Cell diversity and microbiology

• Our bodies are composed of approximately ten trillion (10^13) cells
• Multi-cellular organisms


  • Challenging problems for structure and communication
  • Cells must be connected strongly together and work in a co-ordinated fashion
  • The infrastructure holding us together must also be malleable enough to cope with stress, changing environments and to allow repairs
  • Cells must communicate with each other to ensure each plays its proper part
• Diversity of human cells

  • Red blood cell
  • Nerve cell
  • Goblet cells
  • Osteoclast
  • Skin cells
  • Skeletal muscle cells
• There are more than 200 types of cell in the human body, most can be divided into one of four types of tissue
• Types of tissue


  • Neuronal
  • Epithelial: lining of tissues, cells
  • Connective: tendons, fat
  • Muscle
• Totipotent stem cells

  Capable of producing any cell type
• Pluripotent stem cells

  Capable of producing any cell within a major lineage (ectoderm, endoderm, mesoderm)
• Multi-potent stem cells

  Capable of producing a restricted set of related cells
• Differentiation is (normally) a one way process. Cells can't climb back up the mountain and become stem cells again and they can't cross to adjacent valleys to become another type of cell.
• De-differentiation can occur in nature, for example as part of a regenerative process in amphibians and worms. De-differentiation can occur in cancer, with cancer cells acquiring stem cell like properties.
• Differentiated human skin cells were induced to form pluripotent stem cells. They were then treated with signals that induced differentiation into cardiomyocytes (heart cells). Via growth factors. Twelve days after treatment clumps of cells started beating.
• Organising cells into tissues

  • Adipose tissue
  • Bone
  • Skin
  • Skeletal muscle
  • Cartilage
  • Intestine
• Cells with similar functions

  • Are connected together in tissues
  • Tissues are then organised into organs
  • Cells can be connected in many different ways depending on the required biological or mechanical properties of the tissue
• Types of epithelial tissue

  • Stratified squamous epithelium
  • Pseudostratified columnar epithelium
  • Simple squamous epithelium
  • Simple columnar epithelium
  • Cuboidal epithelium
• Epithelial tissue


  • Linings and main components of most organs
  • Apical surface
  • Basal surface
• Connective tissue


  • Mainly binds and supports other tissues
  • Contains sparsely packed cells scattered throughout an extracellular matrix
  • The matrix consists of fibers in a liquid, jellylike, or solid foundation
• Types of connective tissue

  • Loose connective tissue
  • Blood
  • Cartilage
  • Adipose tissue
  • Bone
  • Fibrous connective tissue
• Components of connective tissue

  • Red blood cells
  • Chondrocytes
  • Chondroitin sulfate
  • Fat droplets
  • Central canal
  • Osteon
  • Nuclei
  • Elastic fiber
  • Collagenous fiber
  • White blood cells
  • Plasma
• Types of muscle tissue

  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle
• Muscle tissue

  • Nuclei
  • Sarcomere
  • Muscle fiber
• Neurons


  • Dendrites
  • Cell body
  • Axon
• Organs consist of multiple types of tissue that are connected together - the brain contains both connective tissues and neuronal tissues.
• Cells are joined together and attached to the extracellular matrix

  • This happens through different types cell junctions
  • Involves the cytoskeleton