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Bones together form the supporting framework of the body is called skeletal system. An infant has 213 bones in the skeleton but an adult has 206 bones. If a bone is treated with hydrochloric acid for some hours, its calcium dissolves and the bone soften. Such bone is called decalcified bone. Bone is the hardest connective tissue in our body. It is composed of 20% water, 30 to 40% organic material and 40to 50% inorganic material. Organic material are bone cells and matrix and inorganic materials are minerals like calcium, magnesium and phosphorous.
Bone found in our body are of different shape and siize. The bones which form the vertebral column are irregular bones. All the bones are covered with a thin and delicate membrane called the periosteum which contains blood vessels to nourish the bones. The inner part of a long bone is hollow and it is called medullary cavity. It contains yellow bone marrow. The two ends of a bone are called spongy bone which is also called red bone marrow.
The skeleton present on the outer surface of the body is called exoskeleton. The hard part present beneath the skin is called endoskeleton.
The bone of the skeleton are divided into two major groups: Axial skeleton and appendicular skeleton.
Skeleton is a group of different types of bones and cartilage, which provides the supporting firework for the muscles and delicate organs.
Its function are as follows:
i) This determines the framework of the body.
ii) The delicate internal organs of human body are protected by the skeleton.
iii) The red blood cells and while blood cells are formed inside the bone called bone marrow.
iv) It helps to store calcium and phosphorous.
The bones of human skeleton can be divided into two main divisions:
a) Axial skeleton
b) Appendicular skeleton.
The basic and central firework of the body is called axial skeleton.
The bones which lie at the sides of the body are called appendicular skeleton.
|Axial skeleton||Appendicular skeleton|
|i)It is at the centre of the body.||ii)It is on the side of the body.|
Vertebra: Vertebral column
Scapula: Pectoral girdle
Femur: Hind limbs
Bone kept in hydrochloric acid becomes soft because HCL reacts with calcium present in bone and destroy it. Hence, it becomes soft.