Stages of Development of Blood Cells

Dr. Sama ul Haque

Dr Rania Gabr

Objectives• Understand the composition of whole blood.

• How to prepare a blood smear.

• Describe the structure of Erythrocyte.

• Enlist different types of leucocytes.

• Explain the differentiation of myeloid and lymphoid stem cells.

• Discuss the development of blood cells in red bone marrow.

Composition of Whole Blood

Preparing a Blood Smear

Formed elements

Red Blood cellsWhite blood cells

Platelets

Granulocytes(Polymorphonucleated)

Agranuloctes(Mononucleated)

Neutrophils Basophils

Eosinophils

Lymphocytes Monocytes

Blood Cells

Blood Cells

ERYTHROCYTE• These cells are:• biconcave disk •no nucleus•~7.8 μm diameter fresh; • 7.2 -7.4 in stained smears•contains hemoglobin The primary function of these cells is to carry oxygen from the lungs to the body cells.

Normally: (4-6 million )erythrocytes per cubic millimeter of blood,

Erythrocyte

Normal Human Erythrocyte

• Diameters greater than 9 um are called:“MACROCTES” Diameters less than 6 um are called:“ MICROCYTES”

• Sickle cell anemia is an inherited condition which results in some erythrocytes being malformed.

• The gene for this condition causes the hemoglobin to be incorrectly formed, which in turn causes some erythrocytes to take on a crescent shape.

• These cells are not able to carry adequate amounts of oxygen to cells.

Leukocytes (6-10,000 per μL)

• Granulocytes (polymorphonuclear leukocytes):–Neutrophils -60-70%–Eosinophils -2-4%–Basophils -0.5-1%

• •Agranulocytes (mononuclear leukocytes)–Lymphocytes -20-30%–Monocytes -3-8%

Types of Human LeucocytesNeutrophils, eosinophils, and basophils have granules that stain specifically with

certain dyes and are called granulocytes. Lymphocytes and monocytes are considered agranulocytes, even though they may show azurophilic granules

(lysosomes), which are also present in other leukocytes.

NeutrophilsNeutrophils can be identified by their multilobulated nuclei, with lobules held

together by thin strands. With this feature the cells are often called polymorphonuclear leukocytes, or just polymorphs.

These cells are capable of phagocytozing

foreign cells, toxins, and viruses.

When taking a Differential WBC Count of normal blood, this type of cell would be the most numerous.

Normally, neutrophils account for 60-70% of all leukocytes.

If the count exceeds this amount(Neutrophilia), the cause is usually due to an acute infection such as appendicitis, smallpox or rheumatic fever.

If the count is considerably less(Neutropenia), it may be due to a viral infection such as influenza, hepatitis, or rubella.

EosinophilsEosinophils are about the same size as neutrophils but have bilobed nuclei and abundant

coarse cytoplasmic granules. The cytoplasm is often filled with brightly eosinophilic specific granules, but also includes some azurophilic granules. (a): A eosinophil next to a neutrophil for comparison with its nucleus and granules. (b): Even with granules filling

the cytoplasm, the two nuclear lobes of eosinophils are usually clear.

(Does it look like a telephone receiver?)

• Function:

1- The granules contain digestive enzymes that are particularly effective against parasitic worms in their larval form.

2- These cells also phagocytize (antigen - antibody complexes).These cells account for less than 5% of the WBC's.

Increases beyond this amount (Eosinopilia): may be due to parasitic diseases, bronchial asthma or hay fever.

Eosinopenia may occur when the body is severely stressed.

BasophilsApproximately the same size as neutrophils and eosinophils, but have large, strongly basophilic specific granules which usually obstruct the appearance of the nucleus

having two or three irregular lobes.

These granules contain histamines (cause vasodilation) and heparin (anticoagulant).

LymphocytesLymphocytes are agranulocytes and lack the specific granules characteristic of

granulocytes. (a): Small lymphocytes are slightly larger than the neighboring erythrocytes with spherical nucleus. (b): Medium lymphocytes are distinctly larger than

erythrocytes. (c): Large lymphocytes, much larger than erythrocytes.

Round, dark, heterochromatic nucleus –like an “ink spot“

These cells play an important role in our immune response.

MonocytesMonocytes are large agranulocytes that circulate as precursors to macrophages and

other cells of the mononuclear phagocyte system. Monocytes show their eccentric nuclei indented, kidney shaped, or U shaped. The largest leucocyte.

PlateletsPlatelets are cell fragments 2–4 µm in diameter derived from megakaryocytes of

bone marrow. Their primary function is to rapidly release the content of their granules upon contact with collagen to begin the process of clot formation and reduce

blood loss from the vasculature. Platelets (arrows) are often found as aggregates.

Summary of Formed Elements

Differentiation of Myeloid And

Lymphoid Stem Cells

1. EPO– Erythropoietin2. CSF– Colony Stimulating Factor3. GM-CSF– Granulocyte+Macrophage CSF4. M-CSF– Macrophage CSF5. G-CSF– Granulocyte CSF

Differentiation of Myeloid And Lymphoid Stem Cells

Development of Blood Cells in Red Bone Marrow

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