What are the functions of RBCs?
to carry oxygen bound to hemoglobin to tissues and carry CO2 to lungs for excretion
What is extramedullary hematopoiesis?
hematopoiesis that takes place outside the bone marrow (often in spleen or liver)
Extramedullary hematopoiesis can be in response to what?
severe anemia or other pathological condition such as neoplasia
What can a pluripotent stem cell become?
depending on various cytokines and hormones, they can become RBCs, granulocytes, platelets or lymphocytes
What is the shape of RBCs in:
- most mammals?
- birds, reptiles, amphibians and fish?
mammals - biconcave disc
camelids - ovoid
birds, reptiles, amphibians and fish - nucleated ovoid
Where is hemoglobin produced?
in the bone marrow while RBC is nucleated and for short time after release as a reticulocyte
What is the main pathway for RBC destruction?
extravascular destruction; hemoglobin is split into heme and globin; globin is broken down in AAs for recycling; iron is split from heme molecule; heme is broken down by heme oxygenase to CO and biliverdin; biliverdin is reduced to bilirubin; bilirubin is bound to albumin for transport to the liver; bilirubin is conjugated to glucuronic acid and excreted into the bile; small amounts of unconjugated bilirubin can be excreted by the kidney
Which animal lacks biliverdin reductase?
birds (this is why they develop green discoloration as hemoglobin is broken down in bruises)
What is the minor pathway for RBC destruction?
intravascular lysis of aged RBCs; plasma protein haptoglobin binds hemoglobin for transport to the liver and hemoglobin's fate is the same as for extravascular destruction
Abnormalities in size of RBCs:
anisocytosis: variation in sizes
macrocytosis: larger than normal
microcytosis: smaller than normal
Abnormalities in color of RBCs:
polychromasia - bluish discoloration to RBC
hypochromasia - decreased hemoglobin content
Abnormalities in shape of RBCs:
poikilocytosis - abnormal shapes
spherocytosis - small dense RBCs
Abnormalities in distribution of RBCs:
rouleaux - stacking of RBCs
agglutination - RBCs sticking to each other
What are the five abnormalities that can occur in RBCs?
abnormalities in size, color, shape and distribution and inclusion bodies/infectious agents
What are acanthocytes?
where there are a few irregular elongations of RBC border with rounded ends often forming a bud
How can you differentiate rouleaux from agglutination?
mix blood with normal saline - rouleaux will dissipate and agglutination will not
What are reticulocytes?
young (immature) erythrocytes prematurely released to the blood from the bone marrow in some anemias
What are the clinical applications of reticulocytes?
evaluation of erythropoiesis in bone marrow and differentiation of regenerative and non-regenerative anemia
How do you calculate corrected reticulocyte percentage (CRP)?
CRP = % reticulocytes x PCV of a sample/normal PCV
How do you interpret RPI?
RPI > 3: very good regeneration
RPI = 1-3: good regeneration
RPI < 1: inadequate regeneration
What are the two types of reticulocytes that cats have?
aggregate (blue stained coarse clumping) and punctate (small, blue stained dots)