CELL DIVISION

• Cell division

  Related to the demand for growth and replacement of tissues
• Cell division

  • Occurs in all adult cell types except of the cells of the CNS and cardiac muscle cells
• Cell division

  1. Rapid process in epithelial tissues subject to wear and tear

  2. Rapid process in blood forming tissues

  3. Rapid process during healing of wounds
• Cell division

  1. Cytokinesis - division of the cytoplasm

  2. Karyokinesis - division of the nucleus
• Karyokinesis without cytokinesis

  • Bi-nucleate
  • Multinucleate
• Types of cellular divisions

  • Amitosis
  • Mitosis
  • Meiosis
• Amitosis

  • Direct cellular division
  • Cytokinesis and karyokinesis
• Amitosis

  • Unequal halving
  • Uneven division of chromatin
  • No nuclear changes
  • Occur under abnormal conditions
  • Rare occurrence
• Mitosis

  • Indirect cell division
  • Happens in Somatic cells
  • Involves nuclear changes - mother cell divides
  • Two daughter cells, each with a chromosomal karyotype identical to that of the mother cell
• Cell cycle

  • Mitosis (4 stages)
  • Interphase
• Stages of interphase

  • Resting phase when cell is not dividing
  • G1 Phase - maintenance of cell, cell growth
  • S Phase - DNA replication happens
  • G2 Phase - cell prepare to divide
• Mitotic phase

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Prophase


  • Chromosomes became tight ply coiled
  • Nuclear envelope and nucleolus disappear
  • Prometaphase, formation of kinetochore
• Metaphase


  • Chromosomes line up in the middle of the cell
• Anaphase


  • Chromatid are pulled apart to opposing poles
• Telophase


  • Nucleoli reappear
  • Nuclear envelope are formed
• Cytokinesis


  The process by which the cytoplasm is divided into two genetically identical cells
• Meiosis

  • Indirect cell division
  • Occurs in sex cells / gametes
  • Involves nuclear changes - mother cell divides
  • Sperm cell: four daughter cells
  • Egg cell: two daughter cells
  • Each daughter cell with a chromosomal karyotype identical to that of the mother cell
• Cytomorphosis

  • Embryonal stage
  • Stage of cell specialization / differentiation and maturity
  • Stages of regression and senescence
  • Cellular death and cell removal
• Embryonal stage

  • Large cell
  • Active cellular division
  • Large nuclei
  • Relatively scanty cytoplasm
  • Lacks visible signs of differentiation
• Stage of cell specialization

  • Signs of differentiation of cells become visible
• Stages of regression and senescence

  • Alteration appears in the character of both the nucleus and cytoplasm
• Cellular death

  Death ensues when the vital processes of the protoplasm ceases
• Cellular death

  • Necrobiosis
  • Necrosis
• Processes that leads to cellular death

  • Pyknosis
  • Karyorrhexis
  • Karyolysis
  • Coagulation
  • Cytolysis
  • Apoptosis
• Necrobiosis gradual degeneration of cells in the tissue