Types of bones. Human Anatomy: Bones

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

Various types of bones that make up the human skeleton, primarily act as a means of support and support of the body. Some of them serve as a container for certain internal organs, for example, the brain located in the bones of the skull, lungs and heart located in the chest, and others.

The ability to make various movements and move, we also owe our own skeleton. In addition, human bones contain up to 99% of the calcium in the body. Of great importance in human life is the red bone marrow. It is located in the skull, spine, sternum, collarbone and some other bones. Blood cells are born in the bone marrow: red blood cells, platelets and white blood cells.

Bone structure

Bone anatomy 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, allowing us to make movements and perform various actions. This is achieved due to their amazing composition.

Bones are composed of organic (up to 35%) and inorganic (up to 65%) substances. The first include protein, mainly collagen, which determines the firmness and elasticity of tissues. Inorganic substances — calcium and phosphorus salts — 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 matter can disappear as a result of calcination of tissues, as well as when exposed to sulfuric acid. Minerals are very resistant to external influences.

Human bones are penetrated by special tubules along 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 its functions. In those areas where resistance to heavy loads is required, the main thing is a dense compact substance. Such a bone consists of many cylindrical plates placed one on top of the other. Spongy substance resembles a honeycomb in its appearance. In its cavities there is a red bone marrow, and in adults - also yellow, in which fat cells are concentrated. The bone is covered by a special connective tissue membrane - the periosteum. It is penetrated by nerves and vessels.

Bone classification

There are various classifications that cover all types of bones of the human skeleton, depending on their location, structure and functions.

1. By location:

• cranial bones;
• bones of the body;
• bones of limbs.

2. By 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, science knows various types of bones. The table makes it possible to more clearly present this classification.

Tubular bones

Tubular long bones consist of both dense and spongy substance. 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.

The pineal gland is located at the ends of the tubular bone - this is the area formed by the spongy substance. Inside it is placed a red bone marrow. The area between the diaphysis and the pineal gland is called the metaphysis.

During the period of active growth of children and adolescents, it contains cartilage, due to which 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, and bones of the forearm. Tubular small bones have a slightly different structure. They possess only one true epiphysis and, accordingly, one metaphysis. These bones include the phalanges of the fingers, bones of the metatarsus. They function as short levers of movement.

Spongy types of bones. Images

The name of the bones often indicates their structure. For example, spongy bones are formed from a spongy substance coated with a thin layer of compact. They do not have developed cavities, so the red bone marrow is placed in small cells. The 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 types of human bones, depending on their location, have a different structure and perform certain functions. The bones of the skull are, above all, protection for the brain. They are formed by two thin plates of dense matter, between which a sponge is located. It contains openings for veins. The flat bones of the skull develop from connective tissue. The shoulder blade and pelvic bones are also flat bones. They are formed almost completely from the spongy substance, which develops from cartilage. These types of bones perform the function of not only protection, but also support.

Mixed bones

Mixed bones are a combination of flat and short spongy or tubular bones. They develop in various ways and perform the functions that are necessary on a particular section 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 clavicle.

Cartilage

Cartilage tissue has an elastic structure. It forms the auricles, nose, and some parts of the ribs. Cartilage tissue is also located between the vertebrae, as it perfectly resists the deforming force of the loads. It has high strength, excellent resistance to abrasion and compression.

Bone joint

There are different types of bone joints that determine their mobility. The bones of the skull, for example, have a thin layer of connective tissue. Moreover, they are absolutely motionless. Such a compound is called fibrous. Between the vertebrae there are also areas of connective or cartilage tissue. Such a connection is called semi-mobile, since the bones, although with a limitation, can move a little.

The joints with the synovial joints possess the highest mobility. The bones in the joint bag are held by the ligaments. These fabrics are both flexible and durable. In order to reduce friction, a special oily fluid is in the joint - synovia. It envelops the ends of the bones, covered with cartilaginous tissue, 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, bone movement is possible in many directions at once. Such joints include the humeral, hip.
• Block joint (ulnar, knee). It involves movement exclusively in one plane.
• The cylindrical joint allows the bones to move relative to each other.
• Flat joint. It is inactive, provides small-scale movements between two bones.
• Ellipsoid joint. Thus, for example, the radius is connected with the bones of the wrist. They can make side-to-side movements within the same plane.
• Thanks to the saddle joint, the thumb can move in different planes.

The effect of physical activity

The degree of physical exertion has 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.

A negative effect on the condition of the bones is a prolonged stay in bed, a sedentary lifestyle. Fabrics become thinner, lose their strength and elasticity, become brittle.

The shape of the bones also changes under the influence of physical exertion. Those places where they are affected by muscles can become flatter. At particularly intense pressures, even small depressions may even occur over time. In areas of strong tension, where ligaments act on bones, thickenings, various irregularities, and tubercles can form. Such changes are especially characteristic of people who are professionally involved in sports.

A variety of injuries, especially those received in adulthood, also affect the shape of bones. When the fracture is fused, all kinds of deformations can occur, which often negatively affect a person's ability to effectively control his body.

Age-related bone changes

At 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, until a certain time, growth is achieved due to an increase in the size of the cartilage, which is gradually replaced by bone tissue. This transformation lasts up to 20 years in women and about 25 in men.

The younger the person, the more organic matter is found in the tissues of his bones. Therefore, at an early age they are flexible and flexible. In an adult, the volume of mineral compounds in bone tissue is up to 70%. At the same time, from a certain moment, the decrease in the amount of calcium and phosphorus salts begins. The bones become brittle, so elderly people often experience fractures, even as a result of a slight injury or careless sharp movement.

Such fractures heal for a long time. There is a special disease characteristic of the elderly, especially women - osteoporosis. To prevent it, when you reach the age of 50, you need to see a doctor to conduct some studies to assess the condition of bone tissue. With appropriate treatment, the risk of fractures is significantly reduced and the healing time is shortened.