Plate 15A Bone Joints	15B Hand Joints	15C Ankle Joints	15D Scull Joints

(Source:http://www.google.co.in/search?hl=en&q=Venetian+Blinds+drawing&bav=on.2,or.r_gc.r_pw.r_
qf.&biw=1328&bih=574&um=1&ie=UTF8&tbm=isch&source=og&sa=N&tab=wi&ei=n443UMG8HczKrA
ewuIHoBg#um=1&hl=en&biw=1328&bih=574&tbm=isch&sa=X&ei=OZY3UIOMHIOIrAeBq4DgCQ&ved=
0CEAQvwUoAQ&q=Skull+joints+to+body&spell=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=ef89f195774131
44 ; Aug. 24, 2012)

Animal beings have multiple hinge joints for various movements. Try to imagine animals without hinges what would happen? Perhaps we do not realize the use of hinges in our life. Natural hinges are fairly common. We have 57 types of joints (plates 15 A-D) in our anatomy that can move in different directions. Among them are connections of the skull to the first vertebra (plate 15D), which allows us to nod our heads, and between the bones of the fingers (plate 15B) and the other type of hinge, a flexible material that bends with the flexure of the joints. It permits bending at joints of rigid elements. There are varieties of mechanical hinges available in market. Human body has large number of such hinges. Hinges in our fingers are based single plane joints. On the other hand, arm-shoulder performs very complex movements due to its multi-direction bending based on ball and socket mechanism. There are joints, which are pin-less hinges that are commonly made of flat, flexible materials, such as paper folder, cloth, leather, and plastics. These materials due to their elastic qualities can bend and flex without any pin joints.

Therefore we cannot imagine without having joints and hinges in our body. It has taught us to invent different joints and hinges for the purpose of bending by extending or contracting.