mod 2

• The cell is the basic structural and functional unit of the body
• Variations in cell structure account for remarkable diversity in the morphology and function of the body’s basic tissues and organs
• Cytology is the study of individual cells and the different structures they contain
• A thorough knowledge of the cell is needed to understand the parts and function of tissues and organs
• Living cells can be studied using a microscope
• Cells can be observed/isolated in an isotonic liquid or physiologic salt solution, or in cell cultures
• Cells appear as irregular, translucent masses of cytoplasm containing a nucleus
• The appearance of organelles in a compound light microscope and electron microscope is differentiated, with the latter allowing the study of ultrastructural features of cells and tissues
• Cell division is related to the demand for growth and replacement of tissues
• Cell division occurs in all adult cells except in the central nervous system (CNS)
• Cell division involves both cytokinesis (division of cytoplasm) and karyokinesis (division of nucleus)
• Karyokinesis can occur without cytokinesis, resulting in the formation of a binucleate cell (e.g. some liver cells) or multinucleate cells in the case of osteoclasts and megakaryocytes
• The cell cycle is made up of mitosis and interphase
• During interphase, DNA is synthesized in the S stage where DNA duplication or synthesis takes place
• After the S stage, cells enter a relatively quiescent period called the post-duplication or G2 stage before passing through prophase, metaphase, anaphase, and telophase
• At the termination of mitosis, daughter cells enter the reduplication or G1 stage of interphase until DNA duplication occurs prior to the succeeding mitosis