URINARY SYSTEM
Chapter 25
Urinary System Organs
 _______________ : major excretory organs
 _______________: transport urine from kidneys to urinary bladder
 _______________ _______________: temporary storage reservoir for urine
 _______________: transports urine out of body
Kidney Anatomy
 _______________ _______________ atop each kidney
 Ureters, renal blood vessels, lymphatics, and nerves enter and exit at
_______________
 Layers of surrounding supportive tissue
o _______________ _______________: anchoring outer layer of dense
fibrous connective tissue
o _______________ _______________ _______________: fatty cushion
o _______________ _______________: prevents spread of infection to
kidney
 _______________ _______________: superficial region
 _______________ _______________: composed of cone-shaped medullary
(renal) pyramids
o Pyramids separated by _______________ _______________ (inward
extensions of cortical tissue)
 _______________: tip of pyramid; releases urine into minor calyx
 _______________: medullary pyramid and its surrounding cortical tissue
(approximately 8 per kidney)
 _______________ _______________: funnel-shaped tube continuous with ureter
 _______________ _______________: drain pyramids at papillae
 _______________ _______________: collect urine from minor calyces and
empty urine into renal pelvis
Urine flow: _______________ _______________ to minor calyx to _______________
_______________ to renal pelvis to _______________ to urinary bladder to
_______________
Kidneys cleanse blood and adjust its composition
 Renal arteries deliver _______________ of blood to kidneys each minute
 _______________ to renal artery to _______________ _______________ to
interlobar artery to _______________ _______________ to cortical radiate
artery to _______________ _______________ to glomerulus to
_______________ _______________ to peritubular capillaries or vasa recta to
_______________ _______________ _______________ to arcuate vein to
_______________ _______________ to renal vein to _______________
_______________ _______________
_______________: structural and functional units that form urine, composed of renal
corpuscle and renal tubule
 _______________ _______________
o _______________: tuft of fenestrated capillaries; highly porous, allows
filtrate formation
o _______________ _______________ (Bowman's capsule): cup-shaped,
hollow structure surrounding glomerulus
 _______________ _______________: simple squamous
epithelium
 _______________ _______________: branching epithelial
podocytes (extensions terminate in foot processes)
 _______________ _______________ between foot
processes allow filtrate to pass into capsular space
_______________ _______________
 _______________ _______________ _______________ (closest to renal
corpuscle)
o Functions in_______________ and _______________
o Confined to _______________
 _______________ _______________
o _______________ and _______________ limbs
 _______________ _______________ _______________ (farthest from renal
corpuscle)
o Distal descending limb (_______________ limb)
o _______________ ascending limb
o Function more in _______________ than _______________
o Confined to _______________
Collecting Ducts
 Two cell types:
o _______________ _______________: maintain water and Na+ balance
(sparse, short microvilli)
o _______________ _______________: maintain acid-base balance of
blood (abundant microvilli)
 Receive filtrate from _______________ nephrons
 Fuse together to deliver urine through papillae into _______________
_______________
Classes of Nephrons
 _______________ _______________: 85% of nephrons; almost entirely in cortex
 _______________ _______________: long nephron loops deeply invade medulla
o Ascending limbs have _______________ and _______________
segments
o Important in production of _______________ urine
Renal tubules associated with two capillary beds
 _______________: specialized for filtration
o Fed by _______________ arteriole and drained by _______________
arteriole
o Blood pressure in glomerulus high because afferent arterioles
_______________ in diameter than efferent arterioles
 _______________ _______________: low-pressure, porous capillaries adapted
for absorption of water and solutes
o Arise from _______________ arterioles and empty into
_______________
o Cling to adjacent renal tubules in _______________
 _______________ _______________: long, thin-walled vessels parallel to long
nephron loops of _______________ _______________
o Arise from _______________ arterioles serving juxtamedullary nephrons
o Function in formation of _______________ urine
Juxtaglomerular Complex (JGC)
 One per nephron
 Important in regulation of rate of _______________ _______________ and
_______________ _______________
 Three cell populations
o _______________ _______________: located in ascending limb;
chemoreceptors that sense NaCl content of filtrate
o _______________ _______________: located in arteriole;
mechanoreceptors that sense blood pressure in afferent arteriole (secrete
renin)
o _______________ _______________ _______________: between
arteriole and tubule cells; may pass signals between macula densa and
granular cells
Mechanisms of Urine Formation
 _______________ fluid processed daily; only _______________ urine produced
 Three processes in urine formation and adjustment of blood composition
o _______________ _______________: produces cell- and protein-free
filtrate
o _______________ _______________: selectively returns 99% of
substances from filtrate to blood in renal tubules and collecting ducts
o _______________ _______________: selectively moves substances from
blood to filtrate in renal tubules and collecting ducts
_______________: produced by glomerular filtration, blood plasma minus proteins
_______________: composed of <1% of original filtrate, contains metabolic wastes and
unneeded substances
Glomerular filtration is _______________ process where _______________ metabolic
energy is required _______________ _______________ forces fluids and solutes
through _______________ _______________
_______________ _______________: porous membrane between blood and interior of
glomerular capsule
 Composed of three layers
o _______________ _______________ of glomerular capillaries
o _______________ _______________ (fused basal laminae of two other
layers)
o Foot processes of _______________ with filtration slits
 Allows molecules smaller than 3 nm to pass (_______________, glucose,
_______________ _______________, nitrogenous wastes)
 _______________ _______________ remain in blood to maintain
_______________ _______________ _______________ which prevents loss of
all water to capsular space
Pressures That Affect Filtration
 _______________ pressures _______________ filtrate formation
o _______________ pressure in glomerular capillaries (HPgc): glomerular
blood pressure, _______________
 Inward forces _______________ filtrate formation
o _______________ pressure in capsular space (HPcs): pressure of filtrate
in capsule, _______________
o _______________ _______________ pressure in capillaries (Opgc):
“pull" of proteins in blood, _______________
_______________ _______________ _______________ :sum of outward pressures
that promote filtrate formation and inward forces that inhibit filtrate formation
 55 mmHg forcing out; 45 mmHg opposing = net _______________
_______________ of 10 mmHg
_______________ _______________ _______________ :volume of filtrate formed per
minute by both kidneys (normal = 120–125 ml/min)
 GFR directly proportional to:
o _______________ _______________ _______________
o _______________ _______________ _______________ available for
filtration
o Filtration membrane _______________
Glomerular Filtration Rate regulation via:
 _______________ _______________: maintains nearly constant GFR allowing
_______________ to make filtrate and maintain extracellular homeostasis
(______________________________)
 _______________ _______________: controls GFR via nervous and endocrine
mechanism in response to changes in _______________ _______________
o _______________ GFR causes _______________ urine output which
results in _______________ blood pressure, and vice versa
Two Types of Intrinsic Controls (Renal Autoregulation):
 _______________ _______________: afferent arterioles reaction to changes in
blood pressure in order to keep the blood flow within the glomerulus constant
 _______________ _______________ _______________: flow-dependent
mechanism directed by macula densa cells in response to filtrate NaCl
concentration
Myogenic Mechanism (Intrinsic Control)
 Increased BP: Increased GFR
o Increased _______________ _______________ in vessels
o _______________ of afferent arterioles
o Restricted _______________ _______________ into glomerulus
o _______________ GFR
 Decreased BP: Decreased GFR
o Reduced _______________ _______________ in vessels
o _______________ of afferent arterioles
o Increased _______________ _______________ into glomerulus
o _______________ GFR
Tubuloglomerular Feedback Mechanism (Intrinsic Control)
 Increased GFR:
o Filtrate _______________ _______________ increase
o Reabsorption time is _______________
o _______________ filtrate levels _______________, detected by
_______________ _______________ _______________
o _______________ of afferent arteriole
o GFR _______________
 Decreased GFR:
o Filtrate _______________ _______________ decrease
o Reabsorption time is _______________
o _______________ filtrate levels _______________, detected by
_______________ _______________ _______________
o _______________ of afferent arteriole
o GFR _______________
Two Types of Extrinsic Controls:
 _______________ _______________: response to lowered blood pressure by
_______________ _______________ _______________
 _______________ _______________: main mechanism for increasing blood
pressure via release of renin by _______________ _______________ (ReninAngiotensin- Aldosterone Mechanism)
Neural Mechanism (Extrinsic Controls)
 _______________ blood pressure
 _______________ released by sympathetic nervous system; _______________
released by adrenal medulla
 Systemic _______________ resulting in _______________ blood pressure
 _______________ of afferent arterioles
 Restricted _______________ _______________ into glomerulus
 _______________ GFR
Endocrine Mechanism: Renin-Angiotensin- Aldosterone Mechanism (Extrinsinc Control)
 Three pathways to_______________ release by _______________
_______________
o _______________ _______________ of granular cells by sympathetic
nervous system
o Stimulation by activated _______________ _______________ cells
when filtrate NaCl concentration low
o _______________ _______________ of granular cells
_______________ _______________: most of tubular contents reabsorbed to
_______________; all _______________ _______________ reabsorbed; water and ion
reabsorption _______________ regulated and adjusted
 Two routes from tubule to peritubular capillary
o _______________ route: pathway through the cells
 _______________ route: pathway between tubule cells
 _______________ tubular reabsorption: movement of
_______________ across basolateral membrane via Na+-K+
ATPase pump
o _______________ _______________ (glucose, amino acids, some ions,
vitamins) reabsorbed by _______________ _______________
_______________ (facilitated diffusion mechanism) across apical;
cotransported with Na+
o _______________ tubular reabsorption: movement of Na+ and other
solutes creates _______________ _______________ for water; water
reabsorbed by osmosis, aided by water- filled pores called
_______________
 Aquaporins always present in _______________
_______________ _______________: obligatory water
reabsorption
 Aquaporins inserted in _______________ _______________ only
if ADH present: facultative water reabsorption
_______________ _______________ for every reabsorbed substance; reflects number
of _______________ in renal tubules available
 When carriers saturated, excess excreted in _______________
_______________ _______________ _______________: site of most reabsorption
 All _______________ (glucose and amino acids)
 65% of _______________ and _______________
 Many _______________
 All _______________ _______________; 1⁄2 _______________
Nephron loop
 _______________ _______________: H2O can leave; solutes cannot
 _______________ _______________: H2O cannot leave; solutes can
 _______________ _______________: passive movement
 _______________ _______________: active movement
DCT and collecting duct: reabsorption _______________ regulated
 _______________ _______________ :insertion of aquaporins in collecting ducts;
reabsorb water
 _______________: insertion of Na+ and K+ channels and Na+-K+ pump in
collecting duct; Na+ reabsorption, water follows
 _______________ _______________ _______________: reduces blood Na+,
reduced water reabsoprtion
 _______________ _______________: acts on DCT to increase Ca2+
reabsorption
_______________ _______________: reabsorption in reverse; almost all in PCT
 _______________, H+, _______________, creatinine, _______________
_______________ and bases move from peritubular capillaries through tubule
cells into filtrate
 Substances _______________ in tubule cells also secreted (HCO3-)
 Disposes of substances (drugs) bound to _______________ _______________
 Eliminates _______________ _______________ passively reabsorbed (urea and
uric acid)
 Rids body of excess potassium (______________________________)
 Controls _______________ _______________ by altering amounts of H+ or
HCO3– in urine
_______________: number of solute particles in 1 kg of H2O, reflects ability to cause
osmosis (osmolality of body fluids expressed in _______________
 _______________ maintain osmolality of plasma at by regulating urine
concentration and volume via the _______________ _______________
 _______________ _______________: occurs when fluid flows in opposite
directions in two adjacent segments of same tubule with hair pin turn (establishes
_______________ _______________ from renal cortex through medulla)
o _______________ _______________: interaction of filtrate flow in
ascending/descending limbs of nephron loops of juxtamedullary nephrons
o _______________ _______________: blood flow in
ascending/descending limbs of vasa recta
Countercurrent Multiplier: _______________ _______________
 _______________ limb is freely permeable to _______________
 H2O passes out of filtrate into _______________ medullary interstitial fluid
 Filtrate osmolality _______________ to ~1200 mOsm
 _______________ limb is impermeable to _______________ and selectively
permeable to _______________
 Na+ and Cl– actively _______________ in thick segment; some passively
_______________ in thin segment
 Filtrate osmolality _______________ to 100 mOsm
 Constant 200 mOsm _______________ between two limbs of nephron loop and
between ascending limb and interstitial fluid
 Difference _______________ along length of loop to ~ 900 mOsm
The Countercurrent Exchanger: _______________ _______________
 Preserves _______________ _______________ by preventing the rapid removal
of _______________ from interstitial space and removing reabsorbed
_______________
 Volume of blood at end of vasa recta _______________ than at
_______________
Osmotic gradient used to raise urine concentration
 _______________: large volume dilute urine, ADH production decreases
 _______________: small volume concentrated urine, maximal ADH released
_______________: chemicals that enhance urinary output
 _______________ _______________ (alcohol)
 _______________ _______________ _______________ resulting H2O
reabsorption (caffeine, drugs for hypertension or edema)
 _______________ _______________ inhibit medullary gradient formation
 _______________ _______________: substance not reabsorbed so water remains
in urine (high glucose of diabetic patient)
_______________ _______________: volume of plasma kidneys clear of particular
substance in given time
 Renal clearance tests used to
o Determine_______________
o Detect _______________ damage
o Follow progress of _______________ _______________
 _______________ (plant polysaccharide): freely filtered; neither
_______________ nor _______________ by kidneys; standard used for renal
clearance (GFR = 125 ml/min)
o If C < 125 ml/min, substance _______________
o If C = 0, substance completely _______________, or not filtered
o If C = 125 ml/min, no net _______________ or _______________
o If C > 125 ml/min, substance_______________ (most drug metabolites)
Physical characteristics of urine is normally_______________ and pale to deep yellow
from _______________ (pigment from hemoglobin breakdown), slightly
_______________ (~pH 6)
 Cloudy may indicate _______________ _______________ _______________
 More _______________ urine has deeper color
 _______________ _______________ (pink, brown, smoky) from food ingestion,
bile pigments, blood, drugs
 Develops _______________ odor upon standing as_______________ metabolize
solutes
Chemical Composition of Urine
 95% _______________ and 5%_______________
 Nitrogenous wastes
o _______________ (from amino acid breakdown) largest solute
component
o _______________ _______________ (from nucleic acid metabolism)
o _______________ (metabolite of creatine phosphate)

Other normal solutes
o _______________, Potassium, _______________ , Sulfate,
_______________, Magnesium, _______________
Ureters: move urine from kidneys to bladder
 Enter _______________ of _______________ through posterior wall, as bladder
pressure increases, distal ends of ureters close, preventing _______________ of
urine
 Three layers of ureter wall from inside out
o _______________: transitional epithelium
o _______________: smooth muscle sheets, contracts in response to stretch
o _______________: outer fibrous connective tissue
_______________ _______________: kidney stones in renal pelvis (crystallized
calcium, magnesium, or uric acid salts)
_______________ _______________: muscular sac for temporary storage of urine
 Contains openings for _______________ and _______________
o _______________: smooth triangular area outlined by openings for
ureters and urethra
 Layers of bladder wall
o _______________: transitional epithelial mucosa
o _______________ _______________: three layers of smooth muscle
o _______________ _______________
 Collapses when empty; _______________ appear
 Full bladder holds _______________
_______________: muscular tube draining urinary bladder
 Two sphincters
o _______________ _______________ sphincter: _______________
(smooth muscle) at bladder-urethra junction
o _______________ _______________ sphincter: _______________
(skeletal) muscle surrounding urethra as it passes through pelvic floor
 _______________ urethra (3 - 4 cm) carries _______________
o External urethral orifice: anterior to vaginal opening; posterior to clitoris
 _______________ urethra (19 – 20 cm) carries _______________ and
_______________
o Three named regions
 _______________ _______________ (2.5 cm): within prostate
 _______________ _______________ (2 cm): passes through
urogenital diaphragm from prostate to beginning of penis
 _______________ _______________ (15 cm): passes through
penis; opens via external urethral orifice
_______________: urination or voiding
 Three simultaneous events must occur
o Contraction of _______________ _______________ of the bladder by
ANS
o Opening of _______________ _______________ sphincter by ANS
o Opening of _______________ _______________ sphincter by somatic
nervous system
 Reflexive urination (urination in infants)
o Distension of bladder activates _______________ _______________
o Excitation of parasympathetic neurons in _______________
_______________
o Contraction of _______________ _______________ of the bladder by
ANS
o _______________ of internal urethral sphincter by ANS
o _______________ of somatic pathways to external sphincter, allowing its
_______________
 _______________ _______________ _______________ (located in the pons)
mature between ages 2 - 3
o Pontine _______________ _______________: inhibits micturition
o Pontine _______________ _______________: allow micturition