Human beings exhibit locomotion. Locomotion is brought about by
the combination of muscular and skeletal system. The bending and
movement of the skeleton is brought about by special structures called
as joints.
Joints
Joint is a point at which two separate bones meet. Joints are held at position by strong cords called as ligaments. Joints can be classified based on the type of movement they bring about. There are three main types of joints in the human body. They include fixed or immovable joints, slightly movable joints and freely movable joints.
a) Fixed or immovable joints are the joints which do not allow the structure to move but they offer protection for the structure in which they are present. Examples are the sutures between the bones of the cranium,ribs in the breast bone, bones of the hip girdle.
b) Slightly movable joints provide support to the structure in which they are present. They also help the structure to move slightly. Example includes joints of the lower jaw which are slightly movable.
c) Freely movable joints are the joints which solely help in the movement of the structure or organ in which they are present. Four immovable joints present in our body are Ball and socket joint, Pivot joint, hinge joint and the gliding joint.
Movement in bones
Joints along with muscles can bring about movement in bones.
Joints
Joint is a point at which two separate bones meet. Joints are held at position by strong cords called as ligaments. Joints can be classified based on the type of movement they bring about. There are three main types of joints in the human body. They include fixed or immovable joints, slightly movable joints and freely movable joints.
a) Fixed or immovable joints are the joints which do not allow the structure to move but they offer protection for the structure in which they are present. Examples are the sutures between the bones of the cranium,ribs in the breast bone, bones of the hip girdle.
b) Slightly movable joints provide support to the structure in which they are present. They also help the structure to move slightly. Example includes joints of the lower jaw which are slightly movable.
c) Freely movable joints are the joints which solely help in the movement of the structure or organ in which they are present. Four immovable joints present in our body are Ball and socket joint, Pivot joint, hinge joint and the gliding joint.
- Ball and socket joint: This joint is formed by two bones in which one end of a bone is rounded and ball-like. It fits into a cup-like depression of the other bone. This joint provides movement in any direction. Examples of a ball and socket joint are shoulder joints and hip joints.
- Pivot joint: This is the joint in which one bone fits into a ring formed by the other bone. It rotates over the pivot-like end of the other bone. Example is the joint which joins the neck to the head. Head rotates over the neck.
- Hinge joint: This is a joint which moves like a hinge in a single plane not more than 180 degrees. It provides back and forth movement of the structure. This is a joint which can be compared to that of a hinge in the door. Examples of a hinge joint are the elbow joint and the knee joint.
- Gliding joints: This is a joint which allows bones to glide over each other. These types of joints provide little movement in all directions. These are the joints present at the ankles,wrist and between vertebrae.
Movement in bones
Joints along with muscles can bring about movement in bones.
- One end of the muscle is attached to a movable bone and the other end of the muscle is attached to a fixed bone.
- Muscles are attached to bones by tough cords called as tendons.
- Muscles work in pairs and bring about movement by contraction and relaxation.
- The paired muscles are biceps and triceps which together help in the movement of the structures like arm, leg etc.
- Contraction brings in the shortening of the muscle and relaxation brings about lengthening of the muscle. It makes the muscle short, thick and stiff to pull the bone .
- When the arm is folded, biceps contract and triceps relaxes and lengthens.
- When the arm is straightened, biceps relax and lengthen whereas triceps contract.
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