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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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:
- Hinge joint
- Ball and socket joint
- Pivot joint
- Gliding 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.
- 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.
- 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 MusclesThere are 3 types of muscles: (i) Voluntary muscles, (ii) Involuntary muscles and (iii) Cardiac muscles.
- Voluntary Muscles: Muscles that are under our control. We can move them out of our will.
- Involuntary Muscles: Muscles that are not under our control. These muscles control the actions of alimentary canal, movement of eye muscles etc.
- 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.