The Structure and Development of the Skeletal System

Bone development is constant throughout our lifetime. They therefore have a dynamic state as they are continuous. They constantly change throughout our lifetime. During the gestation period, the foetus's bone structure is composed of cartilage which is a type of connective tissue that is flexible and can be found in between joints in a person after their bones have fully developed.

Bones are a living structure that develops over a lifetime, they are hard and robust which shows that it is adapted for its purpose. The skeletal system and the bones that compose it serve a numerous of functions. To begin with the skeletal system provides support for our body; they do this with the help of our vertebrae which is out spine that helps to keep our body upright. It also helps to protect our body's internal organs and delicate tissues, the most vital and delicate parts of our body are protected by bones as well. For example our cranium protects both our eyes and brains, our ribs protect our heart and lungs and the vertebrae protect the spinal cord which is an essential part of the nervous system. Our skeletal system also assists in movement; this is because muscles attach to bone through the use of tendons, without bones we wouldn't be able to move. They also store minerals within them, to be specific within compact bone, these minerals include; calcium, zinc and potassium, magnesium and many others.

As mentioned earlier bone is a living structure that grows and is capable of repairing itself. Bone has an outer membrane known as periosteum. Periosteum which is a fibrous connective tissue, it also provides a blood supply as well as nerve supply to the bones. This is essential as the bones need nourishment and the nerve supply is needed, as when the bones are damaged they send signals through neurotransmitters to stimulate regrowth and repair within the bones. The periosteum also contains cells that serve different functions these cells are osteoblasts, osteocytes and osteoclasts.

Osteoblasts are cells that produce collagen which is an elastic fibre and minerals that hardens the bone, which is essential during the process of ossification. Osteoclasts help in regards to repairing bones, this is because they act as a "clean up squad" in the specific area, and this subsequently allows bone regrowth and repair. Osteocytes allow bone to harden and are found in matured bones.

There are many skeletal tissues that can be found throughout the skeletal system that provides various functions. To begin with within the skeletal system we have ligaments. Ligaments are a fibrous connective tissue that contains collagen which is an elastic fibre. Ligaments help connect bone to bone, they can therefore be found within joints. Tendons are also a connective tissue that contains collagen, however they connect bone to muscle instead of bone to bone. They help facillate movement in the bones as they transmit "force" they also act as springs. Cartilage is an extremely important part of the skeletal system, to begin with it helps prevent corrosion between bones as it acts a "cushion". They also help form bones it also facilates flexibility and support. There are three main types of cartilage; elastic, hyaline and fibrocartilage. Elastic cartilage can be found within structures such as the trachea to keep the airway open. Hyaline cartilage can be found within joints to help facilitate movement. Fibrocartilage can be found within the spine such as the intervertebral disks. Cartilage is composed of collagen, however the different types of cartilage contains different forms and amount of collagen.

There are different types and components of the bone. Compact bone tissue helps the skeletal system support itself as it is extremely dense and hard. It therefore helps support and protect the body and it's organs. Cancellous bone tissue is also often referred to as "spongy bone" as it has a honeycomb like structure. This part of the bone helps provide support at the ends of the bone it also contains bone marrow. There are two types of bone marrow red and yellow. The red bone marrow helps produce white and red blood cells which is essential for the functioning of the human body. It also produces yellow bone marrow which helps in regards to the storage of fats.

The structure of long bone can be seen below. There are three key components of a long bone, the epiphysis head, diaphysis shaft and the epiphysis. The diaphysis shaft is tubular and has an outer protective coating known as a compact bone which protects the marrow cavity. Within that marrow cavity is bone marrow which is mentioned above. The epiphysis contains mainly spongy bone. The development of the skeleton is important and our skeleton is fully developed by the end of puberty. A key feature of skeletal growth is the lengthening of bones. Above I have described the anatomy of the bone; the epiphyseal disks are located at both ends of the bone. Bone cannot develop from articular cartilage as that is necessary to form joints, and if bone formed there the joints would be destroyed and it would be hard to have mobility The plates themselves are made from cartilage they can therefore lengthen because of this. .This is because there are cells known as chondrocytes within the epiphyseal disks that constantly divide to make more cartilage. The older cartilage is then replaced by bone, which therefore lengthens the bones, this is done by endochondrial ossification. The lengthening of the bone and the speed to which the chondrocytes divide is controlled by a hormone that is controlled by the pituitary gland. The bones eventually stop growing and the cartilage within the epiphyseal plate is replaced by bone. That is known as the closure of the epiphyseal plate.

The development of the spinal curvature begins while the foetus is 5 weeks. There are three key parts of the spine which is; cervical, thoracic and lumbar. The cervical part of the spine is composed of 7 vertebrae; this part of the spine supports the head. It begins developing once a baby starts lifting their head. Underneath this part if the thoracic spine which is composed of 12 vertebrae. The