Blood & Bone Marrow (Study Guide)

erythrocytes (red blood cells)

anucleate (non-nucleated), biconcave discs containing hemoglobin (”histologic ruler”); transports oxygen from the lungs to the peripheral tissues

acidic (no nucleus or granules), highly deformable, lack mitochondria and rely on anaerobic glycolysis for minimal energy needs

RBC cytoplasm lacks all organelles but is densely filled with hemoglobin (acidophilic), the tetrameric O2-carrying protein that accounts for the cells’ uniform acidophilia

sickle cell disease — point mutation in hemoglobin gene that causes the hemoglobin to be incorrectly formed, in turn causing some erythrocytes to take on a crescent (sickle) shape; cells are unable to transport adequate amounts of oxygen to cells

• occurs because of mutation in beta-globin chain of hemoglobin A (HbA), which makes protien crystallize within erythrocytes at low-oxygen tensions

senescent/worn-out RBCs are recognized and removed from circulation, mainly by macrophages of the spleen, liver, and bone marrow

leukocytes (white blood cells)

defensive role, destroying infecting organisms (bacteria and viruses), as well as assisting in the removal of dead or damaged tissues

granulocytes

neutrophils, basophils, eosinophils

neutrophils

most numerous leukocyte (50-70% of all leukocytes), very tiny light staining granules; first responders, phagocytes; are motile; leave circulation and migrate to their site of action in the connective tissue

• nucleus is frequently multilobed with lobes connected by thin strands of nuclear material

• undergo chemotaxis which allows them to migrate toward sites of infection or inflammation

• granules: azurophilic (primary), antimicrobial (secondary), tertiary

basophils

large granules that stain deep blue to purple; often so numerous that they mask the nucleus; handles allergic responses; granules contain anticoagulant heparin, histamine and heparan sulfate, vasoactive agents which promote dilation of blood vessels (similar to tissue-resident mast cells)

• reaction with an antigen (allergen) specific for IgE triggers the activation and the release of these vasoactive agents from cell granules (degranulation)

• responsible for the severe vascular disturbances associated with hypersensitivity reactions and anaphylaxis

eosinophils

large acidophilic granules that appear pink (or red) in stained preparation with eosin (acidic dye); responds to parasitic infections, handles allergic responses; nucleus often has two lobes (bilobed)

• granules contain enzymes (e.g., eosinophilic peroxidase, major basic protein) that are particularly effective against parasitic worms (degranulation)

• the main effector cells in responses to parasitic infections; also associated with allergic reactions

agranulocytes

nongranular leukocytes; includes lymphocytes and monocytes

lymphocytes

agranular cells with very clear cytoplasm (stains pale blue); very large nucleus (stains dark purple); play important role in immune response

• much smaller than the granulocytes

• T lymphocytes: act against virus infected cells and tumor cells (cellular immunity)

• B lymphocytes: differentiate into plasma cells that secrete antibodies (humoral immunity)

  • originate and mature in bone marrow, emerge from bloodstream into tissue spaces, where they are activated

• cytotoxic T cells and NK Cells (large granular lymphocytes) contain granules with perforin

monocytes

precursor cells of macrophages, osteoclasts, microglia, and other cells of the mononuclear phagocyte system in connective tissue; highly effective phagoctes, circulate in the blood; the largest of the leukocytes; “U” or kidney-shaped nucleus

• during inflammation: monocytes extravasate into surrounding tissue, develop into macrophages and phagocytose bacteria, other cells, and tissue debris (respiratory burst of superoxide anions)

• antigen presenting cells: process and present antigens to CD4+ T lymphocytes as part of mounting an immune response

platelets/thrombocytes

cell fragments; first line of defense against damage to blood vessels, adhering to defects and participating in the blood clotting system; produced by “budding off” from megakaryocytes — giant cells with muliple copies of DNA in the nucleus

• circulate for approx. one week and are then destroyed by spleen and liver

• low platelet counts (thrombocytopenia) increases bleeding risks

• high counts (thrombocytosis) may lead to thrombosis

plasma

proteinaceous solution in which the above-mentioned cells circulate, and carries nutrients, metabolites, antibodies, hormones, proteins of the blood clotting system and other molecules throughout the body

hematopoiesis (hemopoiesis)

occurs in spongy bone

bone marrow

soft, spongy tissue; comprises a network of basculature, hemtaopoietic stem and progenitor cells, mature megakaryocytes, adipose, bony trabeculae

red bone marrow

soft, spongy tissue inside bones that produces RBCs, WBCs, and platelets; lies entirely within the spaces of bone, medullary cavity of young long bones, and spaces of spongy bone; contains cords of active hemopoietic cells that lie within the medullary cavity in children and within the spaces of spongy bone in adults

erythroblastic islets

specialized functional niches in the bone marrow, fetal liver, and spleen; engages in the production and maturation of erythrocytes

sinusoids

specialized units of blood vessels that (in bone marrow) provide the barrier between hemopoietic compartment and peripheral circulation; newly developed blood cells are released into these

adipocytes

specialized cells that primarily compose adipose tissue and are responsible for storage of energy as lipids (fat)

megakaryocytes

giant cells with multiple copies of DNA in the nucleus

Blood is a […] with […] in a […].

1. specialized connective tissue

2. “formed elements” (cells and platelets)

3. fluid matrix (plasma)

Plasma is the […] in which the blood cells circulate, and carries […] throughout the body.

1. proteinacous solution

2. nutrients, metabolits, antibodies, hormones, proteins of the blood clotting system and other molecules

serum definition

plasma that lack coagulation

Erythrocytes (RBCs) […] from […] to […] and […] as a waste product, away from […] and back to […].

1. reversibly transport oxygen

2. the lungs

3. peripheral tissues

4. carbon dioxide

5. peripheral tissues

6. the lungs

Adult erythrocytes are […] because […] is, and they do not contain […].

1. acidophilic

2. hemoglobin

3. a nucleus

Leukocytes (WBCs) have a […] role, […] as well as […].

1. defensive

2. destroying infecting organisms

3. assisting in the removal of dead or damaged tissues

Platelets (thrombocytes) are the first line of defense against damage to […], adhering to […] and participating in […].

1. blood vessels

2. defects

3. the blood clotting system

Composition of whole blood

plasma (~55%) > erythrocytes (~44%) > leukocytes/platelets (~1%)

Leukocytes are classified as […] or […]. Exceptions to the rule: […]

1. granular leukocytes (granulocytes, PMNs)

2. agranular (nongranular) leukocytes (T and B lymphocytes, monocytes)

3. Natural Killer (NK) cells and cytotoxic lymphocytes in the T cell lineage which mainly reside in peripheral tissue have granules containing perforin

Neutrophils are the […] leukocyte; they have three types of granules, […], […], and […].

1. most numerous

2. primary granules that contain myeloperoxidase

3. secondary granules that contain antimicrobial peptides

4. tertiary granules that contain proteolytic enzymes

Neutrophils are the first responders during […] and they are the main […] cells among the granulocytes.

1. an inflammatory response

2. phagocytic effector

Eosinophils are the main effector cells in responses to […]; granules contain […] which accounts for the […] in light microscopic images.

1. parasitic infections

2. major basic protein localized in the crystalline core

3. intense acidophilia of the granule

Basophils are the main effector cells in responses associated with […]; their granules contain the […] and […] which promote […]. They […] to kill their targets.

1. anaphylaxis

2. anticoagulant heparin

3. vasoactive agents, histamine and heparan sulfate,

4. dilation of blood vessels (similar to tissue-resident mast cells)

5. degranulate

hematopoiesis/hemopoiesis definition

process of blood cell formation

Hematopoietic stem cells for blood cell formation reside in […] of children and adults. They are very rare: 1 in […] cells.

1. bone marrow

2. 1,000-2,000

Hematopoietic stem cells give rise to […].

multipotential progenitors with myeloid and lymphoid potential

Multipotential progenitors give rise to […] and […].

1. common myeloid progenitors

2. common lymphoid progenitors

Common lymphoid progenitors ultimately give rise to […], […], and […].

1. T lymphocytes

2. B lymphocytes

3. NK cells

Common myeloid progenitors ultimately give rise to […].

all of the other cell types

Progenitor cells, commited to […], proliferate and differentiate within microenvironmental niches of the […].

1. forming each type of mature blood cell

2. bone marrow (stromal cells, other cells, and ECM with specific growth factors)

Colony forming unit (CFU) assays in […] are used to detect […] and evaluate their […].

1. semi-solid medium (methylcellulose)

2. progenitor cells

3. differentiation potential (ex: CFU-GM = progenitor cell that can give rise to granulocytes and monocytes/macrophages)

Red bone marrow is active in […]; yellow bone marrow consists mostly of […].

1. hemopoiesis

2. adipose tissue

Erythroblastic islets within marrow contain […]; […], …, with suceeding developmental stages that reflect the cytoplasmic transitions from […] to […]. At the last stage of erythopoiesis, […] are extruded, producing […] that still contain some […] but are released into the circulation.

1. the red blood cell lineage

2. proerythroblasts

3. RNA-rich

4. hemoglobin-filled

5. cell nuclei

6. reticulocytes

7. polyribosomes

Megakaryocytes, large polypoid cells that reside in […], produce [….] by […].

1. the bone marrow

2. platelets/thrombocytes

3. releasing them from the ends of cytoplasmic processes

All the formed elements of blood enter the circulation by crossing what?

The discontinuous endothelium of sinusoids in the red marrow