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Menneskets fysiologi > Nyrer > Flashcards

Nyrer Flashcards

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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

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A

Contractile property of smooth muscle cells surrounding arterioles

22
Q

Example of myogenic control of renal blood flow and GRF

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A

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

23
Q

Three basic components of renal function

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A

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

24
Q

Amount excreted in urine of any substance

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A

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

25
Renal handling of p-aminohippurate (PAH)
Some is absorbed in Bowman's space The rest is absorbed by tubule All is filtered and secreted
26
Renal handling of sodium
Some is absorbed in Bowman's space Most is reabsorbed by peritubular capillary Only a tiny amount is secreted Filtered and reabsorbed
27
Renal handling of glucose
Some is absorbed in Bowman's space All is reabsorbed in peritubular capillary Filtered and reabsorbed
28
Renal handling of inulin og creatinine
Filtered Some is absorbed by Bowman's space
29
Arterial input
Venous output + urine output P(S,a) * RPF(a) P = concentration in plasma S = substance a = arterial RPF = renal plasma flow rate
30
Venous output
P(S,v) * RPF(v) P = concentration in plasma S = substance v = venous RPF = renal plasma flow rate
31
Urine output
U(S) * V U = concentration in urine V = urine flow rate S = substance
32
Renal Clearance
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
Clearance of substances can vary between:
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
The clearance of a substance becomes the estimate of GFR in which case?
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
Metabolic source of acids/base
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
Kidneys contribution to acid/base homeostasis
must reabsorb all HCO3^- and secrete nonvolatile acids therefore, kidney acidifies urine Other organs contributing to acid/base balance – lungs and digestive system
37
Nitrogen homeostasis
Excretion of nitrogen compounds In humans, kidney excretes urea N is found in proteins (amino acids) and nucleic acid (nitrogenous bases)
38
Na+ distribution in the body
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
Recovery of Na+ (and Cl-) along the nephron
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
How is the recovery of Na+ examined?
Using micropipette at different places in nephron
41
Na+, Cl-, solutes and water in nephron
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
Coupling of Na+ and water transport in the proximal tubulus
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
Absorption of nutrients and small organic molecules in proximal tubulus, e.g. glucose
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
Cortical collecting tubule (CCT) - fine tuning
Na+ and water transport can be regulated. fine tuning
45
Water permeability along the nephron
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
Vasopressin
Antidiuretic hormone = ADH H2O reabsorption
47
Hormonal regulation of Na+ and water permeability in distal tubules and collecting ducts
Medullary collecting duct: Aldosterone - Na+ transport Vasopressin - water transport
48
Urine concentration: countercurrent multiplier system
Using selective NaCl and water permeability to concentrate urine in the loop of Henle
49
Regulatory mechanisms: key hormones
- Renin - Angiotensin - Aldosterone System (RAAS) - Vasopressin (Antidiuretic Hormone)
50
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?
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

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