18.2 Production of the Formed Elements
3 min read•june 18, 2024
Blood formation is a complex process that occurs primarily in bone marrow. give rise to all types of blood cells through differentiation. This process is crucial for maintaining a healthy blood supply and immune system.
Regulation of blood cell production involves various growth factors and cytokines. These molecules stimulate the production of specific blood cell types in response to the body's needs. The balance between cell production and removal is essential for blood homeostasis.
Hemopoiesis and Blood Cell Formation
Process of hemopoiesis
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- involves the formation of blood cells primarily in the of certain bones (pelvis, sternum, ribs, and vertebrae)
- Hemopoietic stem cells (HSCs) serve as the multipotent precursors capable of differentiating into any type of blood cell
- HSCs divide and differentiate into myeloid and lymphoid lineages
- HSCs reside in specialized microenvironments called stem cell niches
- differentiates into (red blood cells), , and
- Myeloblasts further differentiate into (, , and ) and (white blood cells)
- differentiates into
- Lymphoblasts further differentiate into , , and (white blood cells)
- Precursor cells represent intermediate stages between HSCs and mature blood cells
- Each blood cell type has a specific precursor cell ( for erythrocytes, for platelets)
- involves the progressive specialization of cells into specific blood cell types
Regulation of blood cell production
- , cytokines that stimulate blood cell proliferation and differentiation, regulate blood cell production
- (EPO) stimulates erythrocyte production
- Produced by the kidneys in response to low oxygen levels (hypoxia)
- (TPO) stimulates platelet production
- Produced by the liver and kidneys
- (G-CSF) and (GM-CSF) stimulate granulocyte and monocyte production
- Produced by various tissues (endothelial cells, fibroblasts)
- (IL-3, IL-7) and other cytokines regulate lymphocyte production
- Produced by immune cells (T lymphocytes, macrophages)
- The , including stromal cells and extracellular matrix, supports blood cell development
Sites of blood cell formation
- Before birth, occurs in the , liver, and spleen
- serves as the primary site during the first few weeks of embryonic development
- Liver becomes the main site from the second trimester until shortly before birth
- Spleen plays a minor role during fetal development
- After birth, hemopoiesis occurs primarily in the red bone marrow
- Red bone marrow is found in the spongy bone of the skull, ribs, sternum, vertebrae, and ends of long bones
- In adults, the main sites are the pelvis, sternum, ribs, and vertebrae
- In times of increased demand, the liver and spleen may resume their hemopoietic function ()
- , such as bone marrow, thymus, and lymph nodes, play crucial roles in blood cell production and maturation
Cell turnover and homeostasis
- Blood cell production is balanced with cell removal to maintain homeostasis
- , or programmed cell death, helps regulate blood cell populations and remove damaged or unnecessary cells
Key Terms to Review (48)
Apoptosis: Apoptosis is a process of programmed cell death that occurs in multicellular organisms, where cells systematically dismantle themselves and are removed without releasing harmful substances into the surrounding area. It plays a crucial role in maintaining tissue health by eliminating old, unnecessary, or damaged cells.
Apoptosis: Apoptosis is a form of programmed cell death that occurs in multicellular organisms. It is a highly regulated and controlled process that plays a crucial role in various biological processes, including cell growth and division, tissue injury and aging, production of formed elements, and the adaptive immune response.
B lymphocytes: B lymphocytes, also known as B cells, are a type of white blood cell crucial for the immune response by producing antibodies that neutralize pathogens. They develop in bone marrow and play a key role in the humoral immunity component of the adaptive immune system.
B Lymphocytes: B lymphocytes, also known as B cells, are a type of white blood cell that play a crucial role in the adaptive immune response. They are responsible for producing antibodies, which are proteins that recognize and bind to specific foreign substances, known as antigens, in order to neutralize them or mark them for destruction by other immune cells.
Basophils: Basophils are a type of white blood cell that plays a critical role in the body's immune response by releasing chemicals such as histamine and heparin during allergic reactions and inflammation. They represent less than 1% of the total white blood cell count but are vital for mounting a protective response against pathogens.
Basophils: Basophils are a type of white blood cell that play a crucial role in the body's immune response and inflammatory processes. They are the least common type of leukocyte, accounting for only about 0.5-1% of all white blood cells in the body.
Bone marrow transplant: A bone marrow transplant is a medical procedure performed to replace damaged or destroyed bone marrow with healthy bone marrow stem cells. The process involves infusing these healthy cells into the patient's bloodstream, where they migrate to the bone marrow and begin producing new blood cells.
Cell Differentiation: Cell differentiation is the process by which a cell becomes specialized in structure and function to perform a specific role within an organism. It is a crucial aspect of development and growth, as it allows cells to take on distinct characteristics and carry out specialized tasks.
Eosinophils: Eosinophils are a type of white blood cell that play a crucial role in the body's immune response, particularly in combating parasitic infections and participating in allergic reactions. They contain granules rich in enzymes that help reduce inflammation and fight off pathogens.
Eosinophils: Eosinophils are a type of white blood cell that play a key role in the immune response, particularly against parasitic infections and in allergic reactions. They are characterized by the presence of granules containing cytotoxic proteins that can damage or destroy foreign invaders.
Erythroblasts: Erythroblasts are immature red blood cells (erythrocytes) that are produced in the bone marrow during the process of erythropoiesis. They are the precursor cells that eventually mature into fully functional red blood cells.
Erythrocytes: Erythrocytes, also known as red blood cells (RBCs), are the most abundant type of blood cells in the human body. They are responsible for carrying oxygen from the lungs to the body\'s tissues and carbon dioxide from the tissues back to the lungs, playing a crucial role in the functions of human life, supporting and protecting connective tissue, and maintaining the overall health and homeostasis of the body.
Erythropoietin: Erythropoietin is a glycoprotein hormone produced primarily by the kidneys that stimulates the production of red blood cells in the bone marrow. It plays a crucial role in regulating erythropoiesis, especially in response to low oxygen levels in the blood, which can be caused by various factors such as high altitudes, anemia, or respiratory diseases.
Extramedullary Hemopoiesis: Extramedullary hemopoiesis refers to the production of blood cells outside of the bone marrow, the primary site of hematopoiesis. This process occurs when the bone marrow is unable to meet the body's demand for new blood cells, leading to the formation of blood cell-producing tissues in other areas of the body.
Granulocyte Colony-Stimulating Factor: Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein that stimulates the bone marrow to produce and release granulocytes, a type of white blood cell, into the bloodstream. It plays a crucial role in the production and maturation of neutrophils, a critical component of the body's immune defense system.
Granulocyte-Macrophage Colony-Stimulating Factor: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein that stimulates the production and differentiation of granulocytes and macrophages, two types of white blood cells essential for immune function and response. It plays a crucial role in the production of the formed elements of the blood, as described in the context of 18.2 Production of the Formed Elements.
Granulocytes: Granulocytes are a type of white blood cell that contain granules in their cytoplasm. They are a crucial component of the immune system, responsible for defending the body against pathogens and infections.
Hematopoietic Microenvironment: The hematopoietic microenvironment refers to the specialized cellular and molecular components within the bone marrow that support the production and differentiation of blood cells, known as hematopoiesis. This complex microenvironment provides the necessary signals, growth factors, and physical interactions to regulate the development and maintenance of various blood cell lineages.
Hematopoietic Organs: Hematopoietic organs are the primary sites within the body responsible for the production and development of the formed elements of the blood, including red blood cells, white blood cells, and platelets. These specialized organs play a crucial role in maintaining the body's hematological homeostasis and supporting the immune system.
Hematopoietic stem cell: Hematopoietic stem cells (HSCs) are the undifferentiated cells found in bone marrow that have the unique ability to develop into any type of blood cell, including red blood cells, white blood cells, and platelets. They play a crucial role in the body's ability to replenish its blood supply, maintaining the health and functionality of the cardiovascular system.
Hemocytoblast: A hemocytoblast is a type of stem cell found in the bone marrow that has the potential to develop into any type of blood cell. It is the precursor for both myeloid and lymphoid blood lineages, playing a crucial role in the body's ability to replenish its supply of red blood cells, white blood cells, and platelets.
Hemopoiesis: Hemopoiesis is the process by which the formed elements of blood (such as red blood cells, white blood cells, and platelets) are created in the bone marrow. It involves the differentiation of multipotent stem cells into specialized blood cells to maintain adequate levels and function within the body's circulatory system.
Hemopoiesis: Hemopoiesis, also known as hematopoiesis, is the process by which blood cells are produced and replenished in the body. It is a vital function that ensures the continuous supply of various blood cell types, including red blood cells, white blood cells, and platelets, which are essential for maintaining health and proper bodily functions.
Hemopoietic growth factors: Hemopoietic growth factors are natural substances, often proteins, that stimulate the production of blood cells. They play a critical role in the regulation of both the quantity and types of cells produced by the bone marrow.
Hemopoietic Stem Cells: Hemopoietic stem cells, also known as blood stem cells, are undifferentiated cells found in the bone marrow that have the ability to give rise to all the different types of blood cells, including red blood cells, white blood cells, and platelets. These stem cells are crucial for the production and replenishment of the formed elements of the blood, a process known as hemopoiesis or hematopoiesis.
Interleukins: Interleukins are a group of cytokines (proteins) secreted by white blood cells that mediate communication between cells, especially in response to infection or injury. They play crucial roles in the immune system by regulating cell growth, differentiation, and mobility.
Interleukins: Interleukins are a group of cytokines, or signaling proteins, that are primarily produced by white blood cells and play a crucial role in the regulation and coordination of the immune response. They serve as crucial mediators of communication between different cells of the immune system, facilitating their activation, growth, differentiation, and function.
Leukocytes and Platelets: Leukocytes, also known as white blood cells, are a type of blood cell primarily involved in the body's immune response to identify and combat infections, diseases, and foreign invaders. They vary in function and appearance, playing critical roles from producing antibodies to directly attacking pathogens.
Lymphoblasts: Lymphoblasts are large, immature lymphocytes that play a crucial role in the development of the immune system. These cells are formed from lymphocyte precursors in the bone marrow and undergo rapid proliferation and differentiation into mature lymphocytes, such as B cells and T cells, which are essential for adaptive immunity. Understanding lymphoblasts is key to grasping how the body generates a diverse range of immune responses.
Lymphoid Lineage: The lymphoid lineage refers to the developmental pathway of immune cells that originate from hematopoietic stem cells and give rise to various types of lymphocytes, including T cells, B cells, and natural killer cells. These cells play a crucial role in the adaptive immune response and the body's defense against pathogens and disease.
Megakaryoblasts: Megakaryoblasts are large precursor cells in the bone marrow that give rise to platelets, essential components of blood involved in clotting. These cells undergo a unique process called endomitosis, where they replicate their DNA without dividing, resulting in a larger cell with multiple sets of chromosomes. This characteristic allows megakaryoblasts to develop into megakaryocytes, which ultimately release platelets into the bloodstream.
Monocytes: Monocytes are a type of white blood cell that plays a crucial role in the immune system by engulfing and destroying pathogens and debris. They are the largest type of leukocyte and can differentiate into macrophages and dendritic cells, which further participate in the body's defense mechanisms.
Monocytes: Monocytes are a type of white blood cell that play a crucial role in the immune system. They are the largest of the leukocytes and serve as precursors to macrophages and dendritic cells, which are responsible for engulfing and destroying pathogens, as well as presenting antigens to other immune cells.
Myeloblasts: Myeloblasts are immature precursor cells in the bone marrow that develop into granulocytes, a type of white blood cell crucial for the immune system. These cells are part of the hematopoietic lineage and play a vital role in the production of formed elements within the blood, as they give rise to neutrophils, eosinophils, and basophils, which help combat infections and respond to allergens.
Myeloid Lineage: The myeloid lineage refers to the developmental pathway that gives rise to various types of blood cells, including granulocytes, monocytes, macrophages, and dendritic cells. These cells are collectively known as myeloid cells and play crucial roles in the innate immune response and tissue homeostasis.
Natural Killer Cells: Natural killer (NK) cells are a type of lymphocyte that play a crucial role in the innate immune response. They are part of the body's first line of defense against pathogens and infected or cancerous cells, and their function is closely tied to the production of the formed elements and the barrier defenses of the innate immune system.
Neutrophils: Neutrophils are a type of white blood cell that play a crucial role in the body's immune response by engulfing and destroying pathogens, such as bacteria and fungi. They are the most abundant type of leukocytes in human blood and are among the first responders to microbial infection.
Neutrophils: Neutrophils are a type of white blood cell that play a crucial role in the body's innate immune response. They are the most abundant type of leukocyte and are the first responders to sites of infection or injury, acting as the body's primary defense against invading pathogens and damaged tissue.
Platelets: Platelets, also known as thrombocytes, are small, irregularly shaped cell fragments found in the bloodstream that play a crucial role in blood clotting and hemostasis. They are produced in the bone marrow and are essential for maintaining the integrity of blood vessels and preventing excessive bleeding.
Pluripotent stem cell: A pluripotent stem cell is a type of cell that has the potential to differentiate into any of the three germ layers: endoderm (internal body structures), mesoderm (middle layer structures such as muscle, bone, and blood vessels), or ectoderm (external body structures). These cells can give rise to virtually any type of cell in the body, including those required for the formation of blood elements.
Red Bone Marrow: Red bone marrow is a soft, spongy tissue found inside certain bones that is responsible for the production of the formed elements of blood, including red blood cells, white blood cells, and platelets. It is a crucial component in the body's hematopoietic system, which is the process of blood cell formation and renewal.
Stem Cell Niche: The stem cell niche is the specialized microenvironment that regulates the self-renewal, differentiation, and maintenance of stem cells within a tissue or organ. It provides the necessary signals and physical cues to control the fate and behavior of stem cells.
T Lymphocytes: T lymphocytes, also known as T cells, are a type of white blood cell that play a crucial role in the adaptive immune response. They are responsible for cell-mediated immunity, recognizing and destroying infected or cancerous cells, and regulating the overall immune system function.
Thrombopoietin: Thrombopoietin is a hormone produced primarily by the liver and kidneys that regulates the production of platelets by the bone marrow. It plays a crucial role in maintaining normal platelet counts in the bloodstream, which are essential for blood clotting and wound healing.
Thrombopoietin: Thrombopoietin is a glycoprotein hormone that primarily stimulates the production and maturation of platelets, also known as thrombocytes, from megakaryocytes in the bone marrow. It is a key regulator of platelet production and plays a crucial role in maintaining normal blood clotting and hemostasis.
Totipotent stem cell: A totipotent stem cell is a type of cell that has the potential to develop into any cell type in the body or even a complete organism, including the placenta and extraembryonic tissues. In the context of anatomy and physiology, particularly within the cardiovascular system's study of blood, these cells represent the earliest stage of development from which all blood cell types can ultimately originate.
Yolk sac: The yolk sac is an early embryonic structure that provides nutrients to the developing embryo and plays a critical role in the formation of the digestive system and blood cells. It is among the first structures to develop from the blastocyst in mammalian development.
Yolk Sac: The yolk sac is a membranous structure that forms early in embryonic development and plays a crucial role in the production and nourishment of the formed elements of blood, as well as in the development of the embryo itself.