Available in spongy bones. Spongy bones examples long and short
Bone- the hardest substance present in the human body after tooth enamel. Its unusually high resistance is due to structural features: bone substance is a special type of connective tissue - bone tissue, the characteristic features of which are a hard fibrous intercellular substance impregnated with mineral salts and stellate cells equipped with numerous processes.
Classification of bones
Each bone is an independent organ and consists of two parts: the outer one - the periosteum and the inner one, formed by bone tissue. Inside, in the bone marrow cavities, there is bone marrow - the most important hematopoietic organ in humans.
Depending on the shape determined by the function performed, the following groups of bones are distinguished
- long (tubular);
- short (spongy);
- flat (wide);
- mixed (abnormal);
- pneumatic.
Long (tubular) bone has an elongated, cylindrical or triangular middle part - the body of the bone, the diaphysis. Its thickened ends are called epiphyses. Each epiphysis has an articular surface covered with articular cartilage, which serves to connect to adjacent bones. Tubular bones make up the skeleton of the limbs and act as levers. There are long bones (humerus, femur, bones of the forearm and tibia) and short bones (metacarpals, metatarsals, phalanges of the fingers).
Short (cancellous) bone has the shape of an irregular cube or polyhedron. Such bones are located in certain areas of the skeleton, where their strength is combined with mobility: in the joints between bones (carpus, tarsus).
Flat (wide) bones participate in the formation of body cavities and also perform a protective function (bones of the cranial vault, pelvic bones, sternum, ribs). At the same time, they provide extensive surfaces for muscle attachment, and also, along with tubular bones, are receptacles for bone marrow.
An important feature of evolution is the presence of short bones in the human wrist (which makes the hand suitable for performing various manipulations) and in the toes (which gives special stability in a standing position)
Mixed (abnormal) bones They have a complex structure and varied shape. For example, the vertebral body is a spongy bone, and its arch and processes are flat.
Air bones They have a cavity in the body lined with mucous membrane and filled with air. These include some bones of the skull: frontal, sphenoid, ethmoid, maxilla.
As bone grows, layers of bone tissue are formed successively.
Spongy bone tissue forms the inner part of the bone. Its porous structure makes the bones light and resistant to crushing. Small cavities in the spongy tissue are filled with red bone marrow, which produces blood cells.
Compact bone tissue, tough and very dense, forms the outer layer of bone and provides resistance to pressure and external influences. On its surface there are Haversian canals (osteons), through which blood vessels pass that feed the bones, and inside, in the medullary canal, there is yellow bone marrow - tissue with fatty inclusions.
Chemical composition of bones
Bone tissue is rich in minerals (especially calcium), which provide it with high strength, and collagen, a protein that gives it flexibility. It is constantly renewed due to the balance between two types of special cells: osteoblasts, which produce bone tissue, and osteoclasts, which destroy it. Osteoblasts play a key role in the growth and maintenance of the skeleton and the “repair” of bones after fractures.
The composition of bones includes both organic (fats, proteins, carbohydrate compounds) and inorganic substances (mainly mineral compounds of phosphorus and calcium). The number of the former increases, the younger the organism; This is why bones are flexible and soft in youth, and hard and brittle in old age. In an adult, the amount of mineral substances (mainly hydroxyapatite) is about 60-70% of the bone weight, and organic substances (mainly collagen - connective tissue fibers) - from 30 to 40%. Bones have high strength and offer enormous resistance to compression; they are able to withstand destruction for an extremely long time and are among the most common remains of fossil animals. When bones are calcined, they lose organic matter, but retain their shape and structure; by exposing it to acid (for example, hydrochloric), you can dissolve minerals and obtain a flexible cartilaginous skeleton of the bone.
Yellow bone marrow normally does not perform a hematopoietic function, but with large blood losses, foci of hematopoiesis appear in it. With age, the volume and mass of bone marrow change. If in newborns it accounts for approximately 1.4% of body weight, then in an adult it accounts for 4.6%.
The human skeleton consists of more than 200 bones. They all perform a specific function, generally creating support for external and internal organs. Depending on the load and role in the body, there are several varieties.
Bone structure
In dry form, 1/3 of human bone consists of organic matter - the protein osteoin. It provides its flexibility and elasticity. 2/3 are inorganic calcium salts, due to which their strength is achieved.
The outer shell is made up of the so-called compact substance. These are dense scales of bony tissue. Their densest layer can be observed in the center. Towards their edges, the compact substance becomes thinner.
The motor function is carried out by the bones of the phalanges of the toes and fingers.
When metabolic disorders occur, bones can become very fragile or extremely strong. In both cases, this is dangerous for normal human life.
The internal filling of bones - bone marrow - plays a major role in the formation of blood.
The meaning of red bone marrow
In the human body, the pattern of spongy bone presupposes the obligatory presence of red in it. This substance is so important for life that it is present even in tubular bones, but in smaller quantities.
In childhood, spongy and tubular bones are equally filled with this substance, but with age, the cavities of the tubular bones are gradually filled with fatty yellow bone marrow.
The main task of red bone marrow is the synthesis of red blood cells. As you know, these cells do not have a nucleus and cannot divide themselves. In the spongy substance they mature and enter the bloodstream during metabolism in the bones.
Impaired functioning of the red bone marrow leads to diseases such as anemia and types of blood cancer. Often drug treatment is not effective and a red brain transplant has to be resorted to.
This substance is very sensitive to radiation. Therefore, many victims of it have various forms of blood cancer. This same property is also used in transplantology, when it is necessary to kill infected bone marrow cells.
Possible damage
By its nature, the structure of spongy bone allows it to be quite resistant to mechanical damage. But there are often cases when the integrity of the bone is compromised.
Characterized by compression of the bone due to strong impact on it. The vertebrae are very susceptible to this type of damage. You can get injured during an unsuccessful landing on your feet or a fall. The danger of a fracture is that the vertebra no longer protects the spinal cord, which can lead to damage.
Because most long spongy bones are curved, they can crack when struck hard by hard objects. Such damage is relatively harmless. With timely medical care, cracks heal quite quickly.
Spongy bones can break. In some cases, injuries of this kind are practically harmless. If there was no displacement, they are restored quite quickly. The danger lies in those bones that, when fractured, can move and pierce vital organs. In this case, a relatively harmless fracture becomes a cause of disability and death.
Bones and age-related changes
Like all other human organs, spongy bones are subject to age-related changes. At birth, some of the future bones are either not yet strong or have not been formed from cartilage and connective tissue.
Over the years, bones tend to “dry out.” This means that the amount of organic substances in their composition becomes smaller, while mineral substances replace them. Bones become fragile and take longer to recover from damage.
The amount of bone marrow also gradually decreases. Therefore, older people are prone to anemia.
Classification of bones
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; trunk bones; limb bones.
2. Development The following types of bones are distinguished : primary (appears from connective tissue); secondary (formed from cartilage); mixed.
3. The following types of human bones are distinguished by structure: tubular; spongy; flat; mixed.
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 bone marrow containing fat cells. At the ends of the tubular bone there is an epiphysis - this is an area formed by 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. Long tubular bones include the femur, shoulder, and forearm bones. 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 and metatarsal bones. They function as short movement levers.
Spongy types of bones
The name of the bones often indicates their structure. For example, cancellous bones are formed from 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 first 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 wrist bones and vertebrae.
Flat bones
These types of human bones, depending on their location, have different structures and perform certain functions. The bones of the skull are, first of all, protection for the brain. They are formed by two thin plates of dense substance, between which there is a spongy substance. It contains holes for veins. The flat bones of the skull develop from connective tissue. The scapula and pelvic bones are also a type of flat bone. They are formed almost entirely from spongy substance, which develops from cartilage tissue. These types of bones serve not only as protection, but also as support.
Mixed dice
Mixed bones are a combination of flat and short spongy or tubular bones. They develop in different ways and perform those functions that are necessary in a particular area of the human skeleton. These types of bones, such as mixed ones, are found in the body of the temporal bone and vertebrae. These include, for example, the collarbone.
Cartilage tissue
Cartilage tissue has an elastic structure. It forms the ears, nose, and some parts of the ribs. Cartilage 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 compression.
Bones, hard, durable parts of the skeleton of various sizes and shapes, form the support of our body, perform the function of protecting vital organs, and also provide motor activity, since they are the basis of the musculoskeletal system.
- Bones are the skeleton of the body and vary in shape and size.
- Bones are connected by muscles and tendons, thanks to which a person can make movements, maintain and change the position of the body in space.
- Protect internal organs, including the spinal cord and brain.
- Bones are an organic storehouse of minerals such as calcium and phosphorus.
- Contains bone marrow, which produces blood cells.
Bones are made of bone tissue; Throughout human life, bone tissue is constantly modified. Bone tissue consists of a cellular matrix, collagen fibers and an amorphous substance, which is covered with calcium and phosphorus, which ensure the strength of bones. Bone tissue contains special cells that, under the influence of hormones, form the internal structure of bones throughout human life: some destroy old bone tissue, while others create new one.
The interior of the bone under a microscope: spongy tissue is represented by more or less densely located trabeculae.
The osteoid substance consists of an osteoblast, on top of which minerals are located. On the outer side of the bone, consisting of strong periosteum tissue, there are numerous bony membranes located around the central canal, where a blood vessel passes, from which many capillaries extend. Clusters in which the bone membranes are located close to each other without gaps form a solid substance that provides bone strength and is called compact bone tissue, or compact substance. Conversely, in the inner part of the bone, called cancellous tissue, the bony membranes are not as close and dense, this part of the bone is less strong and more porous - spongy substance.
Despite the fact that all bones consist of bone tissue, each of them has its own shape and size, and according to these characteristics they are conventionally classified as three types of bones:
;Long Bones: tubular bones with an elongated central part - the diaphysis (body) and two ends called the epiphysis. The latter are covered with articular cartilage and participate in the formation of joints. Compact substance(endosteum) has an outer layer several millimeters thick - the most dense, a cortical plate, which is covered with a dense membrane - the periosteum (with the exception of the articular surfaces covered with cartilage).
;Flat bones: come in different shapes and sizes and consist of two layers compact substance; between them is spongy tissue, called diploe in flat bones, the trabeculae of which also contain bone marrow
.
;Short Bones: These are usually small bones that are cylindrical or cubic in shape. Although they differ in shape, they consist of a thin layer compact bone substance and are usually filled with spongy substance, the trabeculae of which contain bone marrow.
The structure of the human bone.
Bones begin their formation even before a person is born, in the embryonic stage, and are completed by the end of adolescence. Bone mass increases as you get older, especially during adolescence. Starting from the age of thirty, bone mass gradually decreases, although under normal conditions the bones remain strong until old age.
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