Lecture 13 Physiology of Micturition & Assessment of Renal Function, Urea, Creatinine and GFR Flashcards

1
Q

Why is the assessment t of renal function important

A

Assess progression of the underlying disease

When GFR falls, excretion falls so drug dose may. need to be adjusted

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2
Q

How is GFR measured

A

Plasma clearance test

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3
Q

What is the equation for the calculation of plasma clearance

A

Plasma Clearance = Urine concentration X Urine flow rate/Plasma Concentration

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4
Q

What is the gold standard for measuring plasma clearance

A

Inulin

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5
Q

Why is inulin used to measure plasma clearance

A

Freely filtered at the glomerulus and isn’t reabsorbed nor secreted

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6
Q

At what rate does the GFR decline

A

1ml/min/year after 30

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7
Q

What is used instead of inulin in clinical practice to measure plasma clearance

A

51Cr-EDTA

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8
Q

Name factors that affect serum creatinine

A

Muscle mass
Dietary intake
Drugs

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9
Q

What is the clearance of glucose and why

A

Zero clearance because all is normally absorbed

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10
Q

Is the clearance of urea less than inulin and why?

A

Yes, because some urea is reabsorbed

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11
Q

What is used to measure real plasma flow

A

Para-amino-hippuric acid (PAH)

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12
Q

How does urine flow from the kidneys to the bladder

A

Through the ureters via peristaltic contractions of the smooth muscle of the ureters

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13
Q

At what angle doe the ureters enter the bladder and why

A

Oblique angles

Prevent reflux

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14
Q

What muscle surrounds the bladder

A

Detrusor muscle

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15
Q

Contraction of what muscle is responsible for the emptying of the bladder during micturition

A

Detrusor muscle

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16
Q

What is the internal urethra made up of

A

Smooth muscle

17
Q

What is the external urethra made up of

A

Skeletal muscle

18
Q

What type of epithelium lines the bladder

A

Transitional epithelium

19
Q

What are the openings in the bladder

A

2 vesicoureteric openings

20
Q

What is the normal daily urine production

A

Varies between 730ml to 2500mls

21
Q

Describe the sphincters of the bladder at rest

A

Internal sphincter- passively contracted

External sphincter- stays contracted

22
Q

What is the parasympathetic motor innervation of micturition

A

Pelvic nerve
S2-S4
Increase in activity- detrusor muscle contraction

23
Q

What is the sympathetic motor innervation of micturition

A
Hypogastric nerve
L1-L3
Inhibit bladder contraction 
Closes internal urethral sphincter 
Prevents reflux of semen into bladder during ejaculation
24
Q

What is the somatic motor innervation of micturition

A

Pudendal nerves
S2-S4
Innervate skeletal muscle of external urethral sphincter

25
Q

Describe the sensory innervation of the bladder

A

Stretch receptor in bladder wall as bladder fills sends a discharge in afferent nerves to spinal cord
Excitation of parasympathetic
Inhibition of sympathetic and somatic

26
Q

In an adult what is the volume of urine in the bladder required to initiate the spinal reflex

A

300-350 mls

27
Q

How is the delay in micturition achieved

A

Inhibit the parasympathetic and stimulate the somatic

28
Q

After urination, how dies female urethras empty

A

By gravity

29
Q

How can urine flow be interrupted once it begins

A

Perineal muscles and external sphincter muscles being contracted voluntarily

30
Q

How is urine remaining in the male urethra expelled

A

Contractions of the bulbocavernous muscle

31
Q

Name 3 abnormalities of the micturition

A
  1. Interruption of afferent nerves
  2. interruption of both afferent and efferent nerves
  3. interruption of facilitatory and inhibitory descending pathways from the brain.