An important part of the human musculoskeletal system is the skeleton, which consists of more than two hundred different bones. It enables people to move, supports internal organs. In addition, human bones are a concentration of minerals, as well as a shell that contains bone marrow.
Skeleton functions
Different types of bones that make up the human skeleton primarily act as a means of support and support for the body. Some of them serve as a container for certain internal organs, such as the brain located in the bones of the skull, the lungs and heart located in the chest, and others.
We also owe the ability to make various movements and move around to our own skeleton. In addition, human bones contain up to 99% of the calcium found in the body. Red bone marrow is of great importance in human life. It is located in the skull, spine, sternum, collarbone and some other bones. Bone marrow produces blood cells: erythrocytes, platelets andwhite blood cells.
Structure of bone
The anatomy of a bone has extraordinary properties that determine its strength. The skeleton must withstand a load of 60-70 kg - this is the average weight of a person. In addition, the bones of the trunk and limbs work as levers that allow us to move and perform various actions. This is due to their amazing composition.
Bones consist of organic (up to 35%) and inorganic (up to 65%) substances. The former include protein, mainly collagen, which determines the firmness and elasticity of tissues. Inorganic substances - s alts of calcium and phosphorus - are responsible for hardness. The combination of these elements gives the bones a special strength, comparable, for example, with cast iron. They can be perfectly preserved for many years, as evidenced by the results of various excavations. Organic substances can disappear as a result of calcination of tissues, as well as when they are exposed to sulfuric acid. Minerals are very resistant to external influences.
Human bones are permeated with special tubules through which blood vessels go. In their structure, it is customary to distinguish between compact and spongy substances. Their ratio is determined by the location of the bone in the human body, as well as the functions it performs. In those areas where resistance to heavy loads is required, a dense compact substance is the main one. Such a bone consists of many cylindrical plates placed one inside the other. The spongy substance in its appearance resembles a honeycomb. In its cavities isred bone marrow, and in adults it is also yellow, in which fat cells are concentrated. The bone is covered by a special connective tissue membrane - the periosteum. It is permeated with nerves and vessels.
Classification of bones
There are various classifications that cover all types of bones of the human skeleton, depending on their location, structure and function.
1. By location:
- cranial bones;
- torso bones;
- bones of limbs.
2. According to development, the following types of bones are distinguished:
- primary (appear from connective tissue);
- secondary (formed from cartilage);
- mixed.
3. The following types of human bones are distinguished by structure:
- tubular;
- spongy;
- flat;
- mixed.
Thus, different types of bones are known to science. The table makes it possible to present this classification more clearly.
| By location | Development | By structure |
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Tubular bones
Tubular long bones are composed of both dense and spongy matter. They can be divided into several parts. The middle of the bone is formed by a compact substance and has an elongated tubular shape. This area is called the diaphysis. Its cavities first contain red bone marrow, which is gradually replaced by yellow, containing fat cells.
At the ends of the tubular bone is the epiphysis - this is the area formed by the spongy substance. Red bone marrow is placed inside it. The area between the diaphysis and the epiphysis is called the metaphysis.
During the period of active growth of children and adolescents, it contains cartilage, due to which the bone grows. Over time, the anatomy of the bone changes, the metaphysis completely turns into bone tissue. The long tubular bones include the thigh, shoulder, bones of the forearm. Tubular small bones have a slightly different structure. They have only one true epiphysis and, accordingly, one metaphysis. These bones include the phalanges of the fingers, the bones of the metatarsus. They function as short movement levers.
Spongy types of bones. Pictures
The name of the bones often indicates their structure. For example, spongy bones are formed from a spongy substance covered with a thin layer of compact. They do not have developed cavities, so the red bone marrow is placed in small cells. Spongy bones are also long and short. The former include, for example, the sternum and ribs. Short spongy bones are involved in the work of muscles and are a kind of auxiliary mechanism. These include the bones of the wrist, vertebrae.
Flat bones
These kinds of bonesof a person, depending on their location, have a different structure and perform certain functions. The bones of the skull are primarily protection for the brain. They are formed by two thin plates of dense substance, between which is located spongy. It has openings for veins. The flat bones of the skull develop from connective tissue. The scapula and pelvic bones also belong to the type of flat bones. They are formed almost entirely from a spongy substance that develops from cartilage tissue. These types of bones perform the function of not only protection, but also support.
Mixed dice
Mixed bones are a combination of flat and short spongy or tubular bones. They develop in different ways and perform the functions that are necessary in a particular part of the human skeleton. Such types of bones as mixed are found in the body of the temporal bone, vertebrae. These include, for example, the collarbone.
Cartilage tissue
Cartilage has an elastic structure. It forms the auricles, nose, some parts of the ribs. Cartilaginous tissue is also located between the vertebrae, as it perfectly resists the deforming force of loads. It has high strength, excellent resistance to abrasion and crushing.
Connection of bones
There are different types of bone connections that determine the degree of their mobility. The bones of the skull, for example, have a thin layer of connective tissue. However, they are absolutely immobile. Such a connection is calledfibrous. Between the vertebrae are also areas of connective or cartilaginous tissue. Such a connection is called semi-movable, since the bones, although limited, can move a little.
The joints that form synovial joints have the highest mobility. The bones in the joint bag are held by ligaments. These fabrics are both flexible and durable. In order to reduce friction, a special oily fluid, synovia, is located in the joint. It wraps around the ends of the bones, covered with cartilage, and facilitates their movement.
There are several types of joints. As the name of the bones is determined by their structure, so the name of the joints depends on the shape of the bones that they connect. Each type allows you to make certain movements:
- Spherical joint. With this connection, the bones move in many directions at once. These joints include the shoulder, hip.
- Block joint (elbow, knee). Assumes movement exclusively in one plane.
- The cylindrical joint allows the bones to move relative to each other.
- Flat joint. It is immobile, providing small range of motion between two bones.
- Ellipsoid joint. Thus, for example, the radius is connected to the bones of the wrist. They can move from side to side within the same plane.
- Thanks to the saddle joint, the thumb can move in different planes.
Influence of physical activity
The degree of physical activityhas a significant effect on the shape and structure of bones. In different people, the same bone can have its own characteristics. With constant impressive physical exertion, the compact substance thickens, and the cavity, on the contrary, shrinks in size.
Negatively affects the condition of the bones of a long stay in bed, a sedentary lifestyle. Fabrics become thinner, lose their strength and elasticity, become brittle.
Changes under the influence of physical activity and the shape of the bones. Those places where muscles act on them can become flatter. With particularly intense pressure, small depressions may even occur over time. In areas of strong stretching, where ligaments act on the bones, thickenings, various irregularities, and tubercles can form. Such changes are especially typical for people who are professionally involved in sports.
The shape of the bones is also affected by a variety of injuries, especially those received in adulthood. When a fracture heals, all kinds of deformities can occur, which often negatively affect a person’s ability to effectively manage their body.
Age-related changes in bones
In different periods of a person's life, the structure of his bones is not the same. In infants, almost all bones consist of a spongy substance, which is covered with a thin layer of compact. Their continuous, up to a certain time, growth is achieved due to an increase in the size of cartilage, which graduallyreplaced by bone tissue. This transformation continues until the age of 20 for women and until about 25 for men.
The younger the person, the more organic matter is contained in the tissues of his bones. Therefore, at an early age, they are distinguished by elasticity and flexibility. In an adult, the volume of mineral compounds in bone tissue is up to 70%. At the same time, from a certain point, a decrease in the amount of calcium and phosphorus s alts begins. Bones become brittle, so fractures often occur in older people, even as a result of a minor injury or sudden, careless movement.
Such fractures heal for a long time. There is a special disease characteristic of the elderly, especially women - osteoporosis. For its prevention, upon reaching the age of 50, it is necessary to consult a doctor for some research to assess the condition of the bone tissue. With appropriate treatment, the risk of fractures is significantly reduced and the healing time is shortened.
