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Learning Objectives:
Describe the cellular and extracellular components of peripheral blood
Distinguish granulocytes from agranulocytes by their morphology and explain their functions
Identify the types of blood cells in a peripheral blood sample and their proportionate ratios, and implications of altered cell ratios
Describe the process of hematopoiesis and the two major cell lineages
Distinguish red vs. yellow bone marrow in terms of histological organization, cellular composition, and age-related changes
No Slide:
What is the difference between blood, plasma, and serum?
Blood is a connective tissue comprising cells, plasma, and serum. Plasma is the extracellular matrix of blood. It is around 90% water but also contains proteins like albumin and fibrinogen. Serum is plasma without the factors in blood that cause clotting.
Write the name of the mature cell that is associated with the lineage including each of the following cells:
Megakaryocyte
Promyelocyte
Reticulocyte
Promonocyte
Megakaryocyte
Platelet
Promyelocyte
Granulocyte (Eosinophil, Basophil, or Neutrophil)
Reticulocyte
Erythrocyte
Promonocyte
Monocyte -> Macrophage
SLU Slide 42: Blood Smear
Iowa Virtual Slidebox: Blood (98)
Note: Most blood smears are stained with Wright’s Stain, which is slightly different from H&E.
Scan the slide at lower power before zeroing in on an area with abundant erythrocytes. These cells are uniform in color (acidophilic) and lack any internal structure. What do they look like in this smear? See if you can estimate the size of one erythrocyte.
Erythrocytes appear as pale pink circles that are either uniformly pink/acidophilic or that have an open space in the center. Erythrocytes are between 7-8 micrometers depending on the preparation, and can be used as a “ruler” in different histological sections.
Return to lower power and identify a spot with more leukocytes. Identify neutrophils, lymphocytes, eosinophils, and monocytes. This slide has very few basophils, which account for less than one percent of the total number of leukocytes. You will also see platelets. Use the chart and images on the following page to assist in identifying these different cell types. Complete the table below, adding drawing or screenshots to help you in the future. Note: You should be able to identify each of these cells.
Figure out how to put a chart here.
What are platelets? What do they do?
Platelets are anucleate fragments of a Megakaryocyte. They function to help form a blood clot.
Iowa Virtual Slidebox: Bone marrow: Smear (99)
Bone marrow is most commonly examined as a smear after being aspirated from bone.
Blood cells or “formed elements” do not replicate in the peripheral blood, but instead are produced in bone marrow, spleen, lymph nodes, and thymus. When you explore a bone marrow smear, you will not be able to identify each cell, but may be able to tell which lineage it belongs to, and how far along it is in terms of maturation.
Megakaryocytes are easy to identify because they are giant. See if you can find a few and measure them. How big are they?
~100 um.
Each morphological stage is correlated with the maturational events that need to occur to produce a mature, functioning cell. For example, picture a mature erythrocyte. Describe its:
Cytoplasm
Nucleus
Size
Cytoplasm: Pink, filled with hemoglobin, does not possess any organelles
Nucleus: Absent
Size: Small
Now examine the chart below and correlate each step with the appearance above.
Each stage is correlated with a decrease in size, a shift in cytoplasmic contents (more hemoglobin, fewer to no organelles), and changes in the morphology of the nucleus from round and central to eventually absent.
Now, picture a Granulocyte (Neutrophil, Eosinophil, or Basophil). Describe its
Cytoplasm
Nucleus
Size
Cytoplasm: Filled with specific granules
Nucleus: Lobed
Size: Moderate
Now examine the chart below and correlate each step with the appearance above.
Granulocytes get smaller as they mature. Specific granules can be differentiated relatively early compared to the morphological changes that occur in the nucleus as its chromatin condenses and becomes more filamentous, and the nucleus itself begins to form the lobes specific to each type of granulocyte.
Remember that half the fun of histology is "cruising" around a slide to see what you can find. Spend some time with these slides and make note of what you find in your notebook.
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