Understanding Bone Physiology and Wellness
The six functions of bone are:
• Support – bones provide a framework to support and anchor the soft organs of the body
• Protection – the skull, vertebrae and rib cage all assist to protect the body from trauma
• Movement – various skeletal muscles are attached to bones and use them as a lever to assist in bodily movement
• Mineral homeostasis
• Site of blood cell production – red blood cell production occurs in the bone marrow
• Storage of energy – fat is stored in the internal bone cavities as well as different minerals which can be mobilised and released into the bloodstream when required
Calcium and Bone Homeostasis
Ossification is the process in which bone forms. This is done one of two ways, either intramembranous or endochondral. Bone growth in length happens in the epiphyseal plate which consists of zones – zone of resting cartilage, zone of proliferating cartilage, zone of maturing cartilage, and the zone of calcified cartilage.
Four types and functions of bone cells are:
• Osteoprogenitor – these can develop into osteoblasts.
• Osteoblasts – they secrete collagen and other organic components needed to build bone tissue.
• Osteocytes – they maintain cell activity such as the exchange of nutrients and waste in the blood.
• Osteoclasts – they function in bone resorption (a process in which bones cells break down their own mineralised components).
There are two types of bone tissue and bones are classified according to shape as certain shapes contain different proportions of the two types of osseous tissue: compact or spongy bone.
Compact bone
Compact bone is very dense and looks smooth. However if you look at it through a microscope you would see it is riddled with canals and passageways.
These all serve as conduits for various nerves, blood vessels and lymphatic vessels. This is a bone that contains of very closely packed osteons. The osteon is the structural unit of the compact bone. It is a group of hollow tubes of bone matrix place one inside the next. Each of the hollow tubes is called a lamellar. This runs along the long axis of the bone. Running through the centre of each osteon is a channel called the Haversian or central channel which contains various blood vessels and nerve fibres. In compact bone, the Haversian systems are all packed tightly together to give the bone the appearance of a solid mass.
Spongy bone
Spongy bone is a great deal lighter and has a lesser density than compact bone. This bone tissue consists of trabeculae (plates) and small bars of bone that are situated adjacent to narrow and irregular cavities that contain bone marrow. The trabeculae are organised in a manner to provide maximum strength. Nutrients reach the osteocytes of spongy bone by diffusing through canaliculi (channels) from the marrow spaces.
