Renal Function Flashcards by pattie o.

How much does a kidney weigh?

150 g

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What are the dimensions of a kidney?

12.5 cm x 6 cm x 2.5 cm

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How long is the ureter?

25 cm

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When is the bladder nerve reflex initiated?

When 150 mL of urine accumulates

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What is the length of the urethra in women and men?

Women: 4 cm, Men: 24 cm

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How often is urine emptied into the bladder from the ureters?

Every 10-15 seconds

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How is urine classified?

Fluid kidney biopsy

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What is the basic structural and functional unit of the kidney?

Nephron

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How many nephrons are there in each kidney?

1 to 1.5 million

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What are the two types of nephrons and their functions?

Cortical: Reabsorption and excretion; Juxtamedullary: Concentration of urine

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What are the components of a nephron?

Glomerulus and renal tubules

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What is the order of urine formation?

(Go Pipay Lika Dance Cheer Red Unan Blue Unan)

Glomerulus > PCT > Loop of Henle > DCT > Collecting Duct > Calyx > Renal Pelvis > Ureter > Bladder > Urethra

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What percentage of total cardiac output do the kidneys receive?

25%

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What is the order of renal blood flow (RAGE PVR)?

Renal artery > Afferent arteriole > Glomerulus > Efferent arteriole > Peritubular capillaries > Vasa recta > Renal vein

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What is the total renal blood flow in both kidneys?

1200 mL/min
|600 per kidney|

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What is the total renal plasma flow?

600-700 mL/min

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What is the working portion of the kidney?

Glomerulus

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Where is the glomerulus located?

Bowman’s capsule

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What cells are attached to the glomerular basement membrane?

Podocytes

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What structure resembles a sieve and acts as the kidney’s working portion?

Glomerulus

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What is the molecular weight cutoff for glomerular filtration?

<70,000 kDa

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What percentage of filtered plasma is excreted in urine?

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What are the components of the glomerular filtration barrier?

Capillary endothelium, Trilayer basement membrane, Filtration diaphragm

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What are the layers of the trilayer basement membrane?

Lamina rara interna, Lamina densa, Lamina rara externa

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Where is the filtration diaphragm found?

Between the podocytes of Bowman's space

How does the glomerulus repel albumin?

Shield of negativity (repels same charge)

What is the specific gravity of glomerular filtrate?

1.010

What substances are filtered by the glomerulus?

Salts, Water, Amino acids, Glucose, Urea

What is the first kidney function affected by renal disease?

Tubular reabsorption

Question

Answer

What is the renal threshold for glucose?

160-180 mg/dL

What is the major site of reabsorption of plasma substances (65%)?

Proximal Convoluted Tubule (PCT)

Where does renal concentration begin?

Descending and ascending loop of Henle

Where is solute concentration highest in the nephron?

Loop of Henle (renal medulla)

Which part of the nephron is highly impermeable to water?

Ascending loop of Henle

What is the movement of substances across **cell membranes into the bloodstream by electrochemical energy** called?

Active transport

What is the **movement of molecules across a membrane by diffusion due to a physical gradient** called?

Passive transport

Which substances are transported via active transport? (GASS C)

Glucose, amino acids, salts, sodium, chloride

Which substances are transported via passive transport? (WUS)

Water, urea, sodium

Where does active transport occur for glucose, amino acids, and salts?

Proximal Convoluted Tubule (PCT)

Where does active transport occur for sodium?

Proximal and Distal Convoluted Tubules (PCT and DCT)

Where does active transport occur for chloride?

Ascending loop of Henle

Where does passive transport of water occur?

PCT, descending loop of Henle, and collecting duct (CD)

Where does passive transport of urea occur?

PCT and ascending loop of Henle

Where does passive transport of sodium occur?

Ascending loop of Henle

What hormone regulates water reabsorption in the DCT and CD?

Anti-diuretic hormone (ADH/Vasopressin)

What happens to ADH levels in diabetes insipidus?

Deficient ADH: Increased urine output

What happens to ADH levels in SIADH?

ADH excess

What hormone regulates sodium reabsorption in the DCT?

Aldosterone

How does RAAS help in sodium and water reabsorption?

By lowering blood pressure

What converts angiotensinogen to angiotensin I?

Renin

Where is renin produced?

Juxtaglomerular cells in the afferent arteriole

What converts angiotensin I to angiotensin II?

Angiotensin Converting Enzyme (ACE)

What are the actions of RAAS?

1) Dilates afferent arterioles and constricts efferent arteriole; 2) Stimulates sodium reabsorption in PCT; 3) Triggers adrenal cortex to release aldosterone; 4) Stimulates ADH release for water reabsorption

What are the functions of tubular secretion?

1) Regulation of acid-base balance by secreting hydrogen ions; 2) Elimination of waste products not filtered by the glomerulus

Where are non-filtered substances removed, and H* ions exchanged for Na* ions?

Proximal Convoluted Tubule (PCT)

What is renal tubular acidosis (RTA)?

Failure to produce an acid urine due to inability to secrete hydrogen ions

What is the test used to evaluate glomerular filtration rate (GFR)?

Clearance test

What is the most common clearance test?

Creatinine clearance

What is the gold standard/reference method for clearance tests?

Inulin clearance

What is a better marker for renal tubular function than GFR?

Beta2-microglobulin

What is the molecular weight of cystatin C?

13,359 Da

What is the formula for creatinine clearance?

UV/P x 1.73m^2/A

What variables are included in the Estimated GFR formula (Cockcroft and Gault)?

Ethnicity, BUN, and serum albumin

What is the recommended MDR IDMS Traceable formula for GFR by NKDEP?

GFR = 175 x serum creatinine^-1.154 x age^-0.203 x 0.742 if female x 1.212 if patient is Black (NO WEIGHT)

What test evaluates tubular reabsorption?

Concentration test

What are the obsolete tests for tubular reabsorption?

Fishberg test and Mosenthal test

What is the specific gravity of urine after 12 hours on a restricted fluid diet (Fishberg test)?

1.022 or more

What is the specific gravity of urine after 24 hours on a restricted fluid diet (Fishberg test)?

1.026 or more

What factors influence specific gravity?

Number and density of particles in a solution

What is influenced by the number of particles in a solution and preferred over S.G?

Osmolality

What are the methods of osmolality measurement?

Freezing point osmometry and vapor pressure osmometry

What is the normal osmolality value?

1-3x serum (275-900 mOsm/kg)

What is the most commonly used/reference method for tubular secretion and renal blood flow?

p-aminohippuric acid test (PAH)

What is an obsolete test for tubular secretion and renal blood flow?

Phenolsulfonapthalein (PSP)

What is measured by urine pH, titratable acidity, and urinary ammonia tests?

Tubular secretion and renal blood flow