Anatomy and physiology of white blood cells
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What are the two subdivisions of WBCs? And what are they separated according to?
- Granulocytes and mononuclear cells (agranulocytes)
- Granulocytes have unusually shaped nuclei and specific staining granules in their cytoplasm
- Mononuclear cells have more normal shaped nuclei and have non-specific staining granules in their cytoplasm
Name all the granulocytes
Name all the mononuclear cells
Name and describe the process by which WBCs are made
Haematopoiesis - all leukocytes originate from a single, undifferentiated pluripotent stem cell. Early branching of the pathways separates the lymphoid stem cells (which produce lymphocytes) from the myeloid stem cells (which produce all other forms of WBCs and also RBCs and platelets).
Where are the following types of WBC made and matured?
a) granulocytes and monocytes
- a) Formed only in the bone marrow
- b) Most immature lymphocytes leave the bone marrow and migrate to lymphoid tissues where they give rise to mature lymphocytes through further mitosis and differentiation.
What does the nucleus of a mature neutrophil look like?
A 'string of sausages'
What is the name of an immature neutrophil? What does it's nucleus look like?
- A band neutrophil
- A horseshoe shape
What type of infection may cause a significant increase in the numbers of circulating neutrophils?
A bacterial infection
What are the two pools of neutrophils in the body?
- Circulating neutrophils - can be picked up by blood sampling
- Marginating neutrophils - these neutrophils stick to the sides of the blood vessels and are not picked up by blood sampling
How long do neutrophils stay in the circulation?
A very short time (~7-14hrs) as they are only using it to get to the tissues they want to be in
Once neutrophils move into the tissues can they return to the blood vascular system?
Describe the role of neutrophils during inflammation
Within just a few hours after the onset of a serious inflammation the number of neutrophils in the blood may increase by up to 4-5 times. Approximately 30 mins after the onset of inflammation a large number of neutrophils reach the affected area. They squeeze between intercellular junctions between endothelial cells lining blood vessels to get to the tissues. Neutrophils phagocytose bacteria and digest them using lysosomes (which contain lysozymes). After it kills the bacterium the neutrophil itself will die. Neutrophils also release cytokines which are transported, via the blood, to the bone marrow where they stimulate the release of stored neutrophils and increase the production of neutrophils and monocytes. Neutrophils also increase the permeability of the blood vessel walls to allow more cells involved in inflammation to reach the tissues.
What does an eosinophil look like?
It typically has a bi-lobed nucleus. The specific staining granules in its nucleus attract eosin (the acid dye in the romanovsky stain) and so their cytoplasm should appear red.
Once released from the bone marrow where do eosinophils move to?
Areas that will be nearest to the environment e.g. skin
What are the functions of eosinophils?
- Eosinophils are involved in the regulation of inflammatory and allergic type reactions
- Phagocytosis of antigen-antibody complexes
- Deactivate histamine and inhibit the release of histamine and serotonin
- Fight parasitic infections e.g. helminthic worms
What does a basophil look like?
It can have a bi-lobed or multi-lobed nucleus. The specific staining granules in its nucleus attract the basic dye in the romanovsky stain so their cytoplasm should appear blue
What is the function of basophils and how do they carry it out?
Basophils play a role in inflammatory and allergic type reactions. They possess vesicles which contain histamine and heparin. IgE antibodies can bind to basophils, as well as mast cells, and cause them to degranulate in the presence of an allergen.
What does a monocyte look like?
This is the largest type of WBC. It typically has an indented nucleus. The cytoplasm appears "foamy" as it only has non-specific staining granules in the cytoplasm.
When monocytes move into tissues what do they become?
What does a lymphocyte look like?
The round, densely stained nucleus of a lymphocyte takes up most of the cytoplasm.
What are the function of different lymphocytes:
a) T cells
b) B cells
- a) cell mediated immune reactions
- b) antibody production / antibody recognition
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