AP Urinary

• controls volume and composition of blood
• produces urine as a by-product
• consists of 2 kidneys, 2 ureters, 1 bladder, 1 urethra

• 2 kidney bean shaped structures - 4" x 2"
• ***retroperineal: located behind the peritonuem on posterior body wall***
• outer tissue layers: renal fascia, adipose capsule, renal capsule
• inner structures: renal pyramids, renal columns, minor calyx, major calyx,

medial depression on each kidney where blood vessels and nerves enter and exit and where ureters exit

small cavity behind hilus on each kidney

• outermost layer of kidney tissue
• dense fibrous CT
• anchors kidney to posterior body wall

• fattly middle layer of kidney tissue
• protects kidney from trauma

• innermost layer of kidney tissue
• thin, transparent membrane that prevents spread of infection to kidney

• outer region of kidney
• lighter in color
• 2 regions: outer cortex, juxtamedullary cortex

• inner region of kidney
• darker in color

• triangular structures in the medulla
• base: touch cortex
• apex: renal papilla that point toward hilus

where cortex extends between pyramids

cuplike structures that surround papilla where pyramids empty urine

• where minor calyces join and empty
• dumps urine into ureters

area behind the hilus

• millions of microscopic filtering units inside each kidney
• functions: filtration, reabsorption, secretion
• anatomy: glomerulus, bowman's capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct, papillary duct
• 2 groups: cortical and juxtamedullary

• G and BC in outer cortex
• L of H short
• most nephrons are cortical

• G and BC near renal medulla
• L of H long
• ***most responsible for urine concentrations***

G and BC

PCT, LOH, DCT, CD, PD

• a bunch of capillaries that are highly specialized for filtration
• the most porest capillaries in the body
• extremely high pressure
• ***only capillaries in the body supplied and drained by an arteriole - only way a constant BP can be maintained***
• supplied by afferent arteriole
• drained by efferent arteriole

• microthin membrane that separates G and BC
• filters blood
• made of simple squamous ET
• 3 layers: endothelium of G, basement membrane of G, visceral layer of BC

• filters out RBCs, WBCs, platelets
• plasma remains

• filters out large proteins
• plasma minue large proteins remains

• contains podocytes, pedicals, and filtration slits
• filters out medium and small proteins
• filtrate remains

• plasma minus proteins
• 180 L/day
• 125 ml/min

• double walled cup that surrounds majority of G
• visceral BC: inner wall
• parietal BC: outer wall
• capsular space: between the walls, full of filtrate

• simple cuboidal ET
• ***microvilli/villi along inner surface to increase surface area (called brush border)***
• 99% of all filtrate reabsorption occurs in PCT

• helps determine overall urine concentration
• descending limb: thin section made of simple squamous ET
• ascending limb: thick section made of cuboidal and columnar ET

• simple cuboidal ET
• 2 unique modifications: princple cells and intercalated cells

• located in the DCT/CD
• help to determine urine concentrations by moving H20 between tubule and blood

help to control urine pH by moving H+ ions

• glomerulus
• peritubular capillaries
• vasa recta

• surround PCT, DCT, and upper CD
• low pressure
• function: reabsorption

• surrounds L of H
• low pressure
• function: reabsorption

• location: where the DCT lies against arterioles
• function: to maintain constant pressure and filtration rate in the G despite changes in systempic BP (constant net filtration pressure)
• arterioles contain JG cells
• DCTs contain macula densa

• stretch receptors in arterioles at the JGA that respond to BP changes by constricting or dilating arterioles
• aka mesingeal cells

chemoreceptors in the DCT at the JGA that respond to solute concentrations in filtrate (especially Na+ ions)

renal artery > segmental artery > interlobar artery > arcuate artery > interlobular artery > afferent arteriole > glomerulus > efferent arteriole > PTC/VR > interlobular vein > arcuate vein > interlobar vein > segmental vein > renal vein

• 10" long
• extend from kidney to bladder
• ***transitional ET***

• hollow organ behind symphysis pubis
• ***transitional ET***

triangular region at base of bladder where both ureters enter and urethra exits

• located at apex of trigon of bladder
• controlled by detrussor muscle

• urination
• max bladder capacity 700-800ml
• at 200-400ml, stretch receptors kick in micturation reflex

• tube that extends from bladder to outside
• ***stratified squamous non-keritinized ET***
• female: 1.5", directly behind symphysis pubis, urine only
• male: 8-10", base of bladder through prostate and penis, urine and semen

• to produce urine and to maintain volume and composition of blood, the kidneys:
• --filter the blood
• --reabsorb H20, nutrients, electrolytes back into blood
• --secrete extra substances and waste into tubule

• non-selective passive process where solutes and solvent are forced across EC membrane by blood pressure
• end product is filtrate - (180 L/day)
• most filtrate reabsorbed back into blood (178-179 L/day)

• BP in G is high
• millions of capillaries in G
• EC membrane extremely permeable

• glomerular blood hydrostatic pressure
• blood colloid osmotic pressure
• capsular hydrostatic pressure

• actual pressure that forces blood across EC membrane
• 60 mmHg

• reverse pressure caused by proteins that have leaked through first layer of membrane
• 32 mmHg

• reverse pressure caused by filtrate already in BC - pushes filtrate back toward G
• 18 mmHg

• GBHP - (BCOP + CHP)
• 10 mmHg

• total amount of filtrate that forms in all renal tubules of both kidneys per day
• 180 L/day - 125 ml/min
• any factors that affect filtration pressures also affect rate
• body works to maintain constant pressures (homeostasis)
• rate controlled by renal autoregulation and by hormones (ANP and AG2)

• negative feedback loop intrinsic to kidney
• involves JGA
• allows kidney to maintain constant NFP despite systemic pressure changes
• ex: systemic BP drops - NFP & GFP drops - receptors in JGA detect drop - dilate afferent arteriole - more blood into G - raises NFP & GFR to normal

• hormone found in R atrium
• released in response to HBP
• causes dilation of afferent arteriole and constriction of efferent arteriole
• elevates NFP > increased GFR > increased urine production > lower BP

• produced by renin-angiotensin system in response to LBP
• JG cells > less stretch > release renin (enzyme) > enters blood > acts on angiotensinogen (inactive blood protein) > AgI > circulates and enters lungs > contacts Ag converting enzyme > AgII
• acts on thirst center in hypothalamus to increase drinking to raise blood volume/BP
• causes release of ADH - extra H20 moves from tubule back to blood to raise blood volume/BP
• dilates afferent arteriole to cause pressure in G to rise - increased BP
• constricts efferent arteriole to cause pressure in G to rise - increased BP
• causes release of ALD to increase sodium reabsorption - H20 follows - increased BP

• purpose: return H20 and needed substances back to blood
• ***90% of all reabsorption occurs in PCT***
• always occurs through PTCs and vasa recta
• substances reabsorbed: H20, nutrients, Na+, Cl-, Ca++, P04-, etc

• ***movement of Na+ out of PCT controls movement of everything else***
• more Na+ in lumen of PCT than any other solute
• Na+ moves PAP (passive, active, passive)

• more Na+ in PCT luman than PCT cuboidal wall - moves passively
• fewer Na+ in PCT cuboidal wall than interstital fluid - moves actively (Na+/K+ pump)
• more Na+ in interstitial fluid than PCTs - moves passively
• after Na+ leaves tubule, filtrate concentration decreases (more H20)
• H20 moves by osmosis from lumen to PCT cuboidal wall to interstitial fluid to blood
• H20 follows sodium
• other solutes (now more concentrated after H20 leaves) diffuse

100% of all filtered nutrients should be reabsorbed through walls of the PCT back to blood by symporters

• upper limit of symporter (mg/min)
• determines how fast a symporter can work and how much nutrient is reabsorbed
• anything above this limit will be excreted in urine

blood concentration at which a nutrient becomes part of urine because Tm has been exceeded (mg/mL)

• 100% of all nutrients should have been absorbed in PCT unless Tm was exceeded
• thin L of H: H20 reabsorbed
• thick L of H: Na+, K+, Cl- symported and reabsorbed
• ***reabsorption in the L of H of a JM nephron is a major factor in determining eventual urine concentration***

controlled by aldosterone and antidiuretic hormone

• produced by adrenal cortex
• causes increased Na+ reabsorption in distal DCT/proximal CD
• H20 follows Na
• increased blood volume, increased BP
• slightly concentrated urine

• ***major factor that controls and determines urine concentration***
• produced by hypothalamus and released by pituitary whenever BP drops
• inserts large H20 channels into principle cells of DCT/CD
• H20 rapidly moves from tubule back into blood
• increased blood volume, increased BP
• extremely concentrated urine
• no ADH (normal/high BP) - principle cells impermeable to H20 - dilute urine

• 90% of all H20 reabsorption controlled by movement of Na+
• occurs in PCT

• 10% of all H20 reabsorption controlled by ADH
• occurs in DCT/CD

• excess nutrients and waste transferred from blood in PTCs to tubes for excretion
• whatever is secreted is always excreted in urine
• substances include: K+, H+, NH4, urea, vitamins, drugs

• imbalance causes cardiac arrythmias
• excess K+ always secreted into renal tubule
• ALD acts as antiport
• Na+/K+ pump (Na+ out, K+ in)
• simple diffusion (K+ in)

• normal blood pH 7.35 - 7.45
• normal urine pH 4-8
• H+ ions built up in blood and are immediately secreted from blood into tubule
• makes blood less acidic, urine more acidic

• NH3 - toxic waste produced in the liver from amino acid breakdown
• immediately converted to NH4 in the liver and becomes urea
• urea is secreted and reabsorbed

• determines how effectively the kidney is filtering substances from blood
• RC = (UV)/P
• U: concentration in urine (mg/mL)
• P: concentration is plasma (mg/mL)
• V: urine flow rate (mL/min)
• high RC: substance efficiently cleared out of blood into filtrate (penicilin)
• low RC: substance remains in blood for a longer period of time (cipro)
• important when prescribing meds (freq/dosage)
• inulin used in RC test

protein polysaccharide used in RC test because it is 100% filtered/0% reabsorbed

• HYPO-osmotic to blood
• watery, clear, large volume
• filtrate at end of PCT is 300 mosm/L (iso-osmotic)
• thick L of H impermeable to water - Na+, K+, Cl- symport out, filtrate 150
• DCT/CD with no ADH present - more ions move out, filtrate 75 mosm/L (4x less concentrated than blood)

• HYPER-osmotic to blood
• dark, concentrated, small volume
• H20 intake reduced - kidneys conserve H20 but still must rid waste - increased H20 reabsorption in DCT/CD
• depends mostly on presence of ADH and solute concentrations of interstitial fluid in renal medulla
• solute concentration of interstitial fluid increases from cortex to inner medulla
• presense of the solutes establish osmotic pressure gradients that allow H20 to move out

• Na+, K+, Cl- symport out of thick ascending limb
• ions become concentrated in outer medulla, slowly descend to inner medulla
• H20 moves out of DCT/CD in presence of ADH
• urea is left behind and recycled - exits CD and re-enters L of H - ***major factor in establishing gradient***

• based on anatomical arrangement of long L of H and overlying vasa recta
• fluid in one tube runs counter and parallel to fluid in the other
• filtrate descends, becomes more concentrated
• filtrate ascends, becomes more dilute

• clear to dark amber
• non-offensive odor
• pH 4-8

degree of urine clodiness

• weight of a volume of urine compared to the weightof an equal volume of distilled water
• water: 1.000
• urine: 1.001 - 1.030
• higher: more solutes (more concentrated)
• lower: less solutes (more dilute)