Name the plates that cause bones to grow in lenght?

Answer 1

The majority of the bones containing growth plates are the long bones (those found in the arms and legs). There is also an intermediate class of bones, called the short bones, that contain some minor growth plates, such as the bones in your fingers (the phalanges). If you think about it, this makes sense: the majority of the growth that happens, especially during your growth spurt as an adolescent, comes from extension in the length of your arms and legs.

Does that mean your other bones don't grow? Absolutely not. All your bones are constantly growing, even after maturity. The key thing to know here is that not only are your bones constantly growing, but they are also constantly being reabsorbed as well. Just like most of the other parts of your body, your bones are constantly being remade. As the older parts of your bones are being destroyed by certain cells in your body called osteoclasts, new bone is being made to replace it by other cells called osteoblasts. In an adult human, the balance between these two forces has a net of zero. The amount of bone that is being destroyed is counterbalanced exactly by the amount of new bone being made, so that over time there is no net difference, and in totality your bones don't seem to grow or shrink. Amazingly, 30 percent of bone in any human is generally destroyed and recreated every year.

As a child or even more importantly as an adolescent, there are signals being released throughout your body that tip this balance toward the positive, so that all your bones generally do grow, but this growth is more noticeable in thickness rather than in length. This explains how some of the flatter bones in your body, like your skull and your ribs, grow proportionally along with the rest of your body. However, if you think about it, the growth lengthwise in your arms and legs during adolescence is not in proportion with the rest of your body. In fact, it's completely out of proportion, which makes some adolescents look a little awkward.

The growth plate, found at both ends of the long bones, is a special zone that is not made of bone but rather of cartilage. The cartilage is made by special cells called chondrocytes that inhabit this growth plate zone. During adolescence, these chondrocytes make cartilage at a very fast pace in the long bones, adding to the length of the bones. This creates a scaffold from which the osteoblasts (the bone-making cells) can form bone quicker than they could otherwise. This process is jump-started by the release in the body of a growth factor called IGF.

However, this process doesn't last forever. The pace at which the osteoblasts turn the cartilage into bone is actually faster than the creation of new cartilage at the other side of the growth plate, so that over time the osteoblasts catch up to the chondrocytes making cartilage. As this happens, the growth plate gradually becomes thinner, until eventually it disappears. At the same time, IGF concentrations in the body also decrease (but not to zero). The lengthwise growth in the long bones stops, and you are as tall as you will ever be.

There can be problems in the regulation of bone growth. For example, some brain tumors can result in the secretion of too much IGF, the factor that causes bones to grow. When this happens in adults, osteoblasts will make bone faster than osteoclasts can destroy it, so the bones grow wider. This results in a disease called acromegaly. Another disease that results from disruptions in the balance of bone turnover is osteoporosis. In this disease, osteoclasts are too active, so that more bone is broken down than is being made. People with this disease, usually women, develop very weak bones that easily break.

In general, only bones in your arms and legs have growth plates, but all of your bones will continue to grow, even after you are an adult. However, they don't grow in length and they will only grow enough to keep from shrinking as other parts of the bone are being broken down.