When a baby is born, it has about 350 bones, all soft because they are composed mostly of a watery substance called cartilage. As the baby grows, calcium phosphate permeates the bones, and they stiffen. This process is called calcification. Eventually calcified cartilage is replaced by true bone, made up largely of calcium phostate, and some of the bones fuse together. An adult has between 206 and 209 bones in his body, depending upon whether he has one or two additional ribs and an extra bone in the coccyx (tailbone).

Calcium phosphate is deposited in bones in two ways. At the outer edge it takes the form of a solid, compact material covered by a membrane called the periosteum. Deeper inside, it becomes a honeycomb of sponge-like, porous material called cancellous bone. A soft material known as marrow fills the spaces inside the cancellous bone. Marrow is actually the manufacturing site of both red and white blood cells, and as such is tunnelled with vessels that move freshly made red and white blood cells out and bring in red ones containing essential nutrients.

Although bones generally stop growing in length during mid-teens for girls and at around age 20 for boys, they never really stop the growing process, because they are constantly rebuilding themselves. Bones contain two types of cells, osteoblasts and osteoclasts. These work together to continually build new bone material on the outside and remove old, unneeded material from the inside. To sustain this growth, the body must have sufficient supplies of certain nutrients including calcium, phosphorus and vitamin D. If there is a shortage of calcium in the bloodstream, the body will remove it from the bones without replacing it. This can eventually cause bones to become weak and porous. Unchecked, it can lead to a severely lifestyle-limiting, sometimes fatal condition known as osteoporosis

Connections
Joints have been called masterpieces of engineering because they are designed to permit movement between bones that must meet, but not touch each other. Their role is to bind two or more bones firmly together while cushioning and lubricating them well enough to last through a lifetime of lifting, swinging, bending, walking, etc.

While their individual construction may vary, most joints are made up of the same elements. The joint is enclosed in a tough, fibrous capsule of connective tissue that secretes a liquid called synovial fluid. The synovial fluid lubricates the moving parts. Outside the capsule, fibrous anchors called ligaments surround the joint and link the bones. Ligaments protect the capsule and help keep all motion of the joint within safe limits. In places where muscle tissues, called tendons or sinews, pass next to large joints so that muscles on one side will be linked to bones on the other, small fluid-filled pouches, or bursae, also act as buffers.

Muscles
Bones and sinews may control the movements of the body, but muscles create them by converting chemical energy from food into mechanical energy.

Muscles perform their work by contracting. This means that they pull, never push, and because of this it takes a pair of them to make a range of movement possible. There are more than 600 muscles in the body consisting of three basic types: heart muscle, smooth muscle, and skeletal muscle. Each muscle is made up of innumerable tiny, string-like fibres, and each of these, in turn, is composed of bundles of infinitesimal filaments varying in length from half an inch to about a foot. Small muscles have just a few fibres, while large ones have a great many.

Muscles grow strong through use. The effort it takes to use muscles makes the heart supply them with more blood and nutrients. This stimulates the growth of new muscle fibres and blood vessels. In effect, exercise enlarges and strengthens muscles just as it does bones.

Regular, lifelong activity is essential to keeping bones and muscles functioning optimally. If a person is never very active, his/her bones won't be able to grow as dense as nature meant them to be. Likewise, if a person is active enough to develop the strongest skeleton possible, but then becomes inactive, the bone that is no longer needed will eventually be lost.

Diet is also extremely important. As mentioned earlier, a shortage of calcium over an extended period of time can spell disaster. In fact, the loss of calcium is the most serious nutritional problem experienced by older Europeans. Bone loss appears to begin as early as age 35, and is particularly serious for women. As they approach menopause, their rate of bone loss accelerates greatly, partly because of a decreased secretion of the hormone oestrogen, which helps maintain bone mass. Men, too, should be cautious, although the number of men experiencing serious loss is only about one-fifth that of women. The National Institutes of Health suggests that a daily calcium intake of at least 1,200 mg is required by adults. Because it is difficult to obtain that amount from food alone, and because some individuals may be allergic to the best dietary sources of calcium, supplementation is recommended

Each hair has three layers, with colour forming in the middle. Its shape and texture is determined by the shape and size of the follicle from which it grows. Cross sections of hair show that straight hair tends to be round, while curly hair is flat or oval. The number of active follicles per square inch determines whether hair is thick or thin, while coarseness or fineness describes the width of the hair itself.

Fingernails have long been known as an indicator of health, and any dramatic changes in their texture, shape, colour or growth rate may be a signal to see a health care professional.

Internal skincare begins with proper nutrition, including whole grains and plenty of fresh fruits and vegetables. It also includes drinking plenty of fresh, pure water, which helps to hydrate skin from the inside out as it helps flush toxins out of the body.

Obesity can make an individual prone to eczema, rashes and fungal infections largely because extreme weight makes people sweat too much. This generally interferes with the body's own systems of self-disinfection.

At the other extreme, a diet containing too few calories can give skin a withered dry, rough, inelastic and even cold appearance. Adequate amounts of nutrients including the B-complex vitamins, vitamin C, vitamin A, vitamin K, essential fatty acids, the minerals zinc and iron, and protein are all important foi healthy skin and hair, as are exercise and rest. Finally, stress has been called one of the biggest enemies of beautiful skin.

For external skincare, a good daily treatment regimen is vital. This can help maintain the skin's current state of health by nourishing and protecting it, as well as removing any oily buildup of debris that accumulates throughout the day.

Like skin, hair is affected by diet, cleanliness and stress. Proper nutrition is essential for healthy hair that looks its best, while thinning hair can sometimes signal anaemia or a hormonal problem. One note: Although the skin on the head renews itself about once a month, occasionally the rate of this regeneration becomes unusually rapid. The result is flaky dead skin cell known as dandruff.

The health of nails can be affected by things as obvious and simple as exposing them to harsh chemicals (while cleaning, etc) or continual moisture. Nutrition also plays an important role. In fact, whitening of the nails may indicate a protein deficient diet, whereas spooning, when the nails become concave, may signal iron deficiency.