Transcript Hematopoietic Organs

MLAB 1415- Hematology
Keri Brophy-Martinez
Chapter 4 :
Hematopoietic
Organs
Hematopoiesis: overview
Medullary

Origin of blood cells and sequential sites of normal
blood production within the bone marrow
Extramedullary

Blood cell production in hematopoietic tissue
other than bone marrow
Liver
Spleen

Compensatory mechanism to provide blood cells
in times of need
Ontogeny (origin) of Hematopoiesis
Begins in mesoderm of yolk sac
forming erythroid
cells. Production continues for
about six weeks before declining
and ends in about two months.
Hemoglobin found in these
embryonic cells consist of Gower
1, Gower 2 and Portland.
Fetal liver now assumes
responsibility for hematopoiesis
during second month. Yolk sac
erythoid cells move to liver and
remain there until the seventh
month
Ontogeny (origin) of Hematopoiesis
From third to sixth month,
hematopoiesis occurs in
kidney, thymus, spleen and lymph
nodes
Other emerging cells


About three months of life, see platelets
About five months of life, see leukocytes
Ontogeny (origin) of Hematopoiesis
Around seventh
month of fetal life,
hematopoiesis shifts
to bone marrow
Fetal marrow fills with
RBCs
Ontogeny (origin) of Hematopoiesis
At birth, liver
and spleen stop
hematopoietic
activity.
Bone marrow
now becomes
active site of
hematopoiesis
Ontogeny (origin) of Hematopoiesis
Children up to teen years,
has hematopoiesis in all
bones
Hematopoiesis gradually
decreases in shafts of long
bones.
Around age 18-20
hematopoiesis shifts to
production in sternum,
ribs, pelvis, vertebrae, and
skull.
After age 40, less area in
these sites available for
hematopoiesis.
Storage Pools
Granulocytes and
platelets also exist in
two pools
•
•
Circulating
Marginal
Bone Derived Cells
Non-hematopoietic cells involved with bone
turnover closely linked with hematopoiesis

Osteoblasts
Responsible for the formation, calcification and maintenance of the
bone structure
Large irregularly shaped cells in the bone marrow that may be confused
with plasmacytes or malignant cells

Osteoclasts
Responsible for absorption of bone
Assist in degradation of bone
Giant multinucleated, irregularly shaped phagocytic
cells in the bone marrow that may be confused with
megakaryocytes
Bone Derived Cells
Osteoblast
Osteoclast
References
Harmening, D. M. (2009). Clinical
Hematology and Fundamentals of
hemostasis (5th ed.). Philadelphia, PA:
F.A. Davis Company.
McKenzie, S. B. (2010). Clinical
Laboratory Hematology (2nd ed.). Upper
Saddle River, NJ: Pearson Education, Inc..