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Physiology > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What is the primary renal function?

A

Regulate our blood volume and pressure

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2
Q

Gluconeogenesis

A

The synthesis of new glucose molecules to provide energy

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3
Q

The kidney hormone secretions (3)

A
  1. Erythropoietin (EPO)
  2. Renin
  3. 1,25-dihydroxyvitamin D, an active metabolite of Vitamin D
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4
Q

The body fluids regulated by the kidney

A

The extracellular fluids: plasma, interstitial fluid, and the cerebrospinal fluid

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5
Q

Aquaporins

A

Specialized water-selective channels in the plasma membrane of cells that are responsible for the rapid diffusion of water

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6
Q

Osmotic pressure

A

The pressure necessary to prevent solvent movement (osmosis)

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7
Q

Tonicity

A
  • determined by the concentration of non-penetrating solutes of an extracellular solution
  • the non-penetrating solutes may influence changes in cell volume
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8
Q

The classes of tonicity

A
  1. Isotonic: same osmolarity inside and outside of cell, no change in cell shape
  2. Hypertonic: extracellular medium has higher osmolarity (higher solutes), so cell will shrink
  3. Hypotonic: extracellular has lower osmolarity, so cell will swell
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9
Q

What is the normal osmolarity inside a cell

A

300 milliosmoles

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10
Q

Hydrostatic pressure

A

The pressure exerted by a fluid (found in every fluid), which pushes a fluid out

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11
Q

The starling forces

A
  • the forces that determine the net pressure and direction of fluid movement
  • The capillary hydrostatic pressure + osmotic force due to interstitial fluid proteins - interstitial fluid hydrostatic pressure - osmotic force due to plasma protein concentration
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12
Q

What is the location of the kidneys

A

Retroperitoneal (back of peritonea)

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13
Q

Hilum

A
  • The inner concave part of the kidney
  • area where arteries start branching in the kidney
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14
Q

Micturition

A

The process of releasing urine outside the body. Aka urination

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15
Q

What is the functional unit of the kidney

A

Nephron (where the urine is made)

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16
Q

Parts of a nephron

A
  1. Renal Corpuscle: Glomerulus (capillary loops), Bowman’s capsule (cup that capillaries sit in)
  2. Renal tubule: proximal convoluted tubule, loops of henle (descending and ascending limbs), distal convoluted tubule, collecting ducts
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17
Q

Podocytes

A
  • Cells closest to which come in contact with the glomerulus capillaries
  • interlocking foot like processes with each other
  • filtration slits are found between the interlocking foot processes
  • foot processes magnify surface area for filtration
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18
Q

Types of nephrons

A
  • renal corpuscles are always found in the cortex
    1. Cortical (85%): Only portions of the Loop of henle are found in the medulla, but mostly in the cortex
    2. Juxtamedullary (15%): Loop of henle and ascending limb are found in the renal medulla. They also regulate the concentration of urine (create osmotic gradients)
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19
Q

Peritubular capillaries

A

Efferent arterioles that were branched off from from glomerulus and settle around the proximal convoluted tubules

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20
Q

Vasa recta

A
  • Capillaries that are found associated with juxtamedullary nephrons in the medullary portion of the kidney
  • important for osmotic gradient
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21
Q

What proteins make up the podocyte semiporous membranes?

A
  1. Nephrins
  2. Podocins
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22
Q

Ultrafiltrate

A
  • The cell-free fluid that has come into Bowman’s space and contains mostly all the substances at the same concentrations as in the plasma
  • The concentration of a substrate filtered through the filtration layers is the same in the plasma and in the filtrate
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23
Q

Proteinuria

A
  • a condition where some of the proteins that are not supposed to pass through the filtration barrier show up in the filtrate and ultimately in the urine
  • does not occur under normal healthy conditions
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24
Q

Glomerular capillary hydrostatic pressure

A
  • Hydrostatic pressure of the blood that is found in the glomerular capillary
  • 60mmHG
  • Pressure that pushes fluid into Bowman’s space
  • favors filtration
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25
Q

Bowman’s space hydrostatic pressure

A
  • fluid pressure in Bowman’s space
  • 15mmHg
  • opposes filtration
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26
Q

Osmotic force due to proteins in plasma

A
  • due to proteins that are present in plasma
  • they act as solute in the capillaries
  • 29mmHg
  • opposes filtration
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27
Q

Filtration fractions

A
  • only 20% of plasma volume is filtered into Bowman’s space
  • 80% goes to the peritubular capillaries
  • 19% of filtered fluid is reabsorbed and enters the peritubular capillaries
  • less than 1% of volume is excreted
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28
Q

What is the healthy number of the glomerular filtration rate?

A

125mL/minute or 180L/day

29
Q

Autoregulation

A
  • Regulated changes in the myogenic reflex as well as by tubulorglomerular effect
  • ensures that that glomerular filtration rate doesn’t change drastically and remains constant
  • Glomerular filtration rate can remain constant from blood pressures f 80mmHg to 180mmHg
30
Q

How is the GFR (glomerular filtration rate) regulated?

A
  1. myogenic response (constrict/dilate arteries)
  2. Hormone/neurotransmitter from autonomic neurons
  3. Tubular glomerular feedback: juxtaglomerular apparatus has tubuloglomerular feedback that controls the autoregulation and affects GFR
31
Q

Juxtaglomerular apparatus

A
  • specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole
  • found next to glomerular
32
Q

The cell types that control the glomerular filtration rate

A
  1. Macula densa: cells on wall of distal tubule at the junction where the ascending limb is beginning to form the distal tubule. They sense an increase in sodium load and increased flow of fluid through the distal tubule. They secrete vasoactive compounds and released adenosine (a paracrine factor) that affects arteriol resistance. Part of the juxtaglomerular apparatus.
  2. Juxtaglomerular cells: granular cells that sit on top of the afferent arteriole. Innervated by sympathetic nerve to change resistsance. Release Renin to control resistance. Part of the JGA
  3. Mesangial cells: found in the triangular region between the afferent and efferent artrioles. Contraction of these cells reduces the surface area of the glomerular capillaries, decreased the filtration rate. Not part of the JGA.
33
Q

Filtered load

A
  • the amount of substance that is filtered by the kidney per day through Bowman’s space
  • calculated by multiplying the GFR by the concentration of the substance in the plasma
  • for glucose, it is 180g/day (same as GFR)
34
Q

Which part does the secretion?

A

periitubular capillaries

35
Q

Body handling of inulin, creatinine, electrolytes, glucose and amino acids, organic acids and bases

A
  1. Inulin (polysaccharide in some plants and veggies): filtration only
  2. Creatinine: filtered only
  3. Electrolytes: Filtered and partially reabsorbed
  4. Glucose and amino acids: filtered and completely reabsorbed
  5. Organic acids and bases: filtered and secreted (completely excreted). PAH (para-aminohippuric acid) is an organic acid that is used to clinically measure renal plasma flow
36
Q

The 2 pathways of reabsorption

A
  1. Diffusion through the tight junctions (paracellular transport)
  2. Mediated transport (transepithelial transport). Major component.
37
Q

Which part does the reabsoption?

A

Proximal tubule

38
Q

Transport maximum

A

The limit of substance that can be transported per unit time as binding sites of transport proteins become saturated

39
Q

What is the glucose renal threshold

A

300mg/100mL (beyond this value, glucose shows up on the urine since the transport maximum is reached)

40
Q

Diabetes mellitus

A
  • capacity to reabsorb glucose is normal, but filtered load is greatly increased and is beyond the threshold for reabsorption
  • this is due to insulin not working correctly, but everything else is functioning normally
41
Q

Renal glucosuria

A
  • Benign glucosuria or familial renal glucosuria
  • genetic mutation of the Na+/glucose cotransporter (SGLT) that result in the inability to transport glucose from the luminal side and across to the peritubular capillaries
42
Q

What is urea reabsorption dependent upon?

A

Dependent on water reabsorption

43
Q

What are the most common tubular secretions?

A

H+, K+, penicillin, choline, creatinine

44
Q

Renal Clearance

A
  • A way of quantifying how well the kindeys are functioning
  • looks at how well kidneys are removing substances
  • measures the volume of plasma from which a substance is completely removed from the kidney per unit time
  • measured as: amount or mass of substance X excreted per unit of time divided by the plasma concentration
45
Q

What is used to measure clearance?

A

Inulin (7.5litres/hour or 180L/day, equal to the GFR)

46
Q

Which cells is K+ secreted by?

A

Distal and collecting duct cells

47
Q

What is water reabsorption dependent on?

A

Dependent on Na+ reabsorption (the osmotic gradient set up by Na+)

48
Q

Which hormone regulates water reabsorption?

A

Vasopressin or ADH, which regulates aquaporins in the collecting ducts

49
Q

What is the highest osmotic gradient in the tubules?

A

1400 milliosmoles found at the bottom of the Loop of Henle hairpin loop

50
Q

How much of Urea is actually excreted?

A

15% of the original amount

51
Q

Diuresis

A

Void/produce a large amount of urine from absence of ADH in the collecting ducts

52
Q

Antidiuresis

A

Reduction or suppression of the excretion of a large volume of urine

53
Q

Where is ADH/Vasopressin made?

A

Hypothalamus in the Supraoptic nucleus (SON) (sensors of osmolarity)

54
Q

What does ADH regulate

A

The insertion of AQP2 in the luminal side of the collecting ducts vis AQP 2 gene transcription

55
Q

Diabetes Insipidus and its types

A
  • associated with large quantities of urine
    1. Central diabetes insipidus: failure to release the ADH from the posterior pituitary
    2. Nephrogenic diabetes insipidus: ADH is secreted in a normal matter but the hormone does not function properly. Problem with the receptor or intracellular signaling pathway or problems within the cells of the nephron
56
Q

Types of diuresis

A
  1. Water: only excess water is secreted without excess solute in the urine
  2. Osmotic: Excess solute in urine which is associated with high levels of water secretion. This is uncontrolled diabetes mellitus
57
Q

Regulating low Na+ in the plasma

A
  1. Short term: baroreceptors regulate GFR
  2. Long term: aldosterone promotes sodium reabsorption. Renin, angiotensin 2 needed for aldosterone secretion
58
Q

Regulating high Na+ levels in the plasma

A
  • Atrial natriuretic peptide (ANP) secreted by cardiac atria
  • ANP regulates GFR and inhibits Na+ reabsorption
  • ANP also inhibits aldosterone
  • Stimulated by most importantly, atrial distension due to increased blood volume in response to increased sodium concentration
59
Q

Where is Aldosterone secreted from?

A

Adrenal cortex

60
Q

What does Aldosterone act on?

A

Acts on the cells of the distal tubule and the cortical collecting ducts to increase Na+ regulation

61
Q

What drug is used to manage high blood pressure?

A
  • ACE inhibitor
  • blocks the ACE enzyme that converts angiotensin 1 to angiotensin 2, which stimulates aldosterone secretion which increases Na+ reabsorption
  • this decreases Na+ reabsorption and lowers blood pressure
62
Q

What is the most important trigger for the release of aldosterone?

A
  • The renin-angiotensin mechanism, which is initiated in response to:
    1. Sympathetic stimulation of renal nerves
    2. decrease in filtrate osmolarity
    3. Decreased blood pressure
63
Q

Where is potassium mostly reabsorbed?

A

Proximal tubule + loop of Henle

64
Q

Where is K+ concentration regulated?

A

Cortical collecting ducts

65
Q

Hyperkalemia

A

Excess K+ in the blood

66
Q

What is aldosterone secretion directly and indirectly sensitive to?

A
  • directly: extracellular K+ levels
  • indirectly: Na+ levels monitored by renin
67
Q

Types pf buffers

A
  1. Extracellular: Bicarbonate (CO2/HCO3-)
  2. Intracellular: phosphate ions and associated proteins (like hemoglobin)
68
Q

What is the ultimate balancer of pH?

A

The kidneys. They play a long-term role.

Physiology (6 decks)

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