Hemopoiesis
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Questions and Answers

What characterizes reticulocytes in terms of polyribosomes?

  • They have a small number of polyribosomes. (correct)
  • They lose all polyribosomes before maturation.
  • They possess a large number of polyribosomes.
  • They do not contain any polyribosomes.

Which granules are formed first during granulopoiesis?

  • Azurophilic granules (correct)
  • Specific granules
  • Lysosomal granules
  • Cytoplasmic granules

Which type of cell is the most immature recognizable cell in the myeloid series?

  • Band cell
  • Promyelocyte
  • Metamyelocyte
  • Myeloblast (correct)

What is the role of the Golgi apparatus during the maturation of granulocytes?

<p>To synthesize proteins for both azurophilic and specific granules. (A)</p> Signup and view all the answers

What feature distinguishes granulopoietic cells from erythropoietic cells?

<p>Granule-filled cytoplasm. (D)</p> Signup and view all the answers

At which stage do specific granules begin to significantly increase in number?

<p>Myelocyte stage (A)</p> Signup and view all the answers

How long does it typically take for a myeloblast to mature into a circulating neutrophil?

<p>10 to 14 days (C)</p> Signup and view all the answers

Which type of precursor cell shows no specific cytoplasmic granules or nuclear lobulation?

<p>Monocyte precursor (D)</p> Signup and view all the answers

What is the primary organ for hemopoiesis during the second trimester of pregnancy?

<p>Liver (D)</p> Signup and view all the answers

Which cells are considered progenitor cells commonly referred to as CFUs?

<p>Colony-forming units (B)</p> Signup and view all the answers

What type of stem cells give rise to both lymphoid and myeloid cells?

<p>Pluripotent stem cells (B)</p> Signup and view all the answers

What structures do lymphoid progenitor cells migrate to for further differentiation?

<p>Spleen and lymph nodes (B)</p> Signup and view all the answers

What type of blood cells are primarily produced from CFU-granulocytes-monocytes?

<p>Granulocytes and monocytes (A)</p> Signup and view all the answers

Which of the following best describes the process of hemopoiesis?

<p>Making of blood cells (D)</p> Signup and view all the answers

During which life stage does the bone marrow become the major hemopoietic organ?

<p>Third trimester of pregnancy (D)</p> Signup and view all the answers

What characterizes hemopoietic stem cells?

<p>They are pluripotent and capable of asymmetric division. (B)</p> Signup and view all the answers

What is the primary function of hemopoietic growth factors in blood cell production?

<p>To stimulate proliferation and differentiation of progenitor cells (C)</p> Signup and view all the answers

What distinguishes red bone marrow from yellow bone marrow?

<p>Red marrow is primarily responsible for blood cell production (A)</p> Signup and view all the answers

Which cell type appears morphologically similar to stem cells and cannot be easily distinguished from them?

<p>Large lymphocytes (A)</p> Signup and view all the answers

Under which condition can yellow marrow revert back to red marrow?

<p>During severe bleeding or hypoxia (D)</p> Signup and view all the answers

What is the role of the local cells and extracellular matrix (ECM) in hemopoiesis?

<p>To support and maintain the microenvironment for blood cell development (B)</p> Signup and view all the answers

Which of the following describes the composition of red bone marrow?

<p>Composed of reticular connective tissue stroma and hematopoietic cells (B)</p> Signup and view all the answers

What is the role of macrophages in relation to erythrocytes?

<p>They undergo phagocytosis of older, defective erythrocytes. (B)</p> Signup and view all the answers

Which cell type is the distinct progenitor of the erythroid series?

<p>Proerythroblast (A)</p> Signup and view all the answers

How do precursor cells differ from stem cells in their rate of division?

<p>Precursor cells divide more rapidly than stem cells (B)</p> Signup and view all the answers

Which feature characterizes the sinusoidal capillaries found in red bone marrow?

<p>Discontinuous endothelium allowing blood cell entry (C)</p> Signup and view all the answers

What major change occurs during erythrocyte maturation?

<p>The formation of a non-nucleated biconcave corpuscle. (A)</p> Signup and view all the answers

How long does it take for an erythrocyte to develop from its first recognizable progenitor to the release of reticulocytes?

<p>Approximately 1 week (C)</p> Signup and view all the answers

What characterizes the basophilic erythroblast stage?

<p>Presence of a large nucleus and no visible nucleolus. (C)</p> Signup and view all the answers

What happens to the nucleus during the late stages of erythrocyte maturation?

<p>It is extruded and subsequently phagocytosed. (A)</p> Signup and view all the answers

What role does erythropoietin play in erythrocyte production?

<p>It triggers production of mRNA for globins. (A)</p> Signup and view all the answers

Which cell type is described by having both basophilic and acidophilic properties?

<p>Polychromatophilic erythroblast (C)</p> Signup and view all the answers

What is the main basis for differentiating monocytes from lymphocytes in smear preparations?

<p>Size and nuclear shape (A)</p> Signup and view all the answers

What is the size range of a promonocyte?

<p>Up to 18 μm in diameter (D)</p> Signup and view all the answers

Which type of cell do monocytes develop into after maturing in tissues?

<p>Macrophages (B)</p> Signup and view all the answers

Which of the following statements about lymphocyte differentiation is true?

<p>Lymphoblasts are the first identifiable progenitors of lymphocytes. (A)</p> Signup and view all the answers

What role does thrombopoietin play in platelet formation?

<p>It drives the differentiation of megakaryoblasts. (C)</p> Signup and view all the answers

What is a characteristic feature of mature megakaryocytes?

<p>They exhibit significant endomitosis. (C)</p> Signup and view all the answers

In which location do B lymphocytes complete their differentiation?

<p>Red bone marrow (D)</p> Signup and view all the answers

What structural changes occur in lymphocytes as they develop?

<p>Nuclei become smaller and cells decrease in size. (B)</p> Signup and view all the answers

Flashcards

Hemopoiesis

The process of creating new blood cells from precursor cells to replace old ones.

Hematopoietic Stem Cells

Specialized cells capable of giving rise to all blood cell types.

Committed Progenitor Cells

These stem cells are committed to producing specific types of blood cells, such as lymphocytes or myeloid cells.

Myeloid Cells

These are cells that develop in the bone marrow and give rise to various cell types, including granulocytes, monocytes, erythrocytes, and megakaryocytes.

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Lymphoid Cells

These are cells that develop in the thymus or other lymphatic tissues and give rise to various types of lymphocytes.

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Colony-forming units (CFUs)

Cells that can create colonies of only one specific type of blood cell when cultured, representing distinct pathways of blood cell development.

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CFU-erythrocytes (CFU-E)

These CFUs are responsible for producing red blood cells.

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CFU-megakaryocytes (CFU-Meg)

These CFUs are responsible for producing platelets, which are essential for blood clotting.

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Stromal cells

Specialized fibroblastic cells that form a meshwork within the bone marrow, providing support for hematopoietic cells and macrophages.

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Progenitor cells

Cells that are committed to producing a specific type of blood cell, such as red blood cells or lymphocytes.

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Hemopoietic growth factors

Glycoproteins that stimulate the proliferation, differentiation, and maturation of specific blood cell lineages.

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Hemopoietic microenvironment

The microenvironment within bone marrow where stem cells are maintained and progenitor cells develop. It includes stromal cells, ECM, and specific growth factors.

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Red bone marrow

The blood-forming type of bone marrow, characterized by its red color due to the abundance of blood and hematopoietic cells.

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Yellow bone marrow

The type of bone marrow filled with adipocytes, replacing most hematopoietic cells, giving it a yellowish appearance.

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Sinusoids

Sinusoidal capillaries within the bone marrow where newly differentiated blood cells and platelets enter the circulation.

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Erythropoiesis

The process of red blood cell development, starting from a proerythroblast and ending with the release of reticulocytes into the bloodstream.

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Proerythroblast

A large cell with loose chromatin, nucleoli, and basophilic cytoplasm. It is the first recognizable progenitor cell of the erythroid series.

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Basophilic Erythroblast

A cell with more strongly basophilic cytoplasm and a condensed nucleus with no visible nucleolus. It's characterized by a large number of polysomes synthesizing hemoglobin.

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Polychromatophilic Erythroblast

A stage where the cell volume shrinks, polysomes decrease, and hemoglobin production begins, resulting in areas of both basophilia and acidophilia.

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Orthochromatophilic Erythroblast

A cell with a uniformly acidophilic cytoplasm, no basophilia, and a condensed nucleus. It's also known as a normoblast.

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Mature Erythrocyte

A small, non-nucleated, biconcave corpuscle, containing hemoglobin and responsible for oxygen transport.

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Erythropoietin

A glycoprotein hormone produced by the kidneys that stimulates red blood cell production.

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Erythrocyte Phagocytosis

The process by which older, defective red blood cells are engulfed and broken down by macrophages in the bone marrow.

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Granulopoiesis

The process of forming mature granulocytes, characterized by changes in cytoplasm due to the synthesis of specific proteins for granules.

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Promyelocyte

Immature granulocyte stage with abundant basophilic cytoplasm and azurophilic granules containing lysosomal enzymes and myeloperoxidase.

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Azurophilic Granules

Granules that contain lysosomal hydrolases, stain with basic dyes, and are similar in all three types of granulocytes.

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Specific Granules

Granules specific to each type of granulocyte, containing proteins that determine each type's function.

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Myeloblast

The most immature recognizable cell in the myeloid series, characterized by finely dispersed chromatin and faint nucleoli.

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Metamyelocyte

The stage where specific granules gradually increase in number and eventually fill most of the cytoplasm.

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Band Cell (Stab Cell)

The stage where the nucleus is elongated, but not yet fully segmented or polymorphic.

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Neutrophil

The most common type of granulocyte, responsible for phagocytizing bacteria and other foreign invaders.

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What are monoblasts?

These cells are responsible for initiating the development of monocytes, the precursors to macrophages, which are essential for immune defense.

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Describe the appearance of a promonocyte.

Promonocytes are large cells with a distinctive lacy chromatin structure and visible nucleoli. They are the direct descendants of monoblasts and undergo further differentiation to become mature monocytes.

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What is the role of monocytes in the body?

Monocytes enter the bloodstream and circulate for a short time before migrating into tissues, where they mature into macrophages. These macrophages have a long lifespan and play a vital role in engulfing and destroying pathogens.

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What is the role of lymphocytes?

Lymphocytes are the primary cells of the adaptive immune system. These cells, derived from lymphoid progenitor cells, are responsible for recognizing specific antigens and launching targeted immune responses.

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What is the role of lymphoblasts in lymphocyte development?

These cells are the earliest identifiable precursors of lymphocytes. They undergo several divisions to produce mature lymphocytes that possess distinct surface proteins.

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What is the function of T lymphocytes?

T lymphocytes, developed in the thymus, are responsible for cell-mediated immunity. These cells recognize and destroy infected or abnormal cells directly.

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What is the function of B lymphocytes?

B lymphocytes, developed in the bone marrow, are responsible for antibody-mediated immunity. They produce antibodies that bind to specific antigens and neutralize them.

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What is the role of platelets in the body?

Platelets, the small, disc-shaped cell fragments, play a critical role in hemostasis. They bind to damaged blood vessels, aggregating to form a platelet plug, which helps to stop bleeding.

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Study Notes

Hemopoiesis

  • Mature blood cells have a short lifespan and need constant replacement.
  • Hemopoiesis (or hematopoiesis) creates new blood cells from precursor cells.
  • In early embryos, blood cells develop in the yolk sac mesoderm.
  • In the second trimester, hemopoiesis primarily occurs in the developing liver, with the spleen playing a lesser role.
  • By the third trimester, bone marrow in specific bones becomes the primary hemopoietic organ.
  • Throughout childhood and adulthood, erythrocytes (red blood cells), granulocytes, monocytes, and platelets are formed from stem cells in the bone marrow.

Hemopoietic Stem Cells

  • Stem cells are pluripotent, capable of both self-renewal and asymmetric division.

  • Some daughter cells differentiate permanently into specific cell types.

  • Other daughter cells remain as a stem cell pool for slow division.

  • A single pluripotent stem cell in the bone marrow gives rise to all blood cell types.

  • Committed pluripotent stem cells create specific blood cells (lymphoid and myeloid).

  • Myeloid cells produce granulocytes, monocytes, erythrocytes, and megakaryocytes.

  • Lymphoid cells produce lymphocytes.

Progenitor & Precursor Cells

  • Progenitor cells, also called colony-forming units (CFUs), give rise to one type of blood cells in cultures or spleen injections.
  • There are four major types of progenitor cells/CFUs: erythroid, thrombocytic, granulocyte-monocyte, and lymphoid.
  • Each progenitor/CFU lineage creates precursor cells (blasts) that develop the characteristics of mature cells.
  • Stem cells maintain a smaller population, while progenitor cells divide to make numerous differentiated, mature cells.

Bone Marrow

  • Bone marrow adjusts blood cell production to the body's needs.
  • Bone marrow is found in the medullary canals of long bones and cancellous bone.
  • Two types of bone marrow include red bone marrow (blood-forming) and yellow bone marrow (adipose tissue).
  • Red marrow is predominant in newborns; yellow marrow is more common in adults.
  • Red marrow can reverse to red under conditions like severe bleeding or hypoxia.

Red Bone Marrow

  • Red bone marrow contains reticular connective tissue stroma.
  • The stroma includes stromal cells (reticular adventitial cells) with supporting reticular fibers.
  • Contains hemopoietic cords (islands) of cells.
  • Sinusoidal capillaries are between hemopoietic cords.
  • The sinusoidal endothelium allows newly differentiated blood cells and platelets to enter circulation.
  • Old or damaged red blood cells are phagocytosed by macrophages, and the iron from them is recycled.

Erythropoiesis

  • Erythropoiesis is the maturation of red blood cells.
  • The cell and nuclear volume decrease, and the nucleoli disappear.
  • Chromatin density increases.
  • Polyribosomes decrease, and hemoglobin increases.
  • Mitochondria and other organelles disappear.
  • Erythropoietin (produced in kidneys) stimulates red blood cell production.

Granulopoiesis

  • Granulopoiesis involves the development of granulocytes (neutrophils, basophils, and eosinophils).
  • Azurophilic granules, similar in all granulocytes are produced first.
  • Specific granules' content differentiates granulocytes.
  • The myeloblast is the most immature recognizable cell in the myeloid series.
  • Promyelocytes have basophilic cytoplasm and azurophilic granules.
  • Granules increase and occupy much of the cytoplasm during the metamyelocyte stage.

Agranulopoiesis

  • Agranulocytes (monocytes and lymphocytes) do not have specific granules.
  • They are distinguished mainly by cell size and nuclear shape.

Monocytes

  • Monoblasts are morphologically similar to myeloblasts.
  • Promonocytes develop from monoblasts, then monocytes.
  • Monocytes mature into macrophages (phagocytic cells) in tissues.

Lymphocytes

  • Lymphocyte progenitor cells originate in bone marrow.
  • Some lymphocytes migrate to the thymus to become T lymphocytes.
  • Other cells become B lymphocytes in bone marrow and then migrate to peripheral lymphoid organs.
  • Lymphocytes develop into smaller cells, with a less-visible nucleolus.

Platelets

  • Platelets (thrombocytes) are cell fragments from megakaryocytes.
  • Megakaryocytes are large cells with multiple nuclei (polyploid).
  • Megakaryoblasts produce megakaryocytes, driven by thrombopoietin.
  • Platelets have actin filaments, mixed polarity microtubules, vesicles, and granules in the proplatelets.
  • These proplatelet extensions penetrate sinusoids and extend into blood.
  • Cytoplasm in loops of platelets pinch off to form platelets.

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Description

Explore the fascinating process of hemopoiesis, the formation of blood cells from stem cells. This quiz covers the role of various organs in blood cell development throughout different stages of life, as well as the characteristics of pluripotent stem cells in the bone marrow. Test your knowledge on how these processes sustain the body's need for new blood cells.

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