Environmental biology examines the impact of human activities on ecosystems, one of the many Biology Topics.
What is Skeleton? And Introduction to the Skeletal System
We move our mouth when we chew food; we move our head up and down while nodding (saying ‘yes’) ; we move our head from side to side while saying ‘no’; we move (or bend) our back to lift something lying on the ground ; we move our arm at the shoulder while bowling a cricket ball; we bend our arm at the elbow while putting food into our mouth ; we bend the fingers of our hand to grip an object (say, a pen); and we move our legs while walking (or running a race). These are just some of the examples of our body movements.
Now, when we move our body parts like mouth, head, arms, hands and fingers, etc., then our body may remain at the same place. But when we walk by using legs, then we move our whole body from one place to another. The ability of a human being (or an animal) to move its body from one place to another, is called locomotion. Human beings (and other animals) show two types of body movements :
- Movements of the body parts (like mouth, head, backbone, arms, hands, legs and foot, etc.), and
- Movement of the whole body from one place to another (which is called locomotion).
In order to understand how the movement of our body parts and locomotion takes place, we should first study the bones present in our body (which form a skeleton), the various types of joints which exist between the bones, and the muscles which make the bones move at joints. We will now discuss all these things one by one. Let us start with the skeleton.
If we press our fingers against the top of our head, face, neck, shoulder, chest, back, arms, hands, fingers, hip, legs, feet and toes, we will feel some hard structures inside them. These hard structures inside our body are the ‘bones’. Actually our body is supported on a hard framework of bones. The bony framework inside our body is called skeleton (see Figure). In human beings, the skeleton is inside the body, so it is called an ‘endoskeleton’ (‘endo’ means ‘inside’). Skeleton is called ‘kankat’ in Hindi.
The bones of skeleton provide a framework which holds our body together. The skeleton also gives a shape to our body. The human skeleton is made mostly of bones with some cartilage in certain parts. Bones are hard and tough but cartilage is softer than bones. The skeleton is made of bones of many different shapes and sizes. We can know the shapes of different bones in our body by looking at the X-ray images of the body parts. The X-ray images show the shape and number of bones in the various parts of our body. An X-ray is usually taken in a hospital to find out whether the bone of a person has been fractured (or broken) during an accident. There are 206 bones in the human skeleton (or human body). The bones of skeleton are interconnected through joints to form various parts of our body. Our skeleton has movable joints between various bones which allow the muscles to move the head, shoulders, arms, legs, and other parts of the body.
Description of Skeleton
The skeleton consists of : Skull, Backbone, Ribs, Breastbone, Shoulder bones, Hip bone, Arm bones and Leg bones. A simple diagram of the human skeleton showing the main bones is given in Figure. We will now describe the human skeleton briefly.
The human skeleton consists of a strong backbone which has skull at its top end (see Figure). The skull has eye sockets, an upper jaw, and a lower jaw in it. Ribs are attached to the upper part of backbone forming a rib cage. There is a breastbone (called sternum) in front of the rib cage. At the lower end of backbone is a wide and strong structure called hip bone.
Just below the neck, there are shoulder bones on both the sides of the skeleton (see Figure). The shoulder bones consist of two bones : collar bone and shoulder blade. The scientific name of collar bone is clavicle and that of shoulder blade is scapula.
The upper limb of human body from the shoulder to the hand is called an arm. There are two arms in the human skeleton. The two arms are attached to the two shoulder blades of the skeleton by ball and socket joints (see Figure). Each arm consists of three parts: upper arm, lower arm (or forearm) and hand. The upper arm is from shoulder to elbow. The upper arm consists of a single bone called humerus (see Figure). The lower arm (or forearm) is from elbow to wrist. The lower arm (or forearm) is made up of two bones : radius and ulna (see Figure). The upper arm bone is connected to lower arm bones by a hinge joint at the elbow. The hand consists of various small bones which form wrist, palm and fingers.
The lower limbs of the body on which a person walks or stands are called legs. There are two legs in the human body. The two legs are attached to hip bone of the skeleton by ball and socket joints (see Figure). Each leg consists of three parts : upper leg, lower leg and foot. The upper leg is from hip to knee. The upper leg consists of a single bone called femur (Femur is commonly known as thigh bone). The lower leg is from knee to ankle. The lower leg consists of two bones : tibia and fibula. The upper leg bone is connected to the lower leg bones at the knee by a hinge joint. There is also a knee cap called patella. The foot consists of various types of small bones which form ankle, middle part of foot and toes.