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Monday, May 27, 2013

B. Bones

The types of bones are classified into two :
1.Cartilage
  There are 3 types of cartilage, such as :
  Hyalin cartilage --->> composed of a similar substance and found in the trachea lining, the   ends of leg and arm bones, joints, and between the ribs and breastbone.
  Elastic cartilage-->>   flexible and found in the nose and earlobes.

  Fibrous cartilage-->>   strong, but less flexible compared   to the other types of cartilage, found in the disks   between the backbones.
2.Hard bones
    The bones develop from cartilage. The development process of cartilage becoming bones is called ossification. But not all bones are made from cartilage, for example the skull, develop from connective tissues under the skin.
  Much of the intercellular space in the bone contains calcium, such as calcium carbonate, calcium phosphate, some adhesive substances, and protein. That is why the bones are hard and not flexible.
  There are two types of bones according to the composing substance. They are :
a.Compact bones possess compact composing substances, for example the outer layers of long bones.
b.Spongy bones possess hollow composing substances, for example the short bones, flat bones, and the ends of the long bones near the bone connection.
    Based on their form, bones are classified into three categories, namely the long bones, the flat bones, and the short bones.
 a.Long bones
    Long bones are long and round
  like a pipe. Both ends of these bones thicken like knobs and are composed of spongy bones. Between the knobs is the compact bone that is surrounded by the periosteum. The middle part of long bones contains yellow marrow and fat. For example upper arm, thigh, calf, toes and fingertips.
b.Flat bones
    Flat bones are flat, with sponge-like hollows inside them.  These bones contain red marrow as the production place of red blood cells. For example ilium bones, the rib bones, the breastbone, the scapula, and the skull bones.
c.  Short bones

  Short bones are short. Just like a flat bones, short bones also contain red marrow. The examples of these bones are the vertebrae, the tarsus bone, and the carpus.
3.  Bone Marrow
  Bone marrow fills the space inside the bones.There are two types of marrow, namely red marrow and yellow marrow.
  Red marrow is where red blood cells produced.

  Yellow marrow  is found in the bones of adults. This yellow marrow is composed of a mixture of connective tissues, like fat tissues and red marrow.
 4. Bone Growth
Bones are living tissues that are able to grow and repair themselves.  Some types of bones develop from cartilage. Other types of bones develop from bones cellThe bones grow bigger and longer.  The increase in length of the bones takes place in the growing area near the end of the bones called the epiphyseal disk or epiphyseal plate. During the growth, the space inside the bones also becomes bigger and longer.

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