Hematology and Hematopoiesis Flashcards
Hematopoiesis
Process by which blood cells are formed
Bone marrow is main site of hematopoiesis in mammals and most other vertebrae
Extramedullary hematopoiesis (EMH)
Hematopoiesis occurring outside of marrow due to inc. demand for blood cells
Primarily occurs in spleen and liver; occurs minimally in health in domestic animals
Bone marrow
Located in flat and long bones
Samples are collected from sites with active hematopoietic tissue:
-Cats and dogs: iliac crest, proximal femur and humeri
-Horses and ruminants, camelids: ribs, sternebrae, and ilium
Bone marrow composition
Red marrow - hematopoietic tissue and blood vessels, called sinusoids
Yellow marrow - mostly fat
Ratio of red:yellow is called “cellularity”
Young animals have higher ratio
Most adult animals have 1:1
Older animals have lower ratio
Bone marrow sampling
Biopsy for histology
Aspiration (liquid sample) for cytology
Hematopoietic stem cell
Multipotent; parent of all blood cells
Myeloid
Four of five main leukocyte/WBC types
Erythrocytes/RBC’s
Platelets and their precursors, megakaryocytes
Lymphoid
B cells
T cells
Natural killer (NK) cells
Erythropoiesis
Process of forming new erythrocytes (RBC’s)
Mature erythrocytes in mammals are anucleate; retain nuclei in all other vertebrate species
Myelopoiesis
Process of forming new leukocytes (WBC’s)
Lymphopoiesis
Lymphoid progenitor cells arise in bone marrow; travel to thymus (to make T lymphocytes) or remain in bone marrow (to make B lymphocytes or NK cells)
Thrombopoiesis
Process of forming platelets; platelets lack nuclei in mammals
Platelets in non-mammals are called thrombocytes and have nuclei
Hematology
Study of blood and blood cells
CBC
Complete Blood Count
Represents a snapshot of cells traveling in blood at that moment - balance between how many cells produced by bone marrow vs. how many cells lost/destroyed/consumed in the body
RBC’s
Anucleate when almost mature
Most RBC’s are mature erythrocytes
Biconcave
Nucleated RBC’s rarely circulate in healthy animals - increase peripheral blood in many pathologic conditions
Reticulocytes
Anucleate but not mature RBC; still actively synthesizing hemoglobin
Identified with new methylene blue (NMB)
Polychromatophils
Anucleate but not mature RBC; still actively synthesizing hemoglobin
Identified with a standard hematology stain
Have less hemoglobin than mature cells and more RNA (blue color)
Blood cell count
Increase - bone marrow regenerative response
Decrease (anemia) - bone marrow isn’t making enough RBC’s; RBC’s are being lost or destroyed peripherally
WBC’s
Also called leukocytes
Perform extravascularly in organs and tissues to fight infection
Species differences in RBC’s
Dogs - strongly biconcave with central pallor
Cats - lack of central pallor; two types of reticulocytes, punctuate and aggregate (only aggregate counted); roleaux; heinz bodies
Horses - minimal central pallor; no reticulocytes from bone marrow; rouleaux
Camelids - oval-shaped RBC’s
Drepanocytes (sickle cells) in goat, sheep, deer
Non-mammals have nucleated RBC’s
5 Types of WBC’s
Granules - Neutrophils, eosinophils, basophils
Mononuclear cells - Monocytes, lymphocytes
Neutrophils
Most common bacteria killer cells in body; ingest bacteria via phagocytosis
Don’t stain in mammals; heterophils in non-mammals stain pink
Immature cells are released from bone marrow during inflammation
Eosinophils
Second most common bacteria killer cells
Take up eosin (pink/red) stain
Basophils
Rarest granulocyte
Take up basic (blue/purple) stain
Lymphocytes
Smallest WBC, round nuclei with minimal cytoplasm
Produced from lymphoid progenitor cells
Cells of adaptive/acquired immunity system
Only lymphocytes recirculate in bloodstream
Divided into B cells, T cells, NK cells
Monocytes
Lumpy, amoeba-shaped nuclei
Become macrophages or dendritic cells - main cells for phagocytosis
