Hematology and Oncology - Anatomy

Question 1

Erythrocyte

• Characteristics
• Functions
• Definitions
  
  • Erythrocytosis
  • Anisocytosis
  • Poikilocytosis
  • Reticulocyte

Answer 1

• Characteristics
  
  • Eryth = red; cyte = cell.
  • Anucleate and biconcave [A], with large surface area-to-volume ratio for rapid gas exchange.
  • Life span of 120 days.
  • Membrane contains chloride-HCO3- antiporter, which allows RBCs to export HCO3- and transport CO2 from the periphery to the lungs for elimination.
• Functions
  
  • Carries O2 to tissues and CO2 to lungs.
  • Source of energy is glucose (90% used in glycolysis, 10% used in HMP shunt).
• Definitions
  
  • Erythrocytosis = polycythemia = increased hematocrit.
  • Anisocytosis = varying sizes.
  • Poikilocytosis = varying shapes.
  • Reticulocyte = immature erythrocyte, marker of erythroid proliferation.

Question 2

Platelet (thrombocyte)

• Characteristics
• Functions
• Pathology
• Receptors
  
  • vWF
  • Fibrinogen

Answer 2

• Characteristics
  
  • Small cytoplasmic fragment [A] derived from megakaryocytes.
  • Life span of 8–10 days.
  • Contains dense granules (ADP, calcium) and alpha granules (vWF, fibrinogen).
  • Approximately 1⁄3 of platelet pool is stored in the spleen.
• Functions
  
  • Involved in 1° hemostasis.
  • When activated by endothelial injury, aggregates with other platelets and interacts with fibrinogen to form platelet plug.
• Pathology
  
  • Thrombocytopenia or decreased platelet function results in petechiae.
• Receptors
  
  • vWF receptor: GpIb.
  • Fibrinogen receptor: GpIIb/IIIa.

Question 3

Leukocyte

• Characteristics
• Functions
• WBC differential from highest to lowest:

Answer 3

• Characteristics
  
  • Divided into granulocytes (neutrophil, eosinophil, basophil) and mononuclear cells (monocytes, lymphocytes).
  • Normally 4000–10,000 cells/mm3.
• Functions
  
  • Responsible for defense against infections.
• WBC differential from highest to lowest:
  
  • Neutrophils Like Making Everything Better
  • Neutrophils (54–62%)
  • Lymphocytes (25–33%)
  • Monocytes (3–7%)
  • Eosinophils (1–3%)
  • Basophils (0–0.75%)

Question 4

Neutrophil

• Characteristics
• Functions
• Pathology

Answer 4

• Characteristics
  
  • Multilobed nucleus [A].
  • Small, more numerous specific granules contain ALP, collagenase, lysozyme, and lactoferrin.
  • Larger, less numerous azurophilic granules (lysosomes) contain proteinases, acid phosphatase, myeloperoxidase, and β-glucuronidase.
• Functions
  
  • Acute inflammatory response cell.
  • Increased in bacterial infections.
  • Phagocytic.
• Pathology
  
  • Hypersegmented polys (5 or more lobes) are seen in vitamin B12/ folate deficiency.
  • Increased band cells (immature neutrophils) reflect states of increased myeloid proliferation (bacterial infections, CML).

Question 5

Monocyte

• Characteristics
• Functions

Answer 5

• Characteristics
  
  • Large, kidney-shaped nucleus [A].
  • Extensive “frosted glass” cytoplasm.
  • Mono = one (nucleus); cyte = cell.
  • Monocyte: in the blood.
• Functions
  
  • Differentiates into macrophages in tissues.

Question 6

Macrophage

• Characteristics
• Functions

Answer 6

• Characteristics
  
  • Activated by γ-interferon.
  • Macro = large; phage = eater.
  • Macrophage: in the tissue.
• Functions
  
  • Phagocytoses bacteria, cellular debris, and senescent RBCs and scavenges damaged cells and tissues [A].
  • Long life in tissues.
  • Macrophages differentiate from circulating blood monocytes.
  • Can function as antigen-presenting cell via MHC II.
    
    • CD14 is a cell surface marker for macrophages.
  • Important component of granuloma formation (e.g., TB, sarcoidosis).

Question 7

Eosinophil

• Characteristics
• Functions
• Causes of eosinophilia

Answer 7

• Characteristics
  
  • Bilobate nucleus.
  • Packed with large eosinophilic granules of uniform size [A].
  • Eosin = a dye; philic = loving.
• Functions
  
  • Defends against helminthic infections (major basic protein).
  • Highly phagocytic for antigen-antibody complexes.
  • Produces histaminase and arylsulfatase (helps limit reaction following mast cell degranulation).
• Causes of eosinophilia (NAACP)
  
  • Neoplasia
  • Asthma
  • Allergic processes
  • Connective tissue diseases
  • Parasites (invasive)

Question 8

Basophil

• Characteristics
• Functions
• Pathology

Answer 8

• Characteristics
  
  • Densely basophilic granules [A] containing heparin (anticoagulant), histamine (vasodilator), and leukotrienes.
  • Basophilic—staining readily with basic stains.
• Functions
  
  • Mediates allergic reaction.
• Pathology
  
  • Isolated basophilia is uncommon, but can be a sign of myeloproliferative disease, particularly CML.

Question 9

Mast cell

• Characteristics
• Functions

Answer 9

• Characteristics
  
  • Mast cells resemble basophils structurally and functionally but are not the same cell type [A].
• Functions
  
  • Mediates allergic reaction in local tissues.
  • Can bind the Fc portion of IgE to membrane.
  • IgE cross-links upon antigen binding, causing degranulation, which releases histamine, heparin, and eosinophil chemotactic factors.
  • Involved in type I hypersensitivity reactions.
  • Cromolyn sodium prevents mast cell degranulation (used for asthma prophylaxis).

Question 10

Dendritic cell

• Characteristics
• Functions

Answer 10

• Characteristics
  
  • Expresses MHC class II and Fc receptor on surface.
  • Called Langerhans cell in the skin.
• Functions
  
  • Highly phagocytic APCs [A].
  • Functions as link between innate and adaptive immune systems.

Question 11

Lymphocyte

• Types
• Characteristics

Answer 11

• Types
  
  • Divided into B cells, T cells, and NK cells.
  • B cells and T cells mediate adaptive immunity.
  • NK cells are part of the innate immune response.
• Characteristics
  
  • Round, densely staining nucleus with small amount of pale cytoplasm [A].

Question 12

B lymphocyte

• Characteristics
• Functions

Answer 12

• Characteristics
  
  • Arises from stem cells in bone marrow.
  • Matures in marrow.
  • B = Bone marrow.
• Functions
  
  • Part of humoral immune response.
  • Migrates to peripheral lymphoid tissue (follicles of lymph nodes, white pulp of spleen, unencapsulated lymphoid tissue).
  • When antigen is encountered, B cells differentiate into plasma cells that produce antibodies, and memory cells.
  • Can function as an APC via MHC II.

Question 13

T lymphocyte

• Characteristics
• Functions
• MHC vs. CD

Answer 13

• Characteristics
  
  • Originates from stem cells in the bone marrow, but matures in the thymus.
  • The majority of circulating lymphocytes are T cells (80%).
  • T is for Thymus.
• Functions
  
  • Mediates cellular immune response.
  • T cells differentiate into cytotoxic T cells (express CD8, recognize MHC I), helper T cells (express CD4, recognize MHC II), and regulatory T cells.
  • CD28 (costimulatory signal) necessary for T-cell activation.
  • CD4+ helper T cells are the primary target of HIV.
  • CD is for Cluster of Differentiation.
• MHC vs. CD
  
  • MHC × CD = 8
  • e.g., MHC 2 × CD4 = 8, and MHC 1 × CD8 = 8).

Question 14

Plasma cell

• Characteristics
• Functions
• Pathology

Answer 14

• Characteristics
  
  • Eccentric nucleus [A]
  • Clock-face chromatin distribution
  • Abundant RER
  • Well-developed Golgi apparatus.
• Functions
  
  • Produces large amounts of antibody specific to a particular antigen.
• Pathology
  
  • Multiple myeloma is a plasma cell cancer.