Granulation

Examples of Granulation in the following topics:

• Types of WBCs

  • A major distinguishing feature is the presence of granules; white blood cells are often characterized as granulocytes or agranulocytes.
  • Granulocytes, also known as polymorphonuclear (PMN) leukocytes, are characterized by stained granules within their cytoplasm under a microscope.
  • These granules are membrane-bound enzymes that act primarily in the digestion of endocytosed particles.
  • They may also cause granule dependent cell-mediated apoptosis through the release of perforins, granzymes, and proteases.
  • Monocytes and their progeny contain toll-like receptors and granules.

• WBC Function

  • When pathogens are encountered, granule dependent apoptosis (a mechanism of cytotoxicity) may be induced in the pathogen by releasing perforins, granzymes, and proteaseases from their granules.

• Phagocytes

  • Mature monocytes have large, smooth, lobed nuclei and an abundant cytoplasm that contains granules, but are not technically considered granulocytes.
  • Macrophages do not have granules, but contain many lysosomes.
  • They also degranulate their granules to release perforin, granzyme, proteases, and other chemicals to do cytotoxic damage to pathogens (and occasionally normal bodily tissues as well).
  • In addition to these functions, mast cells produce cytokines kept in their granules, such as histamine that induce an inflammatory response when a pathogen is detected.

• Overview of the Endocrine System

  • Endocrine glands are typically well vascularized and the cells comprising the tissue are typically rich in intracellular vacuoles or granules which store hormones prior to release.

• Natural Killer Cells

  • NK cells use two cytolytic granule mediated apoptosis to destroy abnormal and infected cells.
  • The granules of NK cells contain proteins such as perforin and proteases known as granzymes.
  • Antibodies that bind to antigens can be recognized by FcϒRIII (CD16) receptors (a type of activating receptor), resulting in NK activation, release of cytolytic granules, and consequent cell apoptosis.

• Characteristics of Nervous Tissue

  • It produces all the proteins and contains specialized organelles such as nucleus, granules and Nissl bodies.

• Cerebrospinal Fluid and Its Circulation

  • CSF is reabsorbed into venous sinus blood via arachnoid granulations.
  • Since the subarachnoid space around the brain and spinal cord can contain only 135 to 150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the superior sagittal sinus.

• Parts of the Cerebellum

  • Within this thin layer are several types of neurons with a highly regular arrangement, the most important being Purkinje cells and granule cells .
  • Due to its large number of tiny granule cells, the cerebellum contains more neurons than the rest of the brain put together, but it only takes up only 10% of total brain volume.

• Overview of Hemostasis

  • The activated platelets then release the contents of their granules, which contain a variety of substances that stimulate further platelet activation and enhance the hemostatic process.
  • Platelets contain secretory granules.

• Microbial Evasion of Phagocytosis

  • These include cytolysins which form pores in the phagocyte's cell membranes, streptolysins and leukocidins which cause neutrophils' granules to rupture and release toxic substances, and exotoxins which reduce the supply of a phagocyte's ATP, needed for phagocytosis.