What is a skeleton?
The human body is supported by a framework of bones known as a skeleton. Along with tendons, ligaments and cartilage, it constitutes the skeletal system. This system protects vital organs, supports the body, helps with movement, stores calcium and produces blood cells.
How many bones do we have?
A newborn baby is born with 300 bones, some of which fuse together as the baby grows into an adult. By the time an adult is 25, they have 206 bones.
What are bones made of?
Bones have several layers –
1. The outermost surface of the bone is called the ‘periosteum’. It is a thin, dense membrane and contains nerves and blood vessels.
2. The next layer is the one you see when you look at a skeleton. It is smooth, hard and made up of compact bone.
3. The spongy layers contained within the bone are known as the cancellous layers. Though they are not hard, they are still quite strong and may contain red bone marrow.
4. The inner most part of the bone contains a jelly-like substance known as bone marrow which produces red blood cells.
Project –
What are bones made out of? Why do doctors encourage young children to drink plenty of milk?
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