Bones are an important part of our body that support all the tissues of the body. Bone growth and development are perfectly regulated by the pituitary gland of the hypothalamus under the production of growth hormones Such as parathyroid hormones and calcitonin, which are working together.
PHYSIOLOGY OF BONES
- Bones allow our body to move from one place to another along with the movement of the attached muscles.
- Bones make our body shape, produce many types of blood cells, and protect our internal organs.
- Bones also determine your body height.
- Retarded bone growth makes you dwarf. Bone growth begins to initiate before you are born and remain continues to grow throughout your childhood and adolescence too. Our body is comprised of 206 bones, some of them are long bones and some are short.
BONES & JOINTS
Bones are joined each other via the synovial fluid to make the JOINTS. This fluid acts as a cushion to protect the bones from fracture and makes the bone move easily without pain. Joint or Articulation is actually the point of bone attachment. Our body has 360 joints which are different in structure and functions.
The structural classification divides the joints into three types depending on the composition of the joint and the presence or absence of a cavity in the joint. These may be
- fibrous
- cartilaginous
- synovial joints.
The functional classification divides the joints into three categories according to their functions:
- synarthroses
- amphiarthroses
- diarthrosis
Bone growth and development is a critical process, is influenced by some vitamins and hormones and including vitamin D, parathyroid hormones, calcitonin, estrogen and other. Therefore, Growth hormones should be produced in a balanced amount to keep the bone growth normal.
Bone Growth Factors
Our body produces many growth factors that are responsible for bone growth and development. Hormonal factors are insulin-like growth factor 1, insulin-like growth factor 2, fibroblast growth factors, transforming growth factors, parathyroid hormones, etc. Vitamins for bone growth are vitamin D and minerals for bone density are phosphorus, magnesium, calcium, etc. These factors work very harmoniously to control the proper procedure of bone formation i.e bone proliferation, bone maturation, and mineralization.
TYPES OF BONE
Bones are divided into two types that are different in structure and functions. Many bones have both types of bone tissues.
1- COMPACT BONE
This also called cortical bone. It is a thick and dense part of the bone. This is the site where ligaments and tendons are attached. Therefore, it works as a mechanical part.
2- Trabecular bone
It also is known as spongy bone or cancellous bone. This bone has trabeculae (meshwork) in the bone marrow and located within the layers of compact bone. This type of bone is involved in metabolic functions.
What Are The Types Of Bones Cells And What They Do?
They are three types of bone cells that formed bone. They are
Osteoblasts
Involved in bone formation. Therefore, also known as bone forming cells.
Osteocytes
Originate from osteoblasts that have moved and trapped in bone matrix.
Lining cells
These cells come from osteoblasts that are flattened. Bone lining cells can easily cover up the bone without disturbing the surrounding structure because they have flat organelles.
How Bone Formation Process Occurs?
Bone formation occurs during your fetal life, childhood life until adolescence. Ossification is the process of bone formation and bone growth from fetal life to childhood. This ossification comprises of two parts i.e
Intramembranous ossification
This is the direct laying down of bone into the primitive mesenchymal connective tissue.
Endochondral ossification.
This typically involves the cartilage and form the callus bone.
Two ossifications occur during complete bone growth and development. They are
- Primary Ossification
- Secondary Ossification
Three Stages of Bone Growth
There are three stages of bone growth and development, during which the whole bone is formed. These stages are
- Bone formation during fetal life
- Bone formation during childhood
- Bone formation during adolescence
1- Bone Formation during Fetal Life
Bone formation starts at about the third week in prenatal life. Bone begins to format the Primary Ossification Center, at which osteoid is formed. What is Osteoid and how it is formed? Cartilage is formed which is a premature shape of the future bone and then the osteoblasts are formed, which are the cells that produce the new bone. These osteoblasts invade the newly formed cartilage and begin to produce the osteoid.
Osteoid is primarily made up of collagen and calcium phosphate crystals. This whole process of osteoid formation starts in the center of the newly formed bone, and this site called the primary ossification center, from which the bone growth starts. Now bone formation moves outwards from the center toward the ends. As the process continues, new blood vessels begin to grow into the bone. End of bones still covered by cartilage.
2- Bone Growth at Childhood
As you grow older, your bones need to grow longer, especially at the ends of the bones. As the bone growth further, more cells are produced to form cartilage and extend the bone ends. Thus, bones continue to grow longer until the age of 16 to 20 years.
3- Bone growth at Childhood
Bones grow during childhood by the same process as the endochondral ossification process occurs, until the epiphyseal plate of the bone ( one end of the bone ) fuses with the shaft of the bone (diaphysis).
THE FIRST BONE TO BE OSSIFIED
The clavicle is the first bone that is ossified in fetal life but the last to complete epiphyseal union. Every bone takes a different time to complete its ossification.
Ossification is the process of bone formation and bone growth from fetal life to childhood. This ossification comprises two parts i.e intramembranous ossification and Endochondral ossification.
HP Thoughts: Ossification during youth but osteoporosis during advanced age. What causes the latter? Read our post to find out — Osteoporosis.
