Hematopoiesis and Blood Cell Morphology

Flashcards on blood cell morphology, maturation sequences, hematopoiesis sites, and bone marrow evaluation.

What is the average blood volume in a human body, and what percentage of body weight does it represent?

Average blood volume is $4\text{--}6\,\text{L}$, representing $8\%$ of total body weight.

What is the normal pH range of human blood?

$$7.35\text{ to }7.45$$

What is the normal proportion of plasma to blood cells in circulation?

$55\%$ plasma to $45\%$ cells.

What are the physical characteristics of a mature red blood cell on a Wright's stained smear?

Biconcave shape, size of $7\text{--}8\,\mu\text{m}$, pink hue with central pallor, and no inclusions.

What is the normal range for platelet count per oil immersion field, and what is their size range?

An average of $7\text{--}15$ per field, with a size range of $2\text{--}4\,\mu\text{m}$.

How do you differentiate a neutrophilic band cell from a neutrophilic segmented cell (seg)?

A band cell has a single lobe with nuclear indentation greater than half the nuclear width and continuous margin lines without filaments. A seg cell has 2 to 5 lobes connected by thin filaments.

What is the rule when you cannot definitively distinguish whether a cell is a band or a segmented neutrophil?

Classify it as the more mature form, which is a segmented neutrophil (SEG).

What are the morphologic features of an eosinophil's granules and nucleus?

The nucleus is coarsely clumped, blue-reddish, and usually bi-lobed or banded. The cytoplasm is filled with large, uniform, evenly dispersed orange-red secondary granules.

What are the characteristic features of basophil granules, and what cell type do basophils become in tissue?

Large, dark blue-black, water-soluble secondary granules that are unevenly dispersed and obscure the nucleus. In tissue, basophils become mast cells.

How can a large lymphocyte be morphologically distinguished from a monocyte?

Lymphocytes have dense/clumped chromatin, clear light-blue cytoplasm that can be indented by RBCs, and sparse countable granules. Monocytes have folded/lacy chromatin, dull gray-blue cytoplasm with a ground-glass appearance, and may form blunt pseudopods.

What are the organs responsible for fetal hematopoiesis in chronological order?

Yolk sac (conception to 2 months), fetal liver (2nd to 7th month), fetal spleen (3rd to 6th month), and fetal bone marrow (7th month onward).

Which skeletal sites perform hematopoiesis in adult humans?

Sternum, ribs, pelvis, vertebrae, and skull.

What is extramedullary hematopoiesis?

Blood cell production occurring outside the bone marrow, specifically in the liver and spleen, when cell demand increases.

What is the cell maturation sequence of the erythroid series using both nomenclatures?

Stem cell -> Rubriblast (Pronormoblast) -> Prorubricyte (Basophilic normoblast) -> Rubricyte (Polychromatic normoblast) -> Metarubricyte (Orthochromatic normoblast) -> Diffusely basophilic erythrocyte (Polychromatophilic erythrocyte/reticulocyte) -> Erythrocyte.

What is the normal lifespan of a mature circulating erythrocyte?

$$120\,\text{days}$$

What stain is used to visualize reticulocytes, and what intracellular structure is revealed?

New Methylene blue, which stains residual RNA in a filamentous pattern.

What hormone regulates red blood cell production, where is it made, and what triggers it?

Erythropoietin (EPO), a glycoprotein hormone produced by the kidneys in response to tissue hypoxia or anemia.

How many mature RBCs are produced from one rubriblast during erythropoiesis?

$14\text{ to }16$ mature RBCs.

At which maturation stage do secondary granules first appear during myelopoiesis?

At the myelocyte stage.

Which cells are included in the mitotic pool of granulopoiesis?

Stem cells, myeloblasts, promyelocytes, and myelocytes.

Which precursor cell stage is depicted in this diagram with prominent nucleoli, high N:C ratio, and scant light blue cytoplasm?

Myeloblast

Which cell maturation stage is illustrated in this diagram featuring primary (azurophilic) granules and less prominent nucleoli?

Promyelocyte

Which cell stage is depicted in this diagram showing a kidney bean-shaped nucleus with indentation less than 1/2 the nuclear diameter?

Metamyelocyte

What are tissue macrophages called, and from what blood cell do they originate?

They are called histiocytes (or macrophages) and originate from circulating monocytes.

Where do T cells and B cells mature, and what type of immunity does each provide?

T cells mature in the thymus and provide cellular immunity; B cells mature in the bone marrow and differentiate into plasmacytes to provide humoral immunity.

What are flame cells, and which immunoglobulin are they associated with?

Plasma cells with reddish cytoplasm, associated with Immunoglobulin A (IgA).

What growth factor regulates megakaryocyte production, and what is the reference range for peripheral platelets?

Thrombopoietin regulates production; reference range is $150,000\text{ to }350,000/\mu\text{L}$.

What is the cell sequence of megakaryocytopoiesis?

Megakaryoblast -> Promegakaryocyte -> Megakaryocyte -> Thrombocyte (Platelet).

What proportion of adult bone marrow volume is occupied by fat (adipose tissue)?

$50\%$ of total bone marrow volume.

What structural components make up an erythropoietic island in the bone marrow?

A central macrophage surrounded by a cluster of maturing erythroblasts.

What are hematogones?

Subsets of early B-lymphocyte progenitor cells found in normal bone marrow that morphologically resemble leukemic lymphoblasts.

What is the most common skeletal site for bone marrow aspiration?

Posterior superior iliac crest.

What are the morphological and functional differences between osteoblasts and osteoclasts in bone marrow?

Osteoblasts synthesize bone matrix and have fine chromatin, prominent nucleoli, and a perinuclear halo. Osteoclasts remodel bone and are large, multinucleated cells with an uneven number of separate oval nuclei and frayed cytoplasmic margins.

What is the average normal Myeloid to Erythroid (M:E) ratio in bone marrow?

$3:1$ (or $3.1$).

What clinical conditions lead to an increased M:E ratio?

Reaction to an infection, leukemia, leukemoid reaction, or erythroid hypoplasia.