Tissues, Organs and Organ Systems

Tissues, Organs and Organ Systems

1. Organs in Animals

   • Tissues
     • Cells differentiate so that they can carry out different functions; differentiation is the process by which cells become specialised
       • A tissue is a group of similar cells that work together to carry put a particular function
         • There are three different types of tissue
           • Muscular; contracts to produce movement
           • Glandular tissue; produces substances such as enzymes and hormones
           • Epithelial tissue; covers some parts of the body
   • Organs
     • Organs are made up of tissues
       • An organ could contain several different types of tissue for example the stomach
         • Muscular tissues in the stomach churns the food and other contents of the stomach
         • Glandular tissues in the stomach produces digestive juices including acid and enzymes
         • Epithelial tissue in the stomach to cove the inner and outer surfaces of the stomach
   • Organ systems
     • Organ systems are groups of organs that carry out a particular function
       • In the body these include: the nervous system, the respiratory system, the reproductive system and the digestive system
         • The digestive system, for example, is made up of the following organs:
           • Pancreas and salivary glands; to produce digestive juices
           • Stomach; to digest food
           • Liver; to produce bile
           • Small intestine; to digest and absorb food
           • Large intestine; to absorb water from undigested food and produce faeces

2. Organs in plants

   • Tissues
     • There are three types of tissue in a plant
       • Epidermal tissue; covers the plant
       • Mesophyll; carries out photosynthesis
       • Xylem and Phloem; transport of substances around the plant (like veins)
   • Organs
     • Examples of organs in plants include:
       • Roots
       • Stems
       • Leaves
         • Leaves are adapted to absorb sunlight for photosynthesis in the following ways
           • Chlorophyll; to absorb sunlight
           • Large surface area; to absorb more light
           • Stomata; to let carbon dioxide diffuse into the leaf
           • Thin; short distance for carbon dioxide to diffuse into the leaves
           • Network of veins; To support the leaf and transport water and carbohydrates
   • The leaf
     • The internal structure of a leaf allows efficient photosynthesis
       • Thin, waxy cuticle; protects leaf without blocking out light
       • Thin, transparent epidermis; allows more light to reach the palisade cells
       • Layer of palisade cells at the top; to absorb light
       • Many chlorplasts in the palisade cells; increases absorption of light
       • Spongy mesophyll, air spaces in the leaf allow carbon dioxide to diffuse through the leaf and increase surface area

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