Tissues

• Tissue


  A group of similar cells that work together to perform a common function
• Histology


  The study of tissues
• Cells can not be seen microscopically, requires us to take thin slices and view them under a microscope
• Most cells are colorless, requires use to stain the cells in order to view them under a microscope
• Different stains target different chemicals allowing us to view different parts of the cells
• Types of Primary Tissue

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nerve tissue
• Epithelial tissue


  • Creates a border or boundary
  • Can be glandular
  • Line the digestive tract organs and other hollow organs
• Connective tissue


  • Many functions
  • Most types support other tissue
  • Lines digestive tract organs and hollow organs
• Muscle tissue


  • Produces movement
  • Highly vascularized
• Nerve tissue


  • Sends electrical impulse for communication
• Nervous tissue: Internal communication
• Muscle tissue: Contracts to cause movement
• Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters, excretion, and sensory reception
• Connective tissue: Supports, protects, binds other tissues together
• Nervous tissue components


  • Brain
  • Spinal cord
  • Nerves
• Muscle tissue types


  • Muscles attached to bones (skeletal)
  • Muscles of heart (cardiac)
  • Muscles of walls of hollow organs (smooth)
• Epithelial tissue locations


  • Lining of digestive tract organs and other hollow organs
  • Skin surface (epidermis)
  • Bones
  • Tendons
  • Fat and other soft padding tissue
• Epithelial Tissue (Epithelium)


  Forms a boundary or border
• Types of epithelial tissue


  • Covering and lining epithelia
  • Glandular epithelia
• Epithelial tissue is always associated with connective tissue for support
• Epithelial tissue is separated by a basement membrane, a thin molecular (noncellular) layer
• Functions of epithelial tissue


  • Protection
  • Absorption
  • Filtration
  • Excretion
  • Secretion
  • Sensory reception
• Five characteristics of epithelial tissue


  • Polarity
  • Specialized contacts
  • Support by connective tissue
  • Avascular, but innervated
  • Can regenerate
• Polarity


  Epithelial cells have an apical surface and a basal surface
• Apical surface


  Side of cell exposed to the cavity or open space
• Basal surface


  Opposite side that attaches to the supportive connective tissue
• Apical surface may be smooth and slick, may contain microvilli or cilia
• Basal surface secretes the basal lamina
• Basal lamina is part of the basement membrane and acts as an adhesive sheet to secure the cell to the next layer of tissue
• Basal lamina selectively filters what substances can pass through the epithelial layer
• Basal lamina acts as a scaffolding for cell migration in wound repair
• Specialized contacts


  Adjacent epithelial cells fit tightly together and form specialized contacts that bind cells together
• Specialized contacts


  • Tight junctions
  • Desmosomes
  • Adherent Junctions: communication
  • Gap Junctions
• All epithelial cells are supported by connective tissue (lamina propria)
• Connective tissue provides physical support, nutrient support and waste removal for epithelial cells
• Four main classes of connective tissue


  • Connective tissue proper
  • Cartilage
  • Bone
  • Blood
• Connective tissue produces the reticular lamina, which is a collagen layer that is part of the basement membrane
• Connective tissue


  • Most abundant and widely distributed of primary tissue
  • Most diverse in function
  • Binding and support
  • Protecting
  • Insulating
  • Transporting substances (blood)
• Basement membrane reinforces the epithelial sheet and defines the epithelial boundary
• Connective tissue


  • During development, all connective tissue starts off as mesenchyme (an embryonic tissue)
  • They have varying degrees of vascularity (blood vessels running through the tissue)
  • They have a nonliving extracellular matrix