stem cell

(noun)

A primal undifferentiated cell from which a variety of other cells can develop through the process of cellular differentiation.

Related Terms

Examples of stem cell in the following topics:

  • Development of Blood and Blood Vessels

    • New blood vessels are formed from endothelial stem cells, which give rise to the endothelial cells which line the vessels.
    • Endothelial stem cells (ESCs) are one of three types of stem cells found in bone marrow.
    • ESCs have the characteristic properties of a stem cell: self-renewal and differentiation.
    • These parent stem cells, ESCs, give rise to endothelial progenitor cells (EPCs), which are intermediate stem cells that lose potency.
    • Progenitor stem cells are committed to differentiating along a particular cell developmental pathway.

  • Development of Blood

    • Hematopoietic stem cells reside in the bone marrow and have the unique ability to differentiate into all of the mature blood cell types.
    • The process of the development of different blood cells from hematopoietic stem cells to mature cells is called "hematopoeisis. "
    • As a stem cell matures, it undergoes changes in gene expression that limit the cell types that it can become and moves it closer to a specific cell type.
    • For the stem cells and other undifferentiated blood cells in the bone marrow, blood cells are determined to specific cell types by random.
    • A comprehensive diagram showing the development of different blood cells from hematopoietic stem cell to mature cells.

  • WBC Formation

    • Haematopoiesis refers to the formation of blood cells components.
    • All cellular blood components are derived from haematopoietic stem cells located within the bone marrow.
    • Haematopoietic stem cells (HSCs) reside in the bone marrow and have the unique ability to give rise to all mature blood cell types through differentiation into other progenitor cells.
    • When they proliferate, at least some daughter cells remain HSCs, so the pool of stem cells does not become depleted over time.
    • The lymphocyte lineage derives from common lymphoid progenitor cells, which in turn become lymphoblasts before differentiating into T cells, B cells, and NK cells.

  • Muscle Development

    • Myogenesis is the formation of muscle tissue during embryonic development from stem cells in the mesoderm.
    • The cells of the inner cell mass (embryoblast), which are known as human embryonic stem cells (hESCs), will differentiate to form four structures: the amnion, the yolk sac, the allantois, and the embryo itself.
    • Human embryonic stem cells are pluripotent; that is, they can differentiate into any of the cell types present in the adult human, and into any of the intermediate progenitor cell types that eventually turn into the adult cell lines. hESCs are also immortal: they can divide and grow in number indefinitely, without undergoing either differentiation or cellular aging (cellular senescence).
    • A myoblast is a type of embryonic progenitor cell that differentiates to give rise to muscle cells.
    • These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.

  • Histology of the Large Intestine

    • The crypts and intestinal villi are covered by epithelium which contains two types of cells, goblet cells (secreting mucus) and enterocytes (secreting water and electrolytes).
    • The basal, further from the intestinal lumen, portion of the crypt contains multipotent stem cells.
    • During each mitosis, one of the two daughter cells remains in the crypt as a stem cell, while the other differentiates and migrates up the side of the crypt and eventually into the villus.
    • Goblet cells are among the cells produced in this fashion.
    • Many genes have been shown to be important for the differentiation of intestinal stem cells.

  • RBC Life Cycle

    • Human erythrocytes are produced through a process called erythropoiesis, developing from committed stem cells to mature erythrocytes in about seven days.
    • Erythrocytes differentiate from erythrotropietic bone marrow cells, a type of hemopoietic stem cell found in bone marrow.
    • Unlike mature RBCs, bone marrow cells contain a nucleus.
    • In the embryo, the liver is the main site of red blood cell production and bears similar types of stem cells at this stage of development.
    • Outline the life cycle of erythrocytes (red blood cells, or RBCs)

  • Maturation of T Cells

    • T cells originate from haematopoietic stem cells in the bone marrow and undergo positive and negative selection in the thymus to mature.
    • They can be distinguished from other lymphocytes, such as B cells and natural killer cells (NK cells), by the presence of a T cell receptor (TCR) on the cell surface.
    • All T cells originate from haematopoietic stem cells in the bone marrow, which are capable of differentiating into any type of white blood cell.
    • A T cell is then signaled by the thymus to become a CD4+ cell by reducing expression of its CD8 cell surface receptors.
    • The remaining cells exit the thymus as mature naive T cells.

  • Blastocyst Formation

    • The morula is a solid ball of about 16 undifferentiated, spherical cells.
    • The blastocyst possesses an inner cell mass (ICM), or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast, which later forms the placenta.
    • The embryoblast is the source of embryonic stem cells and gives rise to all later structures of the adult organism.
    • On the deep surface of the inner cell mass, a layer of flattened cells, called the endoderm, is differentiated and quickly assumes the form of a small sac, called the yolk sac.
    • The blastocyst possesses an inner cell mass from which the embryo will develop, and an outer layer of cells, called the trophoblast, which will eventually form the placenta.

  • Clonal Selection and T-Cell Differentiation

    • This mass production of daughter cells is termed "clonal expansion," in which daughter cells proliferate into several generations of clones of the original parent cells.
    • Cloned daughter cells differentiate into either effector T cells or memory T cells.
    • Cytotoxic effector T cells are finished, but helper T cells continue to differentiate into individual subsets of helper T cells.
    • A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce lymphocytes in the immune system.
    • Clonal selection of lymphocytes: 1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce 2) immature lymphocytes with many different antigen receptors.

  • Lymphoid Cells

    • Lymphocytes develop from lymphoblasts (differentiated blood stem cells) within lymphoid tissue in organs such as the thymus.
    • The three major types of lymphocyte are T cells, B cells, and natural killer cells.
    • Therefore it acts as an inhibitor of NK cell activity, and NK cells will activate and destroy cells when it does not detect MHC class I on that cell surface.
    • Activated NK cells release cytotoxic (cell-killing) granules that contain perforin and granzyme, which can lyse cell membranes and induce apoptosis to kill infected or abnormal cells.
    • T cells are involved in cell-mediated immunity whereas B cells are primarily responsible for humoral immunity.