Leukopoiesis: Topic 1 Flashcards
what is leukopoiesis?
growth, differentiation AND maturation of white blood cells
what is differentiation?
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.
what is maturation?
the movement of a cell through stages, from the first baby stage (blasts) to the final end-product (e.g., monocytes and neutrophils)
what are the types of WBCs?
- granulocytes (neutrophils, eosinophils, basophils)
- monocytes
- lymphocytes
what are the types of granulocytes?
neutrophils, eosinophils, and basophils
what are the three main hematopoietic cell lines?
- red blood cells (erythrocytes)
- white blood cells (leukocytes)
- platelets
where are hematopoietic cells made?
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
Which hematopoietic cell is the only one to develop outside the bone marrow?
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
what kind of stem cells do all the hematopoietic cells come from?
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
what does a myeloid stem cell give rise to?
RBC, granulocytes, monocytes and platelets
what is granulopoiesis?
granulocyte development
what cell types are granulocytes?
neutrophils, eosinophils, and basophils
BEN
what types of cells are agranulocytes?
monocytes and lymphocytes
what’s the difference between granulocytes and agranulocytes?
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
what are the 6 stages of neutrophil maturation?
- myeloblast
- promyelocyte
- myelocyte
- metamyelocyte
- band
- segmented neutrophil
what are myeloblasts?
first stage of neutrophil maturation
medium-sized cells with fine chromatin and a little rim of cytoplasm
what does fine chromatin mean?
chromatin pattern is very even, light staining, and so see- through that you can usually see nucleoli
what are promyelocytes?
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
what are the two features that characterize promyelocytes?
- Size (promyelocytes are huge)
2. Granulation (promyelocytes have tons of primary granules).
what are myelocytes?
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)
what are metamyelocytes?
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
what are band cells?
5th stage in neutrophil differentiation
As the nucleus matures, it becomes thinner and looks more like a U
what are segmented neutrophils?
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
what are the stages of eosinophils and basophils?
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)
In granulocytes, which cell stage is the first one to show differentiation?
promyelocyte stage
the cell has committed itself to becoming either a neutrophil, eosinophil, or basophil
how do monocytes mature?
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
what are the stages of monocyte development?
- monoblast
- promonocyte
- monocyte
SO EASY!! (:
MONOcyte = 1 intermediate, mono
what are promonocytes?
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
how do promonocytes turn into mature monocytes?
As the promonocyte develops into a monocyte, it loses the nuclear folding pattern and develops an indented nucleus
what are the characteristics of a monocyte?
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
what’s the process through which lymphocytes mature?
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
what are the steps in lymphocyte development?
- lymphoblast in bone marrow
- mature lymphocyte
it doesn’t go through different morphologic stages like other hematopoietic cells!
what are the characteristics of lymphoblasts?
- fine chromatin
- round nucleus
- minimal cytoplasm
looks a lot like myeloblasts, you actually can’t tell them apart by just looking at them
at what stage of neutrophil development does specific granulation first appear?
myelocyte
what do promonocytes have that monoblasts don’t?
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
what maturational stage of granulocyte development is the largest?
promelocyte
