Hematopoiesis and Blood Cell Maturation Practice Flashcards

Comprehensive practice flashcard set covering hematopoiesis, cell organelle histology, erythropoiesis, leukopoiesis, megakaryopoiesis, cytokines, cellularity, and hematologic parameters.

What is hematopoiesis?

A continuous, regulated process of blood cell formation.

What four core cellular processes are involved in hematopoiesis?

Renewal, proliferation, differentiation, and maturation.

Where are functional blood cells released once produced in hematopoiesis?

From the bone marrow into circulation.

What key capabilities do Hematopoietic Stem Cells (HSCs) possess?

They are capable of self-renewal and differentiation into all blood cell lineages.

From what embryonic tissue is hematopoietic tissue derived?

Mesenchyme.

What are the two primary functions of hematopoietic tissue?

To produce new blood cells and remove old ones.

What are the two main types of hematopoietic tissue and their locations?

Myeloid tissue (located in bone marrow) and Lymphoid tissue (located in lymph nodes and spleen).

Why is hematopoiesis critical for survival?

It maintains the continuous supply of blood cells (RBCs, WBCs, Platelets) which have limited lifespans.

What is the approximate lifespan of a mature red blood cell (RBC)?

$120\,\text{days}$ (or $100\,\text{days} \pm 20\,\text{days}$).

What are the three developmental stages of fetal hematopoiesis?

Mesoblastic Phase (Yolk sac), Hepatic Phase (Fetal liver), and Medullary/Myeloid Phase (Bone marrow).

When does the Mesoblastic Phase of hematopoiesis begin?

Approximately the $19\text{th}\,\text{day}$ after fertilization.

Where does hematopoiesis occur during the Mesoblastic Phase?

In the yolk sac.

What type of erythroid cells are formed in the Mesoblastic Phase?

Primitive erythroblasts.

Which embryonic hemoglobins are produced during the Mesoblastic Phase?

Gower-1, Gower-2, and Portland.

Does hematopoiesis occur intravascularly or extravascularly during the Mesoblastic Phase?

Intravascularly.

Which precursor cells form future blood vessels during the Mesoblastic Phase?

Angioblasts.

When does the Hepatic (Fetal liver) Phase of hematopoiesis begin?

During the $3\text{rd}\,\text{month}$ of gestation.

Which phase of fetal hematopoiesis marks the onset of definitive hematopoiesis?

The Hepatic Phase.

What is the major organ site for hematopoiesis during the Hepatic Phase?

The fetal liver.

Besides the fetal liver, what other anatomic sites contribute to hematopoiesis in the Hepatic Phase?

Thymus, spleen, and placenta.

Which blast cells are produced during the Hepatic Phase?

Erythroblasts, myeloblasts, and megakaryoblasts.

Which hemoglobin type is predominantly produced during the Hepatic Phase?

Hemoglobin F (HbF), with small amounts of HbA and HbA2.

Does hematopoiesis occur intravascularly or extravascularly during the Hepatic Phase?

Extravascularly.

In which gestational month does hepatic hematopoiesis peak, and when does it decline?

It peaks in the $3\text{rd}\,\text{month}$ and declines after the $6\text{th}\,\text{month}$.

When does the Medullary (Myeloid) Phase of hematopoiesis begin?

During the $5\text{th}\,\text{month}$ of gestation.

Where does hematopoiesis take place during the Medullary Phase?

In the bone marrow cavity.

By which gestational week does the bone marrow become the primary site of hematopoiesis?

By $24\,\text{weeks}$.

What is the approximate Myeloid:Erythroid (M:E) ratio established during the Medullary Phase?

Approximately $3:1$.

Which growth factors are present during the Medullary Phase?

Erythropoietin (EPO), Granulocyte Colony-Stimulating Factor (G-CSF), and Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF).

In this graph of gestational hematopoiesis, which site is active from 1 to 3 months?

The yolk sac.

What are the two tissue components of bone marrow?

Red marrow (active blood cell production) and Yellow marrow (inactive, adipocytes).

What term describes the gradual replacement of active red bone marrow by yellow marrow with advancing age?

Retrogression.

What are the active sites of red bone marrow in adult humans?

Sternum, ribs, pelvis, vertebrae, and proximal ends of long bones.

What percentage of bone marrow is red marrow in a newborn?

$80 - 90\%$ red marrow.

What percentage of bone marrow remains active (red) at age 20 and age 55?

At age 20: $60\%$ At age 55: approximately $40\%$.

Can yellow marrow revert to active red marrow?

Yes, yellow marrow can revert to red marrow during conditions of physiologic stress.

How is bone marrow cellularity defined?

The ratio of marrow hematopoietic cells to fat (red marrow/yellow marrow).

What percentage of hematopoietic cells defines normocellular bone marrow in adults?

$30 - 70\%$ hematopoietic cells.

What defines hypercellular (hyperplastic) bone marrow?

A marrow containing greater than $70\%$ hematopoietic cells.

What defines hypocellular (hypoplastic) bone marrow?

A marrow containing less than $30\%$ hematopoietic cells.

What is the M:E (myeloid to erythroid) ratio?

The ratio of granulocytes and their precursors to nucleated erythroid precursors in the bone marrow.

Which cell types are explicitly excluded when calculating the M:E ratio?

Lymphocytes and monocytes.

What is the normal reference range for the adult bone marrow M:E ratio?

$3:1$ to $4:1$.

What is a typical bone marrow M:E ratio seen in severe infection?

$6:1$.

What is a typical bone marrow M:E ratio seen in leukemia?

$25:1$.

Which cell types comprise the hematopoietic microenvironment (stroma)?

Stromal cells, endothelial cells, macrophages, osteoblasts, and adipocytes.

What functions does the hematopoietic microenvironment provide?

Supplies structural matrix/support and maintains stem cell differentiation and proliferation.

Name three categories of soluble signaling factors produced in the microenvironment to control blood cell activity.

Interleukins, Colony-Stimulating Factors (CSFs), and Interferons.

Which adult organs are classified as primary lymphoid tissues?

Bone marrow and thymus.

Which adult organs are classified as secondary lymphoid tissues?

Spleen, lymph nodes, and Mucosa-Associated Lymphoid Tissue (MALT).

What role does the liver play in adult hematopoiesis during disease states?

Extramedullary hematopoiesis.

What are the three main functions of the spleen related to blood cells?

Filters blood, removes senescent/old RBCs, and stores platelets.

What are the primary functions of lymph nodes?

Filter lymph fluid and serve as sites for adaptive immune responses.

What specific hematopoietic function takes place in the thymus?

T cell maturation.

What is the Monophyletic Theory of stem cell origin?

The theory that all blood cell lineages originate from a single common pluripotent stem cell.

What is the Polyphyletic Theory of stem cell origin?

The theory that each individual blood cell lineage is derived from its own distinct unique stem cell.

What three potential fates can a Hematopoietic Stem Cell undergo?

Self-renewal, differentiation, or apoptosis.

What two models describe how stem cell lineage fate is controlled?

Stochastic model and Instructive model.

Into what specific mature cell types do lymphoid progenitor cells differentiate?

B lymphocytes and T lymphocytes (and Natural Killer cells).

What does the abbreviation CFU-GEMM stand for?

Colony-Forming Unit - Granulocyte, Erythrocyte, Macrophage, Megakaryocyte.

What are cytokines?

Small proteins crucial for controlling the growth and activity of immune system cells and blood cells.

What are interleukins?

Naturally occurring proteins that mediate intercellular communication and regulate cell growth, differentiation, and motility.

What are Colony-Stimulating Factors (CSFs) / growth factors?

Hematopoietic growth factors that induce clonal proliferation and growth of progenitor cells in vitro and in vivo.

According to the cytokines table, which factors stimulate CFU-MEG differentiation into Thrombocytes?

Thrombopoietin (TPO) and GM-CSF.

Which factors act on CFU-GM to produce Monocytes (CFU-M)?

GM-CSF, M-CSF, and IL-3.

Which growth factors act on CFU-GM to produce Neutrophils (CFU-G)?

GM-CSF, M-CSF, and IL-3.

Which factors convert BFU-E and CFU-E into mature Erythrocytes?

Erythropoietin (EPO), GM-CSF, and IL-3.

Which cytokines drive CFU-Eo differentiation into Eosinophils?

GM-CSF, IL-3, and IL-5.

Which interleukins stimulate CFU-Ba differentiation into Basophils?

IL-3 and IL-4.

What is the structural composition of cellular plasma and organelle membranes?

A lipid bilayer consisting of proteins, cholesterol, phospholipids, and polysaccharides.

What primary function do cellular membranes perform?

They separate cellular components and regulate/restrict the exchange of substances.

What is the primary role of the cell nucleus?

It acts as the control center of the cell, contains genetic blueprint (DNA), and governs cellular activity.

Where is the nucleolus located, and what is its dimensions/composition?

Located within the nucleus; measures $2 - 4\,\mu\text{m}$; composed of RNA ($1 - 4$ per nucleus).

What is the main function of the nucleolus?

Synthesis and processing of ribosomal RNA (rRNA).

What is the shape and main function of the Golgi body?

Horseshoe-shaped, system of stacked membrane-bound flattened sacs; involved in modifying and packaging macromolecules for secretion.

What is the structural difference between smooth and rough endoplasmic reticulum?

Smooth ER lacks ribosomes on its surface, whereas rough ER has ribosomes attached.

What function is served by the endoplasmic reticulum?

Stores and transports fluids and chemicals throughout the cell.

What is the size and composition of ribosomes?

Small granules ($100 - 300\,\text{\AA}$) composed of protein and nucleic acid.

What are polyribosomes?

Chains of ribosomes involved in synthesizing large proteins.

What are the dimensions and structural features of mitochondria?

Length $3 - 14\,\text{nm}$, width $2 - 10\,\text{nm}$; double-layered membrane with inner folds called cristae.

What is the primary cellular function of mitochondria?

Produces adenosine triphosphate (ATP) as the cell's main energy source ('powerhouse').

What do lysosomes contain, and what happens if their membrane breaks?

They contain hydrolytic enzymes for cellular digestion; if broken, the enzymes can destroy the cell.

What is the diameter and composition of microfilaments?

Approximately $5\,\text{nm}$ in diameter; composed of actin and myosin (contractile proteins).

What function do microfilaments perform in the cell?

They support the cytoskeleton and mediate cell motility.

What is the diameter of microtubules and from what protein are they polymerised?

$20 - 25\,\text{nm}$ in diameter; polymerized from tubulin.

What roles do microtubules play in cell architecture and division?

Maintain cell shape, support motility, form mitotic spindle fibers, and construct centrioles.

What are the dimensions and microtubule arrangement of a centriole?

Cylinder $150\,\text{nm}$ in diameter, $300 - 500\,\text{nm}$ in length; composed of nine sets of triplet microtubules.

What function does the centriole serve during cell division?

Serves as the insertion point for mitotic spindle fibers.

What is the single essential life function of red blood cells (erythrocytes)?

To transport oxygen from the lungs to systemic tissues where it is released.

What are the secondary physiological roles of RBCs?

Returning carbon dioxide ($\text{CO}_2$) to the lungs and buffering blood pH.

Define erythroblasts.

Nucleated red blood cell precursors residing in the bone marrow.

Define normoblasts.

Developing nucleated erythroid precursor cells that exhibit normal morphology.

Define megaloblasts.

Abnormally large erythroblasts associated with impaired DNA synthesis.

Where is erythroblastic terminology predominantly used?

In Europe.

Where is normoblastic terminology primarily used and why?

In the United States; because it is descriptive of cell appearance.

What advantage is offered by rubriblastic terminology?

It parallels the nomenclature used for white blood cell development.

List the six developmental stages in Normoblastic nomenclature.

1. Pronormoblast
2. Basophilic normoblast
3. Polychromatic normoblast
4. Orthochromic normoblast
5. Polychromatic erythrocyte
6. Erythrocyte.

List the six developmental stages in Rubriblastic nomenclature.

1. Rubriblast
2. Prorubricyte
3. Rubricyte
4. Metarubricyte
5. Polychromatic erythrocyte
6. Erythrocyte.

List the six developmental stages in Erythroblastic nomenclature.

1. Proerythroblast
2. Basophilic erythroblast
3. Polychromic erythroblast
4. Orthochromic erythroblast
5. Polychromatic erythrocyte
6. Erythrocyte.

What kidney-produced hormone stimulates erythropoiesis?

Erythropoietin (EPO).