UretersSlender tubes

propels urine from kidney to bladder

3 layer wall, transitional epithelium & 2 sheets of smooth muscle for peristalsis

Urinary BladderCollapsable muscular

sac temporariliy stores urine

Trigone – 3 openings 3 layers: transitional

epithelium, intermingled smooth muscle, fiberous adventitia

Rugae – folds when empty

Full bladder – 5” long – holds 1 pint of urine (max 1L)

UrethraDrains urine from bladderInternal urethral sphincter –

involuntaryExternal urethral sphincter –

voluntaryFemales 3-4” long, external

urethral orificeMales 8” long, carries urine &

semen3 regions:

prostetic urethra 1” (within prostate)

Membranous urethra 2cm Spongy urethra 15cm long

Fluid, Electrolyte, & Acid-Base BalanceWater: women 50% of mass, men 60%, infants 73%

Intracellular fluid – in cellsExtracellular fluid – plasma & interstitial fluid (lymph,

CSF, eye humors, synovial fluid, etc)Water intake 2.5L/day & metabolic waterWater output: lung vapors, perspiration, feces, urine

SolutesNonelectrolytes – organic molecules w/covalent bondsElectrolytes – dissociate into ions in water

Ph 7.35 (viens) - 7.45 (arteries)Buffers: bicarbonate, phosphate, protein