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Hematopoiesis, the process of blood
formation, in adults occurs in bone marrow, under normal
circumstances. Examine the bony
projections that line the marrow cavity.
- These are covered by a CT layer
called endosteum which may be difficult to see. The stroma, or
loose connective tissue, is filled with blood cell precursors
which are organized in cords or clusters.
- Blood vessels with dilations
called vascular sinuses are also present in marrow.Clinical note:
- Since
hematopoietic populations undergo continuous rapid cell renewal,
they are easily damaged by chemo-therapeutic drugs and ionizing
radiation.
Below is picture of a section from a
needle biopsy of normal bone marrow which retains much of the normal
organization of the marrow in bone. All of the listed elements are
present
- Adipocytes,
- Blood sinusoids,
- Hemopoietic cords,
- Megakaryocytes and
- Stromal cells
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Note the large, multiple, and
polyploid nuclei of the megakaryocyte.
How do megakaryocytes form
platelets?
What is the cellular difference
between red and yellow bone marrow?
How do newly formed blood cells move from the stroma into the
bloodstream?
The circulatory
system is next.. |
