‫كلية تقنيات المختبرات الطبية‪/‬الحدباء‬ ‫المرحلة الثالثة

Learning objectives
Introduction to hematology
Function of blood
Hemopoiesis
Erythropoiesis

Introduction
Hematopathology is structured around disorders of:
red cells
white cells
platelets coagulation.
Remember, however, that individual diseases commonly affect more than one of them.

Physiology
The marrow is a large organ, approaching the size of the liver.
In adults, most of it is in the flat bones, including the sternum, pelvis and vertebrae.
White blood cell precursors form 75% of the marrow and most of the rest consists of erythroid precursors.
Megakaryocytes (from which platelets are formed) are scattered throughout.

It may seem surprising that so much of the marrow is
devoted to the white cell series, given that there are 500 times as many red cells as white cells in the circulation.
However, erythrocytes have a mean life of 120 days
whereas white cells have a circulating lifespan measured in hours.

All blood cells are derived from multipotent, uncommitted stem cells.
These differentiate into the lines of committed stem cells from which red cells, platelets, monocytes, granulocytes and lymphocytes are formed.
The processes of differentiation and proliferation are controlled by growth factors, including interleukins, colony-stimulating factors and erythropoietin.

Normal Haemopoiesis :
Cell hierarchy (Haemopoiesis schematic representation)

Sites of Haemopoiesis
Yolk sac
Liver and spleen
Bone marrow

Haemopoietic growth factors
GM-CSF
Granulocyte-Macrophage colony stimulating factor
M-CSF
Macrophage colony stimulating factor
Erythropoietin
Erythropoiesis stimulating hormone
(These factors have the capacity to stimulate the proliferation of their target progenitor cells when used as a sole source of stimulation)
Thrombopoietin
Stimulates megakaryopoiesis

Haemopoietic growth factors
Cytokines
IL 1 (Interleukin 1)
IL 3
IL 4
IL 5
IL 6
IL 9
IL 11
TGF-β
SCF (Stem cell factor, also known as kit-ligand)
Cytokines have no (e.g IL-1) or little (SCF) capacity to stimulate cell proliferation on their own, but are able to synergise with other cytokines to recruit nine cells into proliferation.