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HAN 202 > Chapter 25 Urinary System > Flashcards

Chapter 25 Urinary System Flashcards

1
Q

Urinary system organs

A
  • kidneys are major excretory organs
  • urinary bladder is the temporary storage reservoir for urine
  • ureters transport urine from the kidneys to the bladder
  • urethra transports urine out of the body
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2
Q

kidney functions

A
  • removal of toxins, metabolic wastes, and excess ions from the blood
  • regulation of blood volume, chemical composition, and pH
  • gluconeogenesis during prolonged fasting
  • endocrine function
  • activation of vitamin D
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3
Q

endocrine functions

A
  • renin- regulation of blood pressure and kidney function

- erythropoietin (EPO)- regulation of RBC production

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4
Q

renal cortex

A

a granular superficial region

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5
Q

renal medulla

A

-the cone shaped pyramids separated by renal columns

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6
Q

renal pelvis

A

the funnel-shaped tube within the renal sinus, continuous with the ureter

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7
Q

urine flow

A

-urine flow from pyramid -> minor calyces -> major calyces -> renal pelvis -> ureter

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8
Q

nephrons

A
  • structural and functional units that form urine
  • about 1 million per kidney (correction pyramid)
  • 2 main parts:
  • renal corpuscle
  • renal tubule
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9
Q

renal corpuscle

A

-capsule (bowman’s) and glomerulus

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10
Q

renal tubule

A

-prox and distal convoluted tubule, nephron loop and collecting duct

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11
Q

two types of nephrons

A
  • cortical nephrons

- juxtamedullary nephrons

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12
Q

cortical nephrons

A
  • 85% of nephrons
  • almost entirely in the cortex
  • has short loop of henle and glomerulus
  • efferent arteriole supplies peritubular capillaries
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13
Q

juxtamedullary nephrons

A

-long loops of henle deeply invade the medulla
-outside the cortex
-important in the production of concentrated urine
efferent arteriole supplies vasa recta

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14
Q

nephron capillary beds: glomerulus

A
  • afferent arteriole -> glomerulus -> Efferent arteriole (only place in body)
  • specialized for filtration
  • blood pressure is high because:
  • arterioles are high pressure
  • afferent arterioles are larger in diameter than efferent arterioles
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15
Q

nephron capillary beds: peritubular capillaries

A
  • low pressure
  • porous
  • meandering
  • associated with cortical nephron
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16
Q

nephron capillary beds: vasa recta

A
  • long and straight vessel loops of Henle
  • juxtamedullary nephrons
  • formation of concentrated urine
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17
Q

renal tubule

A
  • glomerular capsule
  • proximal convoluted tubule (PCT)- functions in reabsorption and secretion
  • loop of Henle- descending and ascending limbs
  • distal convoluted tubule (DCT)- secretion
  • collecting duct- receives filtrate from many nephrons
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18
Q

juxtaglomerular complex (JGC)

A
  • one per nephron
  • important in regulation of filtrate formation and blood pressure
  • involved modified portion of the:
  • distal portion of the ascending limb of the loop of henle
  • afferent (sometimes efferent) arteriole
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19
Q

juxtaglomerular complex: granular cells

A
  • wall of afferent arteriole
  • mechanoreceptors (monitor BP)
  • secrete enzyme renin
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20
Q

juxtaglomerular complex- macular dense cells

A
  • cells in ascending limb of tubule

- chemoreceptors monitor NaCl of filtrate entering the distal convoluted tubule

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21
Q

filtration membrane

A
  • porous membrane between the blood and the capsular space
  • consists of:
    1. fenestrated endothelium (pores) of the glomerular capillaries
    1. visceral membrane of the glomerular capsule (podocytes with foot processes and filtration slits)
    1. basement membrane- negatively charged basement membrane repels large plasma proteins
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22
Q

which of the following is not associated with the renal corpuscle

A
  • a podocyte
  • a vasa recta**
  • a fenestrated capillary
  • an efferent arteriole
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23
Q

which of the following is true about the macula dense cells

A
  • they are mechanoreceptors
  • they are found in the wall of the arteriole
  • they monitor NaCl content*
  • all of the above
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24
Q

mechanisms of urine formation

A
    1. glomerular filtration- “clean out closet”- passive nonselective
    1. tubular reabsorption- returns all glucose and amino acids, 99% of water, salt, and other components to the BLOOD
    1. tubular secretion- reverse of reabsorption - selective addition to urine
25
Q

Step 1- glomerular filtration

A
  • passive, nonselective process (no ATP)
  • filtration membrane (Efficient)
  • large plasma proteins are not filtered and function to maintain colloid osmotic pressure of the blood
  • net filtration pressure (NFP) = pressure responsible for filtration
  • negative pressure drives filtration
  • glomerular filtration rate due to 3 factors:
  • net filtration pressure
  • total surface area (large)
  • membrane permeability
26
Q

Regulation of glomerular filtration rate

A
  • GFR is tightly regulated to serve 2 crucial needs
    1. kidneys need a constant GFR to make filtrate
    1. body as a whole needs a constant BP
  • the 2 are closely related, if GFR increases, urine output increases which reduced blood volume and BP
  • GFR is tightly controlled by two types of mechanisms
  • INTRINSIC CONTROLS
  • EXTRINSIC CONTROLS
27
Q

intrinsic controls of GFR

A
  • renal autoregulation
  • act locally within the kidney
  • maintains a nearly constant GFR when MAP (mean arterial pressure) is in the range of 80-100 mm Hg
  • two types of renal autoregulation
  • myogenic mechanism- (stretch)
  • tubuloglomerular feedback mechanism, which senses changes in Na concentration of filtrate
28
Q

extrinsic controls of GFR

A

-nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function

29
Q

intrinsic controls: myogenic mechanism

A
  • increased systemic BP stretches vascular smooth muscle -> constriction of afferent arterioles
  • prevents glomerulus BP from rising
  • protects glomeruli from damaging high BP
  • decreased systemic BP -> dilation of afferent arterioles
  • helps maintain normal GFR
30
Q

intrinsic controls: tubuloglomerular feedback mechanism

A
  • macula densa cells (in walls of ascending limb, salt monitoring)- flow dependent
  • if GFR increases, filtrate flow rate increases in the tubule
  • NaCl concentration in filtrate will be high because of insufficient time for reabsorption
  • macula dense cells respond to increased NaCl by releasing a chemical that vasoconstricts the afferent arteriole -> decreased GFR (slows down rate of flow)
  • the opposite occurs if GFR decreases and causes vasodilation of afferent arterioles
31
Q

tubuloglomerular mechanism of autoregulation

A
    1. GFR increases
    1. increased filtrate flow
    1. flow past macula dense increases (in JGC)
    1. release of vasoactive chemicals
    1. afferent arteriole contracts
    1. resistance in afferent arteriole increases
    1. hydrostatic pressure in glomerulus decreases
    1. GFR decreases
32
Q

extrinsic controls: sympathetic nervous system

A
  • under normal conditions at rest: renal blood vessels are dilated and renal autoregulation (intrinsic) mechanisms prevail
  • under extreme stress (low BP shock - need to maintain BP):
  • norepinephrine and epinephrine are released
  • both cause constriction of afferent arterioles which inhibit filtration of afferent arterioles which inhibit filtration and renin is released
  • goal: restore blood volume and pressure
33
Q

summary of intrinsic control

A
  • myogenic mechanism- if increased BP, stretches arteriole wall, causes constriction and decreases BP
  • tubuloglomerular feedback- if GFR increases, will have increased flow rate, NaCl will be high, macula dense cells (ascending limb) will detect and release a chemical for constriction
34
Q

which of the following factors contributes to the higher filtration rate in the glomerular capillaries compared with other capillary beds

A
  • the glomerular capillaries are fenestrated
  • the diameter of the efferent arteriole is smaller than the diameter of the afferent arteriole
  • the visceral layer of the glomerular capsule is very porous
  • all of the above contribute*
35
Q

where does filtration occur in the nephron

A
  • glomerular capsule*
  • proximal convoluted tubule
  • loop of henle
  • distal convoluted tubule
36
Q

extrinsic controls renin-angiotensin-aldosterone

A
  • main mechanism for raising BP**
  • low BP causes granular cells to release renin
  • renin assists in changing angiotensinogen to angiotensin 2
37
Q

effects of angiotensin 2

A
    1. constricts arteriolar smooth muscle, causing MAP to rise
    1. triggers aldosterone secretion from adrenal cortex- stimulates the reabsorption of Na+ (Na moves into blood, water follows, conserves blood volume)
    1. stimulates the hypothalamus to release ADH (antidiuretic hormone) and activates the thirst center
38
Q

step 2. tubular reabsorption

A
  • a selective process that begins in the proximal convoluted tubule
  • all organic nutrients are reabsorbed
  • water and ion reabsorption are hormonally regulated
  • includes active (requires ATP) and passive transport
  • different areas of the tubules have different absorptive capabilities
  • if not for tubular reabsorption all our plasma would drain away as urine in 30 mins
39
Q

reabsorption of nutrients, water, and ions

A
  • Na+ reabsorption- active transport
  • organic nutrients (glucose, AA, vitamins)- by secondary active transport (carriers) -> when the carriers are saturated, the excess of that substance is excreted (glucose in urine is sign of DM)
  • water- reabsorbed by osmosis- aided by pores called aquaporins
40
Q

resabsorptive capabilities of renal tubules and collecting ducts

A
  • PCT- site of most reabsorption (ions, water, nutrients)
  • loop of henle- descending limb- H20
  • ascending limb- Na, K, Cl
  • DCT and collecting duct:
  • hormonally regulated
  • Na- aldosterone
  • water- ADH
  • Ca- parathyroid hormone
41
Q

which of the following general functions can be assigned to the renin-angiotensin-aldosterone system

A
  • water conservation
  • blood pressure elevation
  • lowering blood sodium levels
  • both a and b*
  • all of the above
42
Q

if systemic BP is extremely low, epinephrine is released form adrenal medulla. This type of control is called

A
  • extrinsic*
  • myogenic mechanism
  • intrinsic
  • tubuloglomerular feedback
43
Q

step 3: tubular secretion

A
  • eliminates undesirable substances (e.g. urea and uric acid)
  • disposes of substances such as drugs
  • rids the body of excess K+
  • controls blood pH by altering amounts of H+ or HCO3- in urine
  • these solutes move from peritubular capillaries into filtrate
44
Q

regulation of urine concentration and volume

A
  • kidneys make adjustments to keep solute concentration constant, whether dehydrated or overhydrated
  • osmolality of body fluids:
  • the kidneys maintain osmolarity of plasma at about 300 mOsm, using countercurrent mechanisms
  • allow the kidneys to vary urine concentration
45
Q

countercurrent mechanism

A
  • occurs when fluid flows in opposite directions in two adjacent segments of the same tube
  • filtrate flow in the loop of henle
  • blood flow in the vasa recta
  • fluid flows in the opposite direction through two adjacent parallel sections of a nephron loop
46
Q

countercurrent multiplier: loop of henle

A
  • DESCENDING LIMB: reabsorption of water
  • freely permeable to H20 NOT salt
  • filtrate osmolality increases to about 1200 mOsm
  • ASCENDING LIMB: reabsorption of salt
  • selectively permeable to solutes
  • impermeable to water and pumps out salt
  • filtrate osmolality decreases to 100 mOsm
  • filtrate is diluted in the ascending loop
47
Q

dehydrated- maximal ADH

A
  • if ADH is present, aquaporins are inserted in collect ducts
  • water is reabsorbed back into capillaries
48
Q

the descending limb of the nephron loop ___

A
  • is not permeable to water
  • is freely permeable to sodium and urea
  • pulls water by osmosis into the lumen of the tubule
  • contains fluid that becomes more concentrated as it moves down into the medulla*
49
Q

at the collecting ducts, which hormone is required for the reabsorption of Na

A
  • antidiuretic hormone (ADH)
  • parathyroid hormone
  • atrial natriuretic peptide
  • aldosterone
50
Q

diuretics

A
  • chemicals that enhance the urinary output
  • osmotic diuretics- substances not reabsorbed (e.g. high glucose in a diabetic patients, water follows glucose)
  • ADH inhibitors such as alcohol
  • substances that inhibit Na reabsorption and obligatory H2O reabsorption such as caffeine and many drugs
51
Q

physical characteristics of urine

A
  • color and transparency:
  • clear, pale to deep yellow
  • cloudy urine may indicate a UTI
  • pink urine= blood
  • odor:
  • slightly aromatic when fresh
  • develops ammonia odor upon standing
  • may be altered by some drugs and vegetables
  • diabetics= fruity smelling
52
Q

ureters

A
  • convey urine from kidneys to bladder
  • enter the base of the bladder through the posterior wall
  • as bladder pressure increases, distal ends of the ureters close, preventing backflow of urine
53
Q

urinary bladder

A
  • muscular sac for temporary storage of urine
  • collapse when empty; rugae (folded walls) appear
  • trigone (inferior portion of bladder)- infections tend to persist in this region
54
Q

urethra

A
  • sphincters:
  • internal urethral sphincter- involuntary (smooth muscle) at bladder- > urethra function -> internal sphincter opens
  • external urethral sphincter- voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor
55
Q

drinking too much alcohol results in a headache the next day. Why does this happen

A
  • alcohol stimulates pain receptors in the brain
  • alcohol stimulates sodium reabsorption
  • alcohol stimulates aldosterone secretion
  • alcohol inhibits ADH secretion* i think
56
Q

urine flows from kidney to bladder via

A
  • nephrons
  • urethra
  • ureter *
  • loop of henle
57
Q

micturition

A
  • urination or voiding
  • three simultaneous events
    1. contraction of detrusor muscle by ANS
    1. opening of internal urethral sphincter by ANS
    1. opening of external urethral sphincter by somatic nervous system
58
Q

reflexive urination infants

A
  • distention of bladder activates stretch receptors
  • excitation of parasympathetic neurons in reflex center of spinal cord
  • contraction of the detrusor muscle
  • opening of internal sphincter
  • inhibition of somatic pathways to external sphincter, allowing its relaxation (opening)
59
Q

pontine control centers mature between ages 2-3

A
  • pontine storage center inhibits micturition- inhibits parasympathetic pathways and excites sympathetic and somatic efferent pathways
  • pontine micturition center promotes micturition- excites parasympathetic pathways and inhibits sympathetic and somatic efferent pathways

HAN 202 (16 decks)

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