Bone

A bone is a rigid organ that constitutes part of the skeleton in vertebrates. The human body contains 206 bones, which make up about one tenth of the body's weight.

Bone tissue is a type of dense connective tissue.

The bones in your body are connected to each other at junctions termed joints. Some joints, such as your elbow, are basically hinges_ that permit movement in only a single plane. By contrast, ball and socket joints, such as your hip and shoulder, allow a much wider range of motion.

Contents

1   Functions

Bones provides a framework that encases and protects your body's vital internal organs. For example, ribs surround and protect your lungs, heart, liver, and kidneys, while your skill encases the delicate tissue of the brain. The spinal column shield the spinal cord. Bone in the pelvic girdle protect the bladder as well as the reproductive organs.

Bones also server as a repository for vital minerals such as calcium and phosphate_, while the marrow, a spongy core of tissue located in the center of certain bones, manufactures new blood cells.

Bones support and protect the various organs of the body, produce red and white blood cells, store minerals and also enable mobility.

The body can compensate for a temporary deficit in the amount of calcium in the diet by removing calcium from the huge reserves in bone. [7]

2   Properties

Bone is one of the hardest structures of the animal body. Its color, in a fresh state, is pinkish-white externally and deep red within. [1]

3   Substance

Bones come in a variety of shapes and sizes and have a complex internal and external structure.

Bone is composed of two kinds of tissue: compact tissue and cancellous tissue. [1]

Compact tissue is dense in texture, like ivory.

Cancellous tissue (so called from its resemblance to lattice-work)[1]_ consists of slender fibers and lamelle, which join to form a reticular structure.

The relative quantity of these two kinds of tissue varies in different bones, and in different parts of the same bone, according as strength or lightness is requisite.

At an atomic level, bone is composed of calcium (18%). [7]

While the materials in teeth and bone are very similar their arrangement is different. Bone is somewhat similar to a composite material made up of a mixture of collagen fibers and hydroxyapatite crystals with living cells that manage both materials. Teeth have a very similar structure inside (dentin) but in order to have the strength and toughness to serve their purpose and avoid infection the outside of the tooth (enamel) is made up of pretty much entirely hydroxyapatite with no living cells. This is why teeth can't heal like bones can.

4   Diseases

4.1   Rickets

Rickets is a disease that causes soft and bent bones, curved spines, bowed legs, "pigeon" chests, and malformed teeth. It was a problem until the discovery of `Vitamin D`_.

Often called "the English disease," rickets had become common in cities in the northern hemisphere since the Industrial Revolution; by the early 20th century, some estimates put its incidence among children in New York’s teeming, tenement-bound immigrant population at 90 percent.

After spending two years testing diets and therapies, Harriette Chick and members of her team proved definitively that the disease was not an infection. It could be prevented, even cured, they found, by two things: One was cod liver oil. The other was sunshine. [8]

5   References

[1](1, 2) Henry Gray. Anatomy of the Human Body. http://www.medicalcity-iq.net/medlib/Anatomy%20of%20the%20Human%20Body.pdf
[7](1, 2) Human Nutrition. http://users.rcn.commball.ma.ultranet/BiologyPages/N/Nutrition.html/
[8]Brian Alexander. 2013-09-26. THE MILKMAN COMETH. http://www.cincinnatimagazine.com/features/the-milkman-cometh/