hematology Flashcards
what is hematology?
it considers the functions of blood that are directly related to its gross cellular composition, cytology, cellular properties and mechanisms such as coagulation
what three measurements give an indication of capability for gas transport or the respiratory function of blood?
erythrocyte numbers, hemoglobin concentration and hematocrit
what does measurement of numbers and proportions of leukocytes used to determine?
the ability to withstand infection and the index of response to infection
what are two methods of blood sampling?
skin puncture and venipuncture
what does EDTA do, what is it used for, what colour is it?
EDTA (disodium/dipotassium ethylene diaminetetracetic acid) chelates calcium; it does not cause platelet clumping, less effect on WBC than oxalates. the preferred anticoagulant for hematology analysis. it is purple top
what does sodium citrate do, what is it used for, what colour is it
binds calcium. used for coagulation studies, erythrocyte sedimentation rate and transfusion purposes. non-toxic, metabolized readily, and preserves coagulation factors. blue
what does heparin do, what is it used for, what colour is it?
heparin inhibits thrombin and other activated clotting factors through activation of antithrobin III. (don’t use for coagulation studies!)
preferred for osmotic fragility tests. not good for blood morphology staining. green
what do oxalates do and what colour is it?
precipitates calcium as calcium oxalate. not used much any more. can be used for some coagulation studies and osmotic fragility measurements. grey
what does sodium fluoride do?
not used for hematological work; stopes RBC glycolysis so frequently used with blood samples for metabolite assay
what is rouleaux formation?
stacks of RBCs that form because of the discoid cell shape in vertebrates. more common in horses (and cats?)
what is hemolysis?
lysis of red blood cells
what is an erythrocyte ghost?
the membrane and cytoskeletal elements of the erythrocyte devoid of cytoplasmic contents but preserving the original morphology
what does a hemocytometer allow you to measure?
the number of cells per unit of volume
how would you use a hemocytometer to measure leukocytes in a blood sample?
use a diluting fluid that lyses the red blood cells
how is a reticulocyte count performed?
count 1000 cells and identify as a reticulocyte or mature erythrocyte and then express as % of the total number of erythrocytes (usually more meaningful if expressed per litre)
what is a stain that can allow easy visualization of reticulocytes?
new methylene blue stain. it causes ribosomes and polyribosomes containing RNA to clump into granules (it is as a supravital stain)
how is a WBC count made?
with a hemocytometer
what is a leukopenia?
a decrease in total WBC count and may arise from viral infections
what is a leukocytosis?
an increase in total WBC count and most commonly the result of bacterial infection
what is a differential WBC count?
it differentiates leukocytes into groups and expresses their relative incidence as a percentage
why is it important to look at total WBC numbers rather than just relative percentage?
a stimulus may cause a great increase in one type of leukocyte without a great change in total numbers
what are the general characteristics of neutrophils?
they are the “pus” cells
large reserve pools
have lysosomal and secondary granules with bacteriocidal properties
reserve pool of band cells that when released is referred to as left shift
what are the general characteristics of monocytes?
slower than neutrophils to respond to infection. no significant reserve pool
enter tissues to become macrophages; tend to increase in chronic infections
what are the general characteristics of eosinophils?
increased during allergic reactions and parasitic infections. mostly located underlying epithelial barriers to the external environment. phagocytic. granules may have antiparasitic activity. adrenal corticosteroids cause eosinopenia
what are the general characteristics of basophils?
similar to mast cells; contain histamine, heparin, lysozomal enzymes in granules. granule release triggered by certain allergic reactions involving IgE
for every 1 white blood cell there are approximately how many erythrocytes?
1000
approximately how many WBC/L are there?
1-20 million
approximately how many RBCs are there per L
1-10 billion?
what is a coulter counter?
it is involved in automated cell enumeration that can count both RBCs and WBCs due to the change in conductivity which results when a cell passes between the two electrodes
what are most clinical hemoglobin determinations based on?
they perform colorimetric analysis of oxyhemoglobin
what is hematocrit?
it is the fractional volume of red blood cells and is proportional to cell numbers
how do you measure total protein of blood?
use a temperature compensated refractometer; the refractive index of an aqueous solution is a function of the total solids
what are the erythrocyte indices
mean corpuscular volume (MCV)
mean corpuscular hemoglobin (MCH)
mean corpuscular hemoglobin concentration (MCHC)
how can the mean corpuscular volume be calculated?
(packed cell volume * 100)*number of RBCs
how can mean corpuscular hemoglobin be calculated?
amount of hemoglobin/RBC number
how can mean corpuscular hemoglobin concentration be calculated?
amount of hemoglobin/packed cell volume
what are the erythrocyte indices calculated from?
RBC count, PCV, blood hemoglobin concentration (g/L)
how is red blood cell fragility measured?
the red blood cells are placed in hypotonic solutions of NaCl and the optical density of the solution is read.
what does erythrocyte sedimentation rate measure?
it measure the rate of fall of the upper margin of RBCs in blood and this rate is correlated with certain diseases. the falling of the particle is proportional to the square of the radius. increased aggregation of cells increases sedimentation
what is achromia?
pale staining of RBCs due to low hemoglobin
what is polychromasia?
the erythrocytes have a bluish rather than a tan colour
what is anisocytosis?
a wide variation in the size of the cells
what is poikilocytosis?
many of the RBCs have abnormal shape
what is macrocytosis?
the average size of the cells is greater than normal
what is microcytosis?
the average size of the cells is smaller than normal
