MLAB 1415- HematologyMLAB 1415- HematologyKeri Brophy-MartinezKeri Brophy-Martinez

Chapter 4 : Hematopoietic Organs

Hematopoiesis: overviewHematopoiesis: overview

MedullaryMedullary Origin of blood cells and sequential sites of normal Origin of blood cells and sequential sites of normal

blood production within the bone marrowblood production within the bone marrow

ExtramedullaryExtramedullary Blood cell production in hematopoietic tissue Blood cell production in hematopoietic tissue

other than bone marrowother than bone marrowLiverLiverSpleenSpleen

Compensatory mechanism to provide blood cells Compensatory mechanism to provide blood cells in times of needin times of need

Ontogeny (origin) of HematopoiesisOntogeny (origin) of Hematopoiesis

Begins in mesoderm of Begins in mesoderm of yolk sac yolk sac forming erythroid cells.forming erythroid cells.    Production continues for about Production continues for about six weeks before declining and six weeks before declining and ends in about two months. ends in about two months.

Hemoglobin found in these Hemoglobin found in these embryonic cells consist of Gower embryonic cells consist of Gower 1, Gower 2 and Portland.1, Gower 2 and Portland.

Fetal liver Fetal liver now assumes now assumes responsibility for hematopoiesis responsibility for hematopoiesis during second month.  Yolk sac during second month.  Yolk sac erythoid cells move to liver and erythoid cells move to liver and

remain there until the seventh remain there until the seventh monthmonth

Ontogeny (origin) of HematopoiesisOntogeny (origin) of Hematopoiesis

From third to sixth month, From third to sixth month,

hematopoiesis occurs inhematopoiesis occurs in

kidney, thymus, spleen and lymphkidney, thymus, spleen and lymph

nodesnodes

Other emerging cellsOther emerging cells About three months of life, see plateletsAbout three months of life, see platelets About five months of life, see leukocytesAbout five months of life, see leukocytes

Ontogeny (origin) of HematopoiesisOntogeny (origin) of Hematopoiesis

Around seventh Around seventh month of fetal life, month of fetal life, hematopoiesis shifts hematopoiesis shifts to to bone marrow bone marrow    

Fetal marrow fills with Fetal marrow fills with RBCsRBCs

Ontogeny (origin) of HematopoiesisOntogeny (origin) of Hematopoiesis

At birth, liver At birth, liver and spleen stop and spleen stop hematopoietic hematopoietic activity.activity.

Bone marrow Bone marrow now becomes now becomes active site of active site of hematopoiesishematopoiesis

Ontogeny (origin) of HematopoiesisOntogeny (origin) of Hematopoiesis

Children up to teen years, Children up to teen years, has hematopoiesis in all has hematopoiesis in all bonesbones Hematopoiesis gradually Hematopoiesis gradually decreases in shafts of long decreases in shafts of long bones. bones.  Around age 18-20 Around age 18-20 hematopoiesis shifts to hematopoiesis shifts to production in sternum, production in sternum, ribs, pelvis, vertebrae, and ribs, pelvis, vertebrae, and skull.  skull.  After age 40, less area in After age 40, less area in these sites available for these sites available for hematopoiesis. hematopoiesis.

Storage PoolsStorage Pools

Granulocytes and Granulocytes and platelets also exist in platelets also exist in two poolstwo pools

• CirculatingCirculating• MarginalMarginal

  

Bone Derived CellsBone Derived Cells

Non-hematopoietic cells involved with bone Non-hematopoietic cells involved with bone turnover closely linked with hematopoiesisturnover closely linked with hematopoiesis

OsteoblastsOsteoblasts

Responsible for the formation, calcification and maintenance of the Responsible for the formation, calcification and maintenance of the bone structurebone structure

Large irregularly shaped cells in the bone marrow that may be confused Large irregularly shaped cells in the bone marrow that may be confused with plasmacytes or malignant cellswith plasmacytes or malignant cells

OsteoclastsOsteoclasts

Responsible for absorption of boneResponsible for absorption of bone

Assist in degradation of boneAssist in degradation of bone

Giant multinucleated, irregularly shaped phagocytic Giant multinucleated, irregularly shaped phagocytic cells in the bone marrow that may be confused with cells in the bone marrow that may be confused with megakaryocytesmegakaryocytes

Bone Derived CellsBone Derived Cells

Osteoblast Osteoclast

ReferencesReferences

Harmening, D. M. (2009). Harmening, D. M. (2009). Clinical Clinical Hematology and Fundamentals of Hematology and Fundamentals of hemostasishemostasis (5th ed.). Philadelphia, PA: (5th ed.). Philadelphia, PA: F.A. Davis Company. F.A. Davis Company.

McKenzie, S. B. (2010). McKenzie, S. B. (2010). Clinical Clinical Laboratory HematologyLaboratory Hematology (2nd ed.). Upper (2nd ed.). Upper Saddle River, NJ: Pearson Education, Inc..Saddle River, NJ: Pearson Education, Inc..