Animal tissues (cockroach frog)

• In unicellular organisms, all functions like digestion, respiration and reproduction are performed by a single cell
• In the complex body of multicellular animals the same basic functions are carried out by different groups of cells in a well organised manner
• The body of a simple organism like Hydra is made of different types of cells and the number of cells in each type can be in thousands
• The human body is composed of billions of cells to perform various functions
• Tissue

  A group of similar cells alongwith intercellular substances that perform a specific function
• Basic types of tissues in complex animals

  • Epithelial
  • Connective
  • Muscular
  • Neural
• Organ

  When two or more organs perform a common function by their physical and/or chemical interaction, they together form an organ system
• Examples of organ systems

  • Digestive system
  • Respiratory system
• Cells, tissues, organs and organ systems split up the work in a way that exhibits division of labour and contribute to the survival of the body as a whole
• Types of epithelial tissue

  • Simple epithelium
  • Compound epithelium
• Simple epithelium


  • Composed of a single layer of cells
  • Functions as a lining for body cavities, ducts, and tubes
• Types of simple epithelium


  • Squamous
  • Cuboidal
  • Columnar
• Squamous epithelium


  Made of a single thin layer of flattened cells with irregular boundaries
• Cuboidal epithelium


  Composed of a single layer of cube-like cells
• Columnar epithelium


  Composed of a single layer of tall and slender cells with nuclei located at the base
• Ciliated epithelium

  Columnar or cuboidal cells that bear cilia on their free surface
• Glandular epithelium

  Specialised columnar or cuboidal cells for secretion
• Types of glandular epithelium

  • Unicellular
  • Multicellular
• Exocrine glands


  Secrete products through ducts or tubes
• Endocrine glands


  Secrete hormones directly into the fluid bathing the gland
• Compound epithelium

  Made of more than one layer (multi-layered) of cells
• Cell junctions in epithelium

  • Tight junctions
  • Adhering junctions
  • Gap junctions
• Types of connective tissue

  • Loose connective tissue
  • Dense connective tissue
  • Specialised connective tissue
• Loose connective tissue

  Has cells and fibres loosely arranged in a semi-fluid ground substance
• Loose connective tissues

  • Areolar tissue
  • Adipose tissue
• Dense connective tissue

  Fibres and fibroblasts are compactly packed
• Types of dense connective tissue

  • Dense regular
  • Dense irregular
• Dense regular connective tissue

  • Tendons
  • Ligaments
• Cartilage

  Intercellular material is solid and pliable, resists compression
• Bone

  Hard and non-pliable ground substance rich in calcium salts and collagen fibres
• Blood


  Fluid connective tissue containing plasma, red blood cells, white blood cells and platelets
• Types of muscle tissue

  • Skeletal
  • Smooth
  • Cardiac
• Skeletal muscle tissue

  Closely attached to skeletal bones, striated (striped) fibres bundled together
• Smooth muscle tissue

  Tapering fibres without striations, found in walls of internal organs
• Cardiac muscle tissue


  Contractile tissue present only in the heart, cells fused together
• Neural tissue


  Exerts greatest control over the body's responsiveness, composed of neurons and neuroglia
• When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma membrane
• Neuron's endings

  Output zone
• Organ


  Structure made of one or more types of tissues
• Organ system

  Association of organs to perform a specific function