Hematology Chapter 3: Bone Marrow Structure and Function

What components make up the hematopoietic system?

Bone marrow, liver, spleen, lymph nodes, and thymus.

Where does hematopoiesis occur in adults?

In the bone marrow.

What are the two main lineages hematopoietic stem cells differentiate into?

Myeloid and lymphoid cell lineages.

What can bone marrow and peripheral blood smear examination diagnose?

Hematolymphoid disorders.

What are contraindications for bone marrow examination?

Severe hemophilia and severe disseminated intravascular coagulopathy (DIC).

What is the structure of bone marrow composed of?

Hematopoietic cells, adipose tissue, bone and its cells (osteoblasts and osteoclasts), and stroma.

How is hematopoietic marrow organized?

Around the bone vasculature.

What is the role of sinuses in bone marrow?

Sinuses collect blood from the marrow and return it to systemic circulation.

Where does erythropoiesis occur?

In erythropoietic islands.

What is granulopoiesis?

Differentiation and maturation of granulocytes in hematopoietic cords.

What are the two pools of neutrophils?

Proliferating pool and maturation storage pool.

What occurs during megakaryopoiesis?

Production of megakaryocytes occurs adjacent to the sinus endothelium, shedding platelets into circulation.

What is the primary function of bone marrow?

To supply mature hematopoietic cells into the peripheral blood and respond to increased demands.

What factors influence erythropoiesis?

Erythropoietin produced in the kidney and other releasing factors during cell egression.

What are common indications for bone marrow studies?

Hematologic diseases affecting blood cellular elements and systemic diseases requiring diagnosis or monitoring.

What are common sites for bone marrow extraction in adults?

Posterior superior iliac crest, sternum, and rarely the anterior superior iliac crest.

What should the instrument tray for bone marrow extraction contain?

Enough equipment to complete the procedure and prepare tissues for studies.

What is the purpose of keeping the initial aspirate volume small?

To prevent dilution of the sample with sinusoidal blood.

What are hematogones?

Committed progenitor cells of lymphoid lineage, increased in conditions like neuroblastoma and iron-deficiency anemia.

What are the two unique biological characteristics of marrow stem cells?

Self-renewal and multilineage differentiation.

What role do colony-stimulating factors (CSFs) play in bone marrow?

They influence the differentiation of various progenitor cells.

What happens to mature lymphocytes in peripheral lymphoid organs?

They undergo antigen-dependent effector cell proliferation, resulting in cytokines and antibody production.

What is the role of stromal cells in bone marrow?

They produce an extracellular matrix essential for the renewal and differentiation of marrow cells.

What are mast cells and where can they be increased?

Connective tissue cells increased in chronic infections, autoimmune diseases, and lymphoproliferative disorders.

Why is it important to keep the volume of the initial bone marrow aspirate small?

To prevent dilution of the sample with sinusoidal blood.

What is the first-aspirated material used for in bone marrow studies?

It is used immediately for preparing smears.

What technique is used to prepare direct smears from bone marrow aspirate?

The technique for blood film preparation.

How are marrow particles prepared for smears?

By pouring a small amount of aspirate on a slide and transferring particles selectively.

What should be done to the slides after preparing bone marrow smears?

Label them with the patient's name, ID number, and date, then air-dry.

What is the purpose of transferring leftover blood and marrow particles to an EDTA tube?

To prepare for histologic processing.

What is indicated by a 'dry tap' during bone marrow aspiration?

It indicates that the marrow cannot be aspirated due to pathologic alterations.

What is the procedure for preparing a touch preparation from a trephine biopsy?

Support the sample lightly with forceps and touch it on clean slides without rubbing.

What is the first step in the histologic preparation of a bone marrow biopsy specimen?

Immerse the specimen in B-5 or 10% buffered formalin fixative without delay.

What is the purpose of examining bone marrow smears at low magnification first?

To select a suitable area for examination and perform a differential count.

How is bone marrow cellularity estimated?

By the ratio of nucleated hematopoietic cells to fat cells.

What does the bone marrow differential count help diagnose?

Leukemias, refractory anemias, and myelodysplastic and myeloproliferative neoplasms.

What is the M:E ratio in bone marrow examination?

The ratio between all granulocytes and their precursors and all nucleated red cell precursors.

What does an increase or decrease in marrow cellularity with a normal M:E ratio indicate?

Balanced granulocytic and erythrocytic hyperplasia or hypoplasia.

Why is the evaluation of marrow iron stores important?

It is essential in diagnosing anemias, especially refractory and dyserythropoietic anemias.

What does the Prussian blue reaction demonstrate in bone marrow examination?

Intracytoplasmic iron of histiocytes and red cell precursors.

What information should be included in a bone marrow report?

Patient data, specimen identifier, clinical summary, and descriptions of the material received.

What additional data should be included in a bone marrow report?

Complete blood count (CBC), WBC differential count, and a description of the blood smear.

What should be reported regarding the status of iron stores in a bone marrow report?

Normal marrow iron and any special staining procedures performed.

What does the diagnostic conclusion of a bone marrow report encompass?

Separate diagnoses of blood and bone marrow, even if the same diagnosis applies to both.