15- Renal Phys (Kruse & Pierce) Flashcards by Staci Thomas

What is the basic unit of structure in the kidney?

Nephron

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A ________ is used separate to water, ions and small molecules from the blood, filter out wastes and toxins, and facilitates the concentration of urine.

Nephron

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Each nephron contains a tuft of glomerular capillaries called the _________.

Glomerulus

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Glomerular capillaries are covered by epithelial cells and are encased in ________ ________. Large amounts of fluid are filtered from the blood here.

Bowman’s Capsule

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Fluid filtered from the glomerular capillaries flows into Bowman’s Capsules and then into the ________ ________.

Proximal Tubule

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What is actively reabsorbed in the Proximal Tubule (convoluted and straight)?

85% sodium bicarbonate (NaHCO3)
65% sodium chloride (NaCl)
65% potassium (K+)
100% glucose and amino acids

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What is passively reabsorbed in the Proximal Tubule (convoluted and straight)?

Water

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In the Proximal Tubule (convoluted and straight) uses the _________ to maintain low intracellular Na+ concentrations.

Na+/K+ ATPase

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This is an enzyme in the Proximal Tubule that catalyzes the formation/dehydration of carbonic acid.

Carbonic Anhydrase

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In the proximal tubule, acid and base secretory systems secrete drugs into the ________ from the blood (i.e., diuretics, NSAIDs, antibiotics).

Lumen

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What is the Thin Descending Loop of Henle responsible for?

Water reabsorption

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The (THICK/THIN) Ascending Loop of Henle is relatively impermeable to water, and other ions/solutes.

Thin

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What are the main functions of the Thick Ascending Limb?

Impermeable to water
25% sodium reabsorption
Na+/K+/2Cl- Cotransporter (NKCC2)
Reabsorption of cations

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In the Thick Ascending Limb, this is what establishes the ion concentration gradient in the interstitium.

NKCC2

***Na+/K+/2Cl- Cotransporter

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In the Thick Ascending Limb, there is an increase in ______ concentration in the cells that causes back diffusion of ______ into the tubular lumen. This allows a lumen-positive electrical potential to drive reabsorption of cations (Mg2+, Ca2+) via the paracellular pathway.

K+

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Tubular fluid is (DILUTE/CONCENTRATED) in the descending limb and (DILUTE/CONCENTRATED) in the ascending limb.

Concentrated

Dilute

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What are the main functions of the Distal Convoluted Tubule?

10% NaCl reabsorbed
Relatively impermeable to water
Na+/Cl- Cotransporter (NCC)
Ca2+ passively reabsorbed by Calcium channels

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In the Distal Convoluted Tubule, this actively transports NaCl out of the lumen.

NCC

***Na+/Cl- Cotransporter

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In the Distal Convoluted Tubule, Ca2+ is passively reabsorbed by Calcium channels. What is this regulated by?

PTH

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In the Distal Convoluted Tubule, the result if tubular fluid is (DILUTE/CONCENTRATED).

Dilute

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In the Collecting Tubule, this is responsible for 2-5% of Na+ reabsorption. It creates an electrical gradient that facilitates K+ secretion down the concentration gradient.

Epithelial Sodium Channel (ENaC)

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This is the most important site of K+ secretion by the kidney.

Collecting Tubule

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This is the site at which all diuretic-induced changes in K+ balance occur. More Na+ delivered here will induce more K+ secretion.

Collecting Tubule

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In the Collecting Tubule, _______ _______ increase urine acidity.

Proton Pumps

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In the Collecting Tubule, this increases the expression of ENaC and basolateral Na+/K+ ATPase. This increases Na+ reabsorption and K+ secretion which leads to water retention and increase in blood volume and BP.

Aldosterone

This controls permeability of the Collecting Tubule to water by regulating the expression levels of aquaporin-2 (AQP2) water channels.

ADH (vasopressin)

What happens in the Collecting Tubule is there is no ADH?

It becomes impermeable to water and the urine is dilute.

ADH levels are controlled by serum osmolality and volume status. ________ decreases ADH release and increases urine production.

Alcohol

In the Collecting Tubule, the tubular fluid is (DILUTE/CONCENTRATED).

Concentrated

A _______ is an agent that increases urine volume, while a _______ causes an increase in renal sodium excretion.

Diuretic | Natriuretic

These increase the rate of urine flow and sodium excretion.

Diuretics

Diuretics are used to adjust the volume and/or composition of body fluids in a variety of clinical situation including (but not limited to)...

Edematous states -- Heart failure, kidney disease, renal failure, liver disease (cirrhosis) Nonedematous states -- Hypertension, nephrolithiasis (kidney stones), hypercalcemia, and diabetes insipidus

What specific membrane transport proteins do Diuretics target?

Sodium/Potassium/Chloride Transporter (loop diuretics) Sodium/Chloride Cotransporter (thiazide diuretics) Sodium channels (potassium-sparing diuretics)

What enzymes do Diuretics target?

Carbonic Anhydrase (carbonic anhydrase inhibitors)

What hormone receptors do Diuretics target?

Mineralocorticoid receptor (potassium-sparing diuretics)

This is a type of diuretic that inhibits the membrane-bound and cytoplasmic forms of Carbonic Anhydrase.

Carbonic Anhydrase Inhibitors

What occurs from Carbonic Anhydrase Inhibitors?

Decreased H+ formation inside PCT cell Decreased Na+/H+ Antiport Increased Na+ and HCO3- in lumen Increased Diuresis ***Results in increased urine pH and decreased body pH!

Carbonic Anhydrase Inhibitors result in (INCREASED/DECREASED) urine pH and (INCREASED/DECREASED) body pH.

Increased | Decreased

This type of diuretic inhibits the luminal Na+/K+/2Cl- Cotransporter (NKCC2) in the TAL of the loop of Henle.

Loop Diuretics

What occurs from Loop Diuretics?

Decreased intracellular Na+, K+, Cl- in TAL Decreased back diffusion of K+ and positive potential Decreased reabsorption of Ca2+ and Mg2+ Increased Diuresis

In _______ Diuretic, ion transport is virtually nonexistent and they are among the most efficacious diuretic available.

Loop

This type of diuretic cause inhibition of the Na+/Cl- Cotransporter (NCC) and block NaCl reabsorption in the DCT.

Thiazide Diuretics

What occurs from Thiazide Diuretics?

Increased luminal Na+ and Cl- in DCT | Increased Diuresis

In ________ Diuretics, they enhance the reabsorption of Ca2+ in both DCT and PCT. They are also the largest class of diuretic agents.

Thiazide

What are the types of K+ sparing Diuretics?

Aldosterone (Mineralocorticoid) receptor (MR) antagonists | Na+ channel (ENaC) inhibitors

With this type of K+ sparing Diuretics, there is decreased expression of ENaC which increases Na+ excretion and increases diuresis. K+ excretion is decreased. Urine pH is increased and body pH is decreased.

Aldosterone (Mineralocorticoid) receptor (MR) antagonists

With this type of K+ sparing Diuretics, there is decreased activity of ENaC, increasing Na+ excretion and increasing diuresis. K+ excretion is decreased. Urine pH is increased and body pH is decreased.

Na+ Channel (ENaC) Inhibitors

______ and ______ is secreted or reabsorbed in the late DT and cortical CD according to the needs of the body.

Na+ | K+

The most important factors that stimulate sodium reabsorption are...

- - Na+ deficiency, low Na+ diet, hyponatremia - - Na+ loss through severe diarrhea - - Angiotensin II - - Aldosterone

The most important factors that stimulate sodium secretion are...

- - Increased ECF (Na+) | - - Increased tubular flow rate

The most important factors that stimulate potassium reabsorption are...

- - K+ deficiency, low K+ diet, hypokalemia | - - K+ loss through severe diarrhea

The most important factors that stimulate potassium secretion are...

- - Increased ECF (K+) - - Aldosterone - - Increased tubular flow rate - - Na+ delivery to cortical CD

What is the most famous mechanism of ADH?

Water permeability in principal cells

During anti-diuresis, water but not _______ is reabsorbed in the cortical collecting duct. Therefore, _______ flows further through the duct and as a result is concentrated in the inner medullary collecting duct (IMCD).

Urea | Urea

High concentration of urea in the IMCD promotes a passive reabsorption down its concentration gradient from the IMCD into the _________.

Interstitium

_______ flows about the interstitium only to encounter the nearby Loop of Henle, where the concentration is lower than the interstitium, and flows again down its concentration gradient into the LOH, only to get recycled back again. This process repeats.

Urea

ADH increases permeability of NaCl at the apical membrane of thick ascending limb epithelium by increasing the presence of ________ channels. This leads to additional NaCl reabsorption, increasing osmolality of the interstitium. When combined with _______ being reabsorbed from the IMCD, the medullary interstitium becomes very concentrated.

NKCC2 | Urea

T/F. The greater the medullary hyperosmolality, the greater your urine-concentrating ability.

True

What are the 3 ADH biggies to remember?

1) Increases water permeability of principal cells of the late distal tubule and collecting ducts via insertion of aquaporin channels. 2) Increases urea permeability in the IMCD (but not cortical or OMCD). 3) Increases activity of the NKCC2 in TAL.

Medullary osmolality is due to the presence of NaCl and urea. This phenomenon is colloquially known as a _______ _______.

"Salty Medulla"

How does the interstitial gradient get established in the first place?

The salts being actively pumped out by the ascending limb of LOH makes the entire medullary interstitium salty (aka, hypertonic). Since the descending limb is only permeable to water, it's salty for a reason. It's so that water passively leaves the tubule from the descending limb of LOH. This is a major mechanism of regaining water, and the degree of medullary interstitium "saltiness" will contribute to your ability to form a concentrated urine.

This is the difference between water excretion (urine flow rate) and osmolar clearance. It's the rate the body excretes solute-free water. "Free water" means water without any solutes in it.

Free Water Clearance (CH2O)

How do we calculate Free Water Clearance?

CH2O = V - Cosm ***CH2O = V - [ (Uosm x V) / (Posm) ]

When CH2O (Free Water Clearance) is negative, what is happening?

Excess solutes are removed, there is water conservation.

When CH2O (Free Water Clearance) is positive, what is happening?

Water is being excreted, forming dilute urine. Water is in excess.

This is the total clearance of solutes from the blood. It is the volume of plasma cleared of solutes each minute, in the same way that clearance of a single substance is calculated.

Osmolar Clearance

How do we calculate Osmolar Clearance?

Cosm = (Uosm x V) / Posm ***Same equation as Renal Clearance!

This is the minimal volume of urine required to excrete was solutes needing to be excreted form the body. This volume is variable depending on daily solute excretory load and the maximum urinary concentration achievable.

Obligatory Urine Volume (OUV)

The maximal urine concentrating ability in humans is ________, which is dependent on the length of the Loop of Henle.

1200 mOsm/L

How do we calculate Obligatory Urine Volume (OUV)?

OUV = Minimum Solute Excretion per day / Max urine concentrating ability

This is the term for excretion of excessive sodium in the urine. This may be induced by a drug (natriuretic), hormone (ANP), or by significantly elevated renal perfusion pressure (pressure natriuresis).

Natriuresis

This is the term for a large urine output.

Diuresis

When the urine primarily contains water, it is referred to as a water diuresis, which is in contrast to diuresis seen with the administration of diuretic agents. In the latter, the urine output is large, but the urine contains solute plus water, which may be termed a _______ _______.

Solute Diuresis

This is when plasma ADH is high, and a small volume of concentrated urine is excreted.

Anti-diuresis

15- Renal Phys (Kruse & Pierce) Flashcards

(74 cards)