Leukopoiesis: Topic 1

Question 1

what is leukopoiesis?

Answer 1

growth, differentiation AND maturation of white blood cells

Question 2

what is differentiation?

Answer 2

the process by which cells decide which cell line they want to be in

e.g., the monocytic cell line, the neutrophilic cell line, etc.

Question 3

what is maturation?

Answer 3

the movement of a cell through stages, from the first baby stage (blasts) to the final end-product (e.g., monocytes and neutrophils)

Question 4

what are the types of WBCs?

Answer 4

1. granulocytes (neutrophils, eosinophils, basophils)
2. monocytes
3. lymphocytes

Question 5

what are the types of granulocytes?

Answer 5

neutrophils, eosinophils, and basophils

Question 6

what are the three main hematopoietic cell lines?

Answer 6

1. red blood cells (erythrocytes)
2. white blood cells (leukocytes)
3. platelets

Question 7

where are hematopoietic cells made?

Answer 7

born in the bone marrow then almost all of them stay there and undergo maturation before being released into the blood

the only hematopoietic cell that matures outside the bone marrow is the T lymphocyte which mature in the thymus

Question 8

Which hematopoietic cell is the only one to develop outside the bone marrow?

Answer 8

T lymphocytes are the only cell type to develop outside the marrow

They are “born” in the bone marrow, but they leave and mature in the thymus

Question 9

what kind of stem cells do all the hematopoietic cells come from?

Answer 9

trick question: all hematopoietic cells arise from a single type of stem cell in the bone marrow!

that stem cell gives rise to a lymphoid stem cell which gives rise to lymphocytes and a myeloid stem cell which gives rise to everything else: RBC, granulocytes, monocytes and platelets

Question 10

what does a myeloid stem cell give rise to?

Answer 10

RBC, granulocytes, monocytes and platelets

Question 11

what is granulopoiesis?

Answer 11

granulocyte development

Question 12

what cell types are granulocytes?

Answer 12

neutrophils, eosinophils, and basophils

BEN

Question 13

what types of cells are agranulocytes?

Answer 13

monocytes and lymphocytes

Question 14

what’s the difference between granulocytes and agranulocytes?

Answer 14

all leukocytes have granules!!

BUT only granulocytes have specific granules

each granulocyte, neutrophil, eosinophil, and basophil—has its own unique kind of granule that has its own characteristic look and function

Question 15

what are the 6 stages of neutrophil maturation?

Answer 15

1. myeloblast
2. promyelocyte
3. myelocyte
4. metamyelocyte
5. band
6. segmented neutrophil

Question 16

what are myeloblasts?

Answer 16

first stage of neutrophil maturation

medium-sized cells with fine chromatin and a little rim of cytoplasm

Question 17

what does fine chromatin mean?

Answer 17

chromatin pattern is very even, light staining, and so see- through that you can usually see nucleoli

Question 18

what are promyelocytes?

Answer 18

2nd stage of neutrophil maturation

by far the biggest cell of the neutrophil series

They have chromatin that is about as fine as myeloblasts, and they have abundant, deep blue cytoplasm

it’s the granules that really characterize the promyelocyte - they have tons of deep purple, azurophilic (primary) granules in the cytoplasm and overlying the nucleus

Question 19

what are the two features that characterize promyelocytes?

Answer 19

1. Size (promyelocytes are huge)

2. Granulation (promyelocytes have tons of primary granules).

Question 20

what are myelocytes?

Answer 20

3rd stage in neutrophil differentiation?

more condensed chromatin pattern =chromatin is darker-staining

can’t really see nucleoli anymore

**appearance of specific (or secondary) granules. Specific granules are pale pink and much smaller than primary granules. (primary granules are much sparser in myelocytes)

Question 21

what are metamyelocytes?

Answer 21

4th stage in neutrophil differentiation

look quite a bit like myelocytes except they have even more condensed chromatin and an indented or horseshoe-shaped nucleus

Question 22

what are band cells?

Answer 22

5th stage in neutrophil differentiation

As the nucleus matures, it becomes thinner and looks more like a U

Question 23

what are segmented neutrophils?

Answer 23

the nucleus segments: it pinches off in places, so there are 3 or 4 little sections of nucleus joined by thin strings of cytoplasm

Cells at this final, mature stage are called segmented neutrophils

Question 24

what are the stages of eosinophils and basophils?

Answer 24

they go through the same stages of maturation as neutrophils but just with their own unique specific granules appearing at the myelocyte stage

big orange granules in eosinophils; dark blue granules in basophils

All you have to do is put “eosinophilic” or “basophilic” in front of the cell stage (e.g., eosinophilic promyelocyte), and you have the appropriate cell name.

Myeloblasts, though, don’t follow this rule – you just call them myeloblasts, because at that stage, the cell is not differentiated (which means the cell has not decided whether it is going to give rise to neutrophils, eosinophils, or basophils)

Question 25

In granulocytes, which cell stage is the first one to show differentiation?

Answer 25

promyelocyte stage

the cell has committed itself to becoming either a neutrophil, eosinophil, or basophil

Question 26

how do monocytes mature?

Answer 26

Monocytes start out in the marrow as monoblasts which are larger than other kinds of blasts

Monoblasts have:

• fine chromatin
• voluminous cytoplasm
• slightly indented nucleus - tiny cytoplasmic granules

Question 27

what are the stages of monocyte development?

Answer 27

1. monoblast
2. promonocyte
3. monocyte

SO EASY!! (:
MONOcyte = 1 intermediate, mono

Question 28

what are promonocytes?

Answer 28

intermediate stage of monocyte development

nuclei have “tissue-paper” appearance; it looks like tissue paper that has been crumpled up and then partially smoothed out

promonocytes are hard to find promonocytes in normal bone marrow specimens, but you can see what they look like by looking at a leukemia that is composed of promonocytes

Question 29

how do promonocytes turn into mature monocytes?

Answer 29

As the promonocyte develops into a monocyte, it loses the nuclear folding pattern and develops an indented nucleus

Question 30

what are the characteristics of a monocyte?

Answer 30

Mature monocytes have an irregularly shaped nucleus that sometimes looks like a kidney bean and sometimes looks more like a horseshoe

The chromatin is fine (though not as fine as blast chromatin), and it has a “raked” pattern that resembles the patterns made in the sand by Zen garden rakes

Question 31

what’s the process through which lymphocytes mature?

Answer 31

lymphocytes are divided into several groups: B cells, T cells, and NK cells

BUT the morphologic stages of their development are very simple - all lymphocytes basically look the same as they are maturing and you can’t tell whether a lymphocyte is developing into a B cell, a T cell, or an NK cell

Question 32

what are the steps in lymphocyte development?

Answer 32

1. lymphoblast in bone marrow
2. mature lymphocyte

it doesn’t go through different morphologic stages like other hematopoietic cells!

Question 33

what are the characteristics of lymphoblasts?

Answer 33

• fine chromatin
• round nucleus
• minimal cytoplasm

looks a lot like myeloblasts, you actually can’t tell them apart by just looking at them

Question 34

at what stage of neutrophil development does specific granulation first appear?

Answer 34

myelocyte

Question 35

what do promonocytes have that monoblasts don’t?

Answer 35

delicate “tissue paper” nuclear folds that aren’t seen in the other stages of the monocyte series

clumpy smudge chromatin is seen in mature lymphocytes

granules are seen in any stage of monocyte development

Question 36

what maturational stage of granulocyte development is the largest?

Answer 36

promelocyte