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Organs are grouped into 2 main groups:
Primary and secondary lymphoid organs
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primary lymphoid organs include:
bone marrow and thymus
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secondary lymphoid organs include:
spleen and lymph nodes
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There are tertiary lymphoid organs:
GALT, BALT, genitourinary system
**only have effector and memory cells**
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hematopoiesis
formation and development of red and white blood cells
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all blood cells arise form
hematopoietic stem cells (HSC)
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Why are HSCs difficult to study? (2 reasons)
- 1. they are not abundant (1 in 50K cells)
- 2. difficult to grow in vitro
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Hematopoiesis occurs at various sites throughout life.
Where does is occur the first week of development?
fetal?
adult?
where does production decrease after adult stage?
- yolk sac
- liver and spleen
- cranium, pelvis, sternum, ribs, vertebra, long bones
- long bones
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where are HSCs located?
bone marrow
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pluripotent/multipotent
from one cell, other types of cells can be formed.
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unipotent
can make only one kind of cell
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HSCs differentiate into:
- Lymphoid progenitor cells LPC
- Myeloid progenitor cells MPCs
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