Hematopoiesis

Question 1

What is Hematopoiesis?

Answer 1

The generation of blood cells (mature hematopoietic cells) from hematopoietic stem cells

Question 2

Where does hematopoiesis primarily occur?

Answer 2

In the bone marrow, especially flat bones and the ends of long bones

Question 3

True or False: Red bone marrow is active and where hematopoiesis occurs.

Answer 3

True

Question 4

True or False: Red bone marrow is widely distributed in adult animals.

Answer 4

False, it is widely distributed in young animals and limited to flat bones and ends of long bones in mature animals.

Question 5

In pathogenic situations, where else can hematopoiesis occur causing extramedullary hematopoiesis?

Answer 5

Spleen and Liver

Question 6

What three things are required for normal hematopoiesis?

Answer 6

1. Hematopoietic stem cells
2. Cytokines
3. Bone marrow microenvironment

Question 7

Hematopoietic stem cells are capable of division that results in _____-_____, and differentiation into ____ ____ ____, ____ _____ ____, and ______.

Answer 7

• Self-renewal
• Red blood cells
• White blood cells
• Platelets

Question 8

What do hematopoietic stem cells resemble in routine blood marrow aspirates? How can they be purified in order to be identified?

Answer 8

• Resemble small lymphocytes

- Can be purified by CD34 surface antigen expression

Question 9

True or False: Hematopoietic stem cells are present in high numbers and circulate in high numbers

Answer 9

False, they are present in low numbers and circulate in low numbers

Question 10

What is the sequence of development from hematopoietic stem cells to differentiated blood cells? Give examples of the differentiated blood cells. At which stage do they become morphologically recognizable?

Answer 10

Hematopoietic stem cells –> progenitors (lymphoid or myeloid)–> precursors (morphologically recognizable)–> Differentiated Blood Cells (RBC’s, WBC’s, platelets, lymphocytes)

Question 11

Myeloblasts, progranulocytes, myelocytes, metamyelocytes, and bands are all ____ precursors.

Answer 11

Granulolytic

Question 12

Rubriblasts, prorubicytes, rubricates, metarubricytes are all _____ precursors.

Answer 12

Erythroid

Question 13

Hematopoiesis is driven by expression of _____ ______ induced by numerous hematopoietic ______.

Answer 13

• Transcription factors

- Cytokines

Question 14

Where does hematopoiesis occur in mammals?

Answer 14

In the extravascular spaces surrounding sinusoids

Question 15

Where does hematopoiesis occur in birds?

Answer 15

• WBC’s in the extravascular spaces surrounding sinusoids

- RBC’s and thrombocytes (platelets) within the sinusoids

Question 16

Hematopoietic tissue consists of hematopoietic cells, vascular sinuses called sinusoids, and several other types of cells collectively called the ______.

Answer 16

Microenvironment

Question 17

_____ is the production of red blood cells from common myeloid progenitors.

Answer 17

Erythropoiesis

Question 18

What is an erythroid island?

Answer 18

A macrophage surrounded by erythroid precursors where erythropoiesis happens. This occurs around macrophages because they contain the needed iron and serve as nurse cells.

Question 19

During erythropoiesis, as the cells mature, what happens to:

1. cell size
2. Nuclear size/nucleus
3. chromatin condensation

Answer 19

1. cell size decreases
2. nuclear size decreases and the nucleus is extruded
3. chromatin condensation increases

Question 20

As red blood cells mature during erythropoiesis, the cytoplasm becomes less basophilic due to loss of _____ and gain of _____.

Answer 20

• Ribosomes

- Hemoglobin

Question 21

How many days does it take for a rubriblast to differentiate into a mature red blood cell?

Answer 21

About 7 days.

Question 22

True or false: during erythropoiesis, a cell with fine chromatin, a prominent nucleus, and deeply basophilic cytoplasm is very mature.

Answer 22

False, it is in the least mature stage

Question 23

A _________ red blood cell is non-nucleated and takes many stains, therefore it appears more blue in color. It should circulate in low numbers in a healthy animals, but can increase in animals with regenerative anemia.

Answer 23

Polychromatophilic

Question 24

When stained with new methylene blue (NMB), ______ cells have a blue meshwork created by ribosomes and other organelles condensing.

Answer 24

Reticulocyte

Question 25

Where is erythropoietin produced? What stimulates its production?

Answer 25

- It is a glycoprotein that stimulates hematopoietic stem cell commitment to erythroid lineage and proliferation of erythroid progenitors and precursors - Produced in the cortex of the kidney by interstitial cells - Hypoxia (low levels of tissue oxygen) is the stimulus for production

Question 26

What is erythropoietin and what does it do?

Answer 26

It is a glycoprotein that stimulates hematopoietic stem cell commitment to erythroid lineage and proliferation of erythroid progenitors and precursor. It also prevents apoptosis of erythroid precursors, reduces the 7 day production time of red blood cells, increases hemoglobin synthesis, and induces the release of polychromatophiloc cells into circulation.

Question 27

Decreased erythropoietin production can cause what? Is there a medication for this? Is it used in veterinary medicine?

Answer 27

- Nonregenerative anemia, or chronic kidney disease - Recombinant erythropoietin is an option, however its use in the veterinary field is limited as anti-erythropoiten antibodies can be formed and its use is against racing regulations

Question 28

What is granulopoiesis?

Answer 28

production of neutrophils, eosinophils, and basophils from common myeloid progenitors and myeloid precursors

Question 29

During granulopoiesis, as the cells mature, what happens to: 1. cell size 2. nucleus 3. chromatin condensation 4. granule development

Answer 29

1. cell size decreases 2. nucleus becomes segmented 3. chromatin condenses more 4. Primary and secondary granules develop in the cytoplasm

Question 30

In a ____ neutrophil. the nucleus has parallel sides and a horseshoe shape. In a _____ neutrophil, the nucleus has 2-5 lobes.

Answer 30

- band | - segmented

Question 31

Describe cells in the proliferating pool and cells in the maturation and storage pool, including the prevalence of cells in each. Why is this prevalence ratio important?

Answer 31

- Cells in the proliferating pool undergo mitosis and differentiation and account for 10-30% of nucleated nonreythroid cells - Cells in the maturation and storage pool are non-dividing and account for 65%-90% of nonerythroid cells in the bone marrow - Because more cells are in the maturation and storage pool, this shows that the bone marrow does a good job of keeping cells in reserve for when you need them.

Question 32

With increased demand of cells, less mature forms may be released. This is called _____ _____.

Answer 32

Left Shift

Question 33

_____ stimulate and enhance proliferation of progenitors.

Answer 33

Cytokines

Question 34

What is lymphopoiesis?

Answer 34

Common lymphoid progenitors differentiation into B and T lymphocytes and natural killer cells.

Question 35

Where does B cell and T cell maturation occur in mammals?

Answer 35

- B cell: bone marrow | - T cell: thymus