Erythrocytes Flashcards
What is bone marrow transit time?
5 days
Reticulocytes normally remain in bone marrow how long?
2-3 days
Normal HCT range
37-55%
CRF HCT range
22-25%, can be as low as 0%
The original rubriblast produces how many RBCs?
4 divisions - 16 RBCs
How is erithropoietin release regulated?
The kidney responds to hypoxia by activating the hormone erythropoietin.
What does erythropoietin do?
Erythropoietin stimulates stem cell differentation to rubriblasts and early reticulocyte release.
How do androgens effect erythropoiesis?
They stimulate erythropoietion or potentiate its action.
How do estrogens effect erythropoiesis?
Estrogens have an inhibitory effect on erythropoiesis.
RBC life span in dogs
120 days
RBC life span in cats
70 days
RBC life span in cows
160 days
RBC life span in horses
145 days
How do old RBCs leave circulation under normal circumstances?
The major route of blood cell loss is phagocytosis by RE cells. A minor route is intravascular lysis and release of hemoglobin. The routes of RBC destruction are similar in hemolytic anemia.
What is the primary function of hemoglobin (Hb)?
HB carries oxygen and carbon dioxide.
What does hematocrit or packed cell volume measure?
Hematocrit (Hct) or packed cell volume (PCV) is the percentage of blood composed of red blood cells.
What components are evident in a centerfuged capillary tube?
There are three portions of centerfuged whole blood - a red cell layer, a white cell layer (the “Buffy coat”) and plasma.
What can plasma be used to evaluate?
Plasma can be used for plasma protein concentration using a refractometer. Plasma fibrinogen can be measured by using a heat precipatior and refractometer.
What is the normal appearance of plasma in the dog and cat?
clear and colorless
What is the normal appearance of plasma in the horse and cow?
light yellow
What is the appearance of icteric plasma?
yellow and clear
What is the appearance of hemoglobinemic plasma?
Pink to red and clear
What is the appearance of lipemic plasma?
whitish and turpid
Where can microfilaria be found in centerfuged whole blood taken from heartworm positive animals?
Microfilaria can be found in the layer of plasma just above the Buffy coat.
What is hemoglobin concentration?
Hemoglobin concentration is the most direct measure of oxygen transport capacity of the blood. It should be abut 1/3 of the total PCV.
How is hemoglobin concentration determined?
Hemoglobin concentration is most frequently determined via automated methods. Its accuracy is +/- 5% and the presence of lipemia or an abnormal number of Heinz bodies can result in an abnormally high reading.
How is the red blood cell count determined?
There are two methods to determine the red blood cell count. Automatic counters are more accurate. Direct counts using a hemocytometer have a large margin of error +/-20%.
How does anemia effect the Hct, Hb, and RBC counts?
low values
How does absolute polycythemia effect Hct, Hb and RBC counts?
high values
How does splenic contraction effect Hct, Hb and RBC counts?
high values
What species is splenic contraction common in?
excited horses
What does hemoglobin consist of?
Hemoglobin consists of 4 globin chains (made of amino acid sequences) each binding to a heme group.
What nutrient does the diet need to contain an adequate supply of in order to produce globin?
protein
What is body iron content regulated by?
Body iron content is regulated by the rate of iron absorption (rather then excretion).
What is the body’s iron absorption rate regulated by?
The body’s iron absorption rate is regulated by the amount of storage iron (most of which is in hemoglobin) and the rate of erythropoiesis.
What is necessary for the absorption of iron?
a copper containing protein
Where is most of the body’s iron stored?
hemoglobin
What is required for erythropoiesis in only some species?
B vitamins
What are characteristics of a hematopoetic stem cell?
The hematopoetic stem cell is a multipotential stem cell which differentiates into a unipotential cell. It is self-replicating and responsive to erythropoietin.
There are three different types - erythrocytic, granulo-monocytic, and megakaryotic.
Where does erythropoiesis occur?
Erythropoiesis occurs exrtavascularly in bone marrow, and with prolonged stimulus it occurs in places other then bone marrow (ex. spleen).
What is a multipotential stem cell?
Multipotency describes progenitor cells which have the gene activation potential to differentiate into multiple, but limited cell types.
What is an erythroid precursor?
An erythroid precursor cell is a unipotent blood stem cell that has differentiated from a multipotential stem cell.
What is a rubriblast?
A rubriblast is the earliest stage of development of an erythrocyte.
What is a prorubricyte?
Basophilic normoblast
What is a rubricyte?
an immature red blood cell that has a nucleus, is about half the size of developing red blood cells in preceding stages, and has cytoplasm that stains erratically blue, purplish, and gray due to the presence of hemoglobin : polychromatic normoblast
What is a metarubricyte?
a normoblast, the last nucleated stage in the development of an erythrocyte
What is a reticulocyte?
an immature red blood cell without a nucleus, having a granular or reticulated appearance when suitably stained.
What is an erythrocyte?
.a red blood cell that (in humans) is typically a biconcave disc without a nucleus. Erythrocytes contain the pigment hemoglobin, which imparts the red color to blood, and transport oxygen and carbon dioxide to and from the tissues
How do changes in hydration affect Hct, Hb, and RBC count values?
Dehydration results in increased values, and overhydration results in decreased values.
What is splenic contraction?
The spleen has the ability to change how big it is. If a flight animal undergoes stress the spleen contracts, pushing out the blood contained within. Blood in the spleen has a high concentration of RBCs - approximately 80%.
What does mean corpuscular volume indicate?
Mean corpuscular volume (MCV) indicates the average size of the RBCs.
How is mean corpuscular volume determined?
Hct * 10/RBC count (10^6) = MCV (femtoliters)
Automated machines do the calculations today.
How do macrocytic anemias - ex. B12 and folic acid deficiencies - affect MCV values?
increased value
How does reticulocytosis affect MCV values?
transitory increase
How does iron deficiency affect MCV values?
decreased values
Define normocytic.
normally-sized cell
Define microcytic.
abnormally small cell
Define macrocytic.
abnormally large cell
How is mean corpuscular hemoglobin concentration determined?
Hb * 100/Hct = MCHC (g/dL)
Define normochromic.
normally colored
Define hypochromic.
abnormally colored
How does iron deficiency affect MCHC?
decreased value
How does hemolysis affect MCHC?
increased value
How is erythrocyte sedimentation performed?
- Fill winthrobe hematocrit tube
- allow to stand 1 hour
- record level of top of RBC column
What is erythrocyte sedimentation used to evaluate?
Certain autoimmune diseases. Of limited diagnostic value.
What is increased ESR associated with?
Increased ESR is associated with tissue damage, inflammation, and increased fibrinogen.
Where is fibrinogen produced?
Fibrinogen is a plasma protein produced by the liver.
What are the functions of fibrinogen?
Fibrinogen functions in the clotting mechanism of the blood, and moves into the extravascular spaces to assist in localization of disease processes.
How is the plasma protein:fibrinogen ratio calculated?
TPP-F/F = PP:F
What are normal fibrinogen values?
Greater then 15:1 is normal, less then or equal to 10:1 represents an absolute increase in fibrinogen.
What morphological changes are seen during erythropoiesis?
Cells become smaller. Nuclei also become smaller. Division stops in the late rubricyte stage, and the nucleus is extruded during the metarubricyte stage.
How do reticulocytes and erythrocytes migrate into peripheral blood?
Reticulocyes and erythrocytes migrate into the venous sinuses of bone marrow and then to the peripheral blood.
Only mature RBCs enter the bloodstream in which species?
horses
Define pyknotic.
refers to a dying nucleus that has become dense and small
Where is red bone marrow found?
Red bone marrow is found at the ends of the long bones and in the flat bones (ex. scapula, ribs, sternum, etc.)
