How the body works – Part One

How the body works – Part One

I: Bones

Welcome to our continuation of the blog series ‘How the body works’. In today’s article we will step through some understanding of bones. It is generally accepted that the human adult skeleton is made up of 206 bones (with some variation person to person). Some are long, some are short, others flat and irregular. Bones range in size and shape with the smallest measuring approximately 3×2.5mm (the ‘stapes’ bone in the eardrum) and the largest measuring on average 480×23.4mm (the femur bone in the thigh). The femur can support up to 30 times the weight of average adult.

As we discussed last time, Bones are the most foundational organ we have, providing stability and structure to the body much like the slab and frame do in a building. The human skeleton is divided into two major parts – the axial and appendicular skeleton. The axial skeleton is made up of the skull, spine and rib cage with 80bones in total. Twenty- two of these are in the skull! The appendicular skeleton accounts for the remaining 126 bones including the shoulder blade, arm, hand, pelvic, leg and foot bones. In addition to providing stability and structure, bones form the foundation for movement. They further provide protection for many vital organs and structures in our body. In addition to these mechanical components, bones are a site of nutrient storage (accounting for 99% of the body’s calcium) and are also responsible for blood cell formation.

Whilst they may seem static, bone tissue is living and constantly changing! Dry bone (bone that we may observe outside of the body) are not really bones at all. They simply contain hard boney matrix and are lacking in living cells. Bone contains three major cells: Osteoblasts, Osteocytes and Osteoclasts. These cells only account for approximately 3% of bone mass. The remaining 97% is made up of bony matrix, bone marrow and membrane. Simply, osteoblasts create bone matrix, osteocytes maintain it and osteoclasts break down bone matrix. A helpful analogy to use is a construction site. Osteocytes are the site managers, supervisor and maintenance crew. Osteoclasts are the demolition crew. Osteoblasts are the concrete mixers and pourers. Perhaps my old anatomy professor would think this is too simplistic but it makes sense to me! Having said this, unlike a construction site, the project is never fully completed! Let’s discuss this further.

We recall that a primary role of the skeleton is to provide stability and structure to the body. It needs to remain strong and be able to respond to various loads and forces we experience throughout daily life. Amazingly, bone is able to detect and interpret these forces through a process called mechanotransduction. In response, bone cells “renovate” the bone matrix, resulting in stronger bones. You may be thinking – why is this relevant? If you’re anything like me, you will remember in your childhood being told to drink milk, eat broccoli and play in the sun to ‘get big and strong bones’. Vitamin D and Calcium are definitely important for bone health. However, to maintain healthy bones it is as equally important to load our bones.

Peak bone density is reached at approximately 30years of age for both men and women. Then due to normal age-related changes, bone loss begins to occur as we become older. For some women a sudden drop in bone density can occur in their mid-fifties around the time of menopause. Lastly, both men and women may experience a disease known as osteoporosis which describes a process of abnormal bone mineral density loss. But it’s not all doom and gloom! Bone density can be improved with various types of exercise including dynamic loading, muscle pull, weight bearing and progressive resistance training. Balance and falls prevention training also help to minimize the risk of bone fractures. Remember, bone health is important for all of us. If you’d like assistance in maintaining and improving your bone health, please feel free to call our clinic on 07 4613 1394.

Rowland Briese