Our Skeletal System CBSE Science Lesson Class 5 | Class 5 Science Our Sk...

• Our body consists of various organs like hands, legs, heart, lungs etc.


• Each organ performs some specific functions.


• All the organs work with perfect coordination and work like a wonderful machine to the body alive.


• Bones and muscles together work like a team with efficiency and perfect coordination.


• Bones and muscles together help in the movement of the body and the body parts.


• A group of organs that together perform the same function make an organ system. E.g. digestive system, nervous system, respiratory system etc.

Skeletal System

• Human skeleton is a framework of bones.


• An adult human body has 206 bones of different shapes and sizes.


• Human skeleton consists of a skull, a backbone, ribcage and two pairs of limbs.


• The two pairs of limbs (forelimbs and hindlimbs) are attached to two pairs of girdles - the hip girdle and the should girdle.

The Skull

• It is made of 22 bones.


• 8 flat bones that are interlocked and enclose the delicate brain.


• 14 facial bones. Only 2 facial bones are movable and enable us to talk and eat.

The Backbone

• Skull is attached to the backbone which forms the main axis of the skeleton.


• Backbone consists of 33 small ring-like bones called vertebrae which together form the vertebral column.

Ribcage

• It consists of 12 pairs of bow-shaped rib bones that enclose the delicate heart.


• Rib bones are joined to the backbone in the back and to the breastbone in the front.


• The two pairs lowest rib bones are joined only to the backbone and are called floating bones.

Limbs

• The forelimbs i.e. arms are joined to the backbone with the help of shoulder girdles.


• Shoulder girdles consist of a pair of shoulder blades and a pair of collar bones.


• The hindlimbs i.e. legs are made of a strong thigh bone called the femur.


• Femur is the longest bone in our bondy and bears the weight of the body.


• Femur fits into the hip girdle with a ball and socket joint and is connected to the lower leg at the knee joint.


• The long bones of the skeleton are hollow and are filled with a soft, fatty substance called the bone marrow which produces blood cells.

Functions of the skeleton

• Gives shape, support and and strength to the body.


• Protects the delicate internal organs.


• Skull protects the delicate brain and the eyeballs rest inside the eye sockets.


• Backbone protects the spinal cord.


• Ribcage protects the heart and lungs.


• Urinary bladder lies inside the hip girdles.


• Muscles are attached to the bones and help in the movement of the body and body parts.


• The enamel coating on the teeth is the hardest substance in the body.

Joints

• A joint is the meeting point of two bones.


• Two bones join together by a strong tissue called ligament.


• There are many joints in the body.


• All the joints except the joints in the skull are movable.


• The bones in the skull are interlocked making the joints immovable.


• There are two types of joints in the body - (i) Movable joints and (ii) Immovable joints.

Movable Joints:

The joints that can move. The bones at the joints move smoothly because of a fluid which acts like a lubricant.
There are 4 types of movable joints in our body. These are:

1. Hinge joint
2. Ball and socket joint
3. Pivot joint
4. Gliding joint

Hinge Joint

• These joints are like the hinge of a door.


• It can move the joint only in on direction.


• Joints in our elbow, knee, fingers and toes are hinge joints.

Ball and Socket Joint

• In this type of joint one bone has a rounded ball-like end on side that fits into the socket and allows maximum movement.


• This joint is found at the hip and shoulder region.

Pivot Joint

• The skull is joined to the first two vertebrae of the vertebral column with pivot joint.


• The uppermost vertebra is called the atlas.


• This joint allows our head to move in four directions i.e. sideways, up and down.

Gliding Joint

• This joint allows the movement between two vertebrae of the vertebral column.


• It allows our back to bend, twist and turn at each joint.


• It also allows the movement at the wrist and ankle.

Muscles and Movement

• The body muscles contract i.e. tighten up and relax (stretch) to produce movement of the body and body parts.


• There are about 650 muscles in our body. Each muscle causes a particular movement.
• Muscles bend our arms and knees, push food into the digestive canal, allow us to inhale air into the lungs, help us to chew food and make our heart beat.


• Muscles are attached to the bones with strong fibres called tendons. These fibres become strong with regular exercise.

Types of Muscles

There are 3 types of muscles: (i) Voluntary muscles, (ii) Involuntary muscles and (iii) Cardiac muscles.

1. Voluntary Muscles: Muscles that are under our control. We can move them out of our will.


2. Involuntary Muscles: Muscles that are not under our control. These muscles control the actions of alimentary canal, movement of eye muscles etc.


3. Cardiac Muscles: Muscles that are found only in the heart. These muscles are involuntary in function but their structure is like voluntary muscles.

How do muscles work?

• Muscles produce movement in the body by pulling on the bones.


• When the muscles contract, the bones come close to each other.
• When we bend our knee, one muscle contracts and gets shorter, while the other muscles relax.


• When we stretch our leg, the reverse happens.


• Well developed muscles give a graceful appearance to the body.


• To keep the muscles in good shape, we must maintain proper posture while sitting, standing and walking.


• We must maintain good health by doing regular exercise and giving proper rest to the body.


• We must eat healthy diet and avoid junk food.