Tissue

• Cells


  Specialized for particular functions
• Tissues


  Groups of cells with similar structure and function
• Four primary types of tissues

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Epithelial tissues


  • Found in different areas of the body
  • Body coverings
  • Body linings
  • Glandular tissue
• Functions of epithelial tissues

  • Protection
  • Absorption
  • Filtration
  • Secretion
• Epithelium characteristics


  • Cells fit closely together
  • Tissue layer always has one free surface (apical surface)
  • The lower surface is bound by a basement membrane
  • Avascular (have no blood supply)
  • Regenerate easily if well nourished

  
• Classification of epithelium by number of cell layers

  • Simple – one layer
  • Stratified – more than one layer
• Classification of epithelium by shape of cells

  • Squamous – flattened
  • Cuboidal – cube-shaped
  • Columnar – column-like

  
• Simple epithelium


  • Single layer of cells
• Gland


  One or more cells that secretes a particular product
• Gland types


  • Endocrine gland
  • Exocrine gland
• Connective tissue


  • Found everywhere in the body
  • Includes the most abundant and widely distributed tissues
  • Functions to bind body tissues together, support the body, and provide protection
• Connective tissue characteristics


  • Variations in blood supply
  • Extracellular matrix
• Extracellular matrix


  • Non-living material that surrounds living cells
  • Composed of ground substance and fibers
• Connective tissue types


  • Bone (osseous tissue)
  • Hyaline cartilage
  • Elastic cartilage
  • Fibrocartilage
  • Dense connective tissue
  • Areolar connective tissue
  • Adipose tissue
  • Reticular connective tissue
  • Blood
• Bone (osseous tissue)


  • Composed of bone cells in lacunae and hard matrix of calcium salts
  • Large numbers of collagen fibers
  • Used to protect and support the body
• Hyaline cartilage


  • Most common cartilage
  • Composed of abundant collagen fibers and rubbery matrix
  • Entire fetal skeleton is hyaline cartilage, found in nose, trachea, rib ends, joint surfaces
• Elastic cartilage


  • Provides elasticity
  • Examples: external ear, Eustachian or auditory tube, larynx, epiglottis
• Fibrocartilage


  • Highly compressible
  • Examples: cushion-like discs between vertebrae, pubic symphysis, joints subject to severe strain
• Dense connective tissue


  • Main matrix element is collagen fibers
  • Cells are fibroblasts
  • Examples: tendons (attach muscle to bone), ligaments (attach bone to bone)
• Areolar connective tissue


  • Most widely distributed connective tissue
  • Soft, pliable tissue
  • Contains all fiber types
  • Found in dermis, superficial fascia, subcutaneous layer, mucous membranes, around blood vessels & nerves
• Adipose tissue


  • Matrix is an areolar tissue in which fat globules predominate
  • Functions to insulate the body, protect some organs, and serve as a site of fuel storage
• Reticular connective tissue


  • Delicate network of interwoven fibers
  • Forms stroma (internal supporting network) of lymphoid organs like lymph nodes, spleen, bone marrow
• Blood


  • Blood cells surrounded by fluid matrix
  • Fibers are visible during clotting
  • Functions as the transport vehicle for materials
• Types of blood cells

  • Red blood cells/Erythrocytes
  • Platelets/Thrombocytes
  • White blood cells/Leukocytes (granulocytes, agranulocytes)
• Functions of blood


  • Circulates materials around the body (gases, nutrients, & hormones)
  • Maintains homeostasis by controlling body temperature and pH of body fluids
  • Protection through phagocytosis & antibody production
• Muscle tissue


  • Function is to produce movement
  • Three types: skeletal, cardiac, smooth
• Nervous tissue


  • Composed of neurons, neuroglia, & peripheral glia cells
  • Function is to send impulses to other areas of the body (neurons), support & nourishes neurons (neuroglia)
  • Characteristics: irritability, conductivity