B5a - Skeletons

B5a - Skeletons

1. Types of skeletons

   • Internal
     • Features: Grows with the rest of the body, flexible as there are lots of joints, organs are protected
     • Examples of organisms: humans, tigers, penguins, crocodiles
     • Advantages: provides internal framework for the body, flexible due to joints
     • Disadvantages: takes a long time to regrow broken bones
   • External
     • Features: contains a material called chitin.
     • Examples of organisms: arachnids, myria pods
     • Advantages: Can be regrown quickly compared to internal bones
     • Disadvantages: need to shed their exoskeletons when they grow
   • Internal skeletonshave many advanatges over external skeletons: It provides an internal framework for the body, grows with the rest of the body, is flexible due to the many joints and it allows easy attachment of muscles
     • Endo over Exo

2. Bones and cartilage

   • Cartilage and bone are living tissues containing living cells, this means they can be infected by bacteria and viruses. However they are able to grow and repair themselves.
   • A long bone contains of a long shaft containing bone marrow with blood vessels. At each end there is a head covered with cartilage. Long bones are hollow, so they are stronger and lighter than solid bones.
   • At birth the human skeleton is made of cartilage. Ossification is the proccess of slowly replacing the cartilage by bone. If some cartilage remains between the head and shaft - the bone is still growing.
   • In an accident it can be dangerous to move a person with a suspected bone fracture. Broken vertebrae in the backbone can damage the spinal cord, resulting in paralysis or death.
   • Fractures
     • Even though bones are very strong they can easily be broken by a sharp knock. The bones of elderly people can lack calcium and phosphorus which often results in osteoporosis making them prone to fracture.
     • There are threee types of fracture: simple (straight break), compound (comes out of skin) and greenstick (bone not completely broken).

3. Joints and Joint Replacement

   • A joint is where two or more bones meet and muscles act together to cause movement
   • Antagonistic pairs - muscles working together, as one contracts another relaxes.
     • The forearm is raised and lowered by antagonistic muscles - the biceps and triceps. To raise the biceps contract&triceps relax and vice versa.
       • This is an example of a lever, with the elbow acting as a pivot.
   • Coral and liquid bones can be used as joint replacements however artifical substances are at risk of not being accpeted by the immune system.
     • Advantages - it allows patients to live more independantly, improves their quality of life, accidental injuries and amputations can be avoided and there is no worry about rejection.
   • Synovial joints, such as ball and socket joints and hinge joints, contain synovial fluid, a synovial membrane, ligaments and cartilage.
     • Each part of the synovial joint has a special function: the synovial fluis acts as a cushion against shock and a lubricant for easy movement. A synovial membrane holds in the fluid. The cartilage protects protexts the bone head. The ligaments hold the bones in place.
   • A ball and socket joint has a wider range of movement than a hinge joint ( these can only go up-and-down)

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