Urinalysis and Body Fluids 6th Edition by Majorie DiLorenzo, Susan Strasinger

Exercise 35

If crystals shaped like needles are aligned perpendicular to the slow vibration of compensated polarized light, what color are they?

A. White

B. Yellow

C. Blue

D. Red

Step 1 of 2

Monosodium urate (MSU):

The monosodium urate is a primary crystal in synovial fluid. It is also called as “uric acid”.

• The MSU crystal has been found in the cases of “gout”; it is “needle” shaped.

• It exhibits “negative birefringence” polarized light.

• The different crystals can be identified by the color of crystal;

• The color of a crystal is determined by aligning the crystal with slow vibration.

• In MSU crystal, the molecules move parallel to the long axis of the crystal.

o In the slow vibration alignment, the velocity of slow light is passed through the crystal

o The light velocity run against the grain and results in “yellow” color.

Therefore, the crystal shaped needles produces “yellow” color under compensated polarized light. Hence, the correct answer is option “”.