Proerythroblasts, lymphoblasts, myeloblasts, monoblasts, and megakaryoblasts share what precursor cell type?
Pluripotent hematopoietic stem cells
Reticulocytes are precursors for what type of blood cell?
Lymphoblasts are the precursors for what two blood cell types?
B cells and T cells
When B cells and T cells mature, what do they become, respectively?
B cells mature into plasma cells whereas T cells become activated T cells
Monocytes develop from what immediate precursor blood cell type?
What precursors indicate that a stem cell has differentiated into the platelet lineage?
Megakaryoblasts, which become megakaryocytes that form platelets
Neutrophils, eosinophils, and basophils differentiate from what common precursor blood cell type?
Promyelocytes, myelocytes, metamyelocytes, and stab cells are precursors for what three granulocytes?
Neutrophils, eosinophils, and basophils
In a normal blood sample, name the differential of white blood cells from most to least numerous.
Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils (remember: Neutrophils Like Making Everything Better)
What feature of the erythrocyte structure permits easy gas exchange of oxygen and carbon dioxide?
The biconcave disc shape permits a high surface area to volume ratio and facilitates gas exchange
What molecule do erythrocytes depend upon exclusively for energy?
Glucose; remember, they cannot use ketones for energy
What is the average lifespan of an erythrocyte in a normal human host?
Where does an erythrocyte obtain the adenosine triphosphate that it needs for energy?
Glucose: 90% is anaerobically degraded to lactate, whereas 10% goes to the hexose monophosphate shunt
What role does the erythrocyte play in acid/base physiology?
Erythrocytes carry carbon dioxide from the periphery to the lungs for elimination
How do erythrocytes facilitate transport of carbon dioxide away from the peripheral tissues?
The chloride-bicarbonate antiport produces a physiologic chloride shift, resulting in cellular loss of chloride and gain of bicarbonate (and thus carbon dioxide)
How would you describe a peripheral blood smear that shows an increased number of red blood cells and numerous immature red blood cells?
There is an erythrocytosis or polycythemia (increased number of cells) and a reticulocytosis (increased immature cells)
How would you describe a peripheral blood smear showing red blood cells of varying sizes and of varying shapes?
This smear exhibits anisocytosis (varying sizes) and poikilocytosis (varying shapes)
How do mature platelets form from large megakaryocyte precursors?
Small portions of cytoplasm fragment off of megakaryocytes
What is the role of platelets immediately following an injury such as a laceration?
Primary hemostasis; for example, they help prevent leakage of red blood cells from damaged vessels
What happens to platelets when they are in the presence of damaged endothelium?
Platelet activation; sticky platelets aggregate and interact with fibrinogen to form a hemostatic plug
What two types of granules do platelets contain?
Dense granules and alpha granules
What are the contents of the dense granules of platelets?
Adenosine diphosphate, calcium
What are the contents of the granules of platelets?
von Willebrand;s factor, fibrinogen
Where in the body would you typically find the most platelets at any one time?
Approximately one third of the platelet pool is stored in the spleen
What is the life span of a platelet?
You note multiple small red lesions on the skin of a patient that do not blanche with pressure; what are two possible etiologies of these lesions?
These are petechiae, which can be caused by a low platelet count (thrombocytopenia) or dysfunctional platelets
Granulocytes and mononuclear cells are what kind of blood cells?
Leukocytes (leuk = white; cyte = cell)
Name three types of granulocytes.
Basophils, eosinophils, and neutrophils
Name two types of mononuclear cells.
Lymphocytes and monocytes
What is the main function of leukocytes?
To defend against infection
How many leukocytes are normally found per microliter or blood?
4000 to 10,000
What distinguishes the appearance of a basophil from other granulated cells?
The densely basophilic granules, which stain blue with basic stains
What molecules, normally seen as part of the inflammatory cascade, are contained in basophilic granules?
Histamine (which causes vasodilation) and other vasoactive amines, as well as leukotrienes (LTD-4)
Compare and contrast the function and location of basophils and mast cells.
Both types of cells mediate allergic reactions and secrete histamine; however, mast cells bind immunoglobulin E and are found in tissue, whereas basophils are found in the blood
What substances are released when mast cells degranulate?
Histamine, heparin, eosinophilic chemotactic factors
What stimulus causes mast cell degranulation?
Immunoglobulin E binding to receptors on the surface of the mast cell
You note many basophils on a peripheral smear of a patient undergoing an allergic reaction; do you also expect to see mast cells?
No; although both cells are involved in allergic reactions, basophils are found in the blood whereas mast cells are typically only found in tissues
What medication can prevent the release of inflammatory compounds from mast cells in a patient with asthma?
Cromolyn sodium, which stabilizes mast cell membranes and prevents degranulation
What distinguishes an eosinophil from other granulated cells?
They are full of large, uniform eosinophilic (pink) granules (eosin = a dye that stains pink; philic = loving)
What is the role of major basic protein, found in eosinophils?
Major basic protein is released to fight helminth and protozoan infections
Eosinophils are phagocytic cells, particularly in the presence of what?
How do eosinophils and mast cells interact during an allergic reaction?
Eosinophils produce histaminase and arylsulfatase to limit the inflammatory reaction from mast cell degranulation
Name five diagnoses to consider in a patient discovered to have eosinophilia.
Neoplasm, Asthma, Allergic reaction, Collagen vascular disease, Parasites (remember: NAACP)
What is the appearance of granules found in neutrophils?
Large, spherical, azurophilic granules
Under the microscope you note a neutrophil with several granules; what organelle are you looking at?
What are the contents of the granules in neutrophils?
Hydrolytic enzymes, lysozyme, myeloperoxidase, and lactoferrin
A peripheral blood smear shows multiple neutrophils with nuclei that display 6, 7, and even 8 lobes; what lab tests are indicated?
B12 and folate tests; hypersegmented polys (neutrophils) are present in deficiencies of either vitamin
Would you expect to find monocytes in a tissue biopsy?
No. Monocytes are found in the blood, not the tissue; when they enter tissue they differentiate into macrophages
Describe the appearance of monocytes.
Large, kidney-shaped nucleus; frosted glass cytoplasm
What role do macrophages play in the immunologic response to extracellular pathogens?
They are antigen-presenting cells using major histocompatibility complex class II molecules (present phagocytosed extracellular pathogens)
Which cytokine causes activation of macrophages?
What molecules do dendritic cells express on their surfaces that are integral to their role as antigen-presenting cells?
Major histocompatibility complex II and Fc receptor
What are dendritic cells in the skin called?
What is the major function of B lymphocytes?
To produce antibodies
What is the function of T lymphocytes?
They control the cellular immune response and regulate the activity of B lymphocytes and macrophages
B lymphocytes are part of the _____ (cell-mediated/humoral) immune response.
Where do B lymphocytes originate? Where do they mature?
They originate and mature in the bone marrow (remember: B = Bone marrow)
After maturation, where do B lymphocytes migrate to from the bone marrow?
Peripheral lymphoid tissue (lymph node follicles, white pulp of spleen, other uncapsulated lymphoid tissue)
What kind of antibody response occurs when the body encounters an antigen it has previously seen?
Rapidly secreted, previously formed antibodies because B cells have antigenic memory
What is the response of a B cell after encountering a recognized antigen?
B cells differentiate into plasma cells and secrete antibodies
What major histocompatibility complex do B cells possess on the cell surface?
Major histocompatibility complex II, which allows B cells to act as antigen-presenting cells
What organelles create the appearance of the off-center nucleus and abundant cytoplasm in a plasma cell?
The rough endoplasmic reticulum and Golgi apparatus are plentiful (remember: the plasma cell is a protein (antibody) factory!)
How are plasma cells formed?
When B cells encounter a recognized antigen, they differentiate into plasma cells (which have antigenic memory)
You note that a patient;s bone marrow shows a monoclonal proliferation of plasma cells; what is the diagnosis?
What is the site of origin for T lymphocytes? Where do they mature?
They originate in the bone marrow but mature in the thymus (remember: T cells mature in the Thymus)
Name the three types of mature cells into which T cells differentiate.
Cytotoxic T cells, helper T cells, and suppressor T cells
Which major histocompatibility complex and CD molecules are expressed by cytotoxic T cells?
Major histocompatibility complex I and CD8 (MHC CD = 8; MHC I CD8 = 8)
Which major histocompatibility complex and CD molecules are expressed by helper T cells?
Major histocompatibility complex II and CD4 (MHC CD = 8; MHC II CD4 = 8)
T lymphocytes mediate the _____ (cellular/humoral) immune response.
What is the predominate type of lymphocyte found in the circulation?
T cells, which make up approximately 80% of circulating lymphocytes