Introduction to Skeletal System
Each day we perform different kinds of activities. We eat, run, study etc. Our bones and muscles work together to do all these various types of activities. We are not able to see our bones or muscles as they are covered and protected by our skin. The bones in our body are made of living tissues which have their own blood cells which help them to grow and repair on their own. The bones also contain calcium, proteins, vitamins and minerals. We are born with 300 bones. As we grow, the cartilage is replaced with hard bones and some of the bones fuse together and we are left with 206 bones. Our bones not only help in the movement of our body but also protect our delicate internal organs like the Heart, Lungs, Brain, etc. To know this, let us study about the skeleton system.
Skeletal System
The human skeleton is a framework of bones which protects the internal organs and also gives support and shape to our body. An adult has 206 bones. The long bone of the skeleton is hollow and is filled with soft, fatty tissues called the bone marrow. Bone marrow produces red blood cells.
The skeleton system includes the skull, the spine and the ribs.
The Skull
The bones of the head make the skull. The skull protects the brain which is located inside our head. It is made up of 22 bones which are joined together. The upper part of the skull has 8 bones and the face is made up of 14 bones. The upper jaw is fixed and the lower jaw is movable due to which we are able to speak and eat. It contains holes for our nose, eyes, ears and mouth. When you put a hand on your nose you will be able to feel a long structure. That is not a bone, it is a long piece of cartilage which gives shape to our nose. A cartilage is made up of strong tissues which are very flexible.
The Spine
A long flexible column of bones extending from the neck to the end of the back is called the backbone. It is also called the vertebral column. Each bone of the backbone is known as vertebra.
We have 33 small bones in our backbone, but as we grow some bones fuse with one another and we are left with 26 vertebrae. Each vertebra has a cushion of cartilage. It prevents the bone from rubbing. It is due to the vertebrae that we are able to bend and
twist our backbone. Each vertebra has a hole in it. The spinal cord passes through this hole. Therefore, the vertebral column protects the spinal cord.
Rib Cage
Ribs are thin, flat, bow-shaped bones that are enclosed. They form a cage around the heart and lungs to protect them. We have 12 pairs of ribs which are symmetrically paired on the right side and left side, forming a cage. They join the backbone at the back and the sternum (chest bone) in the front. 2 pairs of the lower ribs are not attached to the chest bone; they are only attached to the backbone and are called floating ribs.
Limbs
In the human body there are two pairs of limbs:
Fore limbs (arms)
Hind limbs (legs)
Fore Limbs (Arms)
The bones of the shoulder are attached to our spinal cord with the help of shoulder girdle or pectoral girdle. The fore limb is divided into three parts-the upper arm, the forearm and the hand. The upper arm of the body extends from the shoulder to the elbow. It is a single long bone called humerous. It provides strength for pulling and lifting. The lower arm has two long bones. The wrist and the hand have 27 bones.
Hind Limbs (Legs)
The hind limbs or legs are flat bones which are attached to the backbone which form the pelvic grid. Bones of the lower limbs are attached to the hipbone. Upper half of the legs have a long bone called femur or thigh bone. It is the longest bone in our body. The lower leg has 2 bones namely tibia and fibula. At the end we have the ankle and foot which are made of 26 small bones.
Joints
Joints are a place where two bones meet. Joints help the skeleton to move. All the bones are connected to another bone. The ends of our bones are covered with a thin layer of cartilage which cushions the joints. Stretchy straps called ligaments help to hold the joint together and prevent it from being dislocated.
Immovable Joints
An immovable joint is a place where two bones are joined together, where little or no movement happens. Its function is to protect the delicate organs inside it. For example, the joints between the bones of the skull, joints between the teeth, joints in the pelvis are all immovable joints.
Movable Joints
The joints that we are able to move freely in our body are called movable joints. These types of joints are found in the arms, legs, hip and shoulders. We are able to move these joints freely due the presence of cartilage.
There are four types of movable joints:
Hinge Joint
This type of joint allows movement only in one direction. The elbows, knees, fingers and toes have hinge joints.
Ball and Socket Joint
This type of joint allows movement in all direction and is found in the hip and shoulders. Here, one bone is like a ball and fits into the hollow socket of the other bone.
Pivot Joint
This type of joint is found between our head and neck and allows side to side, upward and downward movement. The joint between the first two vertebrae and the skull is called atlas.
Gliding Joint
Gliding joints allow the bones to slide on each other, glide past one another in any direction along the plane of the joint – up and down, left and right, and diagonally. This type of joint is found in the wrist and ankle.
Do you Know?
The smallest bone in the human body is located in the middle ear know as staples.
Muscles
Our bones cannot move on their own, they need something to move them. Muscles are attached to bones and pull to make them move at joints. Every movement needs muscles. There are 640 muscles in the human body. They are made of tough elastic tissues. Muscles are attached to bones by a tough band of tissues called tendons. Muscles can pull the bones, they cannot push. To move bones in one direction, at least 2 muscles are required. When a muscle contracts, the bones come close to each other due to which we are able to move. For example, to move the lower arm you need 2 muscles- biceps & triceps. So we can say that the muscular system is responsible for the movement of the human body. Muscles are basically of three types:
Voluntary Muscles
These muscles control the movement of the body and are under our control. They work in pairs like one muscle in the pair contracts while other relaxes to produce movement. These are found in arms, legs, eyes, tongue etc. Thus while reading, writing, walking or running, we use voluntary muscles.
Involuntary Muscles or Smooth Muscles
These muscles are not in our control, they work on their own. They are found in internal organs. For example, when we eat our food from the mouth, it is pushed by muscles from the Foodpipe to the stomach.
Cardiac Muscles
These types of muscles are found in the heart. They are involuntary and keep on pumping the blood throughout the body.