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Menneskets fysiologi > Nyrer > Flashcards

Nyrer Flashcards

1
Q

Main functions of kidneys

A

Homeostatic role:
– water, salt, acid/base, nutrient balance

Excretion:
– removal of metabolic waste products (e.g. urea, uric acid, ammonia, creatinine)
- removal of foreign chemicals and excretion in the urine

Endocrine function:
– produces hormones involved in erythrogenesis (EPO), calcium metabolism (1,25-dihydroxy Vit. D) and blood pressure/flow regulation (renin)

Gluconeogenesis

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2
Q

Kidney diseases

A

Various defects
Genetic defects
Regulation defects

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3
Q

Various defects

A

Chronic kidney disease
Diabetic nephropathy
Toxic chemicals (e.g. ochratoxin)
Obstruction of ureter/urethra
Kidney stones
Infections
Glomerulonephritis
Tumors

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4
Q

Regulation defects

A

Impaired response to vasopressin (Diabetes Insipidus)
hypoaldosteroidism
Too much renin - renal hypertension

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5
Q

Genetic defects

A

Defect in Na-K-Cl cotransporter – Barter syndrome
Defect in Na channels – Liddle ́s disease
Defect in AQP2 channels – nephrogenic diabetes insipidus
Polycystic kidney disease – defects in primary cilia

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6
Q

Kidney is also a target for drugs used to treat

A

High blood pressure

Oedema

Type 2 diabetes

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7
Q

Nyren

A

binyre
nyrebark
nyremarv
nyrebækken
nefron

Nyren er forbundet til arterie og vene

også forbundet til urinblæren via urinlederen

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8
Q

Nephron

A

Renal copuscle (nyrelegeme)
- Glomerulus + Bowmans kapsel
–>
Proximal tubulus
–>
Loop of Henle
–>
Distal tubulus
–>
Collecting duct

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9
Q

Main elements of nephron function

A

The nephron forms an ultrafiltrate of the blood plasma and then selectively reabsorbs the tubule fluid and secretes solutes into it

Main renal processes:
Filtration - bulk transport
Absorption - membrane transport processes
Secretion - membrane transport processes
Excretion - filtration + absorption

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10
Q

Filtration

A

Renal corpuscle (nyrelegeme)
- Glomerulus, Bowman’s capsule and Juxtaglomerular apparatus

Ultrafiltrate føres ud til proximal tubulus og videre ud til collecting duct

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11
Q

Ultrafiltrate

A

= glomerular filtrate = pre-urine

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12
Q

What molecules do and do not get into the glomerular filtrate

A

Molecules < 8nm

Water, ions (0.02-0.05 kDa)
Urea (0.06 kDa)
Glukose (0.18 kDa)
Inulin (5.5 kDa)
Myoglobin (17 kDa)

What does not pass through:
- Albumin
- Hemoglobin
- Blood cells
- Protein-bound hormones and minerals

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13
Q

Kidney vascular bed

A

Important for filtrate formation
- and secretion and absorption and for concentrating mechanism

Renal artery
–> afferent arteriole
–> glomerular capillary network
–> efferent arteriole
–> capillary network surrounding renal tubules
–> renal vein

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14
Q

Blood pressure in the kidney vascular bed

A

The blood pressure drops as you move through the kidney vascular bed

Starts around 120 mmHg ved renal artery
Falder til ca. 50 mmHg ved glomerular capillaries
Falder til ca. 15 mmHg ved renal vein

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15
Q

Filtration depends on:

A

Hydrostatic (P) and osmotic (Π) pressures

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16
Q

Net glomerular filtration pressure

A

= P(GC) - P(BS) - Π(GC)

Favoring filtration:
- glomerular capillary blood pressure (P(GC)) (60 mmHg)

Opposing filtration:
- Fluid pressure in Bowman’s space (P(BS)) (15mmHg)
- Osmotic force due to protein in plasma (Π(GC)) (29mmHg)

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17
Q

Glomerular filtration rate (GFR)

A

GFR in healthy person is ca. 125 ml/min (which makes about 1/5th of renal plasma flow)

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18
Q

CALCULATE AND REFLECT: 125 ml/min
How much plasma is filtered each day ?
If plasma volume is 3 L, how many times does kidney filter?

A

How much is filtered each day ? 180 l/day

If plasma volume is 3 L, how many times does kidney filter? 60x day!

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19
Q

Autoregulation

A

The kidney maintains constant renal blood flow (RBF) and glomerular filtration rate (GFR)

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20
Q

Why is auto regulation important

A

Ability of kidney to maintain constant RBF and GFR – innate and occurs in isolated kidney or even a nephron

Aim is to hold RBF and GFR about constant
– or serious consequences to the body water and salt balance – i.e. loss in urine
e.g. increased BP (exercise) > if not regulated increased RPF and GFR> increased urine production

Two mechanism:
a)myogenic control – property of the smooth muscle cells in afferent arteriole, e.g. increase in BP like during exercise will first stretch arteriole, which will reflexly constrict to keep RBF and GFR down
b) tubuloglomerular feedback

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21
Q

Myogenic

A

Contractile property of smooth muscle cells surrounding arterioles

22
Q

Example of myogenic control of renal blood flow and GRF

A

reaction to increased blood pressure Constriction of AA&raquo_space; to maintain stable GFR

23
Q

Three basic components of renal function

A

1) Glomerular filtration
2) Tubular secretion
3) Tubular reabsorption

24
Q

Amount excreted in urine of any substance

A

Amount filtered + amount reabsorbed - amount secreted = amount excreted in urine

25
Q

Renal handling of p-aminohippurate (PAH)

A

Some is absorbed in Bowman’s space
The rest is absorbed by tubule
All is filtered and secreted

26
Q

Renal handling of sodium

A

Some is absorbed in Bowman’s space
Most is reabsorbed by peritubular capillary
Only a tiny amount is secreted

Filtered and reabsorbed

27
Q

Renal handling of glucose

A

Some is absorbed in Bowman’s space
All is reabsorbed in peritubular capillary

Filtered and reabsorbed

28
Q

Renal handling of inulin og creatinine

A

Filtered
Some is absorbed by Bowman’s space

29
Q

Arterial input

A

Venous output + urine output

P(S,a) * RPF(a)

P = concentration in plasma
S = substance
a = arterial
RPF = renal plasma flow rate

30
Q

Venous output

A

P(S,v) * RPF(v)

P = concentration in plasma
S = substance
v = venous
RPF = renal plasma flow rate

31
Q

Urine output

A

U(S) * V

U = concentration in urine
V = urine flow rate
S = substance

32
Q

Renal Clearance

A

The Clearance of a solute/substance is the virtual volume of blood that would be cleared of a given solute in a given time and expressed in units ml/min

Each solute/substance has a its own clearance, depending on how the kidney handles it

C(S) = (urine output)/P(S). (ml/min)

33
Q

Clearance of substances can vary between:

A

up to 700 ml/min - substances that are totally removed from plasma in a single pass through kidney; can be used to estimate renal plasma flow and therefor renal blood flow (substance X, e.g. PAH)

0 ml/min - substances that do not appear in urine, because they are reabsorbed (substance Z, e.g. glucose)

And in special cases

ca. 125 ml/min – substances that are only filtered; can be used to estimate glomerular filtration rate (substance O, e.g. inulin)

34
Q

The clearance of a substance becomes the estimate of GFR in which case?

A

If substance S is inert (such as Inulin), i.e. only filtered and not absorbed or secreted by kidney, Cs becomes an estimate of Glomerular Filtration Rate = GFR

GFR(In) = (U(In) · V) / (P(In)) (ml/min)

35
Q

Metabolic source of acids/base

A

carbonic anhydrase
CO2+H2O <–> H2CO3 <–> HCO3- + H+

Volatile acids:
- CO2 (potential acid)

Nonvolatile acids:
- H+
- phosphate
- sulphate
- uric acid
- oxalic acid
- lactic acid
- keto-acids,
- acetate

36
Q

Kidneys contribution to acid/base homeostasis

A

must reabsorb all HCO3^- and secrete nonvolatile acids therefore, kidney acidifies urine

Other organs contributing to acid/base balance – lungs and digestive system

37
Q

Nitrogen homeostasis

A

Excretion of nitrogen compounds

In humans, kidney excretes urea

N is found in proteins (amino acids) and nucleic acid (nitrogenous bases)

38
Q

Na+ distribution in the body

A

Na+ has a central role in salt and water homeostasis

Diet: 120 mmol/day
–> Gut

Gut:
–> Feces: 5-10 mmol/day
–> 110 mmol/day absorbed in extracellular fluid

extracellular fluid:
–> Sweat: 10-15 mmol/day
–> Kidneys: Filter 25,500 mmol/day and reabsorb 25,400 mmol/day
–> Interchange with intracellular fluid

Kidneys:
–> Urine: 100 mmol/day

39
Q

Recovery of Na+ (and Cl-) along the nephron

A

Most Na+ and other substances are reabsorbed in the proximal tubule

Fine tuning and regulation of salt and water transport in collecting duct

100% Na+ in renal copuscle (nyrelegeme)

30% Na+ towards end of proximal tubulus

10% Na+ after Loop of Henle

3% Na+ around distal tubulus and beginning of collecting duct

1% Na+ at the end of collecting duct

40
Q

How is the recovery of Na+ examined?

A

Using micropipette at different places in nephron

41
Q

Na+, Cl-, solutes and water in nephron

A

Different nephron segments use different transporters and channels for Na+ absorption

Cl- absorption follows via transcellular or paracellular route

Solute transport can be coupled to Na+ transport

Water reabsorption is passive and secondary to solute transport (if epithelium is water permeable)

42
Q

Coupling of Na+ and water transport in the proximal tubulus

A

Major absorption site

H2O uses aquaporin and diffuses

Sekundær aktiv transport af Na+ and solute into cell. Then Na+/K+ ATPase to get Na+ out of cell.

43
Q

Absorption of nutrients and small organic molecules in proximal tubulus, e.g. glucose

A

Na+/glucose symporter into cell. Then glucose uniporter and Na+/K+ ATPase out of cell

Na+/glucose symporter inhibitors used to treat type 2 diabetes?

44
Q

Cortical collecting tubule (CCT) - fine tuning

A

Na+ and water transport can be regulated. fine tuning

45
Q

Water permeability along the nephron

A

Variable

100% H2O permeability in proximal tubulus, following solute transport e.g. Na+. Aquaporins

Descending limp of loop of hence water permeable

ascending limb og Loop of Henle not H2O permeable

H2O permeability regulated in collecting duct by vasopressin. Aquaporins 2.

46
Q

Vasopressin

A

Antidiuretic hormone = ADH
H2O reabsorption

47
Q

Hormonal regulation of Na+
and water permeability in distal tubules and collecting ducts

A

Medullary collecting duct:
Aldosterone - Na+ transport
Vasopressin - water transport

48
Q

Urine concentration: countercurrent multiplier system

A

Using selective NaCl and water permeability to concentrate urine in the loop of Henle

49
Q

Regulatory mechanisms: key hormones

A
  • Renin
  • Angiotensin
  • Aldosterone System (RAAS)
  • Vasopressin (Antidiuretic Hormone)
50
Q

Kidney and cardiovascular system: use of Diuretics and other drugs targeting RAS system

What are they/what do they do?

Why are they so commonly used?

A

What are they/what do they do?
- Increase volume of urine

Why are they so commonly used?
- To treat high blood pressure, fluid retention in body e.g. congestive heart failure

Menneskets fysiologi (15 decks)

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