What types of bone substance do you know? Private anatomy. the study of bones - osteology. The structure of the cortical, spongy layer

A collection of cells and intercellular substance similar in origin, structure and functions is called cloth. In the human body they secrete 4 main groups of fabrics: epithelial, connective, muscular, nervous.

Epithelial tissue(epithelium) forms a layer of cells that make up the integument of the body and the mucous membranes of all internal organs and body cavities and some glands. Through epithelial tissue, metabolism occurs between the body and environment. IN epithelial tissue The cells are very close to each other, there is little intercellular substance.

This creates an obstacle for the penetration of microbes, harmful substances and reliable protection of the tissues underlying the epithelium. Due to the fact that the epithelium is constantly exposed to various external influences, its cells die in large quantities and are replaced by new ones. Cell replacement occurs due to the ability of epithelial cells and rapid.

There are several types of epithelium - skin, intestinal, respiratory.

Derivatives of the skin epithelium include nails and hair. The intestinal epithelium is monosyllabic. It also forms glands. These are, for example, the pancreas, liver, salivary, sweat glands, etc. Enzymes secreted by the glands break down nutrients. The breakdown products of nutrients are absorbed by the intestinal epithelium and enter the blood vessels. The respiratory tract is lined with ciliated epithelium. Its cells have outward-facing motile cilia. With their help, particulate matter trapped in the air is removed from the body.

Connective tissue. A feature of connective tissue is the strong development of intercellular substance.

The main functions of connective tissue are nutritional and supporting. Connective tissue includes blood, lymph, cartilage, bone, and adipose tissue. Blood and lymph consist of a liquid intercellular substance and blood cells floating in it. These tissues provide communication between organisms, carrying various gases and substances. Fibrous and connective tissue consists of cells connected to each other by an intercellular substance in the form of fibers. The fibers can lie tightly or loosely. Fibrous connective tissue is found in all organs. Adipose tissue also looks like loose tissue. It is rich in cells that are filled with fat.

IN cartilage tissue the cells are large, the intercellular substance is elastic, dense, contains elastic and other fibers. There is a lot of cartilage tissue in the joints, between the vertebral bodies.

Bone consists of bone plates, inside of which lie cells. The cells are connected to each other by numerous thin processes. Bone tissue is hard.

Muscle. This tissue is formed by muscles. Their cytoplasm contains thin filaments capable of contraction. Smooth and striated muscle tissue is distinguished.

The fabric is called cross-striped because its fibers have a transverse striation, which is an alternation of light and dark areas. Smooth muscle tissue is part of the walls of internal organs (stomach, intestines, bladder, blood vessels). Striated muscle tissue is divided into skeletal and cardiac. Skeletal muscle tissue consists of elongated fibers reaching a length of 10–12 cm. Cardiac muscle tissue, like skeletal muscle tissue, has transverse striations. However, unlike skeletal muscle, there are special areas where the muscle fibers close tightly together. Thanks to this structure, the contraction of one fiber is quickly transmitted to neighboring ones. This ensures simultaneous contraction of large areas of the heart muscle. Muscle contraction is of great importance. The contraction of skeletal muscles ensures the movement of the body in space and the movement of some parts in relation to others. Due to smooth muscles, internal organs contract and the diameter of blood vessels changes.

Nervous tissue. The structural unit of nervous tissue is a nerve cell - a neuron.

A neuron consists of a body and processes. The body of a neuron can be of various shapes - oval, stellate, polygonal. A neuron has one nucleus, usually located in the center of the cell. Most neurons have short, thick, strongly branching processes near the body and long (up to 1.5 m), thin, and branching processes only at the very end. Long processes of nerve cells form nerve fibers. The main properties of a neuron are the ability to be excited and the ability to conduct this excitation along nerve fibers. In nervous tissue these properties are especially well expressed, although they are also characteristic of muscles and glands. Excitation is transmitted along the neuron and can be transmitted to other neurons or muscles connected to it, causing it to contract. The importance of the nervous tissue that forms nervous system, huge. Nervous tissue not only forms part of the body as part of it, but also ensures the unification of the functions of all other parts of the body.

A person knows a lot about his body, for example, where the organs are located, what function they perform. Why not penetrate deep into the bone and find out its structure and composition? It's very interesting, because chemical composition bones are very diverse. It helps to understand why each bone element is very important and what function it has.

basic information

Living bone in adults has:

• 50% - water;
• 21.85% - substances of inorganic type;
• 15.75% - fat;
• 12.4% - collagen fibers.

Inorganic substances are different salts. Most of them are represented by lime phosphate (sixty percent). Calcium carbonate and magnesium sulfate are present in smaller quantities (5.9 and 1.4%, respectively). Interestingly, all earthly elements are represented in the bones. Mineral salts can be dissolved. To do this, you need a weak solution of nitric or hydrochloric acid. The process of dissolution in these substances has its own name - decalcification. After it, only organic matter remains, which retains its bone form.

Organic matter is porous and elastic. It can be compared to a sponge. What happens when this substance is removed through combustion? The shape of the bone remains the same, but now it becomes brittle.

It is clear that only the interaction of inorganic and organic substances makes the bone element strong and elastic. The bone becomes even stronger due to the composition of the spongy and compact substance.

Inorganic composition

About a century ago, it was suggested that human bone tissue, or rather its crystals, are similar in structure to apatites. Over time this has been proven. Bone crystals are hydroxylapatites, and their shape is similar to rods and plates. But the crystals are only a fraction of the mineral phase of the tissue, the other fraction is amorphous calcium phosphate. Its content depends on the age of the person. Young people, teenagers and children have a lot of it, more than crystals. Subsequently, the ratio changes, so at an older age there are more crystals.

Every day, the bones of the human skeleton lose and gain again about eight hundred milligrams of calcium

The adult human body has more than one kilogram of calcium. It is found mainly in dental and bone elements. When combined with phosphate, hydroxyapatite is formed, which does not dissolve. The peculiarity is that in the bones the main part of calcium is regularly renewed. Every day, the bones of the human skeleton lose and gain again about eight hundred milligrams of calcium.

The mineral lobe has many ions, but pure hydroxyapatite does not contain them. There are ions of chlorine, magnesium and other elements.

Organic composition

95% of the organic type matrix is ​​collagen. If we talk about its significance, then, together with mineral elements, it is the main factor on which the mechanical properties of bone depend. Bone tissue collagen has the following features:

• it contains more hydroxyproline compared to skin collagen;
• it contains many free ε-amino groups of oxylysine and lysine residues;
• it contains more phosphate, the main part of which is associated with serine residues.

Dry demineralized bone matrix contains almost twenty percent non-collagenous proteins. Among them there are parts of proteoglycans, but they are few. The organic matrix contains glycosaminoglycans. They are believed to be directly related to ossification. In addition, if they change, ossification occurs. The bone matrix contains lipids, a direct component of bone tissue. They are involved in mineralization. The bone matrix has another feature - it contains a lot of citrate. Almost ninety percent of it is the share of bone tissue. Citrate is believed to be important for the mineralization process.

Substances of bone

Most of the bones of an adult human contain lamellar bone tissue, from which two types of substance are formed: spongy and compact. Their distribution depends on the functional loads placed on the bone.

If we consider the structure of bones, then the compact substance plays an important role in the formation of the diaphysis of tubular bone elements. It, like a thin plate, covers the outside of their epiphyses, flat, spongy bones, which are built from spongy substance. The compact substance contains a lot of thin tubules, which consist of blood vessels and nerve fibers. Some canals are essentially parallel to the bony surface.

The walls of the channels located in the center are formed by plates whose thickness ranges from four to fifteen microns. They seem to be inserted into each other. One channel near itself can have twenty similar records. The composition of the bone includes an osteon, that is, the union of a canal located in the center with plates near it. Between the osteons there are spaces that are filled with intercalary plates.

In the structure of bone, spongy substance is no less important. Its name suggests that it is similar to a sponge. The way it is. It is built with beams, between which there are cells. Human bone is constantly under stress in the form of compression and tension. They determine the dimensions of the beams and their location.

The bone structure includes the periosteum, that is, the connective tissue membrane. It is firmly connected to the bone element with the help of fibers that extend into its depth. The bone has two layers:

1. External, fibrous. It is formed by collagen fibers, thanks to which the shell is durable. This layer contains nerves and blood vessels.
2. Internal, sprout. Its structure contains osteogenic cells, thanks to which the bone expands and recovers after injury.

It turns out that the periosteum performs three main functions: trophic, protective, bone-forming. Speaking about the structure of bone, we should also mention the endosteum. The bone is covered from the inside with it. It looks like a thin plate and has an osteogenic function.

A little more about bones

Due to their amazing structure and composition, bones have unique characteristics. They are very flexible. When a person performs physical activity and trains, the bones become flexible and adapt to changing circumstances. That is, depending on the load, the number of osteons increases or decreases, and the thickness of the plates of substances changes.

Every person can contribute to optimal bone development. To do this, you need to exercise regularly and moderately. If your life is dominated by sedentary activities, your bones will begin to weaken and become thinner. There are bone diseases that weaken them, for example, osteoporosis, osteomyelitis. Bone structure can be influenced by occupation. Of course, heredity plays an important role.

So, a person is not able to influence some features of the bone structure. Still, some factors depend on it. If, from childhood, parents ensure that the child eats properly and engages in moderate physical activity, his bones will be in excellent condition. This will significantly affect his future, because the child will grow up to be a strong, healthy, that is, successful person.

From school chemistry lessons, everyone knows that the human body contains almost all the elements from periodic table D. I. Mendeleev. The percentages of some are quite significant, while others are present only in trace amounts. But each of chemical elements, located in the body, plays an important role. In the human body, minerals are contained in organic forms such as carbohydrates, proteins and others. A deficiency or excess of any of them leads to disruption of normal life.

The chemical composition of bones includes a number of elements and their substances, mostly calcium salts and collagen, as well as others, the percentage of which is much smaller, but their role is no less significant. The strength and health of the skeleton depends on the balance of the composition, which, in turn, is determined by many factors, ranging from a healthy diet to the ecological situation of the environment.

Compounds that form the skeleton

and inorganic origin. Exactly half of the mass is water, the remaining 50% is divided by ossein, fat and calcareous, phosphorus salts of calcium and magnesium, as well as the mineral part accounts for about 22%, and the organic part, represented by proteins, polysaccharides, citric acid and enzymes, fills approximately 28%. . Bones contain 99% of the calcium found in the human body. Teeth, nails and hair have a similar component composition.

Transformations in different environments

The following tests can be performed in an anatomy laboratory to confirm the chemical composition of the bones. To determine the organic part, the tissue is exposed to a medium-strength acid solution, for example, hydrochloric acid, with a concentration of about 15%. In the resulting environment, calcium salts dissolve, and the ossein “skeleton” remains intact. Such a bone acquires maximum elasticity; it can literally be tied into a knot.

The inorganic component, which is part of the chemical composition of human bones, can be isolated by burning the organic part; it is easily oxidized to carbon dioxide and water. The mineral skeleton is characterized by the same shape, but extreme fragility. The slightest mechanical impact and it will simply crumble.

When bones enter the soil, bacteria process organic matter, and the mineral part is completely saturated with calcium and turns into stone. In places where there is no access to moisture and microorganisms, tissues undergo natural mummification over time.

Through a microscope

Any anatomy textbook will tell you about the chemical composition and structure of bones. At the cellular level, tissue is defined as special type connecting. The base is surrounded by plates composed of a crystalline substance - the calcium mineral - hydroxyapatite (basic phosphate). In parallel, there are star-like voids containing bone cells and blood vessels. Thanks to its unique microscopic structure, this fabric is amazingly light.

The main functions of compounds of different natures

The normal functioning of the musculoskeletal system depends on the chemical composition of the bones and whether they contain organic and mineral substances in sufficient quantities. Calcareous and phosphorus salts of calcium, which make up 95% of the inorganic part of the skeleton, and some other mineral compounds determine the properties of hardness and strength of the bone. Thanks to them, the fabric is resistant to heavy loads.

The collagen component and its normal content are responsible for such functions as elasticity, resistance to compression, stretching, bending and other mechanical influences. But only in a coordinated “union” do organic matter and mineral components provide bone tissue with those unique properties which she possesses.

Composition of bones in childhood

The percentage of substances indicating the chemical composition of human bones may vary within the same representative. Depending on age, lifestyle and other influencing factors, the amount of certain compounds may vary. In particular, in children it is just being formed and consists largely of an organic component - collagen. Therefore, the child’s skeleton is more flexible and elastic.

For the proper formation of a child’s tissues, the consumption of vitamins is extremely important. In particular, such as D 3. Only in its presence is the chemical composition of bones fully replenished with calcium. A deficiency of this vitamin can lead to the development of chronic diseases and excessive fragility of the skeleton due to the fact that the tissue is not filled with Ca 2+ salts in time.

1. Describe the structure and composition of bones.

The composition of bones includes mineral and organic substances. Minerals (bones contain all the phosphorus and calcium of the body, 0.5% magnesium and sodium) give bones hardness and make up 70% of the bone mass. Bones are capable of releasing minerals into the blood. Organic substances give the bones elasticity and resilience and make up 30% of the bone mass. Bone consists of all types of tissues, but bone predominates. Bone tissue is connective tissue and consists of cells (osteocytes, osteoblasts, osteoclasts) and intercellular substance (collagen and osein fibers). The bone is covered with periosteum (connective tissue membrane). The outer layer consists of collagen fibers (give strength), nerves and blood vessels pass through here. The inner layer is bone tissue. It contains bone tissue cells, due to which development, growth in thickness and regeneration of bones after damage occurs.

Functions of the periosteum:

a) protective;

b) trophic;

c) bone-forming.

Bone growth in thickness occurs due to the division of cells on the inner surface of the periosteum, in length - due to the division of cells of cartilaginous plates located near the ends of the bones.

Bone growth is influenced by growth hormones, such as hormones secreted by the pituitary gland. Bone growth occurs until the age of 22-25. The replacement of old bone substance with new continues throughout a person’s life.

The greater the load on the skeleton, the more active the processes of bone renewal occur and the stronger the bone substance becomes.

2. What types of bones are there?

Depending on the shape, structure, function and development, 4 groups of bones are distinguished:

a) Tubular bones are located in parts of the skeleton where movements with large amplitude are performed (limbs). They are divided into long (shoulder, forearm, thigh, lower leg) and short (distal part of the phalanx of the fingers). Tubular bone consists of a diaphysis (bone body) and an epiphysis. Inside the diaphysis - a cavity filled with yellow bone marrow. In the pineal gland— red bone marrow is a hematopoietic organ.

Tubular bones are the basis of the skeleton of the limbs. They are very durable and can withstand heavy physical load. The cavity inside the bones, without reducing strength, significantly reduces their mass.

b) Spongy bones consist of spongy substance, covered with a thin layer of compact. Long (ribs, sternum) and short (vertebrae).

c) Flat bones are 2 plates of compact bone substance, between which there is spongy substance (sternum, roof of the skull). The main function is protective.

d) Mixed bones consist of several parts that have different functions and development (bones of the base of the skull).

3. What types of bone connections are distinguished in the human skeleton? Give a description of each of them. Give examples.

There are three types of bone connections in the human skeleton:

a) Fixed joints are formed by fusion of bones (coccyx vertebrae). The bones of the skull are connected thanks to the numerous protrusions of one bone that fit into depressions of the corresponding shape and size of the other. This connection is called a bone suture. It provides greater strength to the connection of the skull bones that protect the brain.

b) Semi-movable joints. Many bones are connected to each other by cartilage pads that have elasticity and elasticity. For example, cartilage pads between the vertebrae provide flexibility to the spine. Material from the site

c) Movable joints - joints. The most typical plan for the structure of a joint is as follows: on one of the articulating bones there is an articular cavity into which the head of the other bone fits. The glenoid cavity and the head correspond to each other in shape and size, and their surface is covered with a layer of smooth cartilage. The articular surfaces of the bones are in close contact with each other. This is ensured by the presence of intra-articular ligaments - strong strands of connective tissue. The articulating surfaces of the bones are surrounded by an articular capsule. It contains a small amount of mucous fluid that acts as a lubricant, which reduces friction and ensures the head of one bone slides into the glenoid cavity of another bone during movements in the joint. Examples: shoulder, hip joints.

First of all, our bones consist of bone substance, which contains calcium salts. In general, bone as an organ also consists of soft tissues such as articular cartilage and periosteum (in the language of specialists, periosteum), bone marrow inside the bones, as well as blood vessels and nerves that pass through the periosteum and ‎.

Bone substance

Bone matter makes up the bulk of our bones. It is very strong, as it contains calcium (experts talk about calcium salts), its weight can reach up to 70% of the weight of the bones. Bone matter occurs in bones mainly in two forms: compact bone substance And cancellous bone substance.

Compact bone substance is a hard, dense, whitish mass. First of all, it seems to envelop (cover) with a thick layer the bone marrow cavities inside long tubular bones (for example, femurs or humeri). But cancellous bone substance consists of fairly thin plates/bars. It can be found in our short, flat bones, such as the vertebrae.

Bone substance consists of mature bone cells called osteocytes. Osteocytes have processes and with the help of these processes they connect with each other. Working together with young osteoblast cells, which are responsible for bone formation, new bone begins to grow. Bone tissue is destroyed by cells called osteoclasts.

Articular cartilage

Articular cartilage is found in almost all bones, with the exception of the skull bones. They cover the articular surfaces and are the last remaining part of the skeleton from embryonic development.

Periosteum

The periosteum (which experts call the periosteum) covers the outside of all our bones. Therefore, the bone substance itself is nowhere to be seen. It is covered by either periosteum or articular cartilage.

Bone marrow

Bone marrow is the soft mass that is found in cavities inside bones. Bone marrow is red and yellow. Red bone marrow is responsible for hematopoiesis in the body. And yellow bone marrow is mostly adipose tissue.

Yellow bone marrow does not appear in a person immediately, but gradually during human development, red bone marrow is replaced by yellow one. Therefore, the older a person gets, the more yellow bone marrow he has. In adults, yellow bone marrow fills the central part of long tubular bones (this could be, for example, the humerus), which experts call the diaphysis. Red bone marrow is found primarily inside short, flat bones (such as inside the vertebrae).

Blood vessels and nerves

Blood vessels and nerves are found in the bone substance, in the periosteum, and in the bone marrow. They transmit information, nutrients and oxygen to bone cells. Through tiny holes on the surface of the bones, they enter the bone, and from the bone they exit into the circulatory system or, respectively, into the nerves that connect them to the nervous system.