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PMP-101 > Renal system 1 & 2 > Flashcards

Renal system 1 & 2 Flashcards

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1
Q

name the key features of the uraniry system

A

Kidneys

Renal Pelvis (into which urine is drained)

Ureters (carry urine to urinary bladder)

Bladder (stores urine)

Urethra (tube between bladder and external environment)

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2
Q

main function of kidney?

A

filtration
reabsorption
homeostasis

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3
Q

how much weight is the kidneys in the body?

A

1%
Yet receive about 25% of Cardiac Output
¼ of all ‘work’ performed by heart is to perfuse kidneys

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4
Q

smallest Functional unit = is the nephron

A

Approx 2.5 million
Each approx 5 cm in length about 50 µm in diameter
Approx 125 km of tubing (not including blood vessels)

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5
Q

Processes 180 L plasma/day

A

Only about 1.5 drops per nephron
Of which ~ 1% ends up as urine
About 600g of sodium reabsorbed per day

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6
Q

What are the Substances filtered and reabsorbed

A
  1. WATER Glomerular filtrate = 180-200 l/day approx

Urinary volume = 1.5 l/day approx (ie most of water filtered is reabsorbed)

  1. SODIUM CHLORIDE
    Nearly all Na+ and Cl- is reabsorbed to maintain internal O.P.
  2. GLUCOSE
    Reabsorbed as long as plasma glucose < 200 mg/100ml (10 mM)
  3. HYDROGEN IONS –
    Normal diet generates H+ ions and kidney eliminates them.
  4. UREA H2N - CO - NH2
    End product of protein metabolism
    2/3 of that filtered is passed out in urine
    Remainder is reabsorbed
  5. TOXIC SUBSTANCES
    Body metabolites Drugs + Drug metabolites
    Some of these may be actively secreted (removed)
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7
Q

High coinc of what does urine include?

A

Urea
Ureic acie
Creatinine
K+
Other substances that are toxic

rest reabsorbed

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8
Q

blood supply travels to the kidney and substance are filtered ____

A

out

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9
Q

artery divides =

A

interlobular arteries - where they come into contact with the nephron (incl. swealling = where blood supply interacts with nephron)

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10
Q

blood means afferent to efferent

A

afferent - towards the glomerulus
efferent - from something (out efferent arterial)

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11
Q

what two components does the nephron include?

A

vascular (Blood)
Tubular (filtered fluid)

Some of the nephron is in renal cortex
outer region
granular
Some of the nephron is in renal medulla
inner region,
made up of triangles (renal pyramids)

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12
Q

The Nephron: Vascular component

A

Interlobular artery > afferent arteriole (aa)

splits > the glomerulus (g)
a ball of capillaries
responsible for filtration

rejoin > efferent arteriole (ea)
(in other beds, a venule)

splits > peritubular capillaries
a second capillary bed!
supply renal tissue with blood
receives compounds reabsorbed by tubule
source of compounds secreted by tubule

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13
Q

The Nephron: Tubular component
composed of?

A

epithelial cells

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14
Q

The Nephron: Tubular component

A

Bowman’s capsule (BC)
encloses glomerulus
in cortex
where filtration occurs

Proximal Convoluted Tubule (PCT)
in cortex
responsible for most reabsorption/secretion

Loop of Henle (LH)
cortex/medulla
responsible for osmotic gradient in medulla

Distal Convoluted Tubule (DCT)
in cortex
‘fine-tuning’ of solute/water reabsorption

Collecting Tubules/Ducts (CD)
in cortex/medulla
‘fine-tuning’ of urine concentration

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15
Q

Vascular and Tubular nephrons

A

peritubular capillaries

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16
Q

Bowman’s capsule and
Juxta glomerular apparatus

A

JG cells in afferent arteriole
MD in DCT
JG cells and MD form JG apparatus
regulates blood pressure and the filtration rate of the glomerulus

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17
Q

podocytes

A

found in epithelium of BC and surround capillaries (filtration)

MD - densely staining cells of DCT
detect low Na+ in DCT and can alter flow through glomerulus and water volume (fine tuning)

JG cells (afferent arteriole) –
responsible for releasing hormones (Renin) that control how much water is reabsorbed (fine tuning)
Can also control filtration rate

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18
Q

Roles of Kidneys

A

Excretion of waste products (eg urea) / foreign compounds (eg drugs)

Long term control of blood pressure
Via regulation of H2O and electrolytes

Homeostatic regulation of pH/
Long term acid/base balance (H+ and bicarbonate HCO3)

Production of hormones
Control of RBC number via erythropoietin
Production of/conversion to active form of Vit D

Important to regulate H2O because of…
‘volume’ effects ↔ osmotic/hydrostatic forces
Circa 40 L H2O in ‘average’ body

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19
Q

fluid compartments mean

A

water can move between different compartments

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20
Q

what are the fluid compartment barriers

A
  • cell membrane
    Very thin
    Little barrier to H2O movement
    Barrier to solute movement
  • Capillary wall (Interstitial fluid ↔ plasma)
    Thin
    Variable barrier to H2O movement
    Little barrier to solute movement (except protein)
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21
Q

fluid moevments (ml/min) = Dynamic equilibrium

A

Renal adjustment of plasma composition affects other compartments
Renal adjustment of plasma volume affects blood pressure

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22
Q

Link between H2O & solutes

A

Water regn through solute regn
‘Most important’ solute is Na+
Moved via Na-pump
Molecular mechanism
Energy-consuming (ie ATP)
‘Up’ concentration gradient

There is no equivalent molecular H2O pump
H2O only ever moves via osmotic & hydrostatic forces
ie pumping of heart or osmotic effects of Na-pump

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23
Q

What are the Implications for Renal Function?

A

1) Need to maintain solute/H2O balance in body
2) Filtration into nephrons
3) Reabsorption back into peritubular capillaries

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24
Q

renal function = 1) Need to maintain solute/H2O balance in body

A

Intake is ‘unpredictable’

Therefore need both hypertonic and hypotonic urine ( hypertonic sol - greater conc of solutes than another etc)

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25
Q

renal function = 2) Filtration into nephrons

A

125 ml/min (180 L/day, 60x plasma vol)

Protein-free plasma

Topologically on surface of body

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26
Q

renal function = 3) Reabsorption back into peritubular capillaries

A

Major task is to reabsorb most of 180 L/day
-(Secretion is important, but fairly minor in comparison)

Circa 99% fluid reabsorbed
-H2O only ever moves via osmotic & hydrostatic forces
-Renal relies on osmotic forces

27
Q

Basic Renal Processes

A

a) filtration
b) secretion
c) reabsorption

Excreted = Filtered + Secreted - Reabsorbed

AA: Afferent arteriole
GC: Glomerular capillaries
EA: Efferent arteriole
PC: Peritubular capillaries
BC: Bowman’s capsule
T: Kidney Tubule

28
Q

How is Urine Formed?

A

FILTRATION
Passive ultrafiltration at Bowmans Capsule

ACTIVE TRANSPORT (resorption and secretion)
Energy driven retrieval of valuable substances along nephron

OSMOSIS (resorption)
Mainly in Loop PCT+ Collecting duct

29
Q

Recap: Renal Processes
write it out remember

A

Filtration (BC)
Mass movement of water and solutes from plasma to the renal tubule
Depends on Glomerular capillary pressure

Reabsorption
Movement of water and solutes from the tubule back into the plasma

Secretion
Secretion of additional substances into the tubular fluid

Excretion: Components of urine
amount excreted = amount filtered - amount reabsorbed + amount secreted

30
Q

What is the structure of renal corpuscle?

A

combination of glomerulus and Bowman’s capsule

31
Q

What happens in renal corpuscle?

A

Filtration takes place in the renal corpuscle
Epithelium around glomerular capillaries -modified into podocytes

32
Q

Filtration

A

Movement a balance between osmotic/hydrostatic forces

Filtered substances pass through endothelial pores and filtration slits.

33
Q

What are the barriers that are involved in filtration?

A

Glomerular capillary basement membrane

Basal lamina/membrane

Bowmans capsule epithelia (podocytes)

34
Q

Filtering membrane:
1) Endothelial layer what are they?

A

flat cells - fenestrated cytoplasm

cytoplasmic pores (0.9u)

35
Q

Filtering membrane:
2) Basement Membrane

A

Muco-polysaccharide 800A thick (only intact membrane in filter surface)

36
Q

podocytes

A

highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule

split pores 70A
Pedicels
Tubule

37
Q

(vol of fluid/ unit time) Filtration??

A

GFR high 125 ml/min (vol of fluid /unit time )
1/5 plasma filtered into BC (4/5 plasma, proteins, cells PTC)

Lumen of efferent arteriole smaller than afferent

38
Q

Capillary Pressure Causes Filtration > net pressure and flow into ______

A

tubule

39
Q

which components retained in plasma (NOT filtered)?

A

Cells: Fenestrations in capillary wall
Proteins: Basement lamina membrane ‘-’ charged, proteins also ‘-’charged –like charges repel
Size (> 7nm 40KDa excluded AND charge)

40
Q

Hematuria

A

Red blood cells in urine
not Normal

Sign of damage (to barrier)

Maybe from outside or inside kidney

41
Q

Hematuria - outside

A

Kidney stones, tumours (renal pelvis, ureter, urinary bladder, prostate, urethra)

UTI (inflammation of urinary bladder, urethra, prostate)

May also get WBC in urine

42
Q

Hematuria - inside

A

Inflammation of glomeruli (eg glomeruli nephritis) – affects filtration
Infarct – necrosis of kidney

43
Q

Proteinuria

A

Protein in urine

Very little protein found in the urine of healthy people

44
Q

Tubular Re-absorption

A

180/day liters fluid filtered into the tubules

Only about 1.5/2 liters excreted
>99% of fluid entering the tubules must be reabsorbed into the blood

Most takes place in the LH (fluid)/
proximal tubule (solutes)

Some in the distal segments of nephrons (fine tuning)

Re-absorption may be Active or Passive
Water regn through solute (Na) regn

45
Q

PCT: Reabsorption of Na+

A
  1. Movement of Na
  2. Facilliated diffusion (concentration gradient)
    Active transport of Na into interstitial space
    Na/k pump (k can diffuse out of cell)
  3. Diffuse into PTCap

[role of ATP - active transport]

46
Q

Reabsorption in the PCT

A

Reabsorption of most solutes is linked to the diffusion of Na +

Carrier molecules for other molecules that co-transported

Each carrier molecules binds specifically to that substances to be transported and to Na+

Move with Na + into tubule cell

As solutes are transported out of the lumen, through proximal convoluted tubule cells, into the interstitial fluid, water follows by osmosis

volume has been reduced by approximately 65%.

47
Q

Reabsorption: Can Reach Saturation

A

Glucose co-transported with Na+

Uses specific transporters

Finite number of these

Tubular load glucose normally < transport maximum

All glucose reabsorbed – not excreted

But if excess load then not all glucose reabsorbed and some excreted

48
Q

What is Secretion?
How is it efficient?

A

Transfer of molecules from extracellular fluid into the nephron

Metabolites produced in the body / substances brought into the body / or xenobiotics ( eg drugs)

Make excretion is even more efficient

Depends mostly on membrane transport systems

49
Q

What is the Loop of Henle?

A

makes the centre of the kidney v concentrates
(bottom is the most concentrated = the hook [bachdro])

50
Q

Loop of henle - breakdown

A

Cortical (80%) and Juxtamedullary (20%) Nephrons

Juxtamedullary nephrons: hypertonic medulla

Vasa recta: counter current

Long peritubular capillaries that dip into the medulla
Blood flow in the vasa recta moves in the opposite direction from filtrate flow in the loops of Henle

[hypertonic environment in medulla]

51
Q

What does the loop of henle absorb?

A

Further resorption of NaCl and H2O by
COUNTERCURRENT MULTIPLIER
Descending Loop
Permeable to water

Ascending Loop
Impermeable to water
Actively transports Na+ into interstitial space followed by Cl-

52
Q

Osmotic gradients in medulla

A

Descending limb: Filtrate becomes more concentrated as it loses water

Ascending limb: pumps out ions, filtrate

53
Q

What is the ascending loop responsible for?

A

Multiply the concentrations of Na+ deep in the medulla
(hypertonic, high concentration of solutes)

54
Q

What does the vasa recta do?

A

The blood in the vasa recta removes water leaving the loop of Henle

55
Q

Fine-tuning’ urine osmolarity (DCT and CD)

A

Hormonal mechanisms
Renin-angiotensis-aldosterone (RAAS) mechanisms
Antidiuretic hormone (ADH) mechanism
Atrial naturetic peptide (ANP) mechanisms

RAAS and ANP: more sensitive to changes in BP
ADH: more sensitive to blood concentration

56
Q

Fine-tuning’ under hormonal control = Low BP

A

Angiotensin (RAAS)

Macula Densa cells senses low Na in filtrate in dct

JG cells also detect reduced stretch in afferent arteriole
- Renin release from kidney (from JGC)

Converts angiotensinogen (found in plasma) into angiotensin I

ACE (pulmonary capillaries) converts angiotensin I into angiotensin II

Angiotensin II: vasoconstrictor
- Increases TPR

Stimulates release of aldosterone (and thirst)

57
Q

Fine-tuning’ under hormonal control
Low BP
Aldosterone =

A

Steroid hormone / Released from adrenal cortex

Travels to DCT and CD

Bind to receptors

Stimulates Na+ reabsorption from CD into capillaries

Cl- co-transported

Water follows

Increases Blood volume

Increases BP

58
Q

Fine-tuning’ under hormonal control: Low BP or increased solutes in blood

A

Normally dct and collecting ducts impermeable to water

59
Q

What is ADH released by?

A

Released from posterior pituitary
Release sensitive to…

Osmoreceptors (hypothalamus) –
sense when body fluids become concentrated

60
Q

Volume stretch receptors (right atrium) (decrease) which causes ________ osmolarity

A

HIGH or low blood pressure cause vasopressin (ADH) release

61
Q

What happens if ADH is released?

A

Increases permeability of dct and collecting ducts to water

Increases reabsorption in collecting ducts
- Small volume concentrated urine

62
Q

Atrial Natriuretic Peptide (ANP) Opposite effect: Na+ excretion increased

A

ANP Released from right atrium when blood volume increases

Leads to increased loss/excretion of Na+

Decreases Na+ reabsorption
- Na + remains in tubules

Water moves towards Na +

Increases Urine volume while reducing blood volume and BP
- Can inhibit ADH

63
Q

Proteinuria

A

CHARGE, SIZE

Albumin slightly < 7nm (urine minute amounts)

Some protein hormones smaller but actively reabsorbed

V little protein found in the urine of healthy people

Haemoglobin smaller than albumin
V little passes from blood to filtrate

PMP-101 (53 decks)

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