Page 117 - Science Class 06
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The knee is some mes classified as a
modified hinge joint.
Pelvic Girdle
The pectoral girdle is a ached to the Hinge Joint
vertebral column by tendons, which gives it Ball-and-Socket Joints : These joints allow
some mobility and acts as a shock absorber movement in all direc ons. Here, the
in vertebrates. rounded end of one bone, i.e., head fits into
Joints cavity of the other bones.
The place where two or more bones join is For example, joints of hips and shoulders.
called a joint. Some joints are immovable Hip flexor
and are called fixed joints, e.g., upper jaw, musculature
skull, etc.
There are other joints that help in free
movement of the body parts, are called
synovial joints as the cavi es between Shoulder Hips
joints are filled with the synovial fluid which
Pivot Joints : Pivot joints consist of the
helps to lubricate and protect the bones.
rounded end of one bone fi ng into a ring
Types of Synovial Joints formed by the other bone. This structure
Synovial joints are further classified into six allows rota onal movement as the rounded
different categories on the basis of the bone moves around its own axis. An
shape and structure of the joints. The shape example of a pivot joint is the joint of the
of the joint affects the type of movement first and second vertebrae of the neck that
permi ed by the joints. These joints can be allows the head to move back and forth.
described as planar, hinge, pivot, condyloid, The joint of the wrist that allows the palm
saddle or ball-and-socket joints. of the hand to be turned up and down is
also a pivot joint.
Hinge Joints : In hinge joints, the slightly
rounded end of one bone fits into the
slightly hollow end of the other bone. In
this way, one bone moves while the other
remains sta onary, like the hinge of a door.
The elbow is an example of a hinge joint.
Pivot Joints
Science-6 117
