Hematology and Hematopoiesis

Question 1

Hematopoiesis

Answer 1

Process by which blood cells are formed
Bone marrow is main site of hematopoiesis in mammals and most other vertebrae

Question 2

Extramedullary hematopoiesis (EMH)

Answer 2

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

Question 3

Bone marrow

Answer 3

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

Question 4

Bone marrow composition

Answer 4

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

Question 5

Bone marrow sampling

Answer 5

Biopsy for histology
Aspiration (liquid sample) for cytology

Question 6

Hematopoietic stem cell

Answer 6

Multipotent; parent of all blood cells

Question 7

Myeloid

Answer 7

Four of five main leukocyte/WBC types
Erythrocytes/RBC’s
Platelets and their precursors, megakaryocytes

Question 8

Lymphoid

Answer 8

B cells
T cells
Natural killer (NK) cells

Question 9

Erythropoiesis

Answer 9

Process of forming new erythrocytes (RBC’s)
Mature erythrocytes in mammals are anucleate; retain nuclei in all other vertebrate species

Question 10

Myelopoiesis

Answer 10

Process of forming new leukocytes (WBC’s)

Question 11

Lymphopoiesis

Answer 11

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)

Question 12

Thrombopoiesis

Answer 12

Process of forming platelets; platelets lack nuclei in mammals
Platelets in non-mammals are called thrombocytes and have nuclei

Question 13

Hematology

Answer 13

Study of blood and blood cells

Question 14

CBC

Answer 14

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

Question 15

RBC’s

Answer 15

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

Question 16

Reticulocytes

Answer 16

Anucleate but not mature RBC; still actively synthesizing hemoglobin
Identified with new methylene blue (NMB)

Question 17

Polychromatophils

Answer 17

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)

Question 18

Blood cell count

Answer 18

Increase - bone marrow regenerative response
Decrease (anemia) - bone marrow isn’t making enough RBC’s; RBC’s are being lost or destroyed peripherally

Question 19

WBC’s

Answer 19

Also called leukocytes
Perform extravascularly in organs and tissues to fight infection

Question 20

Species differences in RBC’s

Answer 20

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

Question 21

5 Types of WBC’s

Answer 21

Granules - Neutrophils, eosinophils, basophils
Mononuclear cells - Monocytes, lymphocytes

Question 22

Neutrophils

Answer 22

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

Question 23

Eosinophils

Answer 23

Second most common bacteria killer cells
Take up eosin (pink/red) stain

Question 24

Basophils

Answer 24

Rarest granulocyte
Take up basic (blue/purple) stain

Question 25

Lymphocytes

Answer 25

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

Question 26

Monocytes

Answer 26

Lumpy, amoeba-shaped nuclei
Become macrophages or dendritic cells - main cells for phagocytosis