Comprehensive Hematology: Blood Cell Functions, Development, and Diagnostic Tests

What are the primary functions of erythrocytes?

Carry oxygen from lungs to tissues, return CO2 to lungs, and buffer blood pH.

What stimulates the production of erythropoietin (EPO)?

Tissue hypoxia.

Where is erythropoietin synthesized?

In the kidney by peritubular interstitial cells and a little in the liver.

What are the two main components of erythropoietin?

A carbohydrate unit for receptor recognition and a terminal sialic acid unit for biological activity.

What factors stimulate the production of erythropoietin?

Hypoxia, testosterone, and some hormones from the pituitary and thyroid.

What is the role of the microenvironment in the bone marrow?

Provides a sticky surface for anchoring blood cell precursors necessary for proliferation.

What are normoblasts and where are they found?

Normoblasts are erythroid precursors found in clusters adjacent to vascular sinuses.

What is the size and nuclear-cytoplasmic ratio of a pronormoblast?

Size: 20 μm; N:C ratio: 8:1.

What is the significance of basophilic normoblasts in erythropoiesis?

Hemoglobin production begins at this stage but is not visible by Wright stain.

What are the characteristics of polychromatic normoblasts?

Cytoplasm becomes gray due to blue RNA and pink hemoglobin; size: 10-12 μm.

What happens during the transition from polychromatic normoblast to orthochromic normoblast?

The cell undergoes its last mitotic division and hemoglobin production continues.

What is the lifespan of a mature erythrocyte?

Approximately 120 days.

What is the process by which normoblasts enter circulation?

Diapedesis, where the nucleus is extruded and phagocytized by erythroblastic islands.

What is the difference between extravascular and intravascular hemolysis?

Extravascular hemolysis occurs in the spleen; intravascular hemolysis occurs within blood vessels.

What is the significance of reticulocyte counts?

They provide an estimation of bone marrow erythropoietic activity.

What is the typical reticulocyte count in healthy individuals?

Normally about 0.5-1.5%.

What are the characteristics of mature erythrocytes?

Size: 7-8 μm; color: salmon; central pallor occupies about 1/3 of the cell.

What happens to senescent erythrocytes?

They are removed by phagocytosis in the spleen.

How long does it take for a pronormoblast to mature into a reticulocyte?

About 4-7 days.

What is the role of macrophages in erythrocyte destruction?

They engulf and remove old or damaged RBCs.

What is the appearance of reticulocytes when stained with supravital stains?

They show RNA reticulum and are called reticulocytes.

What is the significance of the central pallor in mature erythrocytes?

It indicates the cell's normal size and health.

What does a high level of CO2 in the marrow indicate?

It suggests sluggish blood stasis and may affect hemoglobin elaboration.

What is the reference interval for polychromatic normoblasts in bone marrow?

10-20%.

What is the reference interval for orthochromic normoblasts in peripheral blood?

0% (not normally seen except in newborns).

What is hematology?

The study of blood cells.

What are the three families of blood cells?

Red blood cells (RBCs), white blood cells (WBCs), and platelets (PLTs).

What is the liquid portion of blood called?

Plasma.

What is the normal percentage of plasma in whole blood?

55%.

What is the normal percentage of red blood cells in whole blood?

44%.

What is the function of red blood cells?

To transport oxygen from the lungs to the tissues and clear tissues of carbon dioxide.

What protein do red blood cells contain?

Hemoglobin.

What are reticulocytes?

Young RBCs that contain RNA and normally make up 1% to 2% of RBCs.

What is leukopenia?

A decreased white blood cell count.

What is leukocytosis?

An increased white blood cell count.

What are the two main types of leukocytes?

Granulocytes and agranulocytes.

What are the types of granulocytes?

Neutrophils, eosinophils, and basophils.

What is the purpose of a complete blood count (CBC)?

To measure various components of blood including WBC, RBC, hemoglobin, and indices.

What is the function of platelets?

To aid in blood clotting.

What is the significance of blood film examination?

To assess cell morphology and structure.

What tests are used to monitor coagulation?

Prothrombin time (PT) and partial thromboplastin time (PTT).

What is the role of endothelial cells?

To line blood vessels and regulate blood flow.

What is flow cytometry used for?

To analyze cell populations and differentiate between cell types.

What is the osmotic fragility test used for?

To assess the stability of red blood cells.

What does the glucose-6-phosphate dehydrogenase assay test for?

To check for enzyme deficiencies that can lead to hemolytic anemia.

What is the purpose of hemoglobin electrophoresis?

To separate different types of hemoglobin for analysis.

What are the standard precautions in blood specimen collection?

To minimize the risk of infection and ensure safety.

What is the most important step in routine venipuncture?

Patient identification.

What are the common reasons for specimen rejection?

Improper labeling, contamination, or insufficient volume.

What is the role of quality assurance in hematology?

To ensure accurate and reliable test results.

What is the significance of the Wright-stained smear?

To visualize and differentiate blood cells under a microscope.

What is the function of the tourniquet in venipuncture?

To engorge the veins for easier access.

What is the procedure for blood smear preparation?

Using skin puncture blood or EDTA tube of venous blood to create a smear.

What are the two main types of lymphocytes?

B lymphocytes and T lymphocytes

What are the three main morphologic stages of lymphocyte development?

Lymphoblast, Prolymphocyte, Lymphocyte

What is the fourth stage of lymphocyte development that may occur upon immunologic stimulation?

Plasma cell

What characteristics distinguish a lymphoblast?

Round to oval nucleus, fine nuclear chromatin, 1-3 nucleoli, scant cytoplasm

What features characterize a prolymphocyte?

Round to oval nucleus, clumped nuclear chromatin, single prominent nucleolus

What are the characteristics of a lymphocyte's nucleus?

Usually round, may be slightly indented, not lobulated

What is the role of B lymphocytes?

Involved in humoral immunity and antibody production

Where do B lymphocytes originate and mature?

In the bone marrow

What is the lifespan of a resting B cell?

3-4 days, except for memory cells which are long-lived

What is the role of T lymphocytes?

Involved in cell-mediated immunity

Where do T lymphocytes mature?

In the thymus

What percentage of circulating lymphocytes are T lymphocytes?

70-85%

What are Natural Killer (NK) cells involved in?

Immunosurveillance for tumor cells

What characterizes atypical or reactive lymphocytes?

They respond to stimuli and may appear pleomorphic

What is the typical percentage of lymphocytes that may be reactive under normal conditions?

10-15%

What happens to the percentage of reactive lymphocytes during viral infections?

It can increase to 50-75% or more

What are the unique features of plasma cells?

Eccentric nucleus, dark blue cytoplasm due to active ribosomal activity, perinuclear clear zone

What are flame cells associated with?

Plasma cells producing IgA

What are Mott cells characterized by?

Contain multiple round globules of immunoglobulin

What is the significance of the perinuclear clear zone in plasma cells?

It indicates active ribosomal activity producing antibodies

What is hematopoiesis?

The process of formation and development of various types of blood cells and other formed elements.

What does 'poiesis' mean?

Production or formation.

What are hematopoietic tissues?

Organs or tissues in which blood production occurs.

What is erythropoiesis?

The production of red blood cells (RBCs).

What is leukopoiesis?

The production of white blood cells (WBCs).

What is myelopoiesis?

The production of myeloid cells including monocytes, eosinophils, basophils, and neutrophils.

What is lymphopoiesis?

The production of lymphocytes.

What is megakaryopoiesis?

The production of platelets.

Where does postnatal hematopoiesis occur?

In the bone marrow.

What types of cells are produced in postnatal hematopoiesis?

Erythrocytes, granulocytes, platelets, monocytes, and some B-lymphocytes.

What is extramedullary hematopoiesis?

Blood cell formation at sites other than bone marrow, occurring under stress conditions.

What are the two types of stem cells in hematopoiesis?

Pluripotential stem cells and committed progenitor cells.

What is the ratio of stem cells to total cells in the bone marrow?

1:1000 cells.

What is apoptosis?

Programmed cell death.

What are cytokines?

A diverse group of soluble proteins that modulate functional activities of cells, including stimulation or inhibition of blood cell production.

Name an example of a cytokine.

Interleukins (ILs), lymphokines, monokines, interferons, chemokines, or colony stimulating factors (CSF).

What is the effect of cytokines on stem cells?

Some influence stem cells with multilineage potential, while others influence differentiation of specific cell types.

What is the generative cycle of stem cells?

G0 (resting stage), G1 (RNA & protein synthesis), S (DNA synthesis), G2 (premitotic phase), M (mitosis).

What happens to the nuclear-cytoplasmic ratio during cell maturation?

It decreases.

What are the general features of cell maturation?

Decrease in cell size and nuclear-cytoplasmic ratio.

What is the significance of nucleoli in cell maturation?

Nucleoli disappear as cells mature.

What happens to chromatin during cell maturation?

Chromatin condenses and becomes coarser and clumped.

What is the role of cytokines in apoptosis?

Some cytokines prevent apoptosis, while others may accelerate it.

What is monopoiesis?

The process of producing monocytes from precursor cells in the bone marrow.

Describe the nucleus of a monoblast.

Round to oval; may be irregularly shaped.

What is the cytoplasm color of monoblasts?

Light blue to gray.

Describe the nucleus of a promonocyte.

Irregularly shaped, folded; may have brain-like convolutions.