Blood

The study of normal and pathologic blood development is based on the examination of stained smears of peripheral blood and bone marrow and sections or smears of lymphoid tissue of the thymus, spleen, lymph nodes and lymphoid infiltrations and aggregates along the G.I. tract. The intent of this laboratory exercise is to familiarize the student with the morphology and numerical frequency of mature, peripheral blood cells, and to study the intermediate stages of blood cell development as seen in bone marrow.

The cellular or formed elements of peripheral blood are classified according to the details of their appearance following staining with polychromic stains, e.g. Wright's stain. Four groups or classes of cells or cell fragments are usually present in peripheral blood:

1. Anuclear erythrocytes (red blood cells).
2. Cell fragments (platelets).
3. Granular leukocytes or granulocytes (neutrophils, eosinophils or acidophils, and basophils).
4. Agranular leukocytes (monocytes and lymphocytes).

#12 Blood smear, Wright's stain

To study the cell types in your preparations first scan the smear with the low power objective and select a region where the red cells do not overlie one another and where they are stained pink. After finding an area that is well smeared and well stained, examine the blood cells, and in particular the leukocytes, with the oil immersion objective. Identify neutrophils, lymphocytes, eosinophils, and monocytes; basophils also will be present but they account for less than one percent of the total number of leukocytes. Platelets will also be found.

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