MH 033hr Blood Smear

Red Blood Cells

Red blood cells (or erythrocytes) are the most abundant type of blood cell (98% of all cells).

• Small cells (7 to 8 µm diameter)
• Biconcave disc
• No nucleus
• Eosinophilic cytoplasm (bright pink) because of the high concentration of the protein hemoglobin

Red blood cells are involved in transporting oxygen and carbon dioxide. They circulate in blood for between 100 to 120 days.

Example:

• Red blood cells60x)

The biconcave shape of red blood cells is shown in EM 206 Red Blood Cells by scanning electron microscopy.

Platelets

Platelets are small cell fragments produced by budding from megakaryocytes under the influence of thrombopoietin. Each megakaryocyte produces between 5,000 and 10,000 platelets.

Platelets are much smaller than red blood cells.

• Small discs (2 to 4 µm diameter)
• No nucleus
• Central region is basophilic structure (granulomere)
• Outer region does not stain (hyalomere)

Platelets are typically found as clusters:

Example

• Platelets 60x)

Platelets are involved in the formation of blood clots. Too few platelets can cause excessive bleeding, while too many platelets can cause blood clot formation. Their life span is between 7 to 10 days.

A cross-section of a platelet is shown in EM 159 Platelet by transmission electron microscopy.

Neutrophils

Neutrophils (also known as polymorphonuclear leukocytes [PMN]) are the most abundant type of white blood cells (60-70%).

• 12 to 15 µm diameter
• Segmented nucleus with 2 to 5 lobes
• Cytoplasm is a pale blue-pink
• Specific granules are pink-salmon
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Neutrophil 160x)
• Neutrophil 260x)
• Neutrophil 360x)
• Neutrophils 460x)
• Neutrophil 560x)

Neutrophils phagocytose and destroy bacteria. They circulate in blood for 8 to 16 hrs and survive in peripheral tissues for only 1 to 2 days.

The ultrastructure of neutrophils is shown in EM 169 Neutrophil by transmission electron microscopy. Neutrophil activation and intracellular killing of microbes is also described.

Eosinophils

Eosinophils are a small component of white blood cells (2-4%).

• 12 to 15 µm diameter
• Nucleus is bilobed
• Cytoplasm is a pale blue-pink
• Eosinophilic, specific granules - oval, 1 to 1.5 µm diameter, red/orange
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Eosinophil 160x)
• Eosinophil 260x)
• Eosinophil 360x)
• Eosinophil 460x)

Eosinophils kill multicellular parasites and phagocytose immune complexes. They circulate in the blood for 8 to 16 hrs and survive in peripheral tissues for only 2 to 5 days.

The ultrastructure of eosinophils is shown in EM 161 Eosinophil and EM 119 Eosinophil by transmission electron microscopy. Eosinophil activation and extracellular killing of parasites is also described.

Basophils

Basophils are rare white bloods (<1%).

• Smaller cells (10 to 12 µm diameter)
• Nucleus bilobed or S-shaped
• Cytoplasm is a pale blue-pink
• Specific granules - 1 to 1.5 µm diameter,many very basophilic (blue to black)
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Basophil 160x)
• Basophil 260x)

Basophils are found at sites of infection and release substances mediate inflammatory responses.

The ultrastructure of basophils is shown in EM 168 Basophil by transmission electron microscopy.

Lymphocytes

Lymphocytes are a large component of white blood cells (20 to 25%).

Small Lymphocytes

• Round cells of 6 to 9 µm diameter
• Intense staining of the spherical nucleus of mostly condensed chromatin
• Cytoplasm is limited to a small rim that is pale blue
• No specific granules
• Capable of mitosis

Examples:

• Lymphocyte 160x)
• Lymphocyte 260x)
• Lymphocyte 360x)

Large Lymphocytes

• Round cells of 9 to 15 µm diameter
• Blotchy staining (sometimes referred to as hill and valley) of the spherical nucleus
• More cytoplasm than in small lymphocytes
• No specific granules
• Capable of mitosis

Examples:

• Lymphocyte 160x)
• Lymphocyte 260x)
• Lymphocyte 360x)

Lymphocytes are released from bone marrow into the peripheral circulation. They exit blood into one of the peripheral lymphatic organs and continue to divide.

The ultrastructure of lymphocytes is shown in EM 199 Lymphocyte and EM 171 Lymphocyte by transmission electron microscopy.

Monocytes

Monocytes are the largest type of white blood cell.

• Large cells (12 to 20 µm diameter)
• Large, kidney-shaped or indented nucleus often with a "raked" chromatin pattern
• Cytoplasm is pale blue
• Few azurophilic granules

Examples:

• Monocyte 160x)
• Monocyte 260x)
• Monocyte 360x)

Monocytes are released from the bone marrow into the peripheral circulation. Their time span in blood is only 16 hrs. Monocytes in connective tissue differentiate into macrophages.

Monocytes are involved in phagocytosis and antigen presentation.

The ultrastructure of monocytes is shown in EM 170 Monocyte by transmission electron microscopy.