Question

We all know there are different classifications of joints within the human body (e.g. ball and socket, hinge, pivot, fibrous, etc.). Why the variety? What if the joints between skull bones had more flexibility? It could be beneficial in the event of brain bleeds/swelling, right? Please give me an example or two of a specific joint, name its classification, and explain the current function and why that joint type is a good or poor fit for that body part/location/function/movement. Then imagine a different joint type in its place that would improve, or change, the current function/movement. You may substitute with a known joint type, invent your own joint type, or create a hybrid; it’s up to you.

Answer 1

The human body has different parts and the agility of the body comes due to the special musculoskeletal system we have. The skeleton, which is made up of bones and cartilages, is supported by the various types of joints and the muscles, tendons and ligaments to make the various types of movement. The variety in the joints enables us to move the body in different ways and directions and enables us to perform a varied number of movements, right from sitting, bending, running, walking, lifting, pushing, pulling, and many others. The joints give us a lot of flexibility and help us perform so many different types of tasks.

The skull is made up of several bones which are fixed to each other by sutures which are immovable. The only part of the skull which is movable is the lower jaw and this helps us to speak, eat and perform other tasks with our mouth. The cranial bones are fixed and this is important to protect the brain. If the joints had not been fixed then any movement of the bones, like being pushed inwards, could have injured the brain. The rigidity of the joints in the cranium provides a safe 'box' for the brain.

One example of a body joint is the ball and socket joint in the shoulder. Ball and socket joint is a type of synovial joint in which a ball like swelling of one end of the humerus fits into a cup like depression in the shoulder bone. The ball shaped end fitting into the socket allows the humerus to move around an indefinite number of axes, which have one common center. Hence, our arms are the only part of the body which can move 360 degrees. This is important because we perform most of our tasks with our hands. Ofcourse, the other joints in our arms, like the hinge joint at the elbows, the wrist joints and the joints in the fingers play a great role in helping us perform those tasks, it is the shoulder joints which acts as an anchor for almost all of our hand movements. This joint needs no improvement.

Another joint, the pivot joint, is present vetween the skull and the first bone of the vertebral column. It allows movement of the head. This joint is also very flexible as it allows us to rotate our head upto 180 degrees sideways. We are able to bend our head downwards and raise it upwards due to the presence of the pivot joint. Besides these we can make several other movements like shaking and nodding our head, cocking our head at several angles, etc.

Now, suppose the pivot joint was replaced by a ball and socket joint as in our shoulders. This joint would enable us to rotate our head a full 360 degrees! This would mean that we would be able to look backwards without turning around. This movement would definitely add to our body's flexibility and would be an added advantage to us.