Bone

Bones function in our bodies both structurally and metabolically.  Structurally, bones provide protection, support, and act as levers for movement.  Metabolically, bones are reservoirs for phosphorous and calcium, they store fat, and they produce blood cells.  

Bone Cells

I will now explain how bones are formed through the use of bone cells.  Bones are constantly being remodeled throughout our lifespan. As bones are broken down by osteoclasts, bone building cells called osteoblasts build bone back up.  Osteoclasts are bone cells that break down bones, and in a process known as resorption they release minerals into the bloodstream. The osteoblasts undergo a process called mineralization in which the calcium and phosphorous from our bloodstream gets deposited along the collagen fibrils to make up the calcified bony matrix of our bones.  The goal after our peak bone mass is achieved is to have the bone breakdown = bone formation.

Properties of Bone

As mentioned above bones contain calcium and phosphorous which are inorganic (nonliving) substances, bones store about 99% of the body’s calcium and 85% of the body’s phosphorous.  Water and calcium are other inorganic properties of bone.  The organic properties of bone are basic collagen, proteins, osteoblasts and osteoclasts.

http://david-gan-o-den.blogspot.com/2013/10/bone.html

Bone Tissue

There are two types of bone tissues that will now be discussed 1) woven and 2)lamellar.  As children our bones are composed of woven tissue which is immature, and randomly oriented by collagen.  By the age of 4 lamellar tissue replaces (woven) bone.  Lamellar tissue is organized, collagen fibers that are arranged in parallel alignment so that the bone can withstand force. 

The outer part of the bone is known as compact or cortical bone.  This outer shell is part of the long bones in our body and is solid and dense to provide structure and protection.  The inside part of the bone is known as cancellous or spongy bone.  This part of the bone is softer, less dense and weaker than compact bone.  Its function is to allow bone marrow, blood vessels and connective tissue to interact to maintain metabolism within the bone.

Hormonal Influences- Genetics, Age, Gender

Bones mass and composition are affected by a number of hormones; these hormones are triggered by a certain process or event in the body to maintain the overall health of bones.  The hormones that control bone mass are the parathyroid hormone, calcitonin and vitamin D.

 Parathyroid hormone and calcitonin are antagonists meaning that they perform opposing tasks.  For example the parathyroid is triggered in response to low blood calcium.  Calcitonin is triggered when there is high blood calcium.

Genetics

Some people are naturally prone to having weak or strong bones.  It is surprising how many factors are genetically influenced: peak bone mass, muscle strength, bone geometry, age of onset of menopause, how a person responds to exercise, a person’s dietary intake and bone turnover are all genetically influenced. 

Age

Both males and females aquire all their bone mass by the age of 18-20 and reach maximum bone density around the age of 30.  Bone density will stay steady for about a decade and then endocortical resorption occurs which means bones are going to naturally become weaker.

Gender

Gender is another factor to consider in bone mass formation.  Most people can see that males are stronger than females; they are naturally going to have stronger bones because of their ability to keep up bone remodeling.  Endocortical resorption results as the bone gets smaller and therefore weaker from the inside, the outer shell of the periosteum remains the same while the cortical thickness decreases.   Periosteal apposition is when new lamellar bone is being laid down beneath the surface, increasing the size and therefore the strength of the bone.    Woman do not have strong enough periosteal apposition (bone building) to keep up with the bone loss and therefore have weaker bones. 




Osteoporosis

Osteoporosis occurs as bone tissue deteriorates lowering overall bone mass, causing the bone to become more fragile.  There are ways to prevent this disease but as we age or if you have a family history you will be more prone to developing osteoporosis.

Factors that contribute to osteoporosis: smoking, alcohol intake, steroids, inactivity, genetics (family history of osteoporosis), previous fracture, thyroid excess
Ways to prevent osteoporosis :  a healthy diet, adequate exercise

Supplementing calcium and vitamin D is not recommended until you develop osteoporosis. Making sure you get the adequate amount of these nutrients during development will help ensure rigid, healthy bones prior to developing this disease.

 The calcium dietary guidelines (particularly for children with developing bones):  Children 1-3 years of age should be getting 700 mg of calcium a day, children 4-8 should be getting 1000 mg, and children the ages 9-13 should be getting 1300 mg. 
Food sources for calcium: 
 cauliflower, broccoli, rutabaga, kale, milk, yogurt, cheese, almonds, sesame seeds

 Physical activity:  Children and adolescents should be getting sixty minutes of (aerobic) physical activity each day, 3 days a week should be strengthening exercises

Adults need to continue with aerobic exercise and strength training.

After being diagnosed with osteoporosis these types of exercises are still very important!  2-3 days of exercise is recommended including exercises to build lower body strength and to use body weight as resistance (wearing a weight vest could be useful). 

Ways to assess signs of osteoporosis:

A FRAX calculator is a tool used to assess the fracture rate of bones.  It’s a website where you according to your geographic region, race, height and weight you can determine a 10 year probability of your fracture rate. 
 http://www.shef.ac.uk/FRAX/

A DXA scan measures bone mineral density and is recommended for older people (especially women), and for underweight individuals.  It is not very common for children to get tested for osteoporosis and if you do well in keeping your bones in good shape, hopefully you won’t need a DXA scan!  An indication of osteoporosis is a T score of -2.5 or lower according to the DXA scan.