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N542 Physiology > Renal > Flashcards

Renal Flashcards

0
Q

Where in the body is fluid excreted? Where is fluid absorbed?

A

Excreted from lungs (exhale), skin (sweat), bowel, urinary tract (largest volume excreted)
Absorbed in kidneys

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1
Q

How much of the body is intracellular vs extracellular fluid in adults and how is it different in infants?

A

Adults have 2/3 intracellular, 1/3 extracellular

Infants have more extracellular

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2
Q

What triggers thirst?

A

Increased extracellular fluid (osmolality)

Decreased blood volume

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3
Q

Hydrostatic vs Oncotic pressure

A

Hydrostatic: pressure created by fluid in a space (increased volume will increase pressure)
Oncotic pressure: concentration of solutes creating pressure (from high to low concentration)

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4
Q

How is fluid distributed between interstitial and intracellular?

A

Osmosis, water flows toward higher osmolality, solutes can’t cross semipermeable membrane

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5
Q

ADH: where is it synthesized, where is it secreted?

A

Synthesized by hypothalamus

Secreted from posterior pituitary

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6
Q

What factors cause an increase in ADH release?

A

Increased osmolality of ECF, decreased fluid volume, pain, nausea, stressors

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7
Q

Where is aldosterone synthesized and secreted?

A

Adrenal cortex

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8
Q

What are the major stimulaters for release of aldosterone?

A

Angiotensin 2 (activated by decreased blood volume) and increased concentration of potassium ions in plasma

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9
Q

What causes ANP to be released vs. BNP to be released?

A

ANP: secreted from cells in heart when atria are stretched (increased pressure)
BNP: released from ventricular cells when ventricular diastolic pressure increases (heart failure)

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10
Q

How do Natriuretic peptides work?

A

Cause natriuresis (put sodium in the urine, to be excreted), then water follows sodium

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11
Q

What is the relationship between aldosterone and natriuretic peptides?

A

NPs appose aldosterone, but aldosterone is stronger

Aldosterone holds on to sodium, NPs put sodium in the urine to be excreted

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12
Q

What are two factors that urine volume is highly dependent on?

A

Adequate blood pressure (perfusion of kidneys) and glomerular filtration rate (GFR)

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13
Q

How does the bicarbonate buffer system work?

A

When the body gets too acidic, bicarb ions take up H ions so that carbonic acid can be released by the lungs as CO2
When the body gets too alkaline, bicarb buffer releases H ions

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14
Q

In a normal pH, is there more bicarb ions or carbonic acid?

A

More bicarb ions (20:1)

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15
Q

What is the first, second, and third defense against acid-base imbalance in the body?

A

First: Bicarb buffer system
Second: Respiratory compensation
Third: Metabolic compensation

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16
Q

How does the respiratory system defend against acid-base imbalance?

A

Chemoreceptors sense PaCO2 and pH, then a change in rate and depth of respiration can cause more/less CO2 to be excreted from the lungs (sense of increased PaCO2, resp will hyperventilate)
This will compensate (NOT correct) pH imbalance

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17
Q

Kidneys can excrete any acid from the body except for which acid? What is the significance of this (correct vs. compensate)?

A

Carbonic acid, excreted by the lungs. This is why the kidneys can “correct” for all other imbalances of metabolic acids, and only “compensate” for imbalance of carbonic acid.

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18
Q

How do the kidneys work to compensate for acid-base imbalances?

A

Bicarb can be recycled or excreted (used as a buffer). HPO4 can pick up the H from carbonic acid, making H2PO4 and the bicarb is excreted. Instead of excreting new bicarb, the H can be recycled and added to a new bicarb, making carbonic acid again
Ammonia can pick up an H and become ammonium, which can be peed out (this gets rid of acid.. otherwise, acid is kept if blood is too alkaline)
Note: Takes several days to work

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19
Q

What are the renal functions?

A

Maintain fluid and electrolyte homeostasis, excrete wastes, it goes through about 7 L of fluid/hour, reabsorbs about 99% (mostly in proximal convoluted tubule)

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20
Q

What exocrine functions does the renal system have?

A

Production of erythropoetin, activation of vitamin D (facilitates absorption of calcium in GI system)

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21
Q

What is the anatomical pathway from renal artery to glomerulus to vein?

A

Renal artery -> interlobular artery -> afferent arteriole -> glomerulus -> efferent arteriole -> interlobular vein -> renal vein

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22
Q

What does the glomerulus do?

A

Filters, to make urine
The glomerulus is a capillary network, lays in Bowman’s capsule which leads to the collecting tubules (to the ureters, out of the body)
Note: Bowman’s capsule attaches directly to the proximal convoluted tubule

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23
Q

What is the detrusor muscle?

A

It is in the body of the bladder, when it sense pressure (volume of 300-500), the urge to void is created

24
Q

How does the nephron sense flow rate and content of filtrate?

A

Nephrons have a single cilium that have mechanoreceptors and chemoreceptors to sense flow rate and content of filtrate

25
Q

What are mesangial cells? What can occur if they are injured?

A

Mesangial cells are specialized smooth muscle cell in the glomerulus, they can contract (this alters surface area which can alter GFR) and secrete matrix proteins, phagocytosis, and regulate GFR
When injured, unregulated secretion can occur

26
Q

What are podocytes?

A

the visceral epithelium that wraps around the basement membrane of the capillaries, it gives the glomerulus its structure

27
Q

What part of the renal system does.. 1. filtration, 2. reabsorption, 3. secretion, 4. excretion? How do these all relate?

A

Filtration: glomerulus to proximal convoluted tubule
Reabsorption: lumen of tubule to peritubular capillary
Secretion: peritubular capillary to tubule
Excretion: to collecting duct, ureter
E = F - R + S

28
Q

What is the average GFR

A

Glomerular Filtration Rate = 125 mL/min

29
Q

What is the most important regulator of GFR and what is the range of autoregulation?

A 
Blood volume (as blood volume increases, GFR increases and extra fluid is excreted)
Autoregulation is maintained at a steady rate above 90, it drops when BP is between 60-90, and below 60 there is NO autoregulation
30
Q

How is GFR and filtered load calculated?

A

GFR = fluid filtered per time (mL/min)
Filtered load is the amount of solute filtered per time (mg/min), calculated by GFR x plasma concentration x percent filtered

31
Q

What is the job of the proximal convoluted tubule?

A

Reabsorption!! 2/3 reabsorption occurs here, the convoluted includes extra surface area in order to reabsorb

32
Q

How do the ascending and descending limbs differ in the loop of Henle?

A

Descending only passively reabsorbs water. Ascending is THICKER and IMPERMEABLE to water and contains powerful Na-K-Cl co-transporters to pump ions to the interstitium, has a lower osm. due to solutes being pumped out (makes medulla “salty”)
(descending is thinner and permeable to water, higher osm.)

33
Q

In the loop of Henle, how is urine concentrated and how is fluid reabsorbed?

A

Juxtamedullary nephrons (in the loop) concentrate urine by creating high interstitial osmolarity. Fluid that is reabsorbed is picked up by the vasa recta and returned to venous circulation

34
Q

What is the countercurrent mechanism (multiplier) of the nephron?

A

The formation of the loop of Henle creates the countercurrent mechanism. Descending limb reabsorbs water while ascending limb pumps out Na, K, and Cl. Deep into the medulla, at the bottom of the loop of Henle, solutes are trapped, increasing concentration (to 1200-1400)

35
Q

When comparing a juxtamedullary nephron to a cortical nephron, who has the longer loop of Henle?

A

Juxtamedullary nephrons have the longer loop of Henle, this allows for higher concentrations

36
Q

How is urea created and how does it relate to the difference in osmolarity near the loop of henle/ collecting duct

A

Urea is created by protein breakdown, it leaves the collecting ducts and increases osm in the interstitium

37
Q

What is the osmolarity like in the distal convoluted tubule?

A

Filtrate is hypo-osmotic (about 150) due to removal of electrolytes in the ascending loop of Henle

38
Q

Where in the kidney is the collecting duct ?

A

They come from the distal convoluted tubules and form the medullary pyramids which empty into the minor calices through the papilla to the renal pelvis

39
Q

The collecting duct has two cell types: Principal and Intercalated, what are their roles?

A

Principal cells REABSORB Na (aldosterone, via Na-K pump) and water (ADH, through aquaporin channels)
Intercalated cells SECRETE H ions (acid, via H/K exchanger) and REABSORB bicarb (via Cl/bicarb exchanger)

40
Q

Which cells can produce and secrete renin?

A

Specialized juxtaglomerular cells (they line up next to macula densa cells on the distal tubule)

41
Q

How does the macula densa mechanism work with tubuloglomerular feedback

A

Macula densa signals to the neighboring specialized juxtaglomerular cells. Increased NaCl in distal nephron inhibits renin release, decreased load promotes renin release (renin will increase sodium reabsorption)

42
Q

Besides the macula densa mechanism, what are two other ways that tubuloglomerular feedback work?

A

Baroreceptor: increased pressure in arteriole inhibits juxtaglomerular cells from releasing renin (decreased pressure promotes renin release)
Sympathetic response: Beta-1 stimulates renin release

43
Q

What are ways that the arterioles can increase/decrease GFR?

A

Afferent constriction and efferent dilation decrease GFR
Afferent dilation and efferent constriction increase GFR
Angiotensin 2 is a chemical mediator that helps with vasoconstriction, (adenosine and nitric oxide are other chemical mediators)

44
Q

How do glucose and amino acids effect filtration?

A

The greater the load of tubular glucose and amino acid, the greater the amount of sodium reabsorbed by the proximal tubule
Less sodium transported to the macula densa cells in the tubule contributes to increase GFR

45
Q

How can glucose end up in the urine, what is this referred to as?

A

This is called “renal threshold”, if the load is too much, we can’t keep up with reabsorption and glucose is peed out
SGLT2 is the specific cotransport of glucose that can get overwhelmed

46
Q

What catalyzes the reaction of H + HCO3 H2CO3

A

Carbonic anhydrase (catalyzes in both directions)

47
Q

How do the kidneys excrete acid?

A

When H is recycled and there is no bicarb for it to form carbonic acid with, it ends up getting excreted in a couple different ways..
H combines with HPO4 to be H2PO4 in the collecting duct
H combines with NH3 (ammonia) to make NH4 (ammonium)

48
Q

In the proximal convoluted tubule, what is reabsorbed and secreted? What is the tonicity in the duct?

A

Reabsorbed: NaCl (majority), glucose, K, phos, urea, protein, water
Secreted: H, anions, cations, and foreign substances
Tonicity: isotonic

49
Q

In the loop of Henle, what is the function, what is reabsorbed and secreted, and what is the tonicity?

A

Function: concentration of urine using the countercurrent mechanism
Reabsorption: descending- water (NaCl diffuses in), ascending- Na reabsorbed (keeps water in)
Secretion: urea
Tonicity: isotonic -> hypertonic -> hypotonic

50
Q

In the distal tubule, what is reabsorbed and secreted, and what is the tonicity

A

Reabsorbed: NaCl, water (ADH needed), bicarb
Secreted: K, urea, H, NH3
Tonicity: isotonic or hypotonic

51
Q

Which hormones and other factors have an effect on reabsorption? (stimulate/inhibit reabsorption)

A

Aldosterone and Angiotensin-2 stimulate reabsorption by upregulating epithelial sodium channel
ANP and urodilatin inhibit reabsorption

52
Q

Where does K move and how does it move in the renal system?

A

Na-K pump on the basolateral cell membrane (in the distal tubule, these are regulated by aldosterone, which increase K excretion)
K-H exchanger and plasma K concentration also have an effect on movement

53
Q

Name some diuretic agents and how they work

A

Osmotic diuretics: increase osmolality causing water to shift into the tubule
ACE inhibitors
Loop diuretics block Na-K-Cl pumps in ascending loop of henle
Thiazide: block sodium reabsorption

54
Q

Which diuretic agents are potassium wasting, which are potassium sparing?

A

K wasting: osmotic, ACE inhibitors, loop diuretics and thiazide
K sparing: Aldosterone-blocking agents

55
Q

How do infant’s renal system differ from an adult?

A

low GFR, can’t make concentrated urine yet (fluid is lost easily)

56
Q

How does the renal system in the elderly differ from the adult?

A

After 40, kidneys start to decrease in size, nephrons are lost, renal blood flow is less, decrease in GFR, more susceptible to fluid/electrolyte imbalance and renal damage

57
Q

What are the 3 main steroid hormones that the adrenal cortex produces?

A

S- (Salt) Mineralocorticoids such as aldosterone
E- (Energy) Glucocorticoids such as cortisol
X- (seX) Androgens

N542 Physiology (9 decks)

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