Each bone in your body is made up of three main types of bone material: compact bone, spongy bone, and bone marrow. Cross section showing osteons. The large dark spots are passages for blood vessels and nerves. The little black spots are osteocytes. Compact bone is the heaviest, hardest type of bone. It needs to be very strong as it supports your body and muscles as you walk, run, and move throughout the day.
It makes up the outer layer of the bone and also helps protect the more fragile layers inside. If you were to look at a piece of compact bone without the help of a microscope, it would seem to be completely solid all the way through. If you looked at it through a microscope, however, you would see that it's actually filled with many very tiny passages, or canals, for nerves and blood vessels. Compact bone is made of special cells called osteocytes.
These cells are lined up in rings around the canals. Together, a canal and the osteocytes that surround it are called osteons. Osteons are like thick tubes all going the same direction inside the bone, similar to a bundle of straws with blood vessels, veins, and nerves in the center. Looking at the osteons in bone A under a microscope reveals tube-like osteons B made up of osteocytes C.
These bone cells have long branching arms D which lets them communicate with other cells. Spongy bone is found mostly at the ends of bones and joints. Unlike compact bone that is mostly solid, spongy bone is full of open sections called pores. If you were to look at it in under a microscope, it would look a lot like your kitchen sponge. Pores are filled with marrow, nerves, and blood vessels that carry cells and nutrients in and out of the bone.
Though spongy bone may remind you of a kitchen sponge, this bone is quite solid and hard, and is not squishy at all. The inside of your bones are filled with a soft tissue called marrow. There are two types of bone marrow: red and yellow. Red bone marrow is where all new red blood cells, white blood cells, and platelets are made. Platelets are small pieces of cells that help you stop bleeding when you get a cut.
Red bone marrow is found in the center of flat bones such as your shoulder blades and ribs. Yellow marrow is made mostly of fat and is found in the hollow centers of long bones, such as the thigh bones.
It does not make blood cells or platelets. Both yellow and red bone marrow have many small and large blood vessels and veins running through them to let nutrients and waste in and out of the bone. When you were born, all of the marrow in your body was red marrow, which made lots and lots of blood cells and platelets to help your body grow bigger.
As you got older, more and more of the red marrow was replaced with yellow marrow. The bone marrow of full grown adults is about half red and half yellow. Bones are made of four main kinds of cells: osteoclasts, osteoblasts, osteocytes, and lining cells. Notice that three of these cell type names start with 'osteo. When you see 'osteo' as part of a word, it lets you know that the word has something to do with bones.
Osteoblasts are responsible for making new bone as your body grows. They also rebuild existing bones when they are broken. The second part of the word, 'blast,' comes from a Greek word that means 'growth.
Minerals are then added to osteoid, making it strong and hard. When osteoblasts are finished making bone, they become either lining cells or osteocytes. Osteocytes are star shaped bone cells most commonly found in compact bone. They are actually old osteoblasts that have stopped making new bone.
As osteoblasts build bone, they pile it up around themselves, then get stuck in the center. At this point, they are called osteocytes. Osteocytes have long, branching arms that connect them to neighboring osteocytes. Lack of oestrogen in the body — If you have an early menopause before the age of 45 or a hysterectomy where one or both ovaries are removed, this increases your risk of developing osteoporosis. This is because they cause your body's oestrogen production to reduce dramatically, so the process of bone loss will speed up.
Removal of the ovaries only ovariectomy or oophorectomy is quite rare but is also linked with an increased risk of osteoporosis. Lack of weight-bearing exercise — Exercise encourages bone development, and lack of exercise means you'll be more at risk of losing calcium from the bones and so developing osteoporosis.
Muscle and bone health are linked so it's also important to keep up your muscle strength, which will also reduce your risk of falling. However, women who exercise so much that their periods stop are also at a higher risk because their oestrogen levels will be reduced.
Heavy smoking — Tobacco is directly toxic to bones. In women it lowers the oestrogen level and may cause early menopause. In men, smoking lowers testosterone activity and this can also weaken the bones. It also increases the risk of breaking a bone as a result of a fall.
Family history — Osteoporosis does run in families, probably because there are inherited factors that affect bone development. If a close relative has suffered a fracture linked to osteoporosis then your own risk of a fracture is likely to be greater than normal. Any exercise where the bones are made to carry the weight of the body, such as walking, can speed up the process of new bone growing. The more weight-bearing exercise you do from a young age, the more this will reduce the risk of getting osteoporosis.
If you do have osteoporosis, doing weight-bearing exercise will minimise bone loss and strengthen muscles. However, all forms of exercise will help to improve co-ordination and keep up muscle strength. This is important because muscles can also become weaker as we get older, and this is a risk factor for falling and therefore for fractures. T'ai Chi can be very effective in reducing the risk of falls. It also improves balance. Walking is a good exercise to improve bone strength and it is also good for keeping thigh and hip muscles strong, which is important to help people have good balance and prevent falls.
High-impact exercise such as skipping, aerobics, weight-training, running, jogging and tennis are thought to be useful for the prevention of osteoporosis. These exercises might not all be suitable if you have osteoporosis. For more support, motivation and advice talk to your doctor, a physiotherapist or a personal trainer at a gym about your condition and the best exercise for you. The best sources of calcium are:. If you don't eat many dairy products or calcium-enriched substitutes, then you may need a calcium supplement.
We recommend you discuss this with your doctor or a dietitian. Vitamin D is needed for the body to absorb and process calcium and there's some evidence that arthritis progresses more quickly in people who don't have enough vitamin D. Vitamin D is sometimes called the 'sunshine vitamin' because it's produced by the body when the skin is exposed to sunlight.
A slight lack deficiency of vitamin D is quite common in the UK in winter. The National Institute for Health and Clinical Excellence NICE has issued guidance on safe sunlight exposure which aims to balance the benefits of vitamin D against the risks of skin cancer from too much exposure to sunlight.
Vitamin D can also be obtained from some foods, especially from oily fish, or from supplements such as fish liver oil. However, it's important not to take too much fish liver oil.
Because we don't get enough sunshine all year round in the UK, and because it's difficult to guarantee getting enough vitamin D from what we eat, Public Health England recommends that everyone should take a 10 microgram supplement of vitamin D every day during the autumn and winter. People in certain groups at risk of not having enough exposure to sunlight, or whose skin is not able to absorb enough vitamin D from the level of sunshine in the UK, are encouraged to take a daily supplement of 10 micrograms all year round.
For many people, calcium and vitamin D supplements are prescribed together with other osteoporosis treatments.
Some hospitals also offer falls prevention clinics or support groups — ask your doctor if there's one in your area. Smoking can affect your hormones and so may increase your risk of osteoporosis. We strongly recommend you stop smoking. Support is available if you wish to stop. High-resolution in vivo imaging of bone and joints: a window to micro-architecture. Nat Rev Rheumatol. Muller R.
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We also acknowledge Dr. Amir Ashique and Lorraine Hart who helped to create Fig. Yasmin Carter who collected the raw data utilized to create Fig. Johnston is supported by the University of Saskatchewan.
Cooper, K. You can also search for this author in PubMed Google Scholar. Correspondence to D. Reprints and Permissions. Cooper, D. Curr Osteoporos Rep 14, — Download citation. Published : 13 September Issue Date : October Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.
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