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Biochemistry is a field within Biology Topics that explores the chemical processes in living organisms.
How does the skeleton provide a framework for movement?
The important functions of skeleton are as follows :
- Skeleton holds the whole body together and gives it a shape.
- Skeleton protects many delicate internal organs of the body (such as brain, heart, lungs, liver and spinal cord) from outside damage.
- Skeleton provides numerous points for the attachment of muscles of the body.
- Alongwith muscles, skeleton helps in the movement of body parts and locomotion (walking, etc.).
We will now describe some of the parts of the human skeleton in somewhat detail. Let us start with the skull.
1. Skull
The bony part of our head is called skull (see Figure). It is called ‘khopri’ or ‘kapal’ in Hindi. The skull is made of 22 bony plates joined together. Our brain is inside the skull in its upper part. The brain is made of soft tissue which could be easily damaged without a hard covering. The bones of skull form a strong case around the brain. In this way, skull protects the brain.
The lower part of skull contains the face bones (including nose bone). Our face has sense organs such as eyes, ears and nose. The skull also protects the main sense organs like eyes, ears and nose. The eyes are contained in two large cavities called ‘eye sockets’ in front of the skull (see Figure). From this discussion we conclude that some of the main functions of the skull are as follows :
- Skull protects the brain.
- Skull protects the sense organs of the face (like eyes, ears and nose).
- Skull gives shape to our head.
2. Backbone
If we put our fingers at the centre of the back of our body and move them up and down, we will feel a hard and long structure in the back of our body. This is our backbone (or spine). The backbone is a long, hollow, rod-like structure running from the neck to the hips, inside our body (see Figure). The scientific name of backbone is vertebral column. Backbone forms the main supporting structure of the body (or skeleton). Backbone is not a single bone. Backbone is made up of 33 small bones placed one over the other (see Figure).
The small bones which make up the backbone are called vertebrae (The singular of ‘vertebrae’ is ‘vertebra’). Between the various vertebrae of backbone are the discs of cartilage (soft bone). These discs allow the vertebrae to move slightly and enable the backbone to bend forwards and backwards (or from side to side). If, however, the backbone was made of only one long bone, we would not be able to bend our body. Please note that the top 7 vertebrae of backbone form our neck.
Our backbone supports the head at its top (see Figure). The shoulder bones, rib bones and hip bone, are all joined to the backbone. Each vertebra has a hole in it. Due to this, there is a hollow centre (or cavity) inside the backbone. The spinal cord (main nerve from the brain) passes inside the hollow cavity of the backbone. Thus, backbone encloses and protects the spinal cord from damage. We can now write down the main functions of the backbone as follows:
- Backbone provides main support to the body.
- Backbone supports the head at its top.
- Backbone attaches shoulder bones, ribs and hip bone.
- Backbone protects the spinal cord.
3. Rib Cage
If we take a deep breath, hold it for a while and move our hand on the chest, we will find a number of bones in the chest region. These chest bones are called ribs. Ribs are the curved bones in our chest (see Figure). Ribs exist in pairs.
There are 12 pairs of ribs in the chest of our body. We know that there is a long backbone at the back of our body. There is also a small bone called breast bone in the chest region, in front of our body (see Figure). One end of all the ribs is joined to the backbone and their other end is joined to the breast bone.
In this way, all the rib bones, a part of backbone, and the breast bone, join to form a ‘bony cage’ or ‘box-like structure’. The hollow, bony structure formed by the ribs is called ‘rib cage’ (see Figure). Some of the important internal organs of our body such as heart, lungs and liver lie inside the strong, bony rib cage. The rib cage protects the delicate internal organs like heart, lungs and liver. The rib cage also takes part in our breathing movements. We will study this in detail in higher classes. From the above discussion we conclude that the main functions of the rib cage are the following :
- Rib cage protects the internal organs of the body such as heart, lungs and liver.
- Rib cage takes part in our breathing movements.
4. Shoulder Bones
Shoulders are that part of the body (or skeleton) to which our arms are attached. The human body has two shoulders, one on each side of the neck. There are two shoulder bones : collar bone and shoulder blade (see Figure). The collar bone is a long, curved bone. One end of the collar bone is attached to the shoulder blade and the other end of collar bone is fixed to the breast bone of rib cage (for support). Collar bone keeps the shoulders apart. The shoulder blade is a large and flat triangular bone. The shoulder blade is attached to backbone by muscles to allow the free movement of the shoulder. Each shoulder blade has a cup-shaped socket. The upper arm fits into the socket of shoulder blade forming ball and socket joint (see Figure). The main functions of the shoulder bones are the following :
- Collar bones on the two sides of the neck keep our shoulders apart.
- Shoulder blades attach the arms to our body.
- Shoulder blades provide sites for muscle attachments which move the arms, neck and upper part of our body.
5. Hip Bone
The hip bone forms a large, basin-shaped frame at the lower end of the backbone, to which the legs are attached (see Figure). The hip bone is also known as pelvic bone (or pelvis). Hip bone is not a single bone. It is made up of a number of bones fused together by fixed joints. The hip bone encloses the portion of our body below the stomach. It is also the part of skeleton we sit on. The hip bone has turn sockets (hollow spaces) on the two sides of its lower part.
The thigh bones of our legs are joined to the hip bone by the ball and socket joints (see Figure). Actually, hip bone forms the link between upper part of our body (called trunk) and the legs. We can now write down the important functions of the hip bone as follows:
- Hip bone supports and protects the lower organs of the body such as intestines, urinary bladder and internal sex organs.
- Hip bone attaches the legs to our body.
- Hip bone provides sites for the attachment of muscles that move legs, hips and trunk .
6. Bones of the Hand
Our hand is made up of three parts : wrist, palm and fingers (see Figure). The wrist consists of 8 small bones known as carpals. The palm of hand is composed of 5 longer bones called metacarpals. The fingers (including thumb) are made of jointed bones called phalanges. There are 3 bones (or phalanges) in each finger but the thumb has only 2 bones (or phalanges). The wrist bones (carpals) form movable joint with the bones of forearm. Due to this our wrist is flexible. The palm bones (metacarpals) form movable joints with fingers. The finger bones (phalanges) form movable joints among themselves. There are five fingers in our hand including the thumb. The thumb is shorter than other fingers.
Cartilage
Most of the skeleton consists of hard bones. However, at some places in the skeleton there is a material which is not as hard as bones and which can be bent. It is called cartilage. So, we can now say that though most of the skeleton is made of bones but it has some cartilage too. Cartilage is a firm but flexible material found at some places in the skeleton. Cartilage is much softer than bone. Cartilage can be bent without breaking. In fact, cartilage is a kind of softer and elastic bone. Cartilage is present in the following places in our body :
- Cartilage is present in the pinnae of ears (upper part of ears).
- Cartilage is found at the end of nose.
- Cartilage is found on the end of bones where they meet one another at a joint.
- Cartilage is also present (as cartilage discs) between the vertebrae of backbone.
The upper part of our ear is called pinna and the lower part is called ear lobe. If we press the pinna of our ear and the ear lobe between our fingers, turn by turn, we will find that the pinna is harder than the ear lobe (see Figure). The pinna (upper part) of our ear contains cartilage. Cartilage gives support and shape to the ear.
Cartilage is flexible that is why we can bend the pinna of our ear quite freely, without the danger of breaking. Feel the end of your nose. We can bend the nose easily. There is a is the presence of cartilage which gives support and shape to our nose. From the above discussion we conclude that cartilage gives support and shape to organs like ears and nose.
Cartilage is also found on the ends of bones where they meet one another at a joint. Cartilage is smooth. The layer of smooth cartilage reduces friction and allows the ends of bones to move easily over each other without damaging them. Thus, cartilage is found in the joints of our body.
Discs of cartilage are present between the various small bones (vertebrae) of the backbone. The presence of cartilage discs between vertebrae makes the backbone flexible, so that it can bend. The cartilage discs also absorb the shocks when we run, jump, or do other such activities.