B5a - Skeletons

Types of skeletons
1. Internal
  1. Features: Grows with the rest of the body, flexible as there are lots of joints, organs are protected
  2. Examples of organisms: humans, tigers, penguins, crocodiles
  3. Advantages: provides internal framework for the body, flexible due to joints
  4. Disadvantages: takes a long time to regrow broken bones
2. External
  1. Features: contains a material called chitin.
  2. Examples of organisms: arachnids, myria pods
  3. Advantages: Can be regrown quickly compared to internal bones
  4. Disadvantages: need to shed their exoskeletons when they grow
3. 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
  1. Endo over Exo
Bones and cartilage
1. 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.
2. 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.
3. 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.
4. 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.
5. Fractures
  1. 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.
  2. There are threee types of fracture: simple (straight break), compound (comes out of skin) and greenstick (bone not completely broken).
Joints and Joint Replacement
1. A joint is where two or more bones meet and muscles act together to cause movement
2. Antagonistic pairs - muscles working together, as one contracts another relaxes.
  1. The forearm is raised and lowered by antagonistic muscles - the biceps and triceps. To raise the biceps contract&triceps relax and vice versa.
    1. This is an example of a lever, with the elbow acting as a pivot.
3. Coral and liquid bones can be used as joint replacements however artifical substances are at risk of not being accpeted by the immune system.
  1. 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.
4. Synovial joints, such as ball and socket joints and hinge joints, contain synovial fluid, a synovial membrane, ligaments and cartilage.
  1. 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.
5. 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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B5a - Skeletons

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