Class 6 Science Chapter 8 Bones and Joints, Movements in the Human Body (For CBSE, ICSE, IAS, NET, NRA 2022)

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Bones and Joints

Human Body and Its Movements

  • Movement is the state of changing something՚s position.
  • When there is change in position of the whole organism, its is known as locomotion.
  • Human body can perform a variety of simple and complex functions due to the internal structure.
  • Bones are the hard white structures that protects the internal organs.

Various Movements in Human Body

Illustration 2 for Various_Movements_in_Human_Body

Human Skeletal System

Human Skeletal System

Skull

It is at the top of the vertebral column and composed of two main parts namely cranium and facial bones.

Cranium
  • Part of the skull consisting of the bones enclosing the brain.
  • It doesn՚t include the bones of the face or jaw.
  • Provides protection to the brain.
Facial Bones
  • These bones surround the mouth and nose contributing to the eye sockets.
  • It includes the upper jawbones, the zygomatic, nasal, lacrimal, and palatine bones, the inferior nasal concha and the vomer, lower jawbone, and hyoid bone.

Chest Bone or Rib Cage

  • Rib cage protects heart, lungs, and diaphragm.
  • It also plays important role in the respiration.
  • Rib cage consists of:
    • 12 pairs of ribs
    • Sternum
    • Xiphoid process
    • Costal cartilages
    • 12 thoracic vertebrae

Backbone or Vertebral Column

  • It extends from the base of the skull to the hip.
  • There are 33 small rings known as vertebrate joined from end-to-end.

Hip Bone or Pelvic Girdle

  • A single hip bone forms the pelvic girdle.
  • The hip bone attaches the lower limb to the axial skeleton.
  • Pelvis is formed by the right and left hip bones, plus the sacrum and the coccyx.

Shoulder Bone or Pectoral Girdle

  • The collar bone and the shoulder blade form the shoulder bone.
  • Attached to the upper part of the rib-cage along with the upper arm bone.

Functions of Skeleton

  • The Skeleton system provides support to the body.
  • Provides protection to the internal organs.
  • It gives the body its shape together with the muscles.
  • In bone marrow, there is production of Red blood cells and some white blood cells.

Joints

  • It is also known as an articulation or articular surface.
  • A joint is a location where two more bones meet.
  • Ligaments bind a bone to another bone.
  • Tendons bind a bone to a muscle.

Functional Classification of Joints

Ball and Socket Joints
  • It is a type of synovial joint.
  • Here the rounded end of one bone fits into the cavity (hollow space) of another bone.
  • Permits movements in all directions.
  • Some of the examples are:
    • Joints between shoulder and the upper arm.
    • Joint between thigh and hip.
Pivot Joints
  • One bone has tapped into the other not allowing the full rotation.
  • Allows up and down, side to side movements.
  • One of the examples is of a pivotal joint in the neck.
Hinge Joints
  • Allows movement only in one plane and is similar to the door hinges.
  • Examples of Hinge Joints are the knee joint and elbow joint.
Gliding Joints
  • Bones slide over one another causing the movement in this joint.
  • The wrist joint is an example of gliding joint.
Saddle Joints
  • It is the biaxial joint.
  • Allows the movement on two planes (flexion/extension and abduction/adduction) .
  • Only bone in the human body having a saddle joint is the thumb.
Condyloid Joints
  • Joints with two axes.
  • Also known as a condylar, or ellipsoid joint.
  • Permit up-down and side-to-side motions.
  • These joints can be found at:
    • Base of the index finger.
    • Carpals of the wrist, elbow, and the wrist joints.

Structural Classification of Joints

Fibrous Joints
  • These are immovable joints and are connected by dense connective tissue consisting mainly of collagen.
  • Skull is an example of fixed joint being formed by several fused bones.
  • The upper jaw, rib cage, backbone, and pelvic bone are some other examples.
Cartilaginous Joints
  • These are partly movable joints.
  • These joints are comprised of symphysis or synchondrosis joints.
  • Synchondrosis are temporary cartilaginous joints.
  • The spinal column and the ribcage are some of the examples cartilaginous types of joints.
Synovial Joints
  • The most common type of joints.
  • These joints are flexible, movable, can slide over one another.
  • This joint helps in performing a wide range of motion:
    • Walking
    • Running
    • Typing
  • Synovial joints are found in shoulder joint, neck joint, knee joint, wrist joint, etc.

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