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DS1102 > Week 8 - Renal Systems and Disorders > Flashcards

Week 8 - Renal Systems and Disorders Flashcards

1
Q

What are the kidney’s main functions (3)

A
  • excretion of metabolic waste products
  • Regulation of water balance
  • Regulation of electrolyte salt concentrations
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2
Q

What is the basic functional units of the kidney

A

The nephron

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3
Q

What are the major parts of the nephron

A
  1. corpuscle - they filter blood
  2. Renal tubule - they modify the filtrate
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4
Q

What are the 3 processes in urine formation

A
  1. Glomerular filtration - filtration of blood
  2. Tubular reabsorption - reabsorption of filtered substances form tubules into blood
  3. Tubular secretion - secretion of substance from blood into renal tubules —> removal of substances that we don’t want
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5
Q

What is the glomerular filtration process

A

the glomerular 3 layer filtration barrier facilitating filtration - relatively impermeable to proteins and cellular elements of blood

  • Passive, mostly non selective process
  • fluids and solutes forced through membrane by hydrostatic pressure
  • Does not require metabolic energy - simple mechanical filtration
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6
Q

what ends up in the filtrate after the glomerular filtration process

A
  • Water
  • salts
  • nutrients
  • metabolic waste
  • all blood components minus blood cells and plasma proteins
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7
Q

What enables the glomerular filtration process to occur

A

glomerular filtration pressures (net filtration pressure)
- hydrostatic pressure

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8
Q

What are the 3 glomerular filtration pressures

A
  • Glomerular hydrostatic pressure
  • Capsular hydrostatic pressure
  • Blood colloid osmotic pressure
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9
Q

What is glomerular hydrostatic pressure

A

Glomerular capillary blood pressure
avg = 55 mm Hg

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10
Q

what is the effect of glomerular hydrostatic pressure

A

promotes filtration
avg = 15 mm Hg

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11
Q

What is capsular hydrostatic pressure

A

hydrostatic pressure applied to the filtration membrane by fluid in the capsular space and renal tubule
avg = 30 mm Hg

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12
Q

what is the effect of capsular hydrostatic pressure

A

opposes filtration

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13
Q

what is blood colloid osmotic pressure

A

results from proteins present in blood plasma
avg = 30 mm Hg

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14
Q

what is the effect of blood colloid osmotic pressure

A

opposes filtration

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15
Q

What is the equation for net filtration pressure

A

glomerular hydrostatic pressure - capsular hydrostatic pressure - blood colloid osmotic pressure

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16
Q

What is the glomerular filtration rate

A

the rate at which kidneys filters blood = total amount of filtrate formed

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17
Q

what is the average glomerular filtration rate

A

120 mL/min - adds up to nearly 180L/day

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18
Q

what is average urine production

A

1mL /min

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19
Q

What are the 4 components of the renal tubule

A
  1. proximal convoluted tubule
  2. nephron loop
  3. Distal convoluted tubule
  4. collecting duct
20
Q

What are the 2 main functions of the renal tubule

A
  1. Tubular reabsorption
  2. tubular secretion
21
Q

What is tubular reabsorption

A
  • Removes useful substances from the glomerular filtrate and returns them to the blood
  • coupled with water reabsorption
22
Q

what is the primary site of tubular reabsorption

A

proximal convoluted tubule

23
Q

What is tubular secretion

A

transfers unwanted substances from blood and tubule cells into tubular fluid

24
Q

What is the primary site of tubular secretion

A

proximal convoluted tubule

25
Q
  1. What happens at the proximal convoluted tubule
A
  • reabsorption and secretion occurs here
26
Q

What is reabsorbed in the proximal convoluted tubule

A

Completely reabsorbed
- glucose
- amino acids
Highly reabsorbed
- salt (NaCl)
- water

27
Q

What is secreted in the proximal convoluted tubule

A
  • K+
  • H+
  • organic acids and bases (bile states, oxalate, uric acid)
  • metabolic end products
  • drugs or toxins (penicillin)
  • NH4+
28
Q

What occurs in the descending limb of the nephron loop

A
  • Aquaporins are present here and causes water to be reabsorbed but not salts
  • Causes the urine to have a lower volume and be more concentrated
29
Q

What occurs in the ascending limb of the nephron loop

A
  • There are no aquaporins present so no water is reabsorbed
  • Salts are reabsorbed here (Na+, K+, Cl-)
30
Q

What occurs in the distal convoluted tubule

A
  • Fine tuning of reabsorption and secretion occurs here

Reabsorbed

  • Na+ (under influence of aldosterone)
  • Cl-
  • Ca2+

secreted

  • K+
  • H+
  • NH4+
31
Q

What occurs in the collecting duct

A

Process = Controls final concentration of urine

Reabsorbed

  • Water (under control of ADH)
  • Na+
  • Urea (some reabsorbed to maintain the osmotic gradient in the medulla)

Excreted

  • The remaining water, urea, excess salts and other wastes are excreted as urine
32
Q

What determines the maximum amount of a substance can be reabsorbed

A

the saturation of the specific transport system

e.g. glucose
At high blood levels amount of glucose filtered exceeds kidney’s ability to reabsorb it hence some it lost in urine.

33
Q

what is osmolarity

A

measure of solute to water ratio

34
Q

what nephron component controls urine volume and osmolarity

A

nephron loop

35
Q

where in the nephron is osmolarity the highest

A

the tip of the descending limb of the nephron loop

36
Q

What does ADH stand for

A

Antidiuretic hormone

37
Q

Where does ADH act

A

Acts on the distal tubules and collecting ducts which is normally impermeable to water

38
Q

What is the function of ADH

A

causes the distal tubule and collecting ducts to become permeable to water due to aquaporins.

ADH combined with high salt concentration in surrounding medulla = significant water reabsorption and generation of small volumes of concentrated urine

39
Q

What type of urine does ADH form

A

small volumes of concentrated urine

40
Q

What causes the formation of dilute urine

A

low ADH levels

41
Q

Explain how dilute urine forms

A
  1. Active reabsorption of NaCl from the ascending limb of the nephron loop occurs - causing the tubular fluid to become very dilute
  2. When reabsorption of more NaCl in the distal tubules
  3. When there’s a failure to reabsorb water at low ADH levels in the distal tubules resulting in large volumes of dilute urine
42
Q

What causes concentrated urine to form

A

high ADH levels

43
Q

Explain how concentrated urine forms

A
  1. When there’s active reabsorption of NaCl in the ascending limb of the nephron loop generates a very high solute concentration in the medulla resulting in a driving force for water reabsorption in the presence of high ADH
  2. Fluid leaving the nephron loop is dilute but becomes concentrated as water is absorbed from the distal tubules and collecting ducts due to ADH
44
Q

What controls the reabsorption/secretion of salt in the distal tubule

A

aldosterone hormone

45
Q

What is the function of aldosterone

A
  • Influences how much salt is lost in urine ore retained
  • Aldosterone controls excretion of BOTH Na+ and K+
46
Q

What occurs at high aldosterone levels

A

reabsorption of Na+ in exchange for secretion of K+

47
Q

What occurs at low aldosterone levels

A

secretion of Na+ in exchange for reabsorption of K+

DS1102 (37 decks)

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