ossification

General

Ossification refers to the formation of boil.
A distinction is made between the formation of the bone from connective tissue, which is referred to as desmal ossification, and chondral ossification, in which the bone is formed from an already existing cartilage.
As a rule, ossification is a natural process that builds up the incomplete skeleton, especially in childhood. However, increased ossification can also occur in the context of diseases, which can certainly cause discomfort, namely when the bone grows where it is not intended.

Bone building

In order to understand ossification, it is extremely helpful to know the structure of a bone, so here are some basics about bones.
Basically there are different forms of bones, on the one hand the typical tubular bones, which, as the name suggests, are elongated. Typical representatives are the humerus, which medical professionals call it Humerus referred to, or the thigh bone, the Femur is called.
The inside of these bones is filled with bone marrow that is well supplied with blood.
There are also so-called flat bones, which are more flat, such as most skull bones. Then there are so-called "Sesame bones“, Which look rather rounded and atypical, for example the kneecap or some hand bones.
There are also exotic species such as the air-filled bones, which are hollow on the inside, that is, the bones of the facial skull that contain the sinuses.
The head of long bones is called "Epiphysis", The transition to the actual" pipe "as Metaphysis and the pipe itself is called Diaphysis designated.

The individual bone consists of a fine periosteum that completely surrounds it. It contains the "Compacta"Or"Corticalis“In other words, a particularly dense bone structure that gives the bone its strength. The fibers of the fabric are uniformly aligned, which gives them additional strength.
Inside there is a looser structure called "cancellous bone", which means something like spongy. The bone marrow cavity is located right inside. It contains either fat marrow or blood-forming red bone marrow with very good blood circulation.

The bone tissue itself is a mixture of inorganic and organic substances and a quarter of water. The inorganic components consist mainly of hydroxyapatite, which is composed of calcium and phosphate.

Next to that is also the organic one Collagen present in the bone. This is a proteinwhich is also found in the skin. Individual cells, the so-called "Osteoblasts" and "Osteoclasts". The osteoblasts produce the bone substance and are connected to one another by fine tubules. The osteoclasts, in turn, are the opponents and break down the bone.

As mentioned, the bones in the compacta are arranged uniformly. That is why they are also called Lamellar bone designated. They are the typical bone structure.
At a Broken bone on the other hand, it is first imagined Braided bone, in which the fibers of the tissue grow back and forth through each other. Only gradually does the bone become lamellar bone again, which is then full again stability can reach.

Desmal ossification

The desmal ossification happens from connective tissue. This is from Mesenchymal cells educated.
In ossification, the cells are first close together and then become getting better blood circulation. Then change the mesenchymal cells to Osteoblasts, the cells that make up bones. These then first form the organic parts of the new bone such as collagen.
Then they become in the osteoblasts Calcium vesicles formed that are released. These vesicles burst then and calcium crystals become free. These crystals enlarge and eventually become Hydroxyapatite.
The osteoblast is completely surrounded by bone substance at the end and is then called Osteocyte designated. The one that has now arisen tiny bones eventually settle other osteoblasts and in turn form bone material, so that the bone finally “appositionally”, i.e. by accumulation grows.
Typically be Bones of the skull formed by desmal ossification. Also Broken bones first heal through desmal ossification.

Chondral ossification

In contrast to the previous mechanism, the bone in the chondral ossification from cartilage educated. The bone is first created as cartilage and only replaced by bone in the course of development. Because the bone is first created as cartilage, the chondral ossification is also called indirect ossification designated.

One differentiates even further between perichondral and enchondral ossification. In children, for example, perichondral ossification occurs on the diaphysis, i.e. the shaft of the Humerus instead of. Form here Osteocytes initially one Bone cuff around the cartilage model of the bone. Strictly speaking, perichondral ossification is actually a desmal ossification, as it does not require any cartilage cells.
The typical chondral ossification but takes place directly in the cartilage and is called enchondral growth designated.
In which Humerus finds this ossification on Height of the epiphysis instead of. Here divide in a so-called Proliferation zone the cartilage cells increased.
Because the bone cuff around the cartilage prevents it from expanding in width, the new Cartilage cells arranged lengthways. In this way grows the bone in length.
Further towards the end of the bone, the cartilage cells become larger and calcified. Finally the cartilage cells die and the osteoblasts, i.e. cells that build up bones, begin with the ossification. The Zonein which the bone grows is called Epiphyseal plate designated.
As long as there are cartilage cells in the epiphyseal plate, the bone can grow in length.
Usually the epiphyseal plate closes at the age of 19. By Broken bones through the joint the Ossification considerably disturbed and the growth in length lags behind that of the rest of the body.

Disorders of ossification

Both Diseases, which affect ossification, a distinction is made between diseases that change normal ossification and diseases that lead to one excessive ossification to lead.

A typical disorder of ossification is the Achondroplasiathat to one premature closure of the epiphyseal plates leads. Because there is no longer any cartilage in the long bones, the bone can no longer grow in length because the cartilage cells are missing.
The Thickness growth of the bone is in achondroplasia not affected, because perichondral growth does not need cartilage cells as a precursor. In patients with achondroplasia, the long bones tend to grow in width.
Since the Skull bones arising from desmal ossification is the growth of the skull unaffectedso that the head becomes a normal size and appears too large compared to the extremities. Also the Vertebrae and ribs are Not from achondroplasia affected, so that those affected usually reach almost a normal seat height.

A pathological ossification is the so-called heterotopic ossification, in which "heterotopic"Means"occurring in a different location“.
So there are areas that ossify normally connective tissue should be. It happens often after serious injuries to this heterotopic ossification. It does not matter whether the injury was caused by a accident or one surgery was caused.
The tissue damage stimulates the body, Messenger substances to produce the progenitor cells of bone in tissue to stimulate cartilage to bone. This process will mostly one to two weeks after an operation by pain and redness without any evidence of inflammation in the blood.
After a month can the new bones seen in the X-ray become. Most bone formations do this, however no complaints in the long run and are not noticed.
On the other hand, larger bones alone can do this mechanically Significantly reduce the range of motion of joints. Whether such an excessive ossification occurs depends on the Severity of injury from: Multiple injuries are more likely than patients with simple fractions, patients with Hip replacement more than such with Shoulder surgery. Also Infections and Bruising seem to increase ossification.

Vitamin D in newborns

Another ossification disorder is that rickets.
Rickets is a consequence of Vitamin D deficiency in early childhood. This vitamin deficiency is triggered on the one hand by the immense metabolism that the affected newborns have, but also by lack of sun exposure and vegetarian diet.
Typical complaints are at the beginning Muscle weakness and Softening of the bones at the skullthat eventually turned into a Malformation of the head shape pass over. Also arise Curvature of the legsthat lead to poor posture in later life.
Vitamin D is essential for that Absorption of calcium in the intestine, so that an undersupply of vitamin D also automatically becomes one Calcium deficiency leads. Since the bones largely consist of calcium, the bones can no longer be formed properly and the Ossification is disturbed. For this reason, infants are usually given vitamin D in their first year of life.