7.3 Urinary

Question 1

what releases ADH? what does it cause

Answer 1

released by posterior pituitary gland in repsonse to high blood osmolarity

• causes principal cells of collecting duct to insert inducible aquaporins in apical membranes, increasing water reabsorption

Question 2

what does aldosterone do?

Answer 2

Main function: increase blood pressure/volune and decrease K+ levels

• targets DCT and colelcting ducts to promote synthesis of apical Na+ and K+ channels and basolateral Na+, K+ ATPases for Na+ reabsorption

*net results Na reabs and K secretion

• without alsosterone, daily loss of filtered Na would be 2%, incompatible with life

Main functions: increases blood pressure/volume and dec K+ levels

Question 3

what is atrial natriuretic peptide?

what releases it and what does it do

Answer 3

• released by cardia atrial cells in response to elevated bp/volume
• reduces blood Na+ (decreased aldosterone)
• causes vasodilation
• decreases water intake

*net: decrease blood volume/pressure

Question 4

what does parathyroid hormone do

Answer 4

acts on DCT to increase Ca²⁺ reabsorption

Question 5

where does tubular secretion occur? what substances are invovled

Answer 5

*last of 3 major renal processes

• occurs almsot completely in PCT
• selected substances moved from peritubular capillaries, throuhg tubule out into filtrate

*K+. H+, NH4, creatine, organic acids and basis

* Substances synthesized in tubule cells are secreted (e.g. HCO3–)

Question 6

what is tubular secretion important for

Answer 6

– Disposing of substances, such as drugs or metabolites

– Eliminating undesirable substances that were passively reabsorbed (example: urea and uric acid)

– Ridding body of excess K+ (aldosterone effect)

– Controlling blood pH by altering amounts of H+ or HCO3– in urine

Question 7

Question 8

what is osmolarity?

how many osmol in NaCl and MgCL2

Answer 8

Osmolality = number of solute particles in 1 L of H2O

• 1 mole NaCl = 2 osmol (Na+ and Cl-)
• 1 mole MgCl2 = 3 osmol (Mg2+ and two Cl-)

* body fluid osmotic conc maintained aroind 300mOsm

Question 9

what are the two types of countercurrent mechanisms

Answer 9

• countercurrent multiplier
  
  • creates a gradient through interaction of filtrate flow in ascending/descenign limb of nephron loops of Juxtamedullary nephrons
• Countercurrent exchanger
  
  • preserves gradient using blood flow in ascening/descending limbs of asa recta

*work together to establish and maintian medullary osmotic gradietn from renal cort through medulla

• gradient runs from 300 mOsm in crotex to 1200 mOsn at bottom of meducal

*Collecting ducts can then use gradient to vary urine concentration

Question 10

what are the 3 key players that interact with the medullary osmotic gradient

Answer 10

1. long nephron lops of juxtamedullar nephrons -> create gradient & act as countercurrent multipliers
2. Vasa recta preserve the gradient. They act as countercurrent exchanges
3. the collecting ducts of all nephrons use the gradient to adjust urine osmolarirty

*Juxtamedullary nephrons create as osmotic gradient w/ renal medulla. Allows kidney to produce urine of varying conc

Question 11

how does countercurrent multiplier work in ascending vs descending limb

• whats the main idea of it

Answer 11

• limbs of nephron loop are not in deict contact but are close enough to influence exchanges with surrounding interstitial fluid
• ascening limb of loop is impermeable to H₂O and selectively permeable to solutes

*Na and Cl actively reabs in thick segment, some passive reabs in thin seg

• Descening limb freely perable to H₂O but impermeable to solutes

*H2) passes out filtrate causes remaining filtrate osmolarity to increase to 1200mOsm

Question 12

describe the mechanism of countercurrent multiplier

Answer 12

• the more NaCl the ascening limb actively transports out into interstitial fluid the more water diffuses out descenidng limb
• more water that diffuses out descing that saltier the filtrate becomes
• ascening limb uses the salty filtrate to further raise osmolarity of medulary interstital fluid

*constant diff of 200 mOsm exists btwn two limbs of nephron loop and between ascening limb and interstitial fluid

*difference is “multiplied” along length of loop

Question 13

why is it called counter current multiplier

Answer 13

“Multiplier” refers to the ability of this countercurrent system to increase this small gradient into a much larger one

Question 14

what is the countercurrent exchanger

Answer 14

• preserved medullary gradient by
• > prevenign rapid removal of salt from interstital space
• > removing reabsorbed water
• water in ascending vasa recta comes from descening vasa recta or is reabs from nephron loop and colelcting duct
  result: volume of blood at en fo vasa recta > than at beginning

Question 15

formation of urine durign dehydration or overhydration

Answer 15

* edullary osmoti gradient used to form dilute or conc urine

• Dehydration
  
  • produces small volume of conc urine
  • at maximal ADG ~1200 mOsm
  • severe dehydration: 99% of water is reabs
• Overhydration:
  
  • products large vol of dilute urine
    
    • ADH decreases: urine ~100 mOsm
    • Alsosterone: can cause more ions to be removed causing urien to reach ~50 mOsm

Question 16

how does urea help form the medulalry Osmotic Gradient

Answer 16

1. Urea enters fitrate in descending limb and ascending thin limb of nephron loop by facilitated diffusion
2. cortical colelcting duct reabs water, leading uea behind
3. in deep medulalry region, now have highly conc yrea
   
   • leaves colelcting duct and enters interstitial fluid of medulla
   • urea moves back into ascening thin limb
   • contributes to high osmolality in medulla (called urea recycling)

Question 17

what is diruesis

what diff substances are diuretics

Answer 17

homeostatic process in which urine production is increased

*many common sub are diruetics, but can have diff MOA

• Alcohol: inhibst ADH
• Na+ reabs inhibtors (reduced H2O reabs) like caffeine or drugs for hypertension or edema
• loop diruetics interfere w/ formation of medullary osmotic gradietn
• osmotic diuretics not reabs, so water remains in urine

Question 18

what is renal clearance

Answer 18

volume of plasma kidneys can clear of a particular substance in a given time

• to determine renal clearance: both blood and urine are required

*can help detect glomerular damage and follow progress of renal disease

C = V* (U/P)

– C = renal clearance rate (ml/min)

– U = concentration (mg/ml) of substance in urine

– V = flow rate of urine formation (ml/min)

– P = concentration (mg/ml) of same substance in plasma

Question 19

what does it mean if

C= 125mL/min

C < 125mL/min

C= 0

C > 125mL/min

Answer 19

C= 125mL/minL no net reabs or secteion (ex: inulin a plant by prpduct)

C < 125mL/min, substance reabsorbed

C= 0, substance completely reabsorebd or not filtered

C > 125mL/min, substance was secreted (most drug metabolines)

Question 20

what can you use renal clearance tests to determine

Answer 20

GFR

Question 21

what is chornic renal disease

Answer 21

defined as a GFR < 60 ml/min for 3 months

• filtrate formation decreases, nitrogenous wastes accumulate in blood, pH becomes acidic
• seen in daibetes mellitus and hypertension

Question 22

what is renal failure

Answer 22

– Causes uremia: ionic and hormonal imbalances, metabolic abnormalities, toxic molecule accumulation

– Symptoms: fatigue, anorexia, nausea, mental changes, cramps

– Treatment: hemodialysis or transplant

Question 23

what is the chemical composition of urine?

what nitrogenous wastes are present?

what other solutes present?

Answer 23

chemical comp: 95% water, 5% solutes

nitrogenous wastes: urea (largest solute comp), ruic acid, creatine

also Na+, K+, PO43–, and SO42–, Ca2+, Mg2+ and HCO3–

* Abnormally high concentrations of any constituent, or abnormal components such as blood proteins, WBCs, and bile pigments, may indicate pathology

Question 24

describe olour/transparecy of urine

and odor

Answer 24

• colour/transparence
  
  • clear, cloudy can indicate UTI
  • pale to keep yellow from urochrome (pigment from hemoglobin breakdown)
  • absnoraml colour (pink, brown, smoky)
    
    • can be caused by food, bile pigments, blood or drugs
• Odor
  
  • slghilty aromatic when fresh
  • ammonia odor upon standing bc bacteria metabolize urea
  • may be altered by some drugs/veg
  • disease may alter small

Question 25

describe pH ans specific gravity of urine

Answer 25

* pH * urine is slightly acidic (pH ~6, ranges from 4.5-8) * acidic diet (protein, whole wheat) can cause drop in pH * Alkaline diet (vegetarian), rpologned vomiting, or UT can use inc pH * Specific gravity * raito of mass of substance to mass of equal vol of water * ranges from 1.001 (more filute) to 1.035 (mroe salty)

Question 26

pathway or urine

Answer 26

- kidneys form urine continuously, transported by ureters to bladder for storage - \*ureters = slender retroperitoneal tubes taht convery urine from kidney to blasser (begin at L₂ as continuation of revel pelvis) - ureters enter base of bladder through posterior wall - as blodder pressure inc, distal ends or ureters close -\> prevents backflow or urine - release of urien from blassers thoruhg urethra = microturition

Question 27

what are teh 3 layers or the ureter wall

Answer 27

1. Mucosa: transitional epithelium 2. Muscularis: smooth muscle sheets contract in repsonse to stretch and propels urine itno bladder (gravity alone is not enough -\> must be pushed by **peristalitc wave** action of smooth muscle) 3. Adventitia (outer fibrous connective tissue

Question 28

what is renal caliculi

Answer 28

- kisney stones in renal pelvis (crystalized calcium, magnesium or uric acid salts) - large stones block ureter, causes pressure and pain - may be due to: chornic bacterial ifnection, ruine retention, inc Ca in blood, inc pH or urine shock wave lithotripsy: non invsive producure invovling shcok waves to shallter caliculi

Question 29

strucutre of urinary bladder males vs femlaes

Answer 29

- retroperitonal on pelvic floor - rugae disappear as bladder stretches Males: prostate inferior to bladder neck females: anterior to vagina and uterus

Question 30

what is the trigone

Answer 30

- 3 openings in lader forming a ttriangular area (two for ureters, one fro urethra) \*Clinically important because infections tend to persist here

Question 31

what are the layers of the bladder wall

Answer 31

- Mucosa: transitional epithelial mucosa - Muscular layer: thick Detrusor muscle (3 layers of smooth muscle, inner and outer longitudinal layres w/ circular middle layer) - fibrous adventitia: all but superior surface here it is covered by peritonium

Question 32

storange capcity of bladder

Answer 32

- collapses wen empty and rugae appear - exands and rises superiorly during filling without significant rise in internal pressure - moderately ull bladder is ~12cm long and can hold 500 mL \*can hold twice that amount if necessary but can burst if overdistended

Question 33

hat is the urethra? waht type of tissues does it have

Answer 33

- Muscular tube that drains urinary bladder - mostly pseudostratified columnar epithelium except: - \> transition epithelium near bladder - \> stratified squamous epithelium: near external urethral orifice

Question 34

descirbe the sphincters of the urethra

Answer 34

- internal urethral sphincter: involuntary (smooth) muscle at bladder-rethra jucntion (contracts to oepn) - external urethral sphincter: Voluntary (skeletal) muscle surroudnign urethra as it passes trhu pelvic floor

Question 35

compoennet sof male urethra

Answer 35

- carries semen and urien - prostatis urethra (2.5cm) : in prostate - intermediate part of urethra (2c): passes thru urogenital diaphragm from prostate to beginnign of penis - spongy urethra (15cm): passes thru penis; opena via external orifice

Question 36

what is micturition

Answer 36

\*urination or voiding: ahs 3 simultaneous events 1. contraction of **dextrusor** by ANS (squeezes bladder) 2. Opening of **external urethral sphincter (contraction)** by AND 3. opening of **external urethral sphincter** (relaxation) by somatic NS

Question 37

what is reflexive urination

Answer 37

\*urination in infants - distension of bladder catives stretch receptors - causes excitation of parasympathetic neurons in reflex center in sacral region of spinal cord - leasd to contraction of dextursor and opening (contraction) of **internal sphincter)** **-** inhibition of somatic pathways to external sphincter allow its relaxation and opening

Question 38

how coes pontine micturition contorl centers inhiibt and promtoe micturition

Answer 38

* Inhibits micturtion * inhibits parasympathetic pathways * excited sympathetic and somatic efferent pathways * Promotes micrurition * excites parasympathetic * inhibitc sympathetic and somatic efferent pathways

Question 39

Question 40

describe urinary incontinence

Answer 40

- in adults its usually caused by weakended pelvic muscles * Stress incontinence * increased intraabdominal pressure forces urine through external sphincter * laughing, coughing, or sneezing can cause incontinence * Overflow incontinence * urine dribbed when bladder overfilles