• Every person has a skeleton made up of bones.
• These bones give shape to our body, let us move in many ways, and protect our internal organs.
• The skeletal system is the framework of bones that give support to our body.
What are bones made of?
• If you've ever seen a real skeleton or fossil in a museum, you might think that all bones are dead.
Figure 10: Dinosaur fossil in a museum
• Although bones in museums are dry, hard, or crumbly, the bones in our body are different.
• The bones that make up our skeleton are all very much alive, growing and changing all the time like other parts of our body.
• Every time we walk, settle into a chair, we're using our bones, muscles, and joints.
• Without these important body parts, we wouldn't be able to stand, walk, run, or even sit.
Figure 11: Human skeleton
POINTS TO REMEMBER:
- Our skeleton can be observed by the special pictures (X-rays).
- A doctor decides when we need an X-ray and what body part needs to be x-rayed.
- Doctors can see broken bones and lung infections using X-ray machine.
• Bones are filled with a jelly-like substance called bone marrow.
Figure 12: Skeleton made up of bones
• Our skull protects the most important part of body -- the brain.
• The skull is made up of different bones. Some of these bones protect our brain, whereas others make up the structure of our face.
• If we touch beneath our eyes, we can feel the ridge of the bone that forms the hole where our eye sits.
Figure 13: Skull
• The skull protects the brain, the skull of an adult human being generally contains 28 bones.
• All bones in the skull are fixed, except the lower jaw.
• The movable lower jaw enables us to talk and eat.
• The upper and the lower jaw have teeth. Teeth help us in cutting and chewing food.
• Ribs make a cage of bones around the chest, called the rib cage.
• It's easy to feel the bottom of this cage by running our fingers along the sides and front of our body, a few inches below our heart.
• If we breathe in deeply, we can easily feel our ribs right in the front of our body.
Figure 14: Rib cage
• The rib cage protects our heart and lungs.
• The first seven pairs of ribs attach in the front to the sternum– a long & strong bone in the centre of our chest that holds those ribs in place.
• The ribs are also attached to the backbone. However, the last two pairs of ribs are not attached to the sternum, and so they are called floating ribs.
Figure 14: Floating ribs
• The backbone protects the spinal cord.
• lt is made up of a series of small bones called vertebrae.
• The backbone (spine) lets us twist and bend, and it holds our body upright.
• It also protects the spinal cord, a large bundle of nerves that sends information from our brain to the rest of your body.
Figure 15: Backbone (spine)
• The backbone (spine) is special because it isn't made of one or even two bones.
• There are 33 vertebrae (bones) that make the spine.
• We have two pairs of limbs:
• Our legs are attached to a circular group of bones called pelvis.
• Our leg bones are very large and strong to help support the weight of our body.
Figure 16: Thigh bone-Femur
• The bone that goes from our pelvis to our knee is called the femur.
• The thigh bone or femur is the longest bone in the body.
Functions of Skeletal System:
• The skeletal system is what keeps our body in shape, protects our vital organs, such as the heart, brain, and lungs, and enables us to move.
Human backbone- a part of skeletal system provides support to the body
Figure 17: Bone marrow produces blood cells in our body
• Both red blood cells and white blood cells are created in our bones.
• Cartilage is a tough, elastic substance.
Figure 18: Nose possess cartilage
• It holds the bones in place where they join.
• Cartilage also protects the bones.
• Without cartilage, the bones would rub against each other and wear out.
• Some organs, such as nose and ears, have cartilage.
• Muscles are all made of the same material, a type of elastic tissue.
Figure 19: Muscles made up of an elastic tissue
• Thousands or even tens of thousands, of small fibres make up each muscle.
• Muscles hold the bones together and make movement possible.
• They also help in important processes such as digestion.
• There are three types of muscles in our body.
Figure 20: Three types of muscles
• Skeletal muscles are voluntary muscles, which mean the actions can be controlled by us.
Figure 21: Skeletal muscles
• Our leg won't bend to kick the football unless we want it to.
• The skeletal muscles work together with our bones to give our body– power and strength.
• Some of our biggest and most powerful muscles are in our back & near our spine.
• These muscles help keep us upright.
• Smooth muscles sometimes also called involuntary muscles are usually in sheets, or layers.
• We can't control this type of muscle.
• But smooth muscles are at work all over our body.
Figure 22: Smooth muscles
• In our stomach and digestive system, they contract (tighten up) and relax to allow food to make its journey through the body.
• The muscle that makes up the heart is called cardiac muscle. It is also known as the myocardium.
• The thick muscles of the heart contract to pump blood out and then relax to let blood back in after it has circulated through the body.
Figure 23: Cardiac muscles
• These muscles function automatically.
• Just like smooth muscle, cardiac muscle works all by itself.
• A joint is the place where two bones meet.
• Most joints are movable.
• They make the skeleton flexible — without them, movement would be impossible.
• Fixed joints don't move at all.
• Our skull has some of these joints which close up the bones of the skull.
• There are four kinds of movable joints in our body.
Ball and Socket Joint:
• This type of joint allows movement in many directions.
Figure 23: (a) Ball and socket joint (b) Hip joint
• We can find these joints at our shoulders and hips.
• They are made up of the round end of one bone fitting into a small cup-like area of another bone.
• One of the main types of moving joints is called a hinge joint.
Figure 24: (a) Hinge joint (b) Knee joint
• Our elbows and knees each have hinge joints, which let us bend and then straighten our arms and legs.
• These joints are like the hinges on a door.
• Just as most doors can only open one way, we can only bend our arms and legs in one direction.
• We also have many smaller hinge joints in our fingers and toes.
• Bones in the knee, elbow, fingers, and toes have this type of joint.
• This type of joint is found between the first two vertebrae of our backbone.
Figure 25: (a) Pivot joint (b) A joint present between two vertebrae
• It allows us to move our head up, down, and sideways.
• This type of joint is found in the bones of the wrist and the ankle.
Figure 26: (a) Gliding joint (b) Ankle joint
• It allows these bones to slide against each other in a gliding motion.
POINTS TO REMEMBER
• Strengthen your skeleton by drinking milk and eating other dairy products (like low-fat cheese or yogurt).
• Dairy products contain calcium, which helps bones harden and become strong.
• When we use a skateboard, in-line skates, or a scooter, we must be sure to wear wrist supports and elbow and knee pads.
• Another way to strengthen your bones is through exercise like running, jumping, dancing, and playing sports.