Red blood cells

(azure II and eosin)

Red blood cells (red blood corpuscles) are the most numerous formed elements of the blood. These are factually cell-derived structures.

• The majority of red blood cells in the bloodstream (80-90%) are biconcave discs (called normocytes or discocytes) with an average diameter of 7-8 μm
• Mature RBC have no nuclei
• The cytoplasm is oxyphilic as hemoglobin is stained there
• Discocytes of a blood smear are ring-shaped:
• the peripheral portion of the disc is convex, it is intensively stained
• the central portion of the disc is concave (pallor) and have a light color
• their size and pallor area may vary a lot

Discocytes q.v. #1, #2, #3

Peripheral blood contains also some juvenile types of red blood cells such as reticulocytes (detected by a special staining method) and more mature types: echinocytes (prickle-carrying cells), stomatocytes (dome-shaped, the pallor is narrow and irregular), spherocytes (spherical cells with no pallor)

Echinocytes q.v. #1, #2. Stomatocytes q.v. #1, #2. Spherocytes q.v. #1, #2.

A functional lifespan of red blood cells in the bloodstream is limited to 100-120 days, whereupon they are further eliminated by the spleen and liver. Their principal function is to transport oxygen and carbon dioxide. Red blood cell count for 1 l of the whole blood in males is 3.9-5.5×10¹², and 3.7-4.9×10¹² in females.

For more details see Electron microscopy image of red blood cells

Platelets

(azure II and eosin)

Thrombocytes (platelets) are the smallest formed elements of the blood. These are cell-derived structures formed by a release of cytoplasmic fragments in certain giant cells of the bone marrow called megakaryocytes

• In the bloodstream, they are biconvex discs while their size is 2-4 μm
• In a blood smear, they are rounded or have an irregular shape. They tend to agglomerate
• A new clot recruits platelets, and they develop a lot of projections there
• The peripheral parts of platelets (hyalomere) have stain uniformly, while the central parts (granulomere) contain azurophilic granules
• There is no nucleus in a platelet

Platelets q.v., #2, #3

The lifespan of platelets is 5-10 days; they are eliminated by the spleen. Platelets are involved in blood coagulation. Their blood count for 1 l of the whole blood is 180-320×10⁹.

For more details see Electron microscopy images of platelets