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anatomy & physiology 208 > Urinary Physiology Study Guide > Flashcards

Urinary Physiology Study Guide Flashcards

1
Q

how much filtrate is made each day

A

180 L (47 gallons)

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2
Q

how much urine is made each day

A

1.5 L

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3
Q

Filtrate

A

blood plasma minus its proteins, produced by glomerular filtration

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4
Q

Urine

A

metabolic wastes and unneeded substances, produced from filtrate

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5
Q

3 processes involved in urine formation

A

glomerular filtration, tubular reabsorption, tubular secretion

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6
Q
  1. Glomerular filtration
A

Passive process that does not require metabolic energy, no reabsorption occurs
- Has filtration membrane between the blood and the interior of the glomerular capsule
- Hydrostatic pressure forces fluid and solutes through the membrane into the glomerular capsule
- Cells, proteins, and other larger molecules (> 5nm) don’t fit through membrane

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7
Q
  1. Tubular reabsorption
A

process of selectively reclaiming substances from filtrate and moving them back into blood
- Typically, 99% of water, and all glucose and amino acids are reabsorbed

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8
Q
  1. Tubular secretion
A

process of selectively moving substances from blood into filtrate

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9
Q

3 layers of the filtration membrane

A

Fenestrated endothelium of glomerular capillaries,
Basement membrane,
Foot processes of podocytes of the glomerular capsule

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10
Q

Fenestrated endothelium of glomerular capillaries

A

allows all blood components except cells to pass

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11
Q

Basement membrane

A

allows solutes, blocks all but the smallest proteins

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12
Q

Foot processes of podocytes of the glomerular capsule

A

filtration slits between foot processes, stop all remaining macromolecules

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13
Q

3 pressures involved in glomerular filtration

A

Hydrostatic pressure in glomerular capillaries (HPgc), Hydrostatic pressure in the capsular space (HPcs), Colloid osmotic pressure in glomerular capsule (OPgc)

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14
Q

Hydrostatic pressure in glomerular capillaries (HPgc)

A
  • Glomerular blood pressure
  • Chief force pushing water, solutes, out of blood across filtration membrane
  • High ( 55mmHg) compared to most capillary beds
  • Maintained by the smaller size of efferent arterioles versus the afferent arterioles
  • Outward pressure (promote filtration formation)
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15
Q

Hydrostatic pressure in the capsular space (HPcs)

A

Pressure exerted by the force in the glomerular capsule (~15 mmHg)
Inward pressure (inhibit filtration formation)

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16
Q

Colloid osmotic pressure in glomerular capsule (OPgc)

A

The “pull” of the proteins in the blood (~30mmHg)
Inward pressure

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17
Q

NFP

A

Sum of forces
Pressure responsible for forming filtrate
Main controllable factor for determining glomerular filtration rate GFR
Outward force: net → 10 mmHg (55mmHg forcing in, 45 mmHg forcing out)

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18
Q

GFR

A

Volume of filtrate formed by both kidneys per minute

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19
Q

3 determining factors of GFR

A
  • Net filtration pressure (NFP) - Main controllable factor, primary pressure is outward glomerular hydrostatic pressure, can be controlled by changing arteriole diameters
  • Total surface area available for filtration – controlled by the contraction of mesangial cells
  • Permeability of filtration membrane – much more permeable than other types of capillaries
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20
Q

normal gfr

A

120-125 mL/min

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21
Q

renal failure gfr

A

GFR < 15 mL/min

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22
Q

CKD/CRD gfr

A

GFR < 60 mL/min

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23
Q

relationship between GFR and systemic blood pressure.

A
  • Increase in GFR increases urinary output and decreases BP
  • Decrease in GFR decreases urinary output and increases BP
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24
Q

Intrinsic controls

A

work locally within the kidney to maintain GFR – renal autoregulation

25
Q

Extrinsic controls

A

neutral and hormonal controls that maintain systemic blood pressure

26
Q

MAP

A

Mean arterial pressure (average arterial pressure throughout one cardiac cycle – systole and diastole)
⅓ pulse pressure + diastolic pressure

27
Q

an appropriate MAP range for intrinsic controls to be in control

A

80 - 180 mmHg (MAP outside of this range = extrinsic controls are in control)

28
Q

myogenic mechanism

A

Smooth muscle contracts when stretched
Goals: protect the glomerulus from high BP by restricting blood flow, maintain normal NFP and GFR

29
Q

What happens when BP increases or decreases under myogenic mechanism

A

Increased BP → muscles stretch → constriction of afferent arteriole
Decreased BP → dilation of afferent arteriole

30
Q

tubuloglomerular feedback mechanism

A

GFR increases → flow of filtrate increases -> decreased time for reabsorption → higher levels of NaCl in filtrate
- Response: the afferent arteriole is constricted → NFP and GFR are reduced → increased time for NaCl reabsorption

30
Q

group of cells that direct tubuloglomerular feedback mechanism

A

macula densa cells

31
Q

solute that directs tubuloglomerular feedback mechanism

A

NaCl

32
Q

systemic effects seen in extrinsic neural control by the SNS

A

Extrinsic controls regulate GFR to maintain systemic BP - even if it hurts the kidneys – ex, during hypovolemia, extrinsic overrides intrinsic controls to ensure survival of vital organs

33
Q

how the systemic effects seen in extrinsic neural control by the SNS alters BP

A
  • Normal conditions: renal blood vessels are dilated, intrinsic controls running
  • Abnormal conditions (low BP): norepinephrine, epinephrine released
    – Systemic vasoconstriction to raise BP
    – Constriction of the afferent arterioles will decrease GFR
    – Blood volume and blood pressure increase
34
Q

3 pathways to releasing renin from granular cells

A
  • Direct stimulation of granular cells by sns
  • Stimulation of the granular cells by activated macula densa cells – when NaCl concentration in filtrate is low
  • Reduced stretch of granular cells
35
Q

how renin increases systemic blood pressure

A

Renin → angiotensin II → 2 different ways:
- Increased aldosterone secretion by adrenal cortex → increased Na+ reabsorption by kidney tubules, water follows, → increased blood volume → increased BP
- Vasoconstriction of systemic arterioles, increase in peripheral resistance → systemic blood pressure

36
Q

things that are reabsorbed in tubular reabsorption

A

Almost all organic nutrients – reabsorption of water and ions are hormonally regulated and can be adjusted

37
Q

portion of the renal tubule that conducts the most reabsorption

A

PCT

38
Q

What is reabsorbed in the PCT

A
  • All nutrients (glucose + amino acids)
  • 65% of sodium and water
  • Most of the electrolytes (potassium, calcium, magnesium, etc.)
  • Nearly all uric acid and ½ of the era – these will be secreted into the filtrate again later
39
Q

What is reabsorbed in the Nephron Loop

A

Reabsorption of water is no longer coupled to solute reabsorption
- Descending limb – water can leave, but solute cannot
- Ascending limb – solute can leave (Na+ K+ Cl-), but water cannot

40
Q

What is reabsorbed in the DCT

A
  • Varies with body’s needs
  • Most of the water and solutes have already been reabsorbed
  • Some Na+ Cl- HCO3 H2O
41
Q

ADH

A

released by the posterior pituitary gland, can cause an increase in reabsorption of water

42
Q

Aldosterone

A

increases blood pressure and decreases k+ levels by promoting the reabsorption of Na+

43
Q

Atrial Natriuretic peptide ANP

A

released by cardiac atrial cells, decreases blood volume and blood pressure by reducing the reabsorption of Na+

44
Q

Parathyroid hormone

A

increases reabsorption of Ca2+ by the DCT (regulates calcium)

45
Q

tubular secretion

A
  • Reverse of tubular reabsorption, occurs almost entirely in PCT
  • Selected substances are moved from the peritubular capillaries, through the tubule cells, and back into the filtrate
  • Important for getting rid of unwanted substances and excess amounts of substances, as well as controlling pH
46
Q

things typically secreted in tubular secretion

A

K+, H+, ammonia, creatinine, organic acids and bases

47
Q

renal clearance

A

volume of plasma that kidneys can clear of a particular substance within a given time

48
Q

treatment options for renal failure

A

Hemodialysis or kidney transplant

49
Q

things normally found in urine

A

Water, urea, uric acid, creatinine Na+, K+ PO43-, SO42-, sometimes CA2+, Mg2+, HCO3- are in small amounts

50
Q

things abnormal to be found in urine

A

blood proteins (rhabdo – breakdown of muscles), WBCs, bile pigments, glucose, ketone bodies, hemoglobin, erythrocytes

51
Q

trigone of the bladder

A

Smooth triangular area outlined by the openings for the 2 ureters and the urethra

52
Q

smooth muscle of the bladder

A

Thick detrusor muscle of the muscular layer – has 3 layers of smooth muscle
- Inner and outer layers are longitudinal
- Middle layer is circular

53
Q

max capacity of the bladder

A

1,000mL

54
Q

female urethras

A
  • 3-4 cm/1.5 in long
  • Tightly bound to anterior vaginal wall
  • External urethral orifice is anterior to the vaginal orifice
55
Q

male urethra

A
  • Carries both semen and urine
  • Much longer - 20 cm/8 in – has 3 named regions
    – Prostatic urethra – 2.5 cm, within prostate gland
    – intermediate/membranous urethra – 2cm, passes through urogenital diaphragm from prostate to root of penis
    – Spongy urethra – 15sm passes through the penis, opens via external urethral orifice
56
Q

Internal urethral sphincter

A

involuntary/smooth muscle at the bladder - urethral junction - contracts to open

57
Q

External urethral sphincter

A

voluntary/skeletal muscle surrounding the urethra as it passes the pelvic floor - relaxes to open

58
Q

micturition reflex

A

3 simultaneous events
- Contraction of the detrusor muscle by the ANS
- Opening of the internal urethral sphincter by ANS
– Opens via contraction
- Opening of the external urethral sphincter by -somatic nervous system
– Opens via relaxation
- PNS activity increases
- SNS activity decreases
- somatic motor activity decreases

anatomy & physiology 208 (39 decks)

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