Support, movement and locomotion


Support refers to a skeleton. A rigid skeleton supports the soft part of the body. It raises the body from the ground and maintains the shape of the body during moment.



It’s the ability to move from place to place. Locomotion involves coordination between the nerves, muscles and skeleton system. Muscles used for locomotion are attached to the skeleton thus called skeleton muscles.



Moments refers to the change in position of one part of the body in relation to another part. The skeleton works with muscles which are attached to it to produce movements and many bones of the skeleton act as levers.

Functions of human vertebrate skeleton

  • Support
    The skeleton is the frame work of the body: it supports the softer tissues and provides points of attachment foe the most parts of skeletal muscles.
  • Protection
    The skeleton provides mechanical protection for many of the body’s internal organs, reducing risk of damage to them.
  • Assisting movement
    skeletal muscles are attached to bones; hence as the associated muscles contract they cause bones to move.
  • Storage of minerals
    Bone tissues store several minerals, including calcium and phosphorus. When required, bone releases minerals into the blood.
  • Production of blood cells
    Production of blood cells. The red bone marrow of some bones like vertebrae ribs.


The main parts of human skeleton
The main parts of human skeleton

A synovial joint at a ball and socket joint


The skeletal movements of the body are produced by contraction and shortening of muscles. Skeletal muscles are generally attached by tendons to bones, so when the muscles shorten, the attached bones move. These movements of the skeleton occur at joints, or articulations, where one bone meets another.

A Joint location is at which 2 or more bones make contact. It is constructed to allow movement and mechanical support.

Moveable joint (synovial) are:

  • Ball and socket joint
  • Hinge joint

Synovial joints: Movement at joint could cause friction. The synovial joint is adapted to reduce friction.

Structure of synovial joint
Structure of synovial joint

Hinge joints

  • Move like a hinge of a door
  • Move one in one plane

E.g. elbow

Hinge joints
Hinge joints


Ball and socket joint

  • Rounded head of one bone fix into a cup shaped socket another
  • Move in all planes
  • Provide a greater flexibility

E.g. hip bone

Ball and socket joint
Ball and socket joint

The skeleton of the forearms

The skeleton of the forearms

Scapula: the bone that connects the humerus with the collar bone

Humerus: This long bone is essential for movement and support of the arm. The humerus exists on both arms and thus accounts for 2 bones of the human body.


Radius: The radius is the bone of the forearm or lower arm, extending from the elbow to the wrist. This bone is relatively long and curved, extending parallel to the ulna.

Ulna: the ulna is the third and final bone of the arm. This bone runs parallel to the radius


Action of antagonistic muscles of forearm

  • Antagonist and agonist muscles often occur in pairs, calledantagonistic pairs. As one muscle contracts, the other relaxes.
  • Agonist muscles are those we typically associates with the movement itself, and thus sometimes referred to as primary movers.
  • Antagonist muscles are act as opposing muscles to agonists, usually contracting as a means of returning the limb to its original, resting point.
  • Limb muscles are usually arranged in pairs having opposite effect at the movement.
  • Alternative contraction and relaxation of this pairs bring opposite effect at the movement to the bone at the joint. These muscles re called antagonistic muscles.
  • Muscles which cause bending of the arm at the joint re called flexor muscles. The extensor muscles work in opposite direction to straighten the joint.

Comparison of the bending and straightening of the arm

Comparison of the bending and straightening of the arm

Bending of arm Straightening of arm
Biceps contract Biceps relax
Triceps relax Triceps contract
Arm is pulled upward Arm is pulled downward
Arm is raised and bends Arm is  lowered and straightened
Ulna and radius pull closer to humerus Ulna and radius pull away to humerus

Comparison of the bending and straightening of the upper leg

Comparison of the bending and straightening of the upper leg

Bending of leg Straightening of leg
Flexor contract and become shorter and thinner Extensor contract and become shorter and thicker
Extensor relax Flexor contract
Knee joint flexes Knee joint extends
Tibia and fibula pull closer to femur Tibia and fibula away from femur