The tissue level of organisms

• Histology

  Study of tissues
• Integrity of the epithelium


  • Number of cell layers: Simple, Stratified
  • Shape of apical surface cells: Squamous, Cuboidal, Columnar
• Connective tissue proper


  • Contains fibres, ground substance (viscous fluid), cell population
  • Classified as loose or dense: Loose (Embryonic mesenchyme, mucous connective tissues, Areolar tissue, Adipose tissue, Reticular tissue), Dense (Regular, Irregular)
• Blood


  • Formed elements and plasma
  • Red blood cells, white blood cells and platelets
  • Blood vessels
• Classification of epithelia

  • Exocrine glands – Secrete through ducts onto the surface of the gland
  • Endocrine glands – Release hormones into surrounding fluid
• Four tissue types


  • Epithelial – covering and protection
  • Connective – joins other tissue
  • Muscular – movement
  • Nervous – control and communication
• Levels of organisation

  • Organism
  • Organ system
  • Tissue
  • Cellular
  • Chemical/molecular
  • Collections of specialized cells and cell products organized to perform a limited number of functions
• Glandular epithelia

  • Establishing a structural framework
  • Transporting fluids and dissolved materials
  • Protecting delicate organs
  • Supporting, surrounding and interconnecting tissues
  • Storing energy reserves
  • Defending the body from microorganisms
• Lymph

  • Interstitial fluid enteri
• Epithelial tissue


  • Physical protection
  • Control permeability
  • Provide sensation
  • Produce specialized secretions
  • Perform secretory functions
  • Perform transport functions
  • Maintain physical integrity
  • Ciliated epithelia move materials across their surface
• Skeletal muscle

  • Striated, voluntary, and multinucleated
  • Muscle fibres do not divide
  • New fibres produced by stem cells (satellite cells)
• Cartilage


  • Matrix is a firm gel containing chondroitin sulfate
  • Cells called chondrocytes
  • Cells found in lacunae
• Tissue types

  • Epithelial
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Neural tissue


  • Specialized for conducting electrical impulses
  • Rapidly senses internal or external environment
  • Processes information and controls responses
• Muscle tissue classification

  • Skeletal
  • Cardiac
  • Smooth
• Cardiac muscle

  • Striated, involuntary, and single nucleus
  • Cardiocytes form branching networks connected at intercalated disks
  • Regulated by pacemaker cells
• Connective tissue types

  • Nic mesenchyme
  • Mucous connective tissues
  • Areolar tissue
  • Adipose tissue
  • Reticular tissue
  • Dense regular tissue
  • Dense irregular tissue
  • Blood
  • Blood vessels
  • Lymph
  • Interstitial fluid
• Bone or osseous tissue

  • Osteocytes (bone cells)
  • Little canals (canaliculi) provide nutrients
  • Dense mineralized matrix
  • Surrounded by periosteum
• Neural tissue locations

  • Central nervous system: brain, spinal cord
• Connective tissue


  Supports the rest of the body
• Cartilage types

  • Hyaline
  • Elastic
  • Fibrocartilage
• Muscle tissue types

  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle
• Smooth muscle

  • Nonstriated, involuntary, and single nucleus
  • Smooth muscle cells are small and tapered
  • Can divide and regenerate
• Neurons

  • Cell body contains the nucleus and nucleolus
  • Dendrites receive incoming signals
  • Axon carries outgoing electrical signals to their destination
• 3 types of connective tissue

  • Proper connective tissue
  • Fluid connective tissue
  • Supporting connective tissue
• loose connective tissue

  • firboblast, mast cells, macrophages, and leukocytes
  • lot of ground substance
  • fewer collagen and elastic fibres
• Dense connective tissue (regular)

  • fibroblasts
  • little ground substance
  • collagen fibres in bundles and arranged
  • forms tendons and ligaments
• Dense connective tissue (irregular)

  • firboblasts
  • little ground substance
  • collagen fibers in bundles with random orientation
  • form capsules, e.g. reticular layer of skin
• How do the four types of tissues work together?

  Epithelial tissues act as coverings controlling the movement of materials across the surface. Connective tissue integrates the various parts of the body and provides support and protection to organs. Muscle tissue allows the body to move. Nervous tissues propagate information.