ch-8 Notes on Body Movements | class 6th science

Human Body And Its Movements

The human skeleton is the internal framework which is responsible for giving support, shape and protection to our bodies. It contains 206 bones, each playing a distinct yet important task. The skeleton can be classified into two parts called as the axial and the appendicular. The axial skeleton comprises of the central part of the skull, spine, and ribs and the appendicular skeleton consists of the arms and legs.

Terms –

Limbs: The arms or legs of an animal.

Bones: These are the hard white structures below our skin that protect our internal organs. Bones are incapable of bending.

Joints: These are defined as the points at which two bones are fitted together. These are the points at which we can rotate and bend our bodies.

Figure 1: Body Movements

Types of Joints and their Location in Human Body

• A Pivot joint is a joint that rotates.. Examples of pivot joints in the body in the neck that allows the head to rotate and the ones between the radius and ulna that allow forearm rotation.
• When bones can move along one axis, it indicates the presence of Hinge joint. e.g. Elbows and Knees.
• In the Ball and Socket joint, a partial spherical structure is present inside a socket allowing movement in all directions. e.g. hips and arms
• As the name suggests Fixed joint allows no movement to occur. e.g Skull

Figure 2: Types of Joints

Important Points to remember in a Human Skeleton:

• Bones provide support, protection, movement and perform several other functions.
• The bones in the skull (Cranium, Mandible, Maxilla) give protection to the brain.
• The long bones such as humerus, radius, ulna, tibia, fibula support the weight of body
• The carpals are located in wrist and tarsals are located in ankles. They are examples of short bones.
• The bones protecting the spine are called as the vertebral column. Cervical area (top 7 vertebrae), Thoracic (next 12), Lumbar (bottom 5 vertebrae), Sacrum (5 fused or stuck together bones) and Coccyx (the tiny bit at the bottom of the spine).
• The sternum and rib cage constitute the chest bones.

Figure 3: Human Skeleton

Some More Points to Remember

Gait of Animals

1. Earthworm:

• Does not have bones
• Earthworm body is made up of rings
• A slimy substances secreted by its body aids movement (NSO)

Figure 4: Detailed Movement in Earthworm

2. Snail:

• It has a slimy body, which does not have bones.
• The shell of the snail does not help in movement. It has to be carried along.
• The foot of the snail is a thick structure and is made up of strong muscles.
• A muscular organ called ‘Foot’ helps in locomotion.

Figure 5: A Snail

Cockroach	Belongs to Phylum ArthropodaIts Exoskeleton is hard and stiff.3 pairs of legs help in walking and 4 wings help to flyThe body muscles move the wings when it flies
Fish	Presence of scales on the fish skin reduce  frictional dragIt possess a streamlined shape which enhances locomotionCoordination between muscles and tail help the fish to move.Fins aid the movement in the water
Birds	Their forelimbs are modified into wings Presence of hollow and light bones, which reduces weight.Hind limbs help in walking and perchingThey have strong shoulder bones
Snakes	Presence of long backbone and thin muscles.Loops made by its body help in moving forward.Moves fast but not in a straight lineThey cannot move on frictionless surface.