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adv. anatomy + physiology > m11 + 12 lecture - urinary system > Flashcards

m11 + 12 lecture - urinary system Flashcards

1
Q

what organ does the urinary system include?

A

kidneys
- smaller than a fist
- covered in fat

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2
Q

what are the functions of the kidney?

A
  • clean the blood of waste

maintain:
- BP (RAAS)
- O2 concentration in the blood (RBC production)
- pH and electrolyte balance (albumin, K+, Na+, Cl-, Ca++)

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3
Q

what is the nephron?

A
  • functional unit of the kidneys
  • responsible for urine formation
  • mainly in cortex of kidney, a portion extends into the medullary region (loop of Henle)
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4
Q

what are the steps of urine formation by the nephron?

A

1) filtration
2) reabsorption
3) excretion/secretion

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5
Q

how many nephrons are in each kidney?

A
  • 1 million per kidney
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6
Q

about how many nephrons are cortical and juxtamedullary ?

A

cortical nephron - 85%

juxtamedullary nephron - 15%
- long loop
- helps to concentrate urine

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7
Q

what are the parts of the nephron?

A
  • renal corpuscle
  • glomerulus (podocytes)
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8
Q

what is the renal corpuscle?

A
  • made from the glomerulus and the bowman’s capsule
  • this is the filtration unit of the kidneys
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9
Q

what is the glomerulus?

A
  • a network of very porous fenestrated capillaries, held together by podocytes
  • receives blood from the afferent arteriole and is drained by the efferent arteriole (only kind of capillary bed drained by an arteriole)
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10
Q

what is a podocyte?

A
  • helps prevent rupture of the glomerulus
  • reinforces the membrane and has filtration slits
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11
Q

what is the JG apparatus made of?

A
  • macula densa cells of DCT
  • juxtaglomerular cells (granular cells of afferent arteriole)
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12
Q

what do the juxtaglomerular cells do?

A
  • monitor the BP and O2 content in the afferent arteriole
  • release renin to increase BP (RAAS)
  • produce EPO to increase RBCs and O2
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13
Q

what do the macula densa cells do?

A
  • tubuloglomerular feedback mechanism (TGFM)
  • cells of the DCT which lie close to the glomerulus
  • these cells act as chemoreceptors that sense the concentration of the filtrate
  • change the flow of blood thru the afferent arteriole and the filtration rate thru the glomerulus
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14
Q

what is filtrate formation?

A
  • driven by hydrostatic pressure (BP)
  • kidneys form 180L of filtrate per day
    —-> we reabsorb 178.2L = 99%
    —-> we only secrete 1.8L = 1% in our urine
  • filtrate is the same as plasma except without any protein/cells
  • anything not reabsorbed = considered urine
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15
Q

equation for net filtration pressure (NFP)?

A

glomerular filtration pressure –> GFP
(+/-) colloid osmotic pressure –> COP
(+/-) capsular hydrostatic pressure –> CHP
= net filtration pressure –> NFP

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16
Q

why is filtrate formed?

A
  • due to glomerular filtration pressure - this is the same as glomerular hydrostatic pressure
  • pressure in the glomerulus is much higher than regular capillaries at 55mmHg (vs. 15mmHg normally)
  • this pressure will force fluid and small particles out of the blood into the bowman’s capsule

two factors will oppose this:
- capillary osmotic pressure = around 30 mmHg
- capsular hydrostatic pressure = usually 15 mmHg

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17
Q

what is the glomerular filtration rate (GFR)?

A
  • the rate at which filtrate forms
  • 125mL/min
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18
Q

what factors affect filtrate formation?

A
  • BP changes in the afferent arteriole
  • hydration
  • health of glomerular capillaries
  • age
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19
Q

what happens when BP increases?

A
  • filtrate formation increases
  • reabsorption decreases
    —> urine formation increases and becomes more dilute
    —> nephron does not have time to reabsorb the fluid

* if greatly affected by how much water you take in per day*

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20
Q

through what mechanisms is regulation of GFR done?

A

intrinsic and extrinsic mechanisms

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21
Q

where does renal autoregulation, an intrinsic control of filtrate formation, occur?

A

it is myogenic, in the muscles

22
Q

how does renal autoregulation occur?

A
  • done by controlling the BF through the afferent and efferent arterioles
  • reflex action monitors stretch in the afferent arteriole and will adjust to changes in pressure
    —> maintains BF through the kidneys => maintains GFR if active/resting or in positional changes
23
Q

what is tubuloglomerular feedback mechanism (TGFM)?

A
  • the macula densa cells monitor the concentration (osmotic pressure) of the filtrate in the DCT (quality control)
    –> the GFR influences the reabsorption rate and affects the amt. of materials we lose or reabsorb
  • the goal of TGFM is to maintain an even GFR to prevent a loss or excessive gain in electrolytes
24
Q

what happens to reabsorption if filtration is low? (TGFM)

A

reabsorption is high, the concentration is low and the MD will increase BF - in the afferent arteriole

25
Q

what happens to reabsorption if filtration is high? (TGFM)

A

reabsorption is low, the concentration is high and the MD will decrease BF - in the afferent arteriole

26
Q

what is reabsorption?

A
  • an active process occurring at the PCT and the loop of Henle
  • 80% of energy expenditure is devoted to the reabsorption of Na+

solute pump
- reabsorb Na+
- consume ATP
- generates osmotic pressure
- helps to reabsorb H2O

27
Q

what is reabsorbed in the PCT?

A
  • K+, Na+
    —> glucose, amino acids, vitamins thru co-transport w/ Na+
  • H2O along w/ Na+ (osmosis)
  • small proteins that endocytosed
  • anions –> Cl- and HCO3-
  • Ca+, P, Mg+ are absorbed due to plasma concentrations and hormone stimulus (PTH, testosterone, estrogen)
28
Q

what is absorbed in the loop of henle?

A
  • descending limb - permeable to H2O
  • ascending limb - Na+ reabsorbed
    —> K+ secreted here
  • Na+ reabsorbed by the Na+/K+ pump along the length of the loop of Henle and DCT
    —> as these are reabsorbed, H2O will move along w/ this due to osmotic pressure
29
Q

what is the transport maximum?

A
  • the maximum concentration of a molecule or compound that can be reabsorbed — any concentration above this will be excreted

example: glucose - norm: 110, too much = 300
multivitamins

30
Q

what happens to the CD when dehydrated?

A
  • when a person is dehydrated, ADH makes the CD permeable
31
Q

what are tubular secretions?

A

secretions from the tubes - PCT, DCT

32
Q

what are the actively secreted substances from the PCT and DCT?

A
  • K+
  • drug waste molecules
    ex.) tylenol = hard on the liver
    ibuprofen = hard on the kidneys
33
Q

what are the monitored substances of the PCT and DCT?

A
  • H+ and HCO3- to balance pH
34
Q

what substances are waste from the PCT and DCT?

A

nitrogenous wastes
- urea
- uric acid
- ammonia
- creatinine

35
Q

what processes are activated when a person is dehydrated (forming concentrated urine)?

A
  • hypothalamus to release ADH, increasing permeability of the CD to water (better reabsorption of H2O from urine)
  • RAAS
36
Q

what happens with the hypothalamus when a person is dehydrated? (forming concentrated urine)

A
  • hypothalamus triggers thirst and releasing ADH
  • ADH increases permeability of the CD to water
  • helping us to reabsorb water from the urine
  • ADH is secreted in small amts. to maintain fluid volume in the plasma
37
Q

what happens in RAAS? (Renin Angiotensin-Aldosterone System)

A
  • triggered by loss of pressure and volume
  • JG cells release renin to stimulate the liver to release angiotensin I
  • at the lungs, ACE (angiotensin converting enzyme) changes angiotensin I to angiotensin II, stimulating three things:
    1) vasoconstriction - increases BP to norm.
    2) reinforces ADH prod.
    3) aldosterone prod.
38
Q

what does the release of aldosterone do?

A
  • promotes the reabsorption of Na+ at the loop of Henle to increase H2O reabsorption

ex.) norm. 1200mL, so it increases to 1600-2400mL

39
Q

which is produced more, ADH or aldosterone?

A
  • ADH is prod. more often throughout the day and affects water reabsorption more than aldosterone
  • w/o these two working together, we would dehydrate quickly
40
Q

what blocks ADH?

A

alcohol and caffeine affect the absorption of water in the urine

41
Q

what is the normal amt. of urine formation? and the amt. with diuretic?

A

norm. = 2-3mL/min, go every 3hrs

w/ diuretic (alcohol) = 20-30mL/min, go every 30 min.

42
Q

how much urine is normally produced in a day?

43
Q

what is polyuria?

A
  • more than 2.5L/day is prod.
    due to DM, DI
44
Q

what is oligouria?

A

less than 500mL.day

45
Q

what is anuria?

A

no urine output - kidney failure

46
Q

what is the composition of urine?

A
  • 95-99% water
  • urea, creatinine, uric acid, ammonia, Ca+, Mg+, H+, HCO3-, Na+, K+ and other ions
  • urine is sterile until exiting the body
47
Q

what is renal calculi?

A
  • stones caused by the build up of uric acid salts/Ca++
  • will block the pelvis and get stuck in the ureters
48
Q

about the bladder?

A
  • controlled by the PSNS and the pons
  • internal urethral sphincter relaxes as the bladder contracts
  • external urethral sphincter is done by voluntary control
49
Q

about the urethra?

A

carries urine out the body
- surrounded by the internal and external urethral sphincter

male urethra extends abt 20cm
- surrounded by the prostate gland, which lies just below the bladder

female urethra extends abt 3-4cm
- this accounts for the higher incidence of UTIs in women

50
Q

what is incontinence?

A
  • inability to control micturition
  • happens in: old age, holding it in too long (overflow), stress, pregnancy
51
Q

what is nocturia?

A

urinating at night

52
Q

what is nocturnal enuresis?

A

wetting of the bed

adv. anatomy + physiology (24 decks)

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