Function of skeletal System Classification of Bones and Type of joint Health and physical education

 There are 213 bones in children and 206 bones in adult. This system is a combination of various bones. These bones are joined together by ligament. Bones provided support and protection to the delicate organ of our body. Some of the bones act as levers in our body. Skeleton or skeletal system can be divided into two part for better understanding.
         1. Axial Skeleton
         2. Appendicular Skeleton
1. Axial Skeleton: This is Skeleton consists of the following bones.
       1. Skull   -  28 
       2. Sternum - 1
       3. Ribs - 24
       4. Hyoid bone  -  1
       5. Vertebral column -  26 for adult , 33 for child.

2. Appendicular Skeleton: This is Skeleton consists of the following bones.
        1. Upper limbs   -  64
        2. Lower limbs  -  62

Function of Bones 
   1. Provide Support: The bones are the principal organs of support. They support the whole body. 
   
   2. Provide protection: Bones provide protection for some of the soft and delicate organs of the body such as skull and pelvis. 

  3. Bony System gives shape to the Body: Bones play a vital role in shaping the body. It may be responsible for the long or short stature.

  4. Act as lever: Bones act as lever in our body. These help in doing work easily.

  5. Passive Instruments of Locomotion: Bones are the passive instrument of locomotion or movement. These enable us to move.
                                                

Classification of Bones
      According to the shape and formation of bones, there are various type of bones which are as follow. 
1. Long Bones : These bones act as lever in our body and help in making movement possible. long bones are found mainly in the upper and lower limbs. such as hummers and femur consist of a shaft and two extremities each. Only due to their length these are called long bones. 

2. Short bones: Hence these are called short bones. These bones are short in length. Carpus and tarsus are called short bones. These bones are light in weight but are strong. These bones are made of cancellous bone tissues. These bones are covered with compact tissues. 

3. Flat Bones: Such as the bones of skull scapulae and ribs. There is always a large surface on flat bones for the attachment of muscles. 

4. Sesamoid Bones: These bones are found in knee, hand and foot. 

JOINT OF BONES
    The study of joint s called arthrology. articulating surface of the bones are sometimes separated by a thin membrane, sometimes by connective tissue, or fibrocartilage and in the freely moving these are completely separated. 

We can classify the joint in three categories
  1. Immovable Joint or Synarthroses
  2. Slightly Movable Joint or Amphiarthroses 
  3. Freely Movable Joint or Diarthroses
 
                                                                    

1. Immovable Joint: These joint are found in the bones of skull and face. These joint are also called fibrous joint are fixed and do not move. These are shown in figure given alongside.

2. Slightly Movable Joint: this joint surfaces of bones are separated by some intervening substance and only slight movement is possible. This joint includes two types 
(a) Symphysis: It is a joint where two long bony surfaces are connected by a broad flat disc of fibrocartilage , symphysis pubis and inter vertebral joint.
(b) Synchondrosis: It is a temporary from of joint. The cartilage is changed to bone before adulthood. These joint are found between the long bones.

3.  Freely Movable Joint: These Joint are also called synovial joint. These joint include most of the joint of the body. The adjacent end of the bones are covered with hyaline cartilage and are surrounded by a fibrous articular capsule which is strengthened by ligament. Tendons of muscles pass over these joint and play a vital role in stabilizing the joint. The hyaline cartilage provides a smooth surface for the opposing bones lubricated by synovial fluid. These freely movable joint are further classified into six categories.
(a) Gliding Joint: These joint permit gliding movement only, as in the joint between carpal bones of the wrist and between tarsal bones of the ankle. 
(b) Hinge Joint: These joint permit angular movement in one direction like a door on its hinges. The movement of these joint are called flexion and extension hummers and ulna elbow knee and ankle joint and the joint of phalanges.
(c) Condyloid Joint: These joint allow an angular movement in two direction wrist joint. Movement of this joint include flexion, extension , adduction and circumduction but no rotation.
(d) Saddle Joint These joint permit a great freedom of movement , joint of thumb. It enables the thumb to oppose the finger.