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UROGENITAL > 7. Renal Physiology - Production of URINE > Flashcards

7. Renal Physiology - Production of URINE Flashcards

1
Q

Kidney functions

A
  • regulate BLOOD PRESSURE
  • stimulate synthesis of RED BLOOD CELLS
  • maintain body’s CALCIUM levels
  • regulation of blood composition
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2
Q

KIDNEYS have 2 CAPILLARY BEDS:
(connect arteries and veins)

A
  • GLOMERULUS
  • PERITUBULAR CAPILLARIES
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3
Q

despite fluctuations in SYSTEMATIC BLOOD PRESSURE the kidneys maintain..

A

CONSTANT BLOOD FLOW

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4
Q

BLOOD flows into the GLOMERULUS THROUGH..

A

AFFERENT ARTERIOLE

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5
Q

BLOOD passes OUT the GLOMERULUS through

A

EFFERENT ARTERIOLE

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6
Q

what happens in the RENAL CORPUSCLE

A

production of FILTRATE (water, salts, glucose, amino acids..)

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7
Q

role of PROXIMAL CONVOLUTED TUBULE

A

(most) REABSORPTION of WATER, IONS and all ORGANIC NUTRIENTS including GLUCOSE

  • ALL glucose reabsorbed
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8
Q

ROLE of LOOP OF HENLE
DESCENDING LIMB (thin) :

A

FURTHER REABSORPTION of WATER

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9
Q

ROLE of LOOP OF HENLE
ASCENDING LIMB (thick) :

A

REABSORPTION of SODIUM and CHLORIDE IONS

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10
Q

ROLE of DISTAL CONVOLUTED TUBULE

A

SECRETION of unwanted things eg EXCESS IONS, acids, drugs and toxins

VARIABLE REABSORPTION of WATER,SODIUM IONS and CALCIUM IONS (under HORMONAL CONTROL)

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11
Q

ROLE of COLLECTING DUCT

A

further VARIABLE REABSORPTION of WATER (under HORMONAL CONTROL)

and REABSORPTION or SECRETION of SODIUM, POTASSIUM, HYDROGEN and BICARBONATE IONS

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12
Q

what happens at the PAPILLARY DUCT (end of collecting duct)

A

delivery of URINE to MINOR CALYX

final destination

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13
Q

COMPOSITION of URINE (varies)

A

UREA (most)

POTASSIUM, SODIUM, CHLORIDE (EXCESS IONS)
CREATINE (By-product of cellular metabolism)
BICARBONATE IONS (buffer)
URIC ACID (dissolves and transports HYDROGEN IONS out)

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14
Q

average urine volume per day for an adult

A

1.4 L

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15
Q

URINARY EXCRETION calculation

A

EXCRETION =

FILTRATION - REABSORPTION + SECRETION

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16
Q

where does FILTRATION occur in the KIDNEY

A

in BOWMAN’S CAPSULE of Nephron (from GLOMERULUS)

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17
Q

approx how much FILTRATION SURFACE in each KIDNEY

A

6 m^2

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18
Q

FILTRATION BED of GLOMERULUS has 3 main LAYERS

A

CAPILLARY ENDOTHELIUM (flattened endothelial cells)

BASEMENT MEMBRANE - structural (prevents damage to endothelium)

PODOCYTES (foot-like processes) - wrap around vessels of glomerulus to generate pressure
- come together to create ‘sieve’

19
Q

why does the FILTRATION BED of GLOMERULUS allow MOST SMALL MOLECULES to pass but NOT cells or large proteins

A

it is HIGHLY FENESTRATED

20
Q

both CELLULAR LAYERS of FILTRATION BED of GLOMERULUS - CAPILLARY ENDOTHELIUM & PODOCYTES special feature

A

contain NEGATIVELY CHARGED GLYCOPROTEINS

  • creates REPELLING FORCE to + ions
21
Q

what is there between Pedicels

A

FILTRATION SLITS

22
Q

what should NOT be removed from blood / found in filtrate or urine

A

RED BLOOD CELLS
PLASMA PROTEINS
Plasma components

23
Q

what PASS through FILTRATION BED of GLOMERULUS and are found in FILTRATE (Bowman’s Capsule)

A

UNCHARGED MOLECULES (LESS than 30,000 DALTONS)

  • SALTS/IONS (sodium, potassium, chloride)
  • GLUCOSE
  • SMALL PROTEINS
  • WATER
24
Q

what is the FILTRATION RATE in the RENAL CORPUSCLE

A

approx 125 ml / min

(180 litres / day)

25
Q

what is REQUIRED for FILTRATION

A

PRESSURE

26
Q

what INCREASES PRESSURE in the GLOMERULUS for FILTRATION

A

EFFERENT ARTERIOLE has a SMALL DIAMETER
(afferent wide) so difficult for blood to leave

INCREASES PRESSURE in GLOMERULUS
so MORE BLOOD FILTERED

27
Q

3 TYPES of PRESSURE that add to the NET FILTRATION PRESSURE in the GLOMERULUS and what are their values

A
  • GLOMERULAR HYDROSTATIC PRESSURE (HPg):
    60mm Hg OUT
    (pressure of blood trying to push/filter out)
  • BLOOD COLLOID OSMOTIC PRESSURE (OPg):
    32mm Hg IN
    (trying to retain the water)
  • CAPSULAR HYDROSTATIC PRESSURE (HPc):
    18mm Hg IN
    (structure pushing back In)
28
Q

what is the value of the NET FILTRATION PRESSURE (NFP)

A

10 mm Hg OUT

(HPg = 60 out, OPg = 32 in, HPc = 18 in)

29
Q

RENAL BLOOD FLOW (RBF) is

A

the VOLUME of BLOOD DELIVERED to the KIDNEYS per unit of time

1.2 L / MIN

30
Q

how much of your RBF is your RENAL PLASMA FLOW

A

55% of RBF

PLASMA makes up 55% of BLOOD

31
Q

RATE of RENAL PLASMA FLOW (RPF)

A

0.625 L / MIN
(625 mL / min)

32
Q

what is GLOMERULAR FILTRATION RATE (GFR) and what is the value

A

measure of how much FLUID SQUEEZED THROUGH GLOMERULAR bed per unit time

0.125 L / MIN

(125 mL / min)

33
Q

what is FILTRATION FRACTION (FF) and what is the value

A

PORTION of PLASMA that was DELIVERED TO KIDNEY that is PASSED THROUGH TO the BOWMAN’S CAPSULE

= 20%

= GFR / RPF x 100
GFR = 125 ml / min
RPF = 625 ml/min

34
Q

what is RENAL PLASMA CLEARANCE (RPC)

A

VOLUME of PLASMA that is CLEARED OF A KNOWN SUBSTANCE per unit time

35
Q

CRITERIA for when GFR and RENAL PLASMA CLEARANCE are the SAME
if the substance is:

A
  • FILTERED FREELY
  • NOT SECRETED OR REABSORBED
  • NOT METABOLISED/BROKEN DOWN
  • NOT TOXIC
36
Q

CALCULATION for estimating GFR

A

U V / P

U = SOLUTE CONC in the URINE
V = VOLUME of URINE EXCRETED PER MIN
P = SOLUTE CONC IN PLASMA

37
Q

RBF:
RPF:
GFR:
FF:

A

RBF: 1200 ml/min
RPF: 625 ml/min
GFR: 125 ml/min
FF: 20%

38
Q

only substance where GFR and RPC are the SAME (meets all criteria)

A

INULIN

(not routinely used due to complexity, not naturally in blood)

use COCKROFT-GAULT (CG) formula instead

39
Q

COCKROFT-GAULT formula estimates… and how is it compared to GFR ESTIMATE

A

CREATINE CLEARNACE (Ccr) instead of GFR

OVERESTIMATES GFR by 15-40%
(as also SECRETED by tubules)

40
Q

negative CONSEQUENCES of LOW GFR

A
  • STIMULATION of RAAS SYSTEM. ELEVATED BLOOD PRESSURE
  • DECREASED EXCRETION H+ and DECREASED RETENTION of BICARBONATE causes METABOLIC ACIDOSIS
  • DECREASED ELIMINATION of UREA and CREATINE
  • DECREASED ELIMINATION of DRUG METABOLITES such as aminoglycoside antibiotics, leading to TOXIC levels in blood
41
Q

relationship between BLOOD PRESSURE and GFR

A

INCREASE BP = INCREASE GFR

(more blood entering glomerulus, increased hydrostatic pressure so increased filtration)

42
Q

MECHANISM to REDUCE (control) GFR from increased BP
- MYOGENIC AUTOREGULATION (RAPID response)

A

increased STRETCH of the AFFERENT ARTERIOLE (as a result of high BP) is sensed by GRANULAR CELLS sat around afferent arteriole

  • CONSTRICT
  • REDUCE amount of BLOOD FLOWING INTO GLOMERULUS
  • REDUCES GFR
43
Q

affect of INCREASED BLOOD PRESSURE on CARDIOVASCULAR SYSTEM to decrease it

A

INCREASED STRETCH of ATRIA of HEART

  • INCREASED SECRETION of ANP
  • BLOCKS RELEASE of RENIN
    (renin causes reabsorption of water and salt and increases blood volume normally by RAAS system)

UROGENITAL (19 decks)

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