Urinary System

Function of Kidneys 

Major ____ organ that maintain body’s ____ environment by: 

• Regulating total WATER volume + total ____ [ ] in water 

• Regulating ion [ ] in ECF 

• Ensuring long-term acid-base balance 

• Excreting metabolic wastes, toxins, drugs 

• Producing: 

  • Erythropoietin → regulates RBC production 

  • ____ → regulates BP 

• Activating vitamin D 

• Carrying out gluconeogenesis (during prolonged fasting)

excretory, internal, solute, renin

Kidneys 

• ____ → transport urine FROM kidneys to urinary bladder 

• Urinary bladder → temp ____ reservoir for urine 

• ____ → transport urine OUT of body

ureters, storage, urethra

ANATOMY of KIDNEYS

Location and External Anatomy 

• Retroperitoneal + in SUPERIOR lumbar region (b/w T12 and L5) 

• Right kidney is crowded by liver + LOWER than left 

• ____ (suprarenal) gland sits on top of each kidney 

• Convex lateral surface 

• Concave medial surface w/ vertical ____ ____ leads to internal space → renal sinus 

  • Ureters, renal blood vessels, lymphatics, and nerves ENTER and EXIT at ____

adrenal, renal hilum, hilum

INTERNAL ANATOMY - kidneys (3 regions)

1. Renal ____ → granular-appearing superficial region 

cortex

INTERNAL ANATOMY - kidneys (3 regions)

2. Renal ____ → deep to cortex, composed of cone-shaped medullary (renal) pyramids

• Broad base of pyramid faces cortex 

• ____ → TIP of pyramid + points internally 

• Pyramids are separated by ____ ____ (inward extensions of cortical tissue) 

• ____ = medullary pyramid + its surrounding cortical tissue, abt 8/kidney

medulla, papilla, renal columns, lobe

INTERNAL ANATOMY - kidneys (3 regions)

3. Renal ____ → funnel-shaped tube continuous with ____

• Minor calyces = cup-shaped areas that collect urine draining from ____ ____

• Major calyces = areas that collect urine from ____ ____ + empty urine into renal pelvis 

• Urine flow: renal pyramid → minor calyx → major calyx → renal pelvis → ureter

pelvis, ureter, pyramidal papillae, minor calyces

Blood & Nerve Supply 

• Blood = kidneys cleanse blood + adjust its composition, SO it has a RICH blood supply 

  • Renal arteries deliver about ¼ (1200mL) of CO to kidneys per MINUTE 

  • Arterial flow = renal → segmental → ____ → ____ → cortical radiate (interlobular) 

  • Venous flow = cortical radiate → ____ → ____ → renal veins 

    • NO ____ veins 

• Nerve Supply = through sympathetic fibers from ____ ____

interlobar, arcuate, arcuate, interlobar, segmental, renal plexus

NEPHRONS - Renal Corpuscle (2)

1. Glomerulus 

• Tuft of ____ composed of fenestrated endothelium 

• Highly porous

• Allows for efficient FILTRATE formations 

• Filtrate = plasma-derived fluid that ____ ____ process to form urine

capillaries, renal tubules

NEPHRONS - Renal Corpuscle (2)

2. Glomerular Capsule 

• Aka Bowman’s capsule → cup-shaped, hollow structure surrounding ____

• 2 layers: 

  • Parietal = simple ____ epithelium 

  • Visceral = clings to glomerular caps + branches epithelial ____

    • Extensions end (terminate) in foot processes that cling to basement membrane 

    • ____ ____ b/w foot processes allow filtrate to pass into capsular space

glomerulus, squamous, podocytes, filtration slits

NEPHRONS - Renal Tubule (3)

1. ____ ____ Tubule (PCT) 

• CLOSEST to renal corpuscle 

• ____ cells w/ dense microvilli that form brush border 

  • Increase surface area 

  • Also have large ____

• Functions = ____ + ____

• Confined to cortex

proximal convoluted, cuboidal, mitochondria, reabsorption, secretion

NEPHRONS - Renal Tubule (3)

2. ____ ____

• Aka loop of Henle 

• U-shaped structure consisting of 2 limbs 

• Descending limb = proximal part of it is continuous w/ proximal tubule 

  • Distal portion aka descending ____ limb → simple ____ epithelium 

• Ascending limb 

  • THICK ascending limb → thin in some nephrons 

  • Cuboidal or columnar cells

nephron loop, thin, squamous

NEPHRONS - Renal Tubule (3)

3. Distal convoluted tubule (DCT)

• FARTHEST from renal corpuscle 

• Cuboidal cells w/ very FEW ____

• Function = more in ____ (than reabsorb)

• Confined to cortex 

• drains into ___

microvilli, secretion, collecting duct

Collecting Ducts

• 2 cells types: 

  • ____ cells = maintain WATER and Na+ balance 

    • Not that much + with SHORT microvilli 

  • ____ cells = help maintain ____ balance of BLOOD 

    • Cuboidal cells w/ LOTS of microvilli 

    • 2 types → A and B (both help) 

• Receive filtrate from many nephrons 

• Run through medullary pyramids → give pyramids their ____ look 

• Ducts fuse together to deliver urine through ____ into ____ calyces

principal, intercalated, acid-base, striped, papillae, minor

Classes of Nephrons (2) 

1. ____ Nephrons 

• 85% of nephrons 

• Almost entirely IN cortex 

2. ____ Nephrons 

• Long nephron loops deeply go through (invade) ____

• Ascending limbs have thick and thin segments 

• Important in production of ____ urine 

• More prominent in desert animals

cortical, juxtamedullary, medulla, concentrated

NEPHRON CAPIS BEDS (3)

• Renal tubules have 2 cap beds → ____ + ____ caps 

• Juxta nephrons have 1 → ____ ____

glomerulus, peritubular, vasa recta

NEPHRON CAPIS BEDS (3)

 1. Glomerulus 

• Specialized for ____

• Diff from other cap beds b/c they are fed and drained by arteriole 

  • Afferent arteriole ____ glomerulus via efferent arteriole 

  • Afferent arises from ____ radiate arteries 

  • Efferent feed into either peritubular caps or vasa recta 

• BP is ____ in glomerulus b/c: 

  • Afferent arterioles are LARGER in ____ than efferent 

  • Arterioles are high-resistance vessels

filtration, enters, cortical, high, diameter

NEPHRON CAPIS BEDS (3)

 2. Peritubular Capillaries 

• ____ -____ , porous caps adapted for ____ of water and solutes 

• Arise from ____ arterioles 

• Cling to adjacent renal tubules in cortex 

• Empty into ____

low-pressure, absorption, efferent, venules

NEPHRON CAPIS BEDS (3)

3. Vasa Recta 

• Long, THIN-walled vessels parallel to long nephron loops of juxta nephrons 

• Arise from ____ arterioles serving ____ nephrons 

  • Instead of peritubular caps 

• Function = formation of ____ urine

efferent, juxtamedullary, concentrated

Juxtaglomerular Complex (JGC) 

• EACH nephron has ____ JGC

• Involves modified positions of: 

  • Distal portion of ____ limb of nephron loop 

  • Afferent (sometime efferent) arteriole 

• Important in regulating rate of ____ ____ and ____

one, ascending, filtrate formation, BP

CELLS in JGC (3)

____ ____

• Tall + closely packed cells of ascending limb 

• Has ____ that sense NaCl content of filtrate 

macula densa, chemoreceptors

CELLS in JGC (3)

____ cells (juxtaglomerular, of JG cells) 

• Enlarged + smooth muscle cells of arteriole 

• Acts as ____ to sense BP in ____ arteriole 

• Contain secretory granules that contain enzyme ____

granular, mechanoreceptors, efferent, renin

CELLS in JGC (3)

Extraglomerular ____ cells 

• Located b/w arteriole and tubule cells 

• Interconnected with ____ ____

• May pass signals b/w macula densa and granular cells 

mesangial, gap junctions

Physiology of Kidney 

• 180L of fluid processed daily but ONLY 1.5L of urine is formed 

• Kidneys filter body’s ENTIRE plasma volume 60x each day 

• Consume 20-25% of O2 used by body at ____

• Filtrate (produced by glomerular filtration) → basically blood plasma WITHOUT ____

• Urine is produced from filtrate: 

  • Urine is ____ than 1% of OG filtrate 

  • Contains metabolic wastes + unneeded substances

rest, proteins, less

Processes of Urine Formation & Blood Composition Adjustment

1. ____ ____ → produces FILTRATE (w/o cells and proteins) 

2. Tubular ____ → selectively returns 99% of substances from filtrate to blood in renal ____ and ____ ____

3. Tubular ____ → selectively moves substances from blood to filtrate in renal tubules and collection ducts 

glomerular filtration, reabsorption, tubule, collecting ducts, secretion

STEP 1:  Glomerular Filtration (urine formation)

• A ____ process → NO metabolic energy needed 

• Hydrostatic pressure forces fluids and solutes through ____ ____ into glomerular capsule 

• NO reabsorption into capillaries of glomerulus occurs

passive, filtration membrane

Filtration Membrane

• Porous membrane b/w blood and interior of glomerular capsule 

• Allows water + solutes (smaller than plasma proteins) to pass → normally NO cells can pass 

• 3 layers: 

  • ____ ____ of glomerular capillaries 

  • ____ membrane → fused basal laminae of 2 other layers 

  • ____ ____ of podocytes w/ filtration slits → slit diaphragms REPEL macromolecules

• Macromolecules “stuck” in filtration membrane are engulfed by glomerular ____ cells 

• Allows molecules smaller than 3 nm to pass → so water, glucose, amino acids, nitrogenous wastes 

• Plasma proteins remain in blood to maintain colloid osmotic pressure 

  • Prevents loss of all water to capsular space 

  • Proteins in filtrate indicate membrane problem

fenestrated endothelium, basement, foot processes, mesangial

Pressures Affecting Filtration (2)

Outward Pressures

• ____ filtrate formation

• hydrostatic pressure in ____ ____ (HPgc) → basically glomerular BP 

  • MAIN force pushing water and solutes OUT of blood 

  • HIGH BP→ 55mm Hg

    • Compared to 26 mm Hg seen in most caps beds 

  • High b/c ____ arteriole is a high-resistance vessels w/ a diameter ____ than afferent arteriole

promote, glomerular capillaries, efferent, smaller

Pressures Affecting Filtration (2)

Inward Pressures

• ____ filtrate formation 

  • Hydrostatic pressure in ____ ____ (HPcs) → filtrate pressure in capsule (15 mm Hg) 

  • ____ osmotic pressure in ____ (OPgc) → “pull” of proteins in blood (30 mm Hg) 

• Net filtration pressure (NFP) = SUM of forces 

  • 55 mm Hg forcing OUT minus 45 mm Hg opposing = net outward force of 10 mm Hg 

  • Pressure responsible for ____ formation 

  • Main controllable factor determining ____ ____ ____ (GFR)

inhibit, capsular space, colloid, capillaries, filtrate, glomerular filtration rate

Glomerular Filtration Rate (GFR)

• The ____ of filtrate formed per MINUTE by BOTH kidneys 

• Normal = 120-125 ml/min 

• Directly proportional to: 

  • NFP → primary pressure is glomerular hydrostatic pressure

  • Total ____ ____ available for filtration → glomerular mesangial cells control by contracting 

  • ____ ____ permeability→ much MORE permeable that other capis

volume, surface area, filtration membrane

Regulation of Glomerular Filtration

• CONSTANT GFR is important b/c it allows kidneys to make filtrate and maintain ____ ____

• Goal of local intrinsic controls (renal autoregulation) = maintain ____ in kidney 

• GFR affects systemic BP

  • Increased GFR → causes increased ____ ____ → LOWERS BP (and vice versa) 

  • Goal of extrinsic controls = maintain ____ ____

    • NS and endocrine mechanisms are main extrinsic controls

extracellular homeostasis, GFR, urine output, systemic BP

Regulation of Filtration - Intrinsic Controls: Renal Autoregulation (2)

• Maintains nearly constant GFR when MAP is in range of 80-180 mm Hg 

• Autoregulation STOPS if out of that range

1. ____ Mechanism 

• Local SMOOTH muscle contracts when stretched 

• Increased BP causes muscle to stretch → leads to constriction of ____ arterioles 

  • Restricts blood flow into ____

  • Protects glomeruli from damaging high BP 

• Decreased BP → ____ of afferent arterioles 

• Both help maintain normal GFR despite normal fluctuations in BP

myogenic, afferent, glomerulus, dilation

Regulation of Filtration - Intrinsic Controls: Renal Autoregulation (2)

2. ____ feedback mechanism 

• Flow-dependent mechanism directed by ____ ____ cells 

  • Respond to filtrate’s NaCl [ ] 

• If GFR INCREASES → filtrate flow rate ____

  • Leads to ____ reabsorption time = HIGH NaCl levels in ____

  • Feedback mechanism causes ____ of afferent arteriole → lowers NFP and GFR → allow more time for NaCl reabsorb

• Opposite mechanism for DECREASED GFR

tubuloglomerular, macula densa, increases, decreased, filtrate, constriction

Regulation of Filtration - Extrinsic Controls: Neural & Hormonal

• Purpose = regulate GFR to maintain systemic BP 

• Extrinsic controls will override intrinsic if blood volume needs to be INCREASED

1. Sympathetic NS 

• Under normal conditions at rest: 

  • Renal blood vessels ____

  • Renal autoreg mechanisms win (prevail) 

• ABRNOMAL conditions (extremely low ECF volume, low BP):

  • Norepinephrine is released by sympathetic NS 

  • Epinephrine is released by adrenal medulla 

  • Systemic ____ → increases BP 

  • Constriction of afferent arterioles → decreases GFR 

  • Blood volume + pressure ____

  • Sympathetic NS is activated

dilated, vasoconstriction, increase

Regulation of Filtration - Extrinsic Controls: Neural & Hormonal

2. RAA (renin-angiotensin-aldosterone) 

• MAIN mechanism for increasing BP 

• 3 pathways to renin release by ____ cells 

  • Direct stimulation of granular cells by sympathetic NS 

  • Stimulation by activated ____ ____ cells when filtrate NaCl [ ] is LOW 

  • Reduced ____ of granular cells

granular, macula densa, stretch

STEP 2:  Tubular Reabsorption (urine formation)

• This quickly reclaims most of tubular contents and returns them to BLOOD 

• Selective transepithelial process

  • Almost all ____ nutrients are REABSROBED 

  • Water and ion reabsorption is ____ regulated and adjusted 

• ____ + ____ tubular reabsorption

organic, hormonal, active, passive

Routes for Substances (2)

1. ____ route

   • Solute enters apical membrane of tubule cells 

   • Diffusion through cytosol 

   • Transport across ____ membrane 

     • Often involves lateral intercellular spaces b/c membrane transporters transport ions into these spaces 

   • Enters blood through ____ of ____ capillaries

transcellular, basolateral, endothelium, peritubular

Routes for Substances (2)

2. ____ route → BETWEEN tubule cells 

• Movement through leaky ____ ____ , particularly in the ____

• Limited by tight junctions 

• Movement through interstitial fluid and into capis

• Water, Ca, Mg, K, and some Na in the PCT move through this route

paracellular, tight junction, PCT

Tubular Reabsorption of Sodium (2)

1. Sodium Transport across ____ membrane 

• Na is most abundant cation in filtrate 

• Transport of Na across basolateral membrane of tubule cell is via ____ ____ transport 

• Na-K ATPase pumps Na into interstitial space 

• Na is swept by bulk flow into ____ capis 

basolateral, primary active, peritubular

Tubular Reabsorption of Sodium (2)

2. Transport across ____ membrane 

• Na enters tubule cell at apical surface via ____ ____ transport (cotransport) or facilitated diffusion through channels 

• Active pumping of Na at basolateral membrane = strong electrochemical gradient within tubule cell 

• Result = LOW ____ Na levels that facilitate Na diffusion 

• K leaks OUT of cell into interstitial fluid → leaves a net ____ charge inside cell → which also pulls Na IN

apical, secondary active, intracellular, negative

Tubular Reabsorption of Nutrients, Water, and Ions

Na reabsorption by primary active transport provides ____ and means for reabsorbing almost every other substance 

energy

Tubular Reabsorption of Nutrients, Water, and Ions

Secondary Active Transport 

• Electrochemical gradient created by pumps at ____ surface give “push” needed for transport of other solutes 

• ____ nutrients reabsorbed by secondary active transport → are ____ w/ Na 

  • Ex. glucose, amino acids, some ions, vitamins 

basolateral, organic, cotransported

Tubular Reabsorption of Nutrients, Water, and Ions

Passive tubular reabsorption of WATER

• Movement of Na and other solutes creates osmotic gradient for water 

• Water is reabsorbed by osmosis → helped by water-filled pores called ____

  • ____ water reabsorption → aquaporins ALWAYS present in PCT 

  • ____ water reabsorption → aquaporins are inserted in collecting ducts only if ____ is present

aquaporins, obligatory, facultative, ADH

Tubular Reabsorption of Nutrients, Water, and Ions

Passive tubular reabsorp of SOLUTES 

• Solute [ ] in filtrate ____ as water is reabsorbed 

  • Creates [ ] gradients for solutes → drive their entry into tubule cell and peritubular capis 

• Fat-soluble substances, some ions, and urea → will ____ water into peritubular capis down their [ ] gradients 

• Which is why lipid-soluble drugs and environmental pollutants are reabsorbed even though its bad 

increases, follow

Transport Maximum

• Transcellular transport systems are specific and limited

• Transport maximum (Tm) exists for almost EVERY reabsorbed substances 

  • Reflects number of ____ in renal tubules that are available 

• When carriers for a solute are ____ → excess is excreted in ____

  • Ex. ____ leads to high blood glucose that exceed Tm = so glucose spills over into urine

carriers, saturated, urine, hyperglycemia

Reabsorptive Capabilities of Renal Tubules and Collecting Ducts

PCT 

• Site of MOST reabsorption: 

  • All ____ (like glucose and amino acids) 

  • 65% of Na and water 

  • Many ions 

  • Almost all ____ acid 

  • About HALF of ____ (later secreted back into filtrate)

nutrients, uric, urea

Reabsorptive Capabilities of Renal Tubules and Collecting Ducts

Nephron Loop 

• ____ limb → water can leave, solutes CANNOT 

• ____ limb → water CANNOT leave, solutes can leave 

  • THIN segment is ____ to Na movement 

  • THICK segment has Na-K-2Cl symporters and Na-H antiporters that transport Na INTO cell 

  • Some Na can pass into cell by ____ route in this area of the limb

descending, ascending, passive, paracellular

Reabsorptive Capabilities of Renal Tubules and Collecting Ducts

Distal Convoluted tubule and collecting duct 

• Reabsorption is ____ regulated in these areas:

hormonally

DCT & CD Hormone regulation (4)

1. ADH aka vasopressin 

• Released by ____ pituitary gland 

• Causes ____ cells of collecting ducts to insert aquaporins in apical membranes → increase water absorption 

• Increased ADH levels = increase in water absorption 

posterior, principal

DCT & CD Hormone regulation (4)

2. Aldosterone 

• Targets collecting ducts (principal cells) and distal CT 

• Promotes ____ of apical Na and K channels + basolateral Na-K ATPases → for Na reabsorption (water follows) 

• Result = little Na leaves the body 

• Without aldosterone → daily loss of filtered Na would be 2% which is incompatible with life (can’t survive) 

• Functions = ____ BP and ____ K levels

synthesis, increase, decrease

DCT & CD Hormone regulation (4)

3. ____ Natriuretic Peptide 

• REDUCES blood Na → decreases blood volume and BP 

• Released by cardiac atrial cells if blood volume or pressure is ____

atrial, elevated

DCT & CD Hormone regulation (4)

4. Parathyroid hormone

• Acts on DCT to increase ____ reabsorption

Ca

Step 3: Tubular Secretion (urine formation)

• REVERSE of reabsorption 

• Occurs almost completely in ____

• Selected substances are moved from peritubular capis through tubule cells → then OUT into filtrate 

  • K, H, NH4, creatine, organic acids and bases 

  • Substances ____ in tubule cells are also SECRETED (ex. HCO3)
    

PCT, synthesized

Tubule Secretion Important for:

• Disposing substances (ex. drugs or metabolites) that are bound to plasma ____

• Eliminating undesirable substances that were passively absorbed (ex. urea and uric acid) 

• Getting rid of excess ____ (aldosterone effect) 

• Controlling ____ ____ by altering amounts of H+ or HCO2 in urine

proteins, K+, blood pH

Regulating of Urine [ ] and Volume

• One main function of kidneys → make adjustments needed to maintain body fluid osmotic [ ] (at around 300mOsm)

• Osmolarity = number of solute particles in 1 kg of H2O 

  • 1 osmol = 1 mole of particle per kg H2O

  • Body fluids have much smaller amounts → so expressed in milioosmols (mOsm) 

  • 1 mOsm = 0.001 osmol

• Kidneys produce only ____ amounts of urine if body is dehydrated or ____ urine if overhydrated 

• Accomplish this by using ____ mechanism

  • Fluid flows in opposite directions in 2 adjacent segments of SAME tube with ____ turn (U-shape bend)

small, diluted, countercurrent, hairpin

Countercurrent Mechanisms (2 types)

• 2 countercurrent mechanisms work together to:

  • Establish + maintain medullary ____ ____ from renal cortex through medulla 

  • Gradient runs from 300 mOsm in cortex to 1200 mOsm at bottom of medulla

• Countercurrent MULTIPLIER ____ gradient 

• Exchanger ____ gradient 

• Collecting ducts can then ____ gradient to vary urine [ ]

1. Countercurrent multiplies → interaction of filtrate flow in ascending/descending limbs of nephron loops of ____ nephrons

2. Countercurrent exchanger → blood flow in ascending/descending limbs of ____ ____

osmotic gradient, creates, preserves, use, juxtamedullary, vasa recta

Countercurrent Multiplier

• Involves the nephron loop and depends on: 

  • Filtrate FLOW in opposite directions (descending/ascending)

  • Difference in ____ b/w descending and ascending loop 

  • ____ transport of solutes out of ascending limb

• Limbs of nephron loop are NOT in direct contact but are CLOSE enough to influence each other’s exchange w/ surrounding interstitial fluid

permeabilities, active

Countercurrent Multiplier

• Ascending limb of nephron loop is IMPERMEABLE to water and selectively permeable to solutes 

  • Na and Cl are ACTIVELY absorbed in ____ segment (some passively reabsorbed in THIN segment) 

• Descending limb lets in water but NOT solutes 

  • Water passes out filtrate into hyperosmotic medullary interstitial fluid 

  • Causes remaining filtrate osmolarity to ____ to 1200 mOsm

thick, increase

Countercurrent Multiplier Mechanism

• The MORE NaCl ascending limb actively transports into interstitial fluid = the more water diffuses ____ of descending limb 

• The more water that diffuses OUT of descending limb = the saltier the filtrate becomes 

• Ascending limb then uses salty filtrate to further ____ osmolarity of medullary interstitial fluid

• Constant difference of ____ mOsm ALWAYS exists b/w the 2 limbs and between ascending and interstitial fluid 

• Difference is “multiplied” along length of loop

  • From 300 to 1200 mOsm = difference of 900mOsm

out, raise, 200

Countercurrent Exchanger

• Uses vasa recta → vasa recta is HIGHLY permeable to water and solutes 

• Flow of blood in vasa recta is also countercurrent (hairpin turn) so blood can exchange NaCl and water with surrounding interstitial fluid as it moves through adjacent parallel section of gradient 

  • Blood inside vasa recta remains ____ w/ surrounding interstitial fluid 

  • Vasa recta is able to reabsorb water and solutes w/o ____ osmotic gradient created by countercurrent multiplies

isosmotic, undoing

Countercurrent Exchanger Mechanism

• preserves gradient (2 things):

• Prevents rapid removal of ____ from interstitial space 

• ____ reabsorbed water 

• Water in ascending vasa recta comes from descending vasa recta or is reabsorbed from nephron loop + collecting duct 

  • Result = volume of blood at END of vasa recta is ____ than at beginning

salt, removes, greater

Formation of Dilute or [ ] Urine

• Established medullary osmotic gradient can now be used to form ____ or ____ urine 

• WITHOUT gradient → would NOT be able to raise urine [ ] more than 300 mOsm to ____ water

dilute, concentrated, conserve

Mechanisms

• Overhydration = ____ volume of ____ urine 

  • ADH production ____ → urine about 100 mOsm 

  • If aldosterone is present → additional ions can be ____ causing water to dilute to 50 mOsm 

• Dehydration = ____ volume of ____ urine 

  • Maximal ADH released → urine 1200 mOsm 

  • Severe dehydration → 99% of water reabsorbed

large, dilute, decreases, removed, small, concentrated

Urea Recycling & Medullary Osmotic Gradient

• Urea helps gradient

• Urea enters filtrate in ____ ____ limb by facilitated diffusion 

• Cortical collecting duct reabsorbs water → leaves urea behind 

• In deep medullary region → NO highly concentrated urea leaves ____ ____ → enters interstitial fluid of ____

  • Urea then moves back into ascending thin limb 

  • Contributes to HIGH osmolarity in medulla

ascending thin, collecting duct, medulla

Diuretics

• Chemicals that ____ urinary output (make u pee more)

• ____ ADH (ex. alcohol) 

• Na reabsorption ____ (and resultant water reabsorption) → ex. Coffee or drugs for hypertension or edema 

• Loop diuretics inhibit ____ ____ formation 

• ____ ____ = substance NOT reabsorbed so water remains in urine 

  • Ex. in a diabetic patient, high glucose [ ] pulls water from body

enhance, inhibit, inhibitors, medullary gradient, osmotic diuretics