Exploding Bones

Structure of the Human Skeleton

This section looks at the structure and function of the Human Skeleton.

The human skeleton is made up of 206 bones although we are born with 300: during childhood many of these fuse/join together to form single bones. The skeleton is divided into two parts:

  1. The Axial skeleton - skull, backbone and ribcage
  2. The Appendicular skeleton - limbs and girdles

The human skeleton is designed to stand upright on the hind limbs (bipedal) to enable walking on two legs. It has the added advantage of freeing the upper limbs which can then pick-up and carry objects.

The layout of the skeleton:
The diagram below shows a front view of a human skeleton. To find out more about each of the parts, click on appropriate bone.

Our hands are built on the standard mammal five-digit plan. The wrist bones provide anchorage for the small muscles that help to move the thumb and fingers. Other finger-moving muscles are in the forearm, conected to the fingers by long tendons that run through a "collar" of ligaments in the wrist.

The human hand is also unique because it can oppose/touch its thumb to each finger which enables it to pick up and handle objects in a precise/exact fashion.

We are so used to standing all the time in our lives, that we are not aware of what an amazing balancing feat this is. Other animals may be able to stand on their hind limbs briefly, but they cannot stay standing for long. Compared to the arm, the bones of the human leg are much thicker and stronger to carry the body's weight, all the time.


Dozens of times a day, we reach for something, pick it up with our fingers, and move it or use it in a precise way. The arm stretches out, so that the hand can use something, and is vital to do things in life. The arm is controlled by two antagonistic muscles: the triceps and the biceps, which work together to raise and lower the arm. Without arms it would be almost impossible to do anything.


The pelvis:
The human pelvis is an oddity in the animal world. As most other animals move on four limbs most of the time, they have elongated pelvises. Because we walk on two legs, our pelvis has become distorted to its rounded shape. The name pelvis comes from Latin - pelvis meaning a basin. The bowl shape of the pelvis gives protection to the internal parts of the lower body, such as the intestines and bladder, and in women especially the womb.

Although the head is at one end of the human body, it functions as the body's centre. The skull protects the brain, the controller of the whole body from the outside world, from knocks and bangs. The skull consists of the jaw, the nose hole, the eye holes, the nerve holes, the ear holes, and the tooth holes.

The spine is the backbone of the human body. It forms a vertical supporting rod for the head, arms and legs. It allows us to do many movements that we take for granted, yet it was originally designed as a horizontal girder, to take the weight of the chest and abdomen. Each vertebra can only move a little in relation to its neighbours, but over the whole spine they enable the back to move in all directions.



The lungs need to inflate and deflate, becoming larger and smaller as they breathe; yet they also need protection against being knocked and crushed. A solid cage like the skull would be too rigid, so we have the ribs - made up of moveable bars. They are very strong and flexible, and absorb knocks. When breathing in, muscles lift the ribs upwards and outwards, increasing the volume of the chest and sucking air into the lungs.

The feet:
The human foot has become specialised for walking. Our tiny toes have lost the gripping ability found in our close relatives, the apes. The human foot bears the weight of a whole body and has to provide a springy base to push the body off the ground when walking. The main foot bones are mostly enclosed in the fleshy part of the sole. They are visibly separate only at the ends, where they project into each toe.
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