Spongy bones. Scheme of spongy bone. Structure of a spongy bone

The human skeleton consists of more than 200 bones. All of them perform a certain function, on the whole creating a support for external and internal organs. Depending on the load and role in the body, distinguish several of their varieties.

Structure of bones

In dry form, human bone by 1/3 consists of an organic substance - an osteine protein. It provides its flexibility and elasticity. 2/3 are inorganic calcium salts, due to which their strength is achieved.

The outer shell is the so-called compact substance. These are dense scales of bony tissue. The densest layer of them can be observed in the center of the tubular bones. To their edges, the compact substance becomes thinner.

Depending on the type of bones, the inner part of them may consist of either a spongy substance or a white bone marrow, or it can be filled with air. Spongy bones, in addition, also have red bone marrow.

At the ends, the bone enters the nerves and blood vessels that connect it to the entire body and provide nutrition, growth and recovery.

Varieties of bones of the human body

By structure, the bones are divided into spongy, tubular and pneumatic. Tubular is also called long. They are present in the skeleton of the limbs and are responsible for their movement. These bones consist of a compact substance and a cavity filled with yellow bone marrow. At the ends they have a little spongy substance, filled with red bone marrow.

Spongy bones of a man consist entirely of a spongy substance with a red bone marrow inside, they are covered with a compact substance. They form cavities (thoracic, cranial) and serve as a support in places with the greatest load (spine, phalanges of fingers).

Pneumatic bones have a special structure: inside the compact substance is a cavity, sent by epithelium and filled with air. An example is the skeleton of the upper jaw.

Spongiform bones: detailed scheme

As already noted, the basis of the spongy bone is practically not different from the others. It is a cavity formed by a compact substance and filled with a spongy substance. By origin they are different. Bones of the ribs, for example, are formed from cartilaginous tissue, and the skull covers - from the connective.

Spongy substance consists of a set of thin bone septa, directed in accordance with the movement of substances in the bone. This structure allows you to achieve stronger bones. They break less often and crack.

On the edges of the bones is a cartilaginous tissue, through which nutrients enter and the endings of the nerves penetrate.

The cavities of the spongy substance are filled with red bone marrow, responsible for the formation of erythrocytes. This pattern of spongy bone allows it to perform several very important functions at once.

Varieties

In the structure of the human skeleton, spongy bones have a quantitative advantage. Therefore, scientists distinguish several of their varieties.

There are flat and three-dimensional bones. Flat form the lid of the skull and pelvic cavity. This includes the shoulder blades. Volumetric represented by the ribs and phalanges of the fingers. The vertebrae is referred to a mixed type, since their body consists of a voluminous tubular bone, and the process is flat.

In size, it is customary to allocate long and short spongy bones. One of the longest are the ribs. To the short belong the bones of the phalanx of the fingers and toes.

A unique bone can be called a scapula. It is attached to the body only with connective tissue, while most of the bones are jointed.

Functions of sponge bones

The first and main function performed by spongy bones is the supporting one. They create the basic skeleton of the human skeleton. Vertebrae form the spine, supporting the whole organism in an upright position. The bones of the foot hold the entire body weight.

The second function is protective. Human spongy bones create and surround cavities, protecting their contents from external injuries. This is the skull cap, ribs and pelvic bones.

The motor function is performed by the bones of the phalanges of the toes and hands.

When metabolic disorders occur, the bones can become very brittle or extremely durable. In both cases, this is dangerous for normal human activity.

The internal filling of bones - the bone marrow - plays a major role in the formation of blood.

Significance of red bone marrow

In the human body, the pattern of spongy bone assumes the obligatory presence of red bone marrow in it . It is so important for vital activity that it is present even in tubular bones, but in less quantity.

In childhood, spongy and tubular bones are equally filled with this substance, but with age the tubular cavities gradually fill with the fatty yellow bone marrow.

The main task of the red bone marrow is the synthesis of erythrocytes. As you know, these cells do not have a nucleus and can not share themselves. In the spongy substance, they mature and enter the bloodstream during metabolism in the bones.

Disruption of the functioning of the red bone marrow entails diseases such as anemia and varieties of blood cancer. Often, drug treatment is not effective and one has to resort to red brain transplantation.

This substance is very sensitive to radiation. Therefore, many victims of it have precisely a variety of forms of blood cancer. This same property is also used in transplantology, when it is necessary to kill infected cells of the bone marrow.

Possible damage

By its nature, the structure of the spongy bone allows it to be quite resistant to mechanical damage. But often there are cases when the integrity of the bone is broken.

Compression fractures are characterized by contraction of bone due to a strong impact on it. This kind of damage is very susceptible to vertebrae. You can get injured during an unsuccessful landing on your feet or falling. The danger of a fracture is that the vertebra ceases to protect the spinal cord, which can lead to its damage.

Because most of the long sponge bones are curved, they can crack during strong bumps against hard objects. Such damage is relatively safe. With the timely provision of medical care, the cracks heal fairly quickly.

Can spongy bones and break. In some cases, injuries of this kind are practically not dangerous. If there was no bias, they are restored fairly quickly. The danger is made by those bones that, when fractured, can move and pierce vital organs. In this case, a relatively harmless fracture becomes the cause of disability and death.

Bones and age changes

Like all other human organs, spongy bones are subject to age-related changes. At birth, some of the future bones are either not strengthened or formed from cartilage and connective tissue.

Over the years, bones tend to "dry up". This means that in their composition the amount of organic substances becomes smaller, while the mineral substances replace them. The bones become brittle and recover longer after damage.

The amount of bone marrow is also gradually decreasing. Therefore, older people are prone to anemia.