Welcome to the “Bone Anatomy and Function” section. In this portion of my blog I will be going into depth about the basic anatomy of bone, function of bone, the important cells in bone, bone remodeling, and mechanotransduction.
- Basic Bone Anatomy
Bone is defined as the dense, semirigid, porous, calcified connective tissue forming the major portion of the skeleton of most vertebrates. It consists of a dense organic matrix and an inorganic, mineral component. Bone can be both an organ and tissue. The organic component consists of collagen, non-collagenous proteins, and bone cells. The inorganic component consists of hydroxyapatite, made up of calcium and phosphate. The four general categories of bones are long bones, short bones, flat bones, and irregular bones.- Function of Bones
*Support
*Protection
*Storage of Minerals
*Production of Blood Cells
*Storage of Chemical Energy
- Important Cells In Bones
Bone cells all work together inside of the bones to help keep up the skeletal system. The bone cells do a number of things for the skeletal system, some of these key components are development of new bones, the maintenance of bones, and the regulation of minerals in the body.
****There are four main types of bone cells****:
*Osteoclasts - Osteoclasts are very large cells that are responsible for the breakdown of bones
*Osteocytes - Osteocytes are osteoblasts which have become trapped inside of the bone matrix. Osteocytes hold the bones together.
*Lining cells - Bone lining cells are also responsible for the protection of the bone from harmful chemicals which would eat away the bone.
- Bone Remodeling
Bone remodeling (AKA bone metabolism) is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed. These processes also control the reshaping or replacement of bone following injuries like fractures and breaks, which occurs during normal activity. Remodeling begins before birth and continues until death. The remodeling cycle is composed of four sequential phases. Activation, resorption, reversal, and formation.
- Mechanotransduction
Bone is a dynamic tissue that will adapt to its local loading environment. Mechanotransduction, the process by which cells convert mechanical forces into biochemical signals, is important for maintaining bone health and homeostasis. Mechanotransduction plays a crucial role in the physiology of many tissues including bone. Mechanical loading can inhibit bone resorption and increase bone formation. In bone, the process of Mechanotransduction can be divided into four distinct steps: (1) mechanocoupling, (2) biochemical coupling, (3) transmission of signal, and (4) effector cell response (osteoblast).
- Bone Hormones
- Growth hormone – anterior pituitary gland (origin) – increases the rate of mitosis of chondrocytes and osteoblasts, and increases the rate of protein synthesis (collagen, cartilage matrix, and enzymes for cartilage and bone formation)
- Thyroxine – thyroid gland (origin) – increases the rate of protein synthesis and increases energy production from all food types
- Insulin – pancreas (origin) – increases energy production from glucose
- Parathyroid hormone – parathyroid glands (origin) – increases the reabsorption of calcium from bones to the blood, thereby raising blood calcium levels and increases the absorption of calcium by the small intestine and kidneys
- Calcitonin – thyroid gland (origin) – decreases the reabsorption of calcium from bones thereby lowering blood calcium levels
- Estrogen or Testosterone – ovaries or testes (origin) – promotes closure of epiphyses of long bones, thereby stopping growth, and helps retain calcium in bones, thereby maintaining a strong bone matrix.
- Influential Factors on Bone
There are many factors that can influence bone growth, development and repair. These factors include nutrition, sunlight exposure, hormonal secretions, and physical exercise. One example, Vitamin D is needed for the proper absorption of calcium in the small intestine. When there is an absence of this vitamin, calcium is poorly absorbed, and the inorganic salt portion of bone matrix lacks calcium, thus, softening and deforming bones. In children, this condition is called rickets, and in adults, it is called osteomalacia.- Peak Bone Mass
- Bone DIsease
There is a lot you can do to protect your bones throughout your life. Osteoporosis can cause broken bones that are not part of normal aging. Osteoporosis, is a term used for the thinning of bones, and can result in painful fractures. The major risk factors for osteoporosis include aging, being female, low body weight, low sex hormones or menopause, smoking, and some medications. It is important to protect yourself against bone disease, You’re never too young or too old to improve the health of your bones, here are some essential tips to keep in mind.
What can you do to protect your bones?
- Get enough calcium and vitamin D and eat a well balanced diet.
- Engage in regular exercise.
- Eat foods that are good for bone health, such as fruits and vegetables.
- Avoid smoking and limit alcohol to 2-3 drinks per day.
Getting enough calcium and vitamin D is essential to building strong, dense bones especially when you are older to keep them strong and healthy as you age. There are two types of exercises that are important for building and maintaining bone density: weight-bearing and muscle-strengthening exercises.
Weight-bearing Exercises: These exercises include activities that make you move against gravity while staying upright. Weight-bearing exercises can be high-impact or low-impact. High-impact weight-bearing exercises help build bones and keep them strong. If you have broken a bone due to osteoporosis or are at risk of breaking a bone, you may need to avoid high-impact exercises. If you’re not sure, you should check with your healthcare provider.
Examples of high-impact weight-bearing exercises are:
- Dancing
- Doing high-impact aerobics
- Hiking
- Jogging/running
- Jumping Rope
- Stair climbing
- Tennis
Low-impact weight-bearing exercises: These can also help keep bones strong and are a safe alternative if you cannot do high-impact exercises. Examples of low-impact weight-bearing exercises are:- Using elliptical training machines
- Doing low-impact aerobics
- Using stair-step machines
- Fast walking on a treadmill or outside
Muscle-Strengthening Exercises: These exercises include activities where you move your body, a weight or some other resistance against gravity. They are also known as resistance exercises and include:
- Lifting weights
- Using elastic exercise bands
- Using weight machines
- Lifting your own body weight
- Functional movements, such as standing and rising up on your toes
Yoga and Pilates can also improve strength, balance and flexibility. However, certain positions may not be safe for people with osteoporosis or those at increased risk of broken bones. For example, exercises that have you bend forward may increase the chance of breaking a bone in the spine. A physical therapist should be able to help you learn which exercises are safe and appropriate for you.
- Balance exercises that strengthen your legs and test your balance, such as Tai Chi, can decrease your risk of falls.
- Posture exercises that improve your posture and reduce rounded or “sloping” shoulders can help you decrease the chance of breaking a bone, especially in the spine.
- Functional exercises that improve how well you move can help you with everyday activities and decrease your chance of falling and breaking a bone. For example, if you have trouble getting up from a chair or climbing stairs, you should do these activities as exercises.
Dairy
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Nutrient
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Dairy products such as low-fat and non-fat milk, yogurt and cheese
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Calcium. Some dairy products are fortified with Vitamin D.
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Fish
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Canned sardines and salmon (with bones)
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Calcium
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Fatty varieties such as salmon, mackerel, tuna and sardines
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Vitamin D
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Fruits and vegetables
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Collard greens, turnip greens, kale, okra, Chinese cabbage, dandelion greens, mustard greens and broccoli.
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Calcium
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Spinach, beet greens, okra, tomato products, artichokes, plantains, potatoes, sweet potatoes, collard greens and raisins.
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Magnesium
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Tomato products, raisins, potatoes, spinach, sweet potatoes, papaya, oranges, orange juice, bananas, plantains and prunes.
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Potassium
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Red peppers, green peppers, oranges, grapefruits, broccoli, strawberries, brussels sprouts, papaya and pineapples.
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Vitamin C
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Dark green leafy vegetables such as kale, collard greens, spinach, mustard greens, turnip greens and brussel sprouts.
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Vitamin K
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Fortified Foods
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Calcium and vitamin D are sometimes added to certain brands of juices, breakfast foods, soy milk, rice milk, cereals, snacks and breads.
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Calcium, Vitamin D
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Bad-for-your-Bones Food
Alcohol - Drinking heavily can lead to bone loss. Limit alcohol to no more than 2 - 3 drinks per day.
Salt - Salt saps calcium from the bones, weakening them over time. For every 2,300 milligrams of sodium you take in, you lose about 40 milligrams of calcium, dietitians say. One study compared postmenopausal women who ate a high-salt diet with those who didn't, and the ones who ate a lot of salt lost more bone minerals. Our American diet is unusually salt-heavy; most of us ingest double the 2,300 milligrams of salt we should get in a day, according to the 2005 federal dietary guidelines.
Hydrogenated Oils - Recent studies have found that the process of hydrogenation, which turns liquid vegetable oil into the solid oils used in commercial baking, destroys the vitamin K naturally found in the oils. Vitamin K is essential for strong bones, and vegetable oils such as canola and olive oil are the second-best dietary source of this key nutrient, after green leafy vegetables.
Caffeine - Coffee, tea and soft drinks (sodas) contain caffeine, which may decrease calcium absorption and contribute to bone loss. Choose these drinks in moderation.
Salt - Salt saps calcium from the bones, weakening them over time. For every 2,300 milligrams of sodium you take in, you lose about 40 milligrams of calcium, dietitians say. One study compared postmenopausal women who ate a high-salt diet with those who didn't, and the ones who ate a lot of salt lost more bone minerals. Our American diet is unusually salt-heavy; most of us ingest double the 2,300 milligrams of salt we should get in a day, according to the 2005 federal dietary guidelines.
Hydrogenated Oils - Recent studies have found that the process of hydrogenation, which turns liquid vegetable oil into the solid oils used in commercial baking, destroys the vitamin K naturally found in the oils. Vitamin K is essential for strong bones, and vegetable oils such as canola and olive oil are the second-best dietary source of this key nutrient, after green leafy vegetables.
Caffeine - Coffee, tea and soft drinks (sodas) contain caffeine, which may decrease calcium absorption and contribute to bone loss. Choose these drinks in moderation.
Coffee/tea - Drinking more than three cups of coffee every day may interfere with calcium absorption and cause bone loss.
Soft drinks - Some studies suggest that colas, but not other soft drinks, are associated with bone loss. While more research will help us to better understand the link between soft drinks and bone health, here is what we know:
The carbonation in soft drinks does not cause any harm to bone. The caffeine and phosphorous commonly found in colas may contribute to bone loss
The carbonation in soft drinks does not cause any harm to bone. The caffeine and phosphorous commonly found in colas may contribute to bone loss
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