Cells (Definition) and Cell Division PDF

Ahmed Abdul-Aziz Mohamed. PhD  Cells (definition ) The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane, and contains many membranous and non membranous organelles like Nucleus , Endoplasmic reticulum...

Ahmed Abdul-Aziz Mohamed. PhD  Cells (definition ) The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane, and contains many membranous and non membranous organelles like Nucleus , Endoplasmic reticulum , Golgi apparatus, cytoskeleton, Ribosome and centrosomes ,… According the presence of nuclear membrane cells are classified into Eukaryotic and Prokaryotic cells Electron Microscopic image of cells showing cell organelles and cells membrane  Cell membrane double layer of phospholipids, which are amphiphilic (partly hydrophobic and partly hydrophilic)  Cell membrane function Endocytosis and exocytosis are the processes by which cells move materials into or out of the cell that are too large to directly pass through the lipid bilayer of the cell membrane. Large molecules, microorganisms and waste products are some of the substances moved through the cell membrane via exocytosis and endocytosis. Endocytosis and exocytosis  Inclusions The cell also contains inclusions, which are metabolically inert substances that are also considered transient over time in the cell.These include masses of organic chemicals and often are recognizable microscopically. These inclusions are released from storage by the cell and used as demand dictates. Lipids and glycogen can be decomposed for energy from inclusions in the cell. Melanin is stored as inclusions in certain cells of the skin and oral mucosa and is responsible for the pigmentation of these tissue types. Inclusions also include residual bodies, which are spent lysosomes and their digested material  Cell Division Cell division or mitosis is a complex process involving many of the organelles of the cell. Mitosis functions during tissue growth or regeneration, and its activity is dependent on the length of the individual cell’s lifespan.  Extracellular Materials The cells in each tissue type are surrounded by extracellular materials, which include both tissue fluid and intercellular substance. Tissue fluid (or interstitial fluid) provides a medium or matrix for dissolving, mixing, and transporting substances and for carrying out chemical reactions. Similar to blood plasma in its content of ions and diffusible substances, tissue fluid contains a small amount of plasma proteins.  Intercellular Junctions Cell junctions or junctional complexes, are a class of cellular structures consisting of multiprotein complexes that provide contact or adhesion between neighboring cells or between a cell and the extracellular matrix in animals. Cell junctions From cells to organs Tissue of our body