Red human blood cells in Darkfield illumination

In bright field illumination red blood cells do not show a strong contrast. Staining is a way to overcome it. Dark field microscopy is another way to increase contrast. It is realized in a normal light microscope equipped with a special so-called dark field condenser, which prevents light passing through the lens, creating a dark field, unless light it is scattered by red blood cells (or anything else) present in the preparation.

The red blood cells in the blood bind oxygen to the red blood pigment
(= hemoglobin) which they contain. In this manner, the oxygen from the lungs is transported to all parts of the body (= oxygen transport). The blood contains about 4-5 billion (!) Red blood cells per ml. Red blood cells are always prepared fresh in the red bone marrow, by division of certain bone marrow stem cells (= erythroblasts).

The blood contains three different types of cells:

• Red blood cells.
• White blood cells (= leukocytes) are closely involved in the immune response of the body against infection by micro-organisms (including bacteria, viruses and fungi).
• Platelets (= thrombocytes) initiate the blood coagulation that stops the bleeding after a damage.