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Friday, May 28, 2010


Now in this post we will learn about the structure of the bone. In our human body there are 206 bones of different types are there. The thigh, lower leg, and upper and lower arm consists of long bones. These bones have large surface areas for muscle attachment and are very strong, are broad at the ends where they join with other bones.

There are five types of bones in the human body. The five types are long, short, flat, irregular, and sesamoid.

1. Long bones:- These bones are comprised mostly of compact bone and lower amounts marrow, which is located within the medullary cavity, and spongy bone and are characterized by a shaft, the diaphysis, that is much larger in length than breadth. These bones are mostly present in the limbs, including those of the fingers and toes are long bones. Except the wrist, ankle, and kneecap these long bones are located in most.

2. Short bones:- These short bones are generally cube shaped and having a thin layer of compact bone surrounding a spongy interior. These short bones are found in the wrist and ankle and have small, irregular shapes.
3. Flat bones:- These bones are thin and generally curved, with two parallel layers of compact bones which are sandwiching a layer of spongy bone. Larger number of bones of the skull are flat bones as is the sternum. These flat bones are covered with soft body parts. These are the shoulder bone, ribs, and pelvic bones.

4. Irregular bones:- These bones do not fit into the above various bones. They contains of thin layers of compact bone surrounding a spongy interior. According to the name itself their shapes are irregular and complicated. These bones are in the spine and hips.

5. Sesamoid bones:- These bones are small, rounded bones resembling a grain of sesame in shape. They are found near the joints. The best example of this types of bone are present in kneecap. Because these bones are embedded in tendons. They hold the tendon further away from the joint, the angle of the tendon is increased and thus the leverage of the muscle is increased. The best examples of these sesamoid bones are the patella and the pisform. 

In the next lesson we will learn about the remaining structure of the bone.


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