UNIT 2 - Lecture 1: Kidney Review Flashcards by Bianca Zayas

What are the 6 main functions of the kidney?

Endocrine functions
Elimination of waste
Electrolyte balance
Acid-base balance
Conservation of nutrients
Water balance

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What 5 hormones are produced by the kidney?

EPO
Active Vit D (calcitriol)
Prostaglandins
Renin
Aldosterone

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EPO production increases with _____ leading to stimulation of _____.

hypoxia, erythropoiesis

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How does the kidney make active Vit D (calcitriol)?

It is converted from inactive Vit D (calcidiol)

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What spp lacks the enzyme required for conversion from inactive to active Vit D? What does this result in?

horses; results in Ca absorption being dependent on the amt of dietary Ca and not on Vit D

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What effect does PTH have on production of calcitriol?

It increases it

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Calcitriol _____ intestinal and renal absorption of Ca²⁺ and phosphate and promotes Ca²⁺ and phosphate release from _____.

increases, the bone

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What are prostaglandins?

Vasodilators important in maintaining renal medullary blood flow

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Admin of _____ inhibit renal prostaglandin production –> can result in medullary _____ and kidney damage.

NSAIDs, hypoxia

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What is the main stimulus for renin secretion?

Hypoperfusion of the kidney and decreased Cl^-

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Renin converts _____ –> _____

angiotensin I, angiotensin II

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What are 2 main actions of angiotensin II?

Vasoconstriction –> increased BP
Increased Na⁺ and H₂O retention to expand plasma volume

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What inhibits renin?

Atrial natriuretic peptide (ANP)

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What does aldosterone do?

Promotes Na+ retention and K+ excretion to enhance water retention

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T/F: Aldosterone promotes acid excretion

True

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What stimulates aldosterone?

Angiotensin II, hyperkalemia, ACTH

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What inhibits aldosterone?

Dopamine and ANP

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ADH is a hormone that _____ on the kidney and is not _____ by it.

acts, produced

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What is another name for ADH?

vasopressin

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What stimulates ADH release?

Dehydration (increases plasma osmolality)

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ADH acts on _____ tubular epithelial cells –> _____ water –> _____ urine

collecting, resorb, concentrate

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What are 2 endogenous wastes the kidney produces?

Nitrogenous and Creatinine

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What exogenous wastes does the kidney produce?

Drugs and metabolites

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Nitrogenous wastes are formed from _____.

protein catabolism

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Where is creatinine produced and from what?

In muscle from creatine

Where is creatinine filtered and how easily?

Freely by the glomerulus (is not resorbed)

What electrolytes does the kidney balance?

Na, Cl, K, Ca, P, Mg

What plasma analytes are conserved by the kidney?

Water, glucose, AAs and proteins, Na, Cl, bicarbonate, Ca, Mg

What plasma analytes are excreted by the kidney?

Urea, creatinine, ammonia, phosphates, K, H+, lactate, ketones, bilirubin, hemoglobin, myoglobin

How is urine concentration or dilution assessed?

with a urine specific gravity (USG)

What is urine concentration?

Formation of urine hyperosmotic compared to plasma

What is urine dilution?

Formation of urine hypoosmotic compared to plasma

What 2 things does urine concentration and dilution require (in functional tubules)?

1. Countercurrent mechanism 2. Concentration gradient and ADH

What are the 3 requirements for the kidney to make concentrated urine?

1. ADH 2. Epithelial cells of the distal nephron must be *responsive* to ADH 3. Must have a concentration gradient

For the kidney to make concentrated urine, osmolality of interstitial fluid of renal medulla must be _____ osmolality of fluid in the tubules.

greater than

What 2 things does the kidney require to make diluted urine?

1. Na+ and Cl- must be delivered to the loop of Henle 2. Very little to no water removed from tubular fluid by distal nephron

What is osmolality?

Measure of dissolved particles in a fluid

What is isosthenuria and what are the USG parameters?

Urine osmolality ~= plasma osmolality USG 1.007-1.013

What is hyposthenuria and what are the USG parameters?

Urine osmolality \< plasma osmolality (urine is diluted) USG = \< 1.007

What is hypersthenuria and what are the USG parameters?

Urine osmolality \> isosthenuric values (urine is concentrated) USG = \>1.013

What are the 3 main processes controlling renal excretion of H2O and solutes?

1. Glomerular filtration (passive) 2. Tubular resorption (active and passive) 3. Tubular secretion (active and passive)

What are the 3 components of the glomerular filtration barrier?

1. Capillary endothelium 2. Basement membrane 3. Glomerular epithelial cells (podocytes)

Glomerular filtration is the major route for _____ and _____ excretion.

solute, water

Passage thru healthy glomerular filtration barrier depends on _____ and \_\_\_\_\_.

molecular size, electrical charge

What is GFR?

Rate that fluid moves from plasma to glomerular filtrate

Why is albumin not seen in urine in large amounts?

It is too big too pass and is negatively charged

What spp can have small amounts of albumin in the urine in health?

dogs

What is the flow of urine?

Glomerulus --\> proximal tubule --\> loop of Henle --\> distal tubule --\> collecting tubule --\> collecting duct --\> urine

Glomerular filtration is \_\_\_\_\_-selective while tubular reabsorption is \_\_\_\_\_-selective.

non, highly

What is the path of molecules that are reabsorbed in the kidney?

Substance transported thru tubular epithelial membrane --\> renal interstitial fluid --\> peritubular capillary membrane --\> blood

\_\_\_% of water is passively resorbed in the proximal tubule.

~75%

What molecules are resorbed in the proximal tubules?

Small hydrophilic molecules (electrolytes and minerals)

Most _____ is conserved in the proximal tubule.

bicarbonate

The proximal tubule is the site of action for \_\_\_\_\_.

angiotensin II

The loop of Henle is the site of action for \_\_\_\_\_.

furosemide

In the descending loop of Henle, \_\_\_, \_\_\_, and ___ are secreted into ultrafiltrate while ___ is passively absorbed.

Na, Cl, urea, water

In the ascending loop of Henle, \_\_\_, \_\_\_, \_\_\_, \_\_\_, and ___ are resorbed while ___ is not.

Cl, Na, K, Ca, Mg, water

The ascending loop of Henle is impermeable to \_\_\_\_\_.

water

What is the juxtaglomerular complex and where is it found?

Feedback control of GFR and blood flow; in the distal tubule

The JGC absorbs most ions including \_\_\_, \_\_\_, and ___ while it is virtually impermeable to ___ and \_\_\_.

Na, K, Cl, water, urea

The distal tubule is the site of action for \_\_\_\_\_.

thiazide diuretics

The collecting tubule resorbs \_\_\_% water and Na.

\<10%

What controls water resorption in the collecting tubule?

ADH