A bone is actually a stiff organ that constitutes part of the vertebrate skeleton. Bones help to support and protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, as well as enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions.
Bone tissue forms the rigid part of the bone and is made up of different types of bone cells. Bone tissue is a mineralized tissue of two types, cortical and cancellous bone. The tissue gives rigidity to the bone and a honeycomb-like matrix internally. Other types of tissue found in bones include bone marrow, endosteum, periosteum, nerves, blood vessels and cartilage.
Bones are living, growing and changing parts of our bodies. Babies’ skeletons are made up from more than 300 parts, but by the time we become adults we only have 206 bones! The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.
When it comes to building strong bones, there are two key nutrients: calcium and vitamin D. Calcium supports our bones and teeth structure, while vitamin D improves calcium absorption and bone growth. These nutrients are important early in life, but they may also help as you age. If you develop osteoporosis, a disease characterized by brittle and breaking bones, getting plenty of calcium and vitamin D may slow the disease and prevent fractures.
Adults up to age 50 should get 1,000 milligrams of calcium and 200 international units (IUs) of vitamin D a day. Adults over 50 should get 1,200 milligrams of calcium and 400 to 600 IU of vitamin D.
Types of Bone
There are four different types of bone in the human body:
- Long bone: It has a long, thin shape. Examples include the bones of the arms and legs (excluding the wrists, ankles and kneecaps). With the help of muscles, long bones work as levers to permit movement.
- Short bone: It has a short, cubed shape. Examples include the bones that make up the wrists and the ankles.
- Flat bone: It has a flattened, broad surface. Examples include ribs, shoulder blades, breast bone and skull bones.
- Irregular bone: It has a shape that does not conform to the above three types. Examples include the bones of the spine (vertebrae).
What Are Bones Made Of?
Now that you know about bones, let’s take a look at what they’re made of and their anatomy.
Each bone in your body is made up of three main types of bone material: compact bone, spongy bone, and bone marrow.
Compact bone is the heaviest and 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. About 80% of the bone in your body is compact. 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.
Spongy bone is found mostly at the ends of bones and joints. About 20% of the bone in your body is spongy. 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 spongy 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 has 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.
What Causes Bone Loss?
Bone loss occurs when more bone is resorbed than is formed by the body. Many factors determine how much old bone is resorbed and how much new bone is made. Some factors people have control over (such as diet), but some factors are out of their control (such as age).
Most new bone is added throughout childhood and teenage years. As a result, bones become larger, heavier, and stronger (denser). Bone formation continues until the peak bone mass is reached. Peak bone mass (or bone density) is reached around age 30. After age 30, bone resorption slowly begins to exceed new bone formation. This leads to bone loss. Bone loss in women occurs fastest in the first few years after menopause, but bone loss continues into old age. Factors that can contribute to bone loss include having a diet low in calcium, not exercising, smoking, and taking certain medications such as corticosteroids. Corticosteroids are medications prescribed for a wide range of diseases, including arthritis, asthma, inflammatory bowel disease, lupus, and other diseases. Corticosteroids may cause osteoporosis when used frequently.
Men are also at risk for bone loss. Even though bone loss usually occurs later in life compared to women, men can still be at high risk for osteoporosis. By age 65, men catch up to women and lose bone mass at the same rate. Additional risk factors such as a small body frame, long-term use of corticosteroids (which are medications prescribed for a wide range of diseases, including arthritis, asthma, Crohn disease, lupus, and other diseases), or low testosterone (or sex hormone) levels can increase the risk of osteoporosis in men.
Functions of Bones
The skeleton of an adult human is made up of 206 bones of many different shapes and sizes. Added together, your bones make up about 15% of your body weight. Newborn babies are actually born with many more bones than this (around 300), but many bones grow together, or fuse, as babies become older. Some bones are long and thick, like your thigh bones. Others are thin, flat, and wide, like your shoulder blades.
Like a house is built around a supportive frame, a strong skeleton is required to support the rest of the human body. Without bones, it would be difficult for your body to keep its shape and to stand upright.
Bones form a strong layer around some of the organs in your body, helping to keep them safe when you fall down or get hurt. Your rib cage, for example, acts like a shield around your chest to protect important organs inside such as your lungs and heart. Your brain is another organ that needs a lot of protection. The thick bone layer of your skull protects your brain. For this purpose, being “thick-headed” is a very good thing.
Many of your bones fit together like the pieces of a puzzle. Each bone has a very specific shape which often matches up with neighboring bones. The place where two bones meet to allow your body to bend is called a joint.
Some bones, like your elbow, fit together like a hinge that lets you bend your arm in one specific direction. Other bones fit together like a ball and socket, such as the joint between your shoulder and arm. This type of joint lets you rotate your shoulder in many directions, or swing it all the way around in a circle like softball pitchers do.
The movement of our bodies is possible because of both joints and muscles. Muscles often attach to two different bones, so that when the muscle flexes and shortens, the bones move. This allows you to bend your elbows and knees, or pick up objects. A skeleton has plenty of joints, but without muscles, there is nothing to pull the bones in different directions. More than half of the bones in your body are actually located in your hands and feet. These bones are attached to many little muscles that give you very exact control over how you move your fingers and feet.
4. Blood Cell Formation
Did you know that most of the red and white blood cells in your body were created inside of your bones? This is done by a special group of cells called stem cells that are found mostly in the bone marrow, which is the innermost layer of your bones.
Bones are like a warehouse that stores fat and many important minerals so they are available when your body needs them. These minerals are continuously being recycled through your bones–deposited and then taken out and moved through the bloodstream to get to other parts of your body where they are needed.
Methods of building stronger bones
Building strong bones should start in childhood, and it’s something to work on throughout your life. Bones are made up of collagen and calcium. However, they’re far from the lifeless skeletons that appear every Halloween. Your body is continuously breaking down and renewing your bones through remodeling. Like remodeling a house, your body breaks down and discards old bone tissue and replaces it with new tissue. Keeping bones strong is particularly important for women because 1 in 2 women will have an osteoporosis-related fracture in their lifetime. For men, the lifetime risk is 1 in 4. While some people are naturally at a higher risk of weaker bones than others, there are many things you can do to build stronger bones throughout your life.
1. Sufficient Calcium
Calcium is an important nutrient for building bone and slowing the pace of bone loss. But it’s not a single magic bullet, and some scientists recommend that too much calcium or dairy products may be unhealthy. Keep in mind that in addition to calcium, there are other nutrients and foods that help keep your bones strong — most importantly vitamin D, but also vitamin K.
The recommended daily intake for calcium is 1,000 milligrams (mg) a day for adults up through age 50 and 1,200 mg a day for people ages 51 and older, when bone loss increase speed. With age, the intestines absorb less calcium from the diet, and the kidneys seem to be less efficient at conserving calcium. As a result, your body can steal calcium from bone for a variety of important metabolic functions.
Because some research suggest that high calcium intake may increase the risk of prostate cancer, men should avoid taking calcium supplements or taking too many calcium-rich antacids.
- Choose calcium-fortified soymilk, almond milk, and other dairy substitutes. Tofu can also be enriched with calcium. Some juices and other beverages have added calcium, too.
- Vegetable sources rich in calcium include turnip and collard greens, Chinese cabbage (bok choy), black-eyed peas, kale, and broccoli. Spinach is healthy, but it’s not as effective as a source of calcium as other greens because its oxalic acid content reduces the availability of its calcium to your body.
- Canned sardines and canned salmon are excellent sources of calcium because the bones are meant to be eaten. Sardines and salmon are also excellent sources of omega-3 fatty acids, which improve brain health and may contribute to better mood. They also contain vitamin D, which helps your body absorb calcium.
- Particularly for children, choose whole-grain breakfast cereals that have been fortified with calcium and other nutrients. These are a consistent source of calcium because so many people eat these cereals daily with milk. Sugary cereals, though, can promote obesity, so look for cereals that have low sugar.
2. Enough Vitamin D
In building bone, calcium has a crucial assistant: vitamin D. This vitamin helps the body absorb calcium, and some researchers think that increasing vitamin D can help prevent osteoporosis. Milk sold in the United States is fortified with vitamin D. Vitamin D is also prevalent in fortified breakfast cereals, eggs, and vitamin supplements. Some brands of yogurt are fortified with it, as well as some juices.
If possible, a small amount of sun exposure can help your body manufacture its own vitamin D — about five to 30 minutes of sunlight between 10 a.m. and 3 p.m. twice a week to your face, arms, legs, or back without sunscreen will enable you to make enough of the vitamin. People with fair skin that burns easily should protect themselves from skin cancer by limiting sun exposure to 10 minutes or less.
Food and sun exposure should suffice, but if not, some experts advise getting 1,000 IU of vitamin D daily from a supplement.
3. Regular Exercise
Physical activity during childhood and adolescence increases bone density and strength. Children who regularly exercise are more likely to reach their peak bone density (maximum strength and solidness) than those that do not exercise. People who reach their peak bone density, which usually occurs by age 30 years, are less likely to have significant bone loss that leads to osteoporosis.
The best exercise to prevent bone loss is weight-bearing exercise that works against gravity. These kinds of exercises include walking, hiking, jogging, climbing stairs, playing tennis, and dancing. The second type of exercise is resistance.
Elderly people, people with osteoporosis, and people who have not exercised for most of adulthood should check with their health-care provider before beginning any exercise program.
4. Quit Smoking
Smoking is bad for the bones as well as for the heart and the lungs. Women who smoke have lower estrogen levels compared to women who do not smoke. Lower estrogen levels lead to increased bone loss. Women who smoke often go through menopause earlier. Remember that bone loss is most rapid in the first few years after menopause, but it continues even in the postmenopausal years. This means that the earlier menopause occurs, the more years bone loss is experienced and the weaker the bones will become over time. Men and women who smoke may absorb less calcium from their diets. Less calcium from the diet means the body breaks down the bones for the calcium it needs, which leads to bone loss.
5. Limit Alcohol Intake
Regular consumption of 2-3 ounces of alcohol a day may be damaging to bones, even in young women and men. Heavy drinkers are more likely to have bone loss and fractures. This is related to both poor nutrition and increased risk of falling. However, some evidence indicates that moderate alcohol intake may have beneficial effects on bone mass.
6. Lighten up on coffee
Drinking 2-3 cups of coffee a day can weaken bones. That’s because caffeine inhibits with calcium absorption, particularly as women age.
If you’re not ready to go cold turkey, take these steps:
- Be sure to get at least the daily recommended calcium intake (1,000 mg for women ages 19-50).
- Add skim milk to your coffee. Fat-free milk has more calcium than whole milk, according to the NIH.
7. Choose bone-healthy foods
Milk and other dairy products aren’t the only calcium-rich foods. “To assimilate calcium into bone, you need vitamin K, magnesium and a range of trace minerals,” says Debra Brammer, ND, associate clinical dean of naturopathic medicine at Bastyr University in Kenmore, Wash. You’ll find these in leafy greens such as kale, Swiss chard, collard greens, and other vegetables like Brussels sprouts and broccoli. “Mix greens into soups and stews or just toss in oil and garlic and stir-fry,” Brammer says.
Bone building Foods
Just one cup of yogurt provides 300 to 400 mg of bone-building calcium.
2. Fermented foods (sauerkraut, miso, natto)
Fermented foods are well-known for being a rich source of probiotics, are also high in vitamin K2, which is the form of vitamin K that is responsible for depositing calcium into bones.
Spinach is an excellent source of vitamin K1, a fat-soluble vitamin that helps your body in the bone-building process. Vitamin K also plays a role in clotting, so if you take blood-thinning medication, discuss increasing your intake of vitamin K-rich foods with your healthcare provider.
4. Wild (Alaskan) salmon
Wild salmon is an excellent source of omega-3 fatty acids, which decrease inflammation that causes bone to be broken down. In addition, it is an excellent source of vitamin D, magnesium and phosphorus.
Walnuts are a good source of both manganese, a mineral important in creating bone’s connective tissue components, and the omega-3 fatty acid ALA.
Avocados are a good source of boron, which helps support production of bone-supporting hormones estrogen, testosterone, and DHEA, and may support calcium absorption.
7. Sesame seeds
Sesame seeds are an excellent source of copper, which is vital for bone mineralization.
8. Pumpkin seeds
One ounce of pumpkin seeds provides one-third of your daily needs for phosphorous, a mineral necessary for bone formation.
Childhood, adolescence and early adulthood up to mid-20s, when the skeleton is growing, are the time for building strong bones.
Young people aged five to 18 are recommended to do energetic intensity activities that strengthen muscle and bones, on at least three days a week.
Examples of muscle and bone-strengthening activities:
Under 5s not walking:
- tummy time
- active play
Under 5s walking unaided:
- running games
Children and young adults:
- ball games, such as football, basketball, hockey and netball
- racket sports, such as badminton, squash and tennis
- martial arts, such as karate and taekwondo
- skipping and jumping
- body weight exercises such as press-ups and squats/lunges
- exercise to music such as aerobics and boxercise
- rock climbing
- dance-related activities
Bone loss years
To reduce the rate of natural bone loss that occurs from age 35 onwards, aim to do muscle-strengthening activities at least two days a week.
Examples of other suitable activities for adults include:
- brisk walking, including Nordic walking
- moderate-resistance weightlifting
- stair climbing
- carrying or moving heavy loads such as groceries
- exercising with resistance bands
- heavy gardening, such as digging and shovelling
- cross-training machines
Interesting Bone Facts
- The smallest bone in the human body is called the stirrup bone, located deep inside the ear. It’s only about 2.8 mm long.
- The longest bone in the human is called the femur, or thigh bone. It’s the bone in your leg that goes from your hip to your knee. In an average adult, it’s about 20 inches long.
- The Femur is also the heaviest bone in the human body.
- In the olden days, whale bones were used to make corsets – for women and men. These corsets would squash in the person’s body so that they looked slimmer or a different shape.
- Animal bones have been used for playing games for thousands of years. Jacks or knucklebones and dice used to be made of bones – nowadays they are usually made of plastic.
- 1 in 8 men over the age of 50 has osteoporosis.
- 54 bones in the hand, fingers and wrists allow you to write, use a smartphone and play piano.
- The hands and feet contain over half of the body’s bones.
- Some people have an extra rib that can cause health issues.
- Ancient Egyptians developed the world’s first functional prosthetic bone.
- Human species have been dealing with bone tumors for 120,000 years.
- Sharks lose thousands of teeth in their lifetimes.
- Arms are among the most commonly broken bones, accounting for almost half of all adults’ broken bones.
- Bones stop growing in length during puberty.
- The only bone in the human body not connected to another is the hyoid, a V-shaped bone located at the base of the tongue.
- The only bone fully grown at birth is located in the ear.
- Human face is made up of 14 bones.
- Bones account for 14% of the body’s total weight.
- The strongest bone in the skeleton is the jawbone.
- A broken bone will take about 12 weeks to heal.
- Humans and giraffes have the same number of bones in their necks.
- Bones consist of 50% water and 50% solid matter.
- America is in a Calcium Crisis: 9 out of 10 women, 7 out of 10 men, and 3 out of 4 teenagers do not get enough calcium.
- Dinosaur bones were first found in Sussex in 1822 but it was not until 1841 that the word ‘dinosaur’ was coined by Sir Richard Owen.
- The ancient Greeks and Romans used sheep knucklebones as dice.
- Every second our bone marrow produces two million red blood cells.
- Over a period of about seven years, each bone in our body is slowly replaced until it is a new bone.
- Teeth are not counted as bones. They are considered part of the skeletal system, though.
- The jawbone is the only bone in your body you can actually move. It does so when you speak or eat.
- Osteoporosis is the Most Common Bone Disease.
- You should exercise at least 2½ hours every week for strong bones.