Formed Elements Review

erythrocytes

• 5.2 million microliter (4.4 - 6.0 million)

• flattened biconcave disk; no nucleus; pale red color

• transport oxygen and some carbon dioxide between tissues and lungs

• lifespan approx 120 days

leukocytes (white blood cells)

• 7000 microliter; (5000-10,000)

• obvious dark-staining nucleus

• all function in body defenses

• exit capillaries and move into tissues; lifespan to usually a few hours or days

granulocytes

• abundant granules in cytoplasm; nucleus normally lobed

• nonspecific (innate) resistance to disease

• neutrophils

• eosinophils

• basophils

agranulocytes

• lack abundant granules in cytoplasm; have a simple-shaped nucleus that may be indented

• body defenses

• lymphocytes

• monocytes

neutrophils

• 4150 microliter; (1800-9950)

• nuclear lobes increase with age; pale lilac granules

• phagocytic; particularly effective against bacteria

• release cytotoxic chemicals from granules

• most common leukocyte; lifespan of minutes to days

eosinophils

• 165 (0-700)

• nucleus generally two-lobed; bright red-orange granules

• phagocytic cells; particularly effective with antigen-antibody complexes. Release antihistamines. Increase in allergies and parasitic infections

  • least common leukocyte; lifespan unknown

Basophils

• 44 (0-150)

• nucleus generally two-lobed but difficult to see due to presence of heavy, dense, dark purple granules

• promotes inflammation

• least common leukocyte; lifespan unknown

lymphocytes

• 2185 (1500-4000)

• spherical cells with a single often large nucleus occupying much of the cell’s volume; stains purple; seen in large (natural killer cells) and small ( B and T cells variants

• primarily specific (adaptive) immunity; T cells directly attack other cells (cellular immunity); B cells release antibodies (humoral immunity); natural killer cells are similar to T cells but nonspecific

• initial cells originate in bone marrow, but secondary production occurs in lymphatic tissue; several distinct subtypes; memory cells form after exposure to a pathogen and rapidly increase responses to subsequent exposure; lifespan of many years

monocytes

• 455 (200-950)

• largest leukocyte with an indented or horseshoe-shaped nucleus

• very effective phagocytic cells engulfing pathogens or worn out cells; also serve as antigen-presenting cells (APCs) for other components of the immune system

• produced in red bone marrow; referred to as macrophages after leaving circulation

platelets

• 350,000 (150K-500K)

• cellular fragments surrounded by a plasma membrane and containing granules; purple stain

• hemostasis plus release growth factors for repair and healing of tissue

• formed from megakaryocytes that remain in the red bone marrow and shed platelets into circulation