blood and hematopoietic cells


Blood is a mesenchymal tissue including extracellular matrix, plasma, is liquid.

The adult human body contains about 5 liters of blood in the blood vessels.

Excluding ships, coagulated blood.

Plasma is an aqueous protein solution, lipids, carbohydrates and minerals, it also contains dissolved gases : oxygen, azote, carbon dioxide

F IGURES elements of the blood are, is true cells, leukocytes (white blood cells), either elements devoid of nuclei, erythrocytes (or red blood cells ) and platelets, including only cytoplasmic structures. These elements are specific anucleate blood and only come out of that & rsquo vessels; for bleeding. The leukocytes are in transit in the blood and function only develop in the connective tissues.

The blood that circulates throughout the & rsquo; organization ensures the constancy of the internal environment (PH, hydration, Temperature) and transmits to every tissue nutrients and defense needed. It brings the & rsquo; oxygen and nutrients, C02 discharges and waste, it carries hormones from their place of synthesis up & rsquo; their target cells.


The blood cell formation process is the & rsquo; hematopoiesis. Blood elements

All take their origin, in the & rsquo; adult, in the bone marrow hematopoietic red which is contained in the cavities of the & rsquo; cancellous bone.

The hematopoiesis includes maintaining d & rsquo; a stock of stem cells undifferentiated. The production of blood cells is very important, every day are renewed 1% erythrocyte ( 250 billion ),

10% platelet and granulocyte totalities.

They exist in the bone marrow stem cells capable of giving all lines, les CFU ( Colony Forming Unit )

Many growth factors are involved in all stages of the & rsquo; hematopoiesis.

A / Lineage erythrocyte :

L & rsquo; red blood cell or erythrocyte, also called erythrocyte is the & rsquo; figurative element of the most abundant blood, it represents the final stage of differentiation of erythroid.

The red blood cell has a disk shape biconcave. Its diameter is 7,2 at 7,9 µm.

At & rsquo; fresh, hue isolated erythrocytes is orange yellow, c & rsquo; is their accumulation that gives blood its characteristic red color. L & rsquo; red cell is enucleated, c a d core devoid.

The red blood cell is very deformable and can s & rsquo; stretch to pass through the finer capillaries or even by holes 0,2 .mu.m of diameter.

Its plasma membrane has cell-coat or glycocalyx, with a sugar composition of AB system determines the blood group O.

L & rsquo; erythropoiesis :

L & rsquo; erythropoiesis is & rsquo; all differentiation process, proliferation and maturation leading to the totipotent strain circulating red blood cell wall. The corresponding cell stages are included in the attached table.

Divisions occur at all previous stages l & rsquo; erythroblast polychromatophilic II. This evolution s & rsquo; accompanies many cytoplasmic and nuclear maturation.

L & rsquo; red blood cell leaves the bone marrow as d & rsquo; a cell remainder is the reticulocyte which still contains some traces of & rsquo; cytoplasmic organelles. In 48 hours, maturation s & rsquo; ends.

The entire process of & rsquo; erythropoiesis lasts about a week. The lifetime of the & rsquo; red blood cell in the circulating blood is d & rsquo; about 120 days and normal reticulocyte count is 1 at 2%.

The regulation of the & rsquo; erythropoiesis is done by & rsquo; main action of a stimulating factor : l & rsquo; erythropoietin, glycoprotein primarily prepared by the kidney, it induces CFU to the red line.

B / platelet lineage :

Blood platelets are anucleate elements that are essential to stop the bleeding and coagulate, vary in diameter from 2 at 5 /Others.

In the circulating blood, they are lenticular, to irregular contours : c & rsquo; is the unactivated form or DI5COCYTE. When the wafer is turned, it shrinks and emits long processes, c & rsquo; is the form ECHINOCYTE.

Platelets play a fundamental role in & rsquo; hemostasis and blood coagulation. These very complex phenomena take place in four phases with the & rsquo; platelet activation, membership in a support, l & rsquo; platelet aggregation and contraction.

Platelet formation :

Platelet formation or thrombopoiesis is performed by fragmentation of the cytoplasm of large cells, megakaryocytes.

From the specialized cell strain ( CFU-AAK ) are born megakaryoblasts ( 30 uM Diam ).

Not dividing, the megakaryoblast gradually becomes basophilic megakaryocyte ( 50 μm de

dIAM) core monstrous lobule, the cell s & rsquo; enriched in granulation and becomes a granular megakaryocyte thrombocytogène which releases platelets.

C / lymphocyte lineage :

Lymphocytes present in the blood represents only & rsquo; a small portion of the lymphocyte population, most of & rsquo; them are in the lymphoid tissue.

Lymphocytes are generally small size ( 8 at 10 µm), are the small lymphocytes, d & rsquo; other so-called large lymphocytes have a more abundant cytoplasm and sometimes richer in lysosomes. It s & rsquo; is hematopoietic stem cells or NK cells (Natural Killer).

The precursors of the cells found in bone marrow hematopoietic, but most of these cells form when the immune reaction.

D / Line monocytairc :

The monocyte is the largest cell that & rsquo; it is found in the blood ( 15 at 18 μm photo ), its core is reniform.

The monocyte is actually the undifferentiated form, immature du macrophage, it differs

completely in peripheral connective tissues after a blood transit 24 at 48 hours.

The monocyte derived d & rsquo; a common stem cell with neutrophils, la CFU-6M (granule monocytaire) derivant elle-même the CFU-6EMM (Granulocyte-monocyte erythro-mégacaryo)

Very little is known intermediate stages between CFU and monocytes.

E / Lineage granulocytic :

Granulocytes or neutrophils possess numerous cytoplasmic granules and a core "plurilobé.

They are highly mobile cells that play a critical role in the defense of the & rsquo; body.

Because of the different staining properties of their granules, we distinguish neutrophils, eosinophils and basophils.

a- Neutrophils :

cell 10 at 12 Diam pm, spherical in circulating blood, its core has 2 at 5 well individualized lobes.

The cytoplasm contains 3 types of granules : the specific granules or grains B, most numerous ( 80% ) , the granules or grains azurophile A , are fewer (15%) and granules nucleated ,rares ( 5% )

b- Eosinophilic granulocytes :

Eosinophilia usually has a lobed nucleus and numerous granules and bulky,

c- Les granulocytes basophiles :

The least abundant of blood granulocytes ( 0,5% on average ), is about 8 of Diam. Granulopoïése

The three granulocyte lineages seem to derive from three different stem cells, the neutrophils being common with the monocyte.

During the & rsquo; evolution, specific granules of the three lines are synthesized at the stage of myelocyte. Maturation ends normally in the marrow.

The regulation granulopoiesis is related to levels of circulating granulocytes and peripheral application.

F / Marrow Hematopoietic :

Bone marrow is contained in the internal cavities of the bone, in the large medullary cavity of the long bones. L & rsquo; adult human body contains between 2 and 4 bone marrow which is only a small part bloodborne.

There are three varieties of morphological and functional bone marrow : red marrow, yellow marrow and cord gray. In fact only the first hematopoietic and c & rsquo; is its rich red blood cells that determines its color

Table III-6 : Offspring of hematopoietic stem cells BFU : Burst-Forming-Unit. CFU : Colony-Forming–Unit. GEMM : Grain-erythro-Mégacaryo-Monocytaire. L : lymphocyte. E : Erythrocytaire. MK : megakaryocytic. GM : Grain-Monocytaire. It's the : eosinophilic. B : Basophile.
Figure 6-4 : Diagram of the major components of blood platelets. When switching from the discocyte shape of rest to the activated form échinocyte, the sub-structures membrannaires (microtubules and heatwaves) are disorganized.
Table 6-V : erythropoiesis
Tableau 6-VII : Granulopoïèse
Table VI-6 : Platelet formation

Course of DR Hamza KHALFAOUI – Faculty of Constantine