What are bones made of

Bones can be said to be a very important component of the human body. Bones already exist when we are born. When we are young, our bones are not fully developed and are still relatively soft. However, as we grow older and take in various nutrients, our bones continue to grow until we reach adulthood. So, what are bones made of? Mainly cells and minerals!

Bone tissue is made up of a mixture of living cells and minerals (mainly calcium and phosphorus), which give bones their solid physical properties.

Bones come in different shapes and sizes, for example, arm bones are long bones, wrist bones are short bones, the sternum and skull are flat bones, and vertebrae are irregular bones. The bones of adults are mainly composed of two types of tissues: hard compact bone on the outside and porous cancellous bone, also known as spongy bone, on the inside. The thigh bone, or femur, is filled with fat called yellow marrow.

Bones grow in a unique way: first new cells are formed, then these cells produce a special organic substance that becomes the matrix around themselves, and finally calcium salts are deposited in the matrix, making it gradually harden.

Human bones begin to form as early as the second month of gestation. After that, their bones continue to grow until around the age of sixteen for girls and around the age of eighteen for boys. The sternum stops hardening at around the age of 25, but the strength and calcium content of other bones continue to increase until around the age of 35. Throughout most of a person's life, bones are constantly being remodeled and bone tissue is constantly being consumed and replenished.

During the fetal period, bones are formed in two ways. The bones of the skull vault begin to grow in a connective tissue membrane, while most other bones begin as "rudimentary" cartilage. The embryonic cartilage is similar to real bone, but it is softer and suitable for rapid growth, and will eventually be replaced by real bone. The embryonic cartilage is gradually replaced by bone tissue. The process of replacing long bones begins in the center of the shaft and at the ends of the bone; eventually only a thin layer of cartilage, called a growth plate, is left between the shaft and the ends. The growth plates continually form new cartilage, which is then replaced by true bone, allowing the bone to grow.

The main component of bones is calcium carbonate. The average calcium content in an adult's body is 1000 to 1250 grams, 99% of which is concentrated in bones and teeth, and the remaining 1% of calcium exists in cells, extracellular fluid and blood, which is called miscible calcium. There is a state of mutual transformation between the calcium in the bones and the soluble calcium outside the bones. That is, the calcium in the bones is constantly dissolving into soluble calcium, and at the same time, the soluble calcium is constantly deposited into bones. In this process of dissolving bones and forming bones at the same time, if the amount of calcium dissolved is equal to the amount of calcium deposited, it is called a balanced state. If more calcium dissolves and less calcium is deposited in the same period of time, osteoporosis will occur.

The length of human bones generally stabilizes at around the age of eighteen, which means they will no longer grow taller. However, bone density continues to increase. After the age of 40, bone density begins to show a downward trend. The speed of descent depends on the person's physical condition. Generally, people who are physically active or like sports progress more slowly.