Hemocytometer Flashcards
What is the basic purpose of hemocytometers?
to determine the concentration of cells in a suspension
Give some examples of when a hemocytometer would be useful
in a medical lab to determine the concentration of red blood cells or platelets in a patient’s blood sample
an ecologist could use it to measure the number of blue green algae cells in a water sample
a cell biologist could use it to determine the proper cell density for subculturing a cell line
Describe the original hemocytometer device
a microscope slide that has been fitted with chambers and etched with fine grid lines to provide volume measures
What was the hemocytometer originally developed for?
determining red blood cell density (hence the name ‘hemo-‘ = blood, ‘cyto’ = cell, ‘meter’ = to measure)
What draws the sample to the viewing area where the grid lines are etched into the slide?
capillary action
What is the first magnification you would view the hemocytometer under? How would the hemocytometer look at this point?
100x total
the 1 mm x 1 mm grid would fill most of the field of view
How do you decide which square size you will use to measure cell density?
count the cells in a primary square (1mm x 1mm)
if there are less than 200 cells in a primary square, find the average number of cells for the 2 primary squares (four outer corners)
Which squares are the primary squares?
the 1 mm x 1 mm squares at 100x
the 4 outer corner squares
What do you do if there are more than 200 cells in a primary square?
increase magnification to clearly see the secondary squares (0.2 mm x 0.2 mm)
Which are the secondary squares?
the 0.2 mm x 0.2 mm squares
within the middle square, they are the 4 outer corners and the middle most square
What do you look for in the secondary squares?
if there are less than 100 cells in a secondary square, you find the average number of cells for all 5 squares
What do you do if there are more than 100 cells in a secondary square?
focus on the center of the hemocytometer grid and find the average of the 4 0.05 x 0.05 squares
How do you ensure accuracy while you count cells?
choose two sides of the square and for those 2 sides count all the cells that touch any of the lines (including which corners you will count when there are double or triple lines)
count the cells that touch no lines (the center cells)
do not count the cells that touch any of the lines on the 2 other sides
maintain consistency with all the squares you count (use the same sides)
How tall is the hemocytometer chamber?
100 um
What is the volume of each primary square?
10^-4 mL (0.0001 mL)
