Renal Physiology Flashcards by Miyaki Jan Lim

study of the physiology of the kidney

Renal physiology

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the smallest functional unit of the kidney

nephron

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Each nephron begins with a filtration component that filters blood entering the kidney

This filtrate then flow along the length of the __________, which is a tubular structure lined by a single layer of specialized cells and surrounded by capillaries.

The major functions of these lining cells are the reabsorption of water and small molecules from the filtrate into the blood, and the secretion of wastes from the blood into the urine.

nephron

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Proper function of the kidney requires that it receives and adequately filters blood. This is performed at the microscopic level by many hundreds of thousands of filtration units called

renal corpuscles

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renal corpuscles is composed of a

glomerulus and a Bowman’s capsule

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A global assessment of renal function is
often ascertained by estimating the rate of filtration, called the

glomerular filtration rate (GFR)

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chief regulators of the internal environment of the body.

They do this by regulating the concentration of ions, water, and pH in the various body fluids

kidneys

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The million nephrons in the kidneys contain two main structures, the

glomerulus and the renal tubule

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As blood passes through the kidneys, it is filtered through the ________ , and the filtrate then passes into the _______

glomerulus (120 mL/min)

renal tubule

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is similar to blood plasma in composition, except the large molecules (having molecular weights of more than 70,000) are excluded (e.g. plasma proteins)

tubular filtrate

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passes along the proximal and distal tubules, most of the water is reabsorbed, and many essential substances are actively or passively reabsorbed into the bloodstream.

tubular filtrate

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Toxic by-products of metabolism and substances in excess are retained in the filtrate or are secreted into the filtrate and finally excreted in the urine

true

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the final composition of the urine is quite different from that of the glomerular filtrate and reflects the integrity of kidney function and changes in blood composition.

true

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An analysis of urine can yield valuable information about the health of the kidney and of the body in general

URINALYSIS

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Various diseases are characterized by abnormal metabolism, which causes abnormal byproducts of metabolism to appear in the urine.

true

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appears in the urine in phenylketonuria (PKU)

phenylpyruvic acid

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phenylpyruvic acid in urine, a disease resulting in mental retardation

phenylketonuria (PKU)

deficient production of insulin by the pancreas results in the appearance of glucose in the urine (glycosuria)

diabetes mellitus

SPECIFIC GRAVITY

🔬 Normal Range:
1.005 to 1.030

💧 Low Specific Gravity (<1.005) might indicate:
Overhydration

Diabetes insipidus

Renal tubular damage

🌡️ High Specific Gravity (>1.030) might indicate:
Dehydration

Glycosuria (as in uncontrolled diabetes mellitus)

Proteinuria

SIADH (Syndrome of Inappropriate Antidiuretic Hormone)

MICROSCOPIC EXAMINATION

prism-like-appearance

Alkaline urine (pH > 7)

Urinary tract infections (UTIs) caused by urease-producing bacteria (e.g., Proteus, Klebsiella, Pseudomonas)

Can be a major component of struvite stones (infection stones)

magnesium ammonium phosphate crystals

Urine is approximately ________ water and includes the following dissolved substances: pigments, electrolytes, hormones such as estrogen and nitrogenous wastes, such as uric acid, urea, creatinine and ammonia

95%

MICROSCOPIC EXAMINATION

can be dumbbell shaped or spherical with striations

Not typically associated with pathology

Considered benign or insignificant in many cases

May occasionally appear in herbivores or rarely in humans with certain diets or supplements

calcium carbonate crystals

MICROSCOPIC EXAMINATION

needle-like, granular appearance and are often very small and yellow in color.

Almost always pathologic

Indicates bilirubinuria, which occurs when conjugated (direct) bilirubin is present in urine

bilirubin crystal

MICROSCOPIC EXAMINATION

Oxalate dihydrate crystals are envelope-shaped and sometimes are termed the Maltese cross crystal

In larger numbers, may be associated with:

Hyperoxaluria

Ethylene glycol poisoning (esp. in cases with monohydrate forms)

Kidney stones (calcium oxalate stones are very common)

Diet high in oxalate (spinach, rhubarb, nuts, etc.)

calcium oxalate dihydrate crystals

MICROSCOPIC EXAMINATION Fine, colorless to yellow needle-like crystals Radiate in sheaves or rosettes (like a bouquet or brush-like clumps) May be mistaken for bilirubin crystals, but tyrosine tends to be more delicate and radiating trongly associated with: Severe liver disease (e.g., advanced cirrhosis, hepatitis) Tyrosinemia (a rare inborn error of metabolism) Aminoacidurias

tyrosine crystals

MICROSCOPIC EXAMINATION Colorless, hexagonal plates Flat and uniform in size May appear singly or in layers Not birefringent (unlike some other crystals) are always pathologic and are a key diagnostic clue for cystinuria, a rare inherited disorder affecting amino acid transport in the kidneys.

cystine crystal

TEST FOR URINARY BILIRUBIN reagent

concentrated nitric acid

MICROSCOPIC EXAMINATION Oval, dumbbell-shaped, or spindle-shaped Sometimes resemble picket fence posts Colorless and highly refractile Can be difficult to distinguish from other small crystals without experience May be normal in small amounts Frequently seen in: Ethylene glycol poisoning

calcium oxalate monohydrate crystals

MICROSCOPIC EXAMINATION brown spheres with spiky thorns. They almost resemble small bugs. They're often found in alkaline urine, but they can also be seen in normal urine. Sometimes ammonium biurate crystals only appear because the urine sample is old or has been poorly preserved.

ammonium biurate crystals

MICROSCOPIC EXAMINATION Shocks of wheat Needle-like crystals Sheaves, rosettes, or fan-shaped bundles Yellow to brown in color Often birefringent under polarized light are drug-induced urinary crystals that can form in patients taking sulfonamide antibiotics, especially when urine is acidic and the patient is dehydrated.

sulfonamide crystals

URINALYSIS

MACROSCOPIC EXAMINATION SPECIFIC GRAVITY MICROSCOPIC EXAMINATION LABSTIX TEST

which are ubiquitous in the environment and, therefore, common urine contaminants

macroconidia of the fungus Alternaria sp

are relatively common urine contaminants

Septate fungal hyphae

TEST FOR URINARY PROTEIN reagent

three drops of 10% acetic acid to the test tube

TEST FOR URINARY PROTEIN results

If precipitate is observed, then albumin and globulins are present and this indicates a positive test for proteins.

TEST FOR URINARY GLUCOSE reagent

Benedict's reagent

TEST FOR URINARY GLUCOSE result

Clear blue or green with no precipitate - no sugar yellow to brick red precipitated - positive Green with yellow precipitate Yellowish green with a yellow precipitate Brownish orange with a yellow precipitate Orange to brick red precipitate

TEST FOR URINARY BILIRUBIN results

A green color is positive for biliverdin. Bilirubin is not stable in urine and is oxidized to biliverdin.

TEST FOR UREA reagent

concentrated nitric acid

TEST FOR UREA result

When crystals (urea nitrate) begin to form, examine under the low power objective of your microscope. hexagonal

a type of hydrometer, was used for measuring the specific gravity of urine. 'Specific gravity' is a function of the number, density and weight of the solute particles present in the urine, and is used as a measure of the concentrating power of the kidney.

urinometer