enteroendocrine cells

Examples of enteroendocrine cells in the following topics:

• Intestinal Phase

  • Stretching of the duodenum accentuates vagal reflexes that stimulate the stomach, and peptides and amino acids in the chyme stimulate G cells of the duodenum to secrete more gastrin, which further stimulates the stomach.
  • Chyme also stimulates duodenal enteroendocrine cells to release secretin and cholecystokinin.
  • The enteroendocrine cells also secrete glucose dependent insulinotropic peptide.

• Gastric Phase

  • Histamine is a paracrine secretion from the enteroendocrine cells in the gastric glands.
  • Gastrin is a hormone produced by enteroendocrine G cells in the pyloric glands.
  • All three of these stimulate parietal cells to secrete hydrochloric acid and intrinsic factor.
  • The chief cells secrete pepsinogen in response to gastrin and especially Ach, and ACh also stimulates mucus secretion.
  • Below pH of two, stomach acid inhibits the parietal cells and G cells: a negative feedback loop that winds down the gastric phase as the need for pepsin and HCl declines.

• Cephalic Phase

  • Cephalic phase causes ECL cells to secrete histamine and increase HCl acid in the stomach.
  • There will also be an influence on G cells to increase gastrin circulation.
  • Chemical stimuli (i.e., partially digested proteins, caffeine) directly activate G-cells (enteroendocrine cells) located in the pyloric region of the stomach to secrete gastrin; this in turn stimulates gastric glands to secrete gastric juice.

• Cellular Differentiation

  • Three basic categories of cells make up the mammalian body: germ cells, somatic cells, and stem cells.
  • Pluripotent stem cells undergo further specialization into multipotent progenitor cells that then give rise to functional cells.
  • Hematopoietic stem cells (adult stem cells) from the bone marrow that give rise to red blood cells, white blood cells, and platelets
  • Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to stromal cells, fat cells, and types of bone cells;
  • Epithelial stem cells (progenitor cells) that give rise to the various types of skin cells

• Gene Expression in Stem Cells

  • In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues.
  • Stem cells can now be artificially grown and differentiated into specialized cell types with characteristics consistent with muscle or nerve cells through cell culture.
  • In one, the daughter cells are initially equivalent but a difference is induced by signaling between the cells, from surrounding cells, or from the precursor cell.
  • Stem cells are indicated by (A), progenitor cells by (B), and differentiated cells by (C).
  • Pluripotent, embryonic stem cells originate as inner cell mass (ICM) cells within a blastocyst.

• Dendritic Cells

  • Dendritic cells are immune cells that function to process antigens and present them to T cells.
  • Immature dendritic cells (e.g.
  • Mature dendritic cells reside in the T cell zones of the lymph nodes, and in this location they display antigens to T cells.
  • Dendritic cells are constantly in communication with other cells in the body.
  • This communication can take the form of direct cell-to-cell contact based on the interaction of cell-surface proteins.

• Cell Theory

  • Cell theory states: living things are composed of one or more cells; the cell is the basic unit of life; cells arise from existing cells.
  • The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.
  • "All cells only arise from pre-existing cells.
  • Cells carry genetic material passed to daughter cells during cellular division
  • The cell is the basic unit of life and the study of the cell led to the development of the cell theory.

• Specific T-Cell Roles

  • T helper cells assist the maturation of B cells and memory B cells while activating cytotoxic T cells and macrophages.
  • Differentiation into helper T cell subtypes occurs during clonal selection following T cell activation of naive T cells.
  • Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also cause much of the damage in in transplant rejection and autoimmune diseases.
  • Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells), which have different properties and release different cytokines.
  • Regulatory T cells (Treg cells), also known as suppressor T cells, are crucial for the maintenance of immunological tolerance.

• The Role of the Cell Cycle

  • In other words, that original single cell is the ancestor of every other cell in the body.
  • Single-celled organisms use cell division as their method of reproduction.
  • While there are a few cells in the body that do not undergo cell division, most somatic cells divide regularly.
  • A somatic cell is a general term for a body cell: all human cells, except for the cells that produce eggs and sperm (which are referred to as germ cells), are somatic cells.
  • The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells.

• Classes of T Cells

  • T cells play a central role in cell-mediated immune response through the use of the surface T cell receptor to recognize peptide antigens.
  • T cells do not produce antibody molecules.
  • Effector cells include helper T cells, and cytolytic or cytotoxic T cells.
  • Another class of T cells called regulatory T cells function to inhibit immune response and resolve inflammation.
  • T cells promote the killing of cells that have ingested microorganisms and present foreign antigens on their surface.