Red Blood Cell

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 cells (60x)

Platelet

Platelets are small cell fragments produced by budding from megakaryoctyes 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.

Also see EM 159 Platelet.

Neutrophil

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 #1 (60x)

• Neutrophil #2 (60x)

• Neutrophil #3 (60x)

• Neutrophils #4 (60x)

• Neutrophil #5 (60x)

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.

Eosinophil

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 #1 (60x)

• Eosinophil #2 (60x)

• Eosinophil #3 (60x)

• Eosinophil #4 (60x)

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

Basophil

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 #1 (60x)

• Basophil #2 (60x)

Basophils mediate inflammatory responses.

Lymphocyte

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

• Small Lymphocyctes
• 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 #1 (60x)

• Lymphocytes #2 (60x)

• Lymphocyte #3 (60x)

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

Examples:

• Lymphocyte #1 (60x)

• Lymphocyte #2 (60x)

• Lymphocyte #3 (60x)

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

Monocyte

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 #1 (60x)

• Monocyte #2 (60x)

• Monocyte #3 (60x)

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.