School at the Russian Embassy in Turkey. Externship
II quarter
Subject:Musculoskeletal system
What is included in the musculoskeletal system?
B) skeleton and skeletal muscles;
C) stomach muscles, skeleton;
D) only skeletal muscles.
What refers to the hematopoietic organs here?
B) red bone marrow;
C) the spleen;
D) yellow bone marrow.
What tissue does bone and cartilage belong to?
B) muscular;
B) connecting;
D) nervous.
Due to the division of which cells, the bone grows in length?
B) tendons;
B) bone tissue;
D) cartilage tissue.
Define flat bones:
B) the frontal and pelvic bones;
B) humerus;
D) parietal bones and spine.
Which of the following is the result of not following the correct posture at the desk?
B) flat feet;
C) curvature of the spine;
D) dwarfism.
How are the bones of the medullary part of the skull connected?
B) motionless;
B) movably;
D) this is one whole bone.
Bone growth in thickness is due to:
B) bone cells;
B) cartilage tissue;
D) tendons.
^ Which of these bones form the skeleton of the torso?
B) 1, 2, 3, 4;
B) 1, 2, 3, 5;
What are the bones of the upper limb girdle?
B) scapula and clavicle;
C) the bones of the shoulder and forearm;
D) bones of the cervical vertebrae.
What bones are involved in the formation of the shoulder joint?
B) scapula, clavicle and humerus;
B) humerus and forearm bones;
D) humerus and sternum.
^ Which of these bones are tubular bones?
B) bones of the skull and vertebrae;
C) scapula and sternum;
D) femur and tibia.
What paired bones does the cerebral section of the skull consist of?
B) frontal and parietal;
C) frontal and temporal;
D) temporal and parietal?
14. To the belt lower limbs relate:
A) thigh bones; c) the bones of the lower leg;
B) pelvic bones; d) all the bones of the leg.
^ 15. Bones of the upper limbs:
A) bones of the forearm, shoulder and hand;
B) shoulder blades and shoulder bones;
C) the bones of the shoulder and collarbone;
D) clavicle and scapula.
^ 16. What determines the hardness of bones?
A) organic substances;
B) spongy structure;
D) tubular structure.
^ 17. Modified human bones associated with upright posture:
A) the bones of the skull;
B) scapula and clavicle;
B) bones of the forearm and shoulder;
D) the spine and pelvic bones.
^ 18. What first aid can be provided to a victim with a fracture of the bones of the foot?
A) the imposition of splints below the knee joint;
B) the imposition of splints from the knee joint and below;
B) a sufficiently tight bandage of the foot;
D) to provide first aid is useless.
^ 19. The lightness and strength of bones is determined by:
A) organic substances;
B) inorganic substances;
B) spongy structure;
D) tubular structure;
E) all together (a, b, c, d).
II quarter
Subject: Sense organs.
^ 1. Where are the eye's light-sensitive receptors located?
A) in the retina;
B) in the lens;
B) in the iris;
D) in the tunica albuginea.
^ 2. What are the names of the protective membranes of the eye?
A) retina and iris;
B) lens and pupil;
B) the choroid;
D) tunica albuginea and cornea.
^ 3. In which part of the analyzer does the difference in stimuli begin?
A) in receptors;
B) in the sensory nerves;
C) in the spinal cord;
D) in the cerebral cortex.
^ 4. Pigmentation of which part of the eye determines its color?
A) the retina;
B) the lens;
B) the iris;
D) tunica albuginea.
5. Place of projection of the object in the eyeball:
A) retina;
B) the lens;
C) the pupil;
D) tunica albuginea.
^ 6. In which part of the ear are sound receptors located?
A) in the auditory ossicles;
B) in the eardrum;
B) in the auditory zone;
D) in the snail.
^ 7. Where are the sound-conducting bones located?
A) in the outer ear;
B) in a snail;
C) in the auditory area of the cerebral cortex;
D) in the middle ear.
^ 8. What external stimuli distinguish the receptors in the nasal cavity?
A) smells;
B) taste;
C) the shape of the object;
D) temperature.
^ 9. Name the sensitive part of the visual analyzer:
A) rods and cones;
B) the pupil;
C) the optic nerve;
^ 10. Conductive part of the visual analyzer:
A) retina;
B) the pupil;
C) the optic nerve;
D) the visual area of the cerebral cortex.
^ 11. The cause of myopia in children:
A) the elongated shape of the eyeball;
B) nervous inhibition in the visual zone;
C) loss of flexibility of the lens;
D) fatigue of the optic nerve.
^ 12. Where is the formation of colored visual images carried out?
A) in rods and cones;
B) in the iris;
C) in the optic nerve;
D) in the visual area.
^ 13. Where is the transformation of the vibration of sound waves into biocurrents?
BUT) in auditory ossicles;
B) in the receptors of the snail;
B) in the auditory zone;
D) in the auditory nerves.
^ 15. What colors and their combinations have the most favorable and beneficial effect on the highest nervous activity person?
A) red and white;
B) red and yellow;
B) blue and green;
D) their diversity and brightness.
^ 16. How to explain the case when they say “I see poorly, my eyes are tired”?
A) fatigue of the eyelids and lens;
B) only by fatigue of the optic nerve;
C) inhibition in the visual area of the cerebral cortex;
D) b) and c);
D) there is no correct answer.
17. Name possible reasons hearing impairment:
A) inflammation and damage to the inner ear;
B) damage to the auditory nerve;
B) sulfur plug;
D) nervous fatigue;
E) answers c) and d).
18. What analyzer determines the shape of objects at a distance?
A) hearing and vision;
B) sight and touch;
B) muscle and vision;
D) tactile and organ of balance.
The human skeleton contains about 200 bones of various shapes and sizes. By shape, there are long (femoral, ulnar), short (wrist, tarsus) and flat bones (scapula, skull bones).
The chemical composition of bones. All bones are composed of organic and inorganic (mineral) substances and water, the mass of which reaches 20% of the mass of bones. Bone organic matter - ossein - has well-pronounced elastic properties and gives the bones elasticity. Minerals - salts of carbonate, calcium phosphate - give the bones hardness. High bone strength is provided by the combination of ossein elasticity and bone mineral hardness. With a lack of vitamin D in the body of children the process of mineralization of bones is disrupted and they become flexible, easily bent. This disease is called rickets. In older people, the amount of mineral salts in the bones increases significantly, the bones become fragile, and more often than at a young age, they break.
Bone structure. Bone tissue belongs to connective tissue and has a lot of intercellular substance, consisting of ossein and mineral salts. This substance forms bony plates that are concentric around microscopic tubules that run along the bone and contain blood vessels and nerves. Bone cells, and therefore bone, are living tissue; it receives nutrients from the blood, metabolism takes place in it and structural changes can occur.
Different bones have a different structure. The long bone looks like a tube, the walls of which are composed of a dense substance. Such tubular structure long bones give them strength and lightness. In the cavities of tubular bones is yellow bone marrow- loose connective tissue rich in fat. The ends of the long bones contain cancellous bone substance. It also consists of bony plates that form a multitude of crossed septa. In places where the bone is exposed to the greatest mechanical stress, the number of these septa is the highest. The spongy substance contains red bone marrow, whose cells give rise to blood cells. Short and flat bones also have a spongy structure, only on the outside they are covered with a layer of dense substance. The spongy structure also gives bones strength and lightness.
Outside, all bones are covered with a thin and dense film of connective tissue- the periosteum. Only the heads of the long bones are devoid of the periosteum, but they are covered with cartilage. The periosteum contains many blood vessels and nerves. It provides nourishment to the bone tissue and takes part in the growth of bone in thickness. Thanks to the periosteum, broken bones grow together.
Connecting bones. Three types of bone connection can be distinguished: fixed, semi-movable and movable. Fixed a joint type is a joint due to bone fusion (pelvic bones) or sutures (skull bones). When semi-movable At the junction, bones are connected together by cartilage, such as the ribs with the sternum or the vertebrae with each other. Mobile the type of connection is typical for most bones of the skeleton and is achieved using a special connection of the bones - joint. The end of one of the bones forming the joint is convex (the head of the joint), and the end of the other is concave (the glenoid cavity). The shape of the head and cavity correspond to each other and to the movements that are carried out in the joint. The head and cavity are covered with a layer of smooth cartilage, which reduces friction in the joint and cushions shock. The bones of the joint are covered with a common, very strong sheath of connective tissue - joint bag. It contains a fluid that lubricates the surfaces of the contacting bones and reduces friction. Outside, the articular capsule is surrounded by ligaments and muscles attached to it, and passes into the periosteum.
The bones of the skeleton constitute a complex system of levers, with the help of which the muscles carry out the most varied movements of the body and its parts, which are the basis of labor processes.
There are 206 of all human bones; of which 170 are paired and 36 are unpaired. The bones are very different in appearance. Depending on their role and position in the human body, they have various shapes and sizes. According to the shape, the bones are usually divided into tubular cylindrical or prismatic, to which most of the long bones of the extremities belong, such as: femur, humerus, tibia, etc.; wide or flat - the bones of the skull, scapula, ilium, etc.; short - small bones of the foot and hand, giving flexibility to these parts of the skeleton, and, finally, mixed bones - vertebrae, bones of the base of the skull, etc.
On the bones in the places of origin or attachment of muscles, ligaments, adjacent tendons, vessels and nerves, there are various kinds of processes, tubercles, canals, holes, grooves. Especially in this respect, the bones of the base of the skull stand out, which are penetrated by numerous holes and channels for the passage of blood vessels and nerves.
The bone system, like any other, cannot be considered in isolation, because it is a necessary part of the whole organism, which reflects the various processes taking place in it. There is a close relationship between the development of the skeleton and the general structure of the body. The structure and development of the skeleton largely depends on the work of muscles and the activity of internal organs.
Bone structure. Before proceeding to consider the skeleton as a whole and in its parts, let's see what a separate bone is - the main supporting unit of the skeleton. Take the thigh bone for example. It is a tubular bone, like all long bones of the skeleton. It is a cylindrical rod thickened at the ends, having a longitudinal closed medullary cavity inside, which runs almost along the entire length of the bone, slightly not reaching only the terminal thickened sections, which is why this type of bone is called tubular by its resemblance to tubes. The thickened ends of the bone, separated during development by the growth, the so-called metaepiphyseal cartilage, are uneven outside, tuberous, rough (these are the places of attachment of muscle tendons and ligaments); they bear the articular surfaces and are called epiphyses. The free ends of the epiphyses have smooth surfaces that face the joint cavity when articulated with other bones. The middle part of the bone is called the diaphysis. Outside, the bone consists of a compact bone substance, forming a rather thick wall of the bone tube on the diaphysis, and lying in a thinner layer on the epiphyses. There is no cavity in the epiphyses; they are filled with spongy bone substance. It is built from a large number of bony beams and beams of varying thickness. The thinnest crossbeams consist of only one bone plate, while the thickest ones consist of several plates joined together (Fig. 38). Short and flat bones for the most part consist entirely of cancellous substance and are covered from the outside with a thin layer of compact bone substance.
The spaces between the plates and crossbars of the cancellous substance, as well as the bone cavity, are filled with bone marrow and many blood vessels. At a young age, the entire bone marrow is red; in an adult, red bone marrow remains only in the spongy substance, while in the cerebral cavity, due to the deposition of fat here, it turns yellow. Bone marrow is a type of connective tissue (reticular); the development of the cellular elements of the blood occurs in it.
A tubular bone with its cavity inside turns out to be much stronger to fracture in comparison with a solid rod with the same amount of material, since mechanics teaches that hollow tubes are no less strong than solid rods of the same thickness. Therefore, for example, in various structures, hollow metal pillars and tubes are used instead of massive solid ones. Everyone knows that, for example, bicycle frames and some parts of other machines that cannot be made very heavy (airplanes, etc.), are made not from thin rods, but from wide hollow tubes.
The looped structure of cancellous bone tissue also does not compromise strength: the bars and plates are located in a certain direction with the expectation that, with the least waste of material, achieve the greatest lightness, stability and strength so that the pressure and tension experienced by the bone in a living organism are distributed evenly over the entire bone , as is the case, for example, in modern railway bridges, cranes and other structures. The lightness of the bones of the skeleton is an extremely valuable quality, very beneficial for the body. If our skeleton was entirely composed of dense bone tissue, it would be about 2 or 2 1/2 times heavier. It is interesting to note that in birds, for example, for which it is especially important to reduce the weight of bones during flight, the bone cavities are filled with air. The marrow of our bones is the lightest tissue in our body, and the numerous channels that penetrate the bone matter, in turn, lighten the weight of the tissue.
The periosteum (periosteum), which is a thin plate in which two layers are distinguished, is tightly grown to each bone from the outside. The outer layer consists of dense connective tissue and is protective. The inner layer (osteogenic) is built from loose connective tissue; it is rich in nerves and blood vessels and contains cells (osteoblasts) that are involved in bone development and growth. This layer of the periosteum is of great importance for bone regeneration; it plays a particularly large role in the embryonic period, as well as in early childhood, taking part in the formation of bone tissue.
Bone is a living part of our body. It is equipped not only with blood vessels, but also with nerves, it grows and rebuilds; with a change in the functional load, its structure changes accordingly. With prolonged inactivity, the bone can dissolve, for example, the wall of the tooth cell after tooth extraction. Living bone is one of the plastic formations built very firmly, economically and beneficial for the body in the given conditions of its life.
The chemical composition of the bone. The composition of the bone of an adult includes organic matter ossein (30%) and lime salts (70%). But this also includes significant amounts of water and fat. Therefore, a more accurate composition of bone tissue will be as follows: water 50%, organic matter 12.45%, salts 21.85% and fat 15.7%. The composition of bone mineral salts, in addition to calcium salts, includes salts of potassium, phosphoric acid, etc. If fresh bone is soaked in a concentrated solution of hydrochloric (or nitric) acid, the mineral salts dissolve, the bone decalcifies and only soft and elastic, strong to break , a translucent substance that retains the shape of a bone, is bone cartilage (ossein). With the removal of minerals, the bone loses its hardness, completely retaining its elasticity. Such a bone can be bent like a rubber one, it can even be tied in a knot; thanks to its organic fiber backing, it will return to its original shape after being untied. If the bone is calcined over high heat, then the organic matter (ossein) will burn out and remain a white, hard and extremely fragile mass of calcareous salts, which retains the shape of the bone. The content of mineral and organic matter in bones is subject to great fluctuations. Those bones, which are subjected to a large mechanical load, are richer in lime salts; for example, the human thighbone contains more of them than the humerus, and accordingly it is stronger and harder than the humerus.
The combination of organic matter with mineral matter in the bone gives it very valuable properties as a building material for the skeleton. Normal (unaltered) bone combines the properties of both of its constituent parts - strength, elasticity and hardness.
Both the composition and the structure of the bones make them very strong. The elasticity of bones is constantly tested under possible mechanical influences (various kinds of shocks, blows, etc.). Even a skull, isolated from soft tissues, usually does not break when it falls on a hard floor from a height of 1.7 m: at the moment of impact, it deforms, but due to its elasticity, it immediately returns to its previous shape. The hardness of the bone can be judged by the following figures: fresh human bone can withstand a pressure of 15 kg per 1 mm 2, while a brick can withstand only 0.5 kg, that is, the pressure resistance of a bone is 30 times greater than that of a brick. The hardness and tensile strength of bone is close to that of cast iron. It is many times greater than strength the best varieties wood. Of technical materials in terms of hardness and elasticity, only reinforced concrete can be compared with bone.
How significant the strength of the bones is, can be seen from such examples: the human femur, reinforced horizontally with the ends on two supports, can withstand a weight of 1200 kg suspended from the middle. And the tibia, on which the greatest weight falls with the support of the body, in an upright position withstands a load equal to the weight of 27 people, that is, approximately 1650 kg, if this load presses on it directly from above (Fig. 39).
With age chemical composition bone changes. In children, bones are much richer in organic matter and poorer in mineral salts. Therefore, the bones of a child are more resilient and less fragile than the bones of an adult. This is why bone fractures are less common in children. By old age, the bones are more and more saturated with lime salts, the content of which can reach 80% or more, while the content of organic matter decreases and the bones become harder, but also more fragile. Therefore, in the case of falls and bruises, old people are much more likely to have bone fractures.
BONE, dense connective tissue, characteristic only of vertebrates. Bone provides the structural support of the body, thanks to which the body retains its general form and sizes. Some bones are located such that they provide protection for soft tissues and organs, such as the brain, and withstand attacks by predators unable to break the hard shell of prey. Bones give strength and rigidity to limbs and also serve as attachment points for muscles, allowing limbs to act as levers in their important locomotion and foraging function. Finally, thanks to high content mineral deposits of the bone turn out to be a reserve inorganic substances which they store and spend as needed; this function is essential for maintaining the balance of calcium in the blood and other tissues. With a sudden increase in the need for calcium in any organs and tissues, bones can become a source of its replenishment; for example, in some birds, the calcium necessary for the formation of the eggshell comes from the skeleton.
Antiquity of the skeletal system.
Bones are present in the skeleton of the earliest known fossil vertebrates - armored jawless Ordovician period (about 500 million years ago). In these fish-like creatures, bones served to form rows of outer plates that protected the body; some of them, in addition, had an internal bone skeleton of the head, but there were no other elements of the internal bone skeleton. Among modern vertebrates, there are groups characterized by the complete or almost complete absence of bones. However, most of them know the presence of a bone skeleton in the past, and the absence of bones in modern forms is a consequence of their reduction (loss) in the course of evolution. For example, in all species of modern sharks, bones are absent and replaced by cartilage (very a large number of bone tissue can be at the base of the scales and in the spine, consisting mainly of cartilage), but many of their ancestors, now extinct, had a developed bone skeleton.
The original function of the bones has not yet been precisely established. Judging by the fact that most of them in ancient vertebrates were located on or near the surface of the body, it is unlikely that this function was supporting. Some researchers believe that the original function of the bone was to protect the ancient armored jawless from large invertebrate predators, such as racoscorpions (eurypterids); in other words, the outer skeleton literally played the role of armor. Not all researchers share this point of view. Another function of bone in the earliest vertebrates may have been to maintain calcium balance in the body, as is observed in many modern vertebrates.
Intercellular bone substance.
Most bones are made up of bone cells (osteocytes) scattered in the dense intercellular bone that is produced by the cells. Cells occupy only a small part of the total bone volume, and in some adult vertebrates, especially in fish, they die off after they contribute to the creation of intercellular substance, and therefore are absent in mature bone.
The intercellular space of the bone is filled with substance of two main types - organic and mineral. Organic matter - the result of cell activity - consists mainly of proteins (including collagen fibers that form bundles), carbohydrates and lipids (fats). Normally, most of the organic component of bone matter is collagen; in some animals, it occupies more than 90% of the volume of bone substance. The inorganic component is primarily calcium phosphate. During normal bone formation, calcium and phosphates enter the developing bone tissue from the blood and are deposited on the surface and in the thickness of the bone along with organic components produced by bone cells.
Most of our information on changes in bone composition during growth and aging comes from the study of mammals. In these vertebrates, the absolute amount of the organic component is more or less constant throughout life, while the mineral (inorganic) component gradually increases with age, and in an adult organism it accounts for almost 65% of the dry weight of the entire skeleton.
Physical properties
bones correspond well to the functions of protection and support of the body. The bone must be strong and tough and at the same time elastic enough not to break under normal conditions of life. These properties are provided by the intercellular bone substance; the contribution of the bone cells themselves is insignificant. Rigidity, i.e. the ability to resist bending, stretching or compression is provided by an organic component, primarily collagen; the latter gives the bone and elasticity - a property that allows you to restore the original shape and length in case of slight deformation (bending or twisting). The inorganic component of the intercellular substance, calcium phosphate, also contributes to the rigidity of the bone, but mainly gives it hardness; if calcium phosphate is removed from the bone by special treatment, it will retain its shape, but will lose a significant proportion of its hardness. Hardness - important quality bones, but, unfortunately, it is she who makes the bone prone to fractures under excessive load.
Bone classification.
The structure of bones differs significantly both in different organisms and in different parts bodies of one organism. Bones can be classified by their density. In many parts of the skeleton (in particular, in the epiphyses of long bones), and especially in the skeleton of the embryo, the bone tissue has many cavities and channels filled with loose connective tissue or blood vessels, and looks like a network of crossbars and struts resembling the construction of a metal bridge. The bone formed by such bone tissue is called cancellous. As the body grows, much of the space occupied by loose connective tissue and blood vessels fills with additional bone material, resulting in an increase in bone density. This kind of bone with relatively sparse narrow canals is called compact or dense.
The bones of an adult organism are composed of a dense, compact substance located along the periphery, and a spongy substance located in the center. The ratio of these layers in the bones different types different. So, in cancellous bones, the thickness of the compact layer is very small, and the bulk is occupied by the cancellous substance.
Bones can also be classified by the relative number and location of bone cells in the extracellular substance and the orientation of collagen bundles, which make up a significant part of this substance. IN tubular bones, bundles of collagen fibers intersect in the most different directions, and bone cells are distributed over the intercellular substance more or less randomly. Flat bones have a more ordered spatial organization: they consist of successive layers (plates). IN different parts Collagen fibers, as a rule, are oriented in one direction in a single layer, but in adjacent layers it can be different. Flat bones have fewer bone cells than tubular bones, and they can be found both inside the layers and between them. Osteon bones, like flat bones, have a layered structure, but their layers are concentric rings around narrow, so-called. Haversian canals, through which blood vessels pass. The layers are formed starting from the outer one, and their rings, gradually narrowing, reduce the channel diameter. The Haversian canal and the layers surrounding it are called the Haversian system or osteon. Osteonic bones are usually formed during the transformation of cancellous bone into a compact bone.
Superficial membranes and bone marrow.
Except for those cases where closely spaced bones touch in a joint and are covered with cartilage, the outer and inner surfaces of the bones are lined with a dense membrane, which is vital for the function and preservation of the bone. The outer membrane is called the periosteum or periosteum (from the Greek. peri- around, osteon- bone), and the internal one, facing the bone cavity, is the internal periosteum, or endostome (from the Greek. eondon- inside). The periosteum consists of two layers: the outer fibrous (connective tissue) layer, which is not only an elastic protective sheath, but also the place of attachment of ligaments and tendons; and an inner layer that allows the growth of the bone in thickness. The endosteum is essential for bone regeneration and is to a certain extent similar to the inner layer of the periosteum; it contains cells that support both growth and resorption of bone.
The musculoskeletal system is the basis of the body. The skeleton protects individual organs from mechanical damage, therefore the vitality of a person as a whole depends on its condition. In this article, we will consider the composition of bones, the features of their structure and the substances that are necessary for their growth and development.
Features of the structure of bone tissue
Bone is a type of connective tissue. It consists of specialized cells and a large amount of intercellular substance. Taken together, this structure is both strong and elastic. Bones are hardened, first of all, by specialized cells - osteocytes. They have many outgrowths, with the help of which they are connected to each other.
Visually, osteocytes resemble a network. is an elastic base of bone tissue. It is composed of collagen protein fibers, a mineral base.
Bone composition
One fourth of everything is water. It is the basis for all metabolic processes. Inorganic substances give the bones hardness. These are salts of calcium, sodium, potassium and magnesium, as well as phosphorus compounds. Their percentage is 50%.
A simple experiment can be carried out to prove their significance for a given type of fabric. To do this, the bone must be placed in a hydrochloric acid solution. As a result, the minerals will dissolve. This will make the bone so elastic that it can be tied in a knot.
Organic matter accounts for 25% of the chemical composition. They are represented by an elastic protein called collagen. It gives elasticity to this fabric. If the bone is calcined over low heat, the water will evaporate and the organic matter will burn. In this case, the bone will become brittle and may crumble.
What substances make bones hard
The chemical composition of bone tissue changes throughout a person's life. At a young age, organic matter predominates in it. During this period, bones are flexible and soft. Therefore, with an incorrect body position and excessive stress, the skeleton can bend, causing poor posture. Systematic sports and physical activity can prevent this.
Over time, the amount of mineral salts in the bones increases. At the same time, they lose their elasticity. Mineral salts, which include calcium, magnesium, phosphorus, fluorine, give the bones hardness. But under excessive loads, they can lead to disruption of integrity and fractures.
Calcium is especially important for bones. Its mass in the human body is 1 kg for women and 1.5 kg for men.
The role of calcium in the body
99% of the total amount of calcium is in the bones, forming a strong skeleton. The remaining percentage is blood. This macronutrient is a building material for teeth and bones, necessary condition for their growth and development.
In the human body, calcium also regulates the work of muscle tissue, including the heart. Together with magnesium and sodium, it affects the level of blood pressure, and with prothrombin - on its coagulation.
The activation of enzymes, which triggers the mechanism of the synthesis of neurotransmitters, also depends on the level of calcium. It is biologically active substances, through which the impulse is transmitted from the cells of the nervous tissue to the muscles. This macronutrient also affects the activation of a number of enzymes that perform various functions: the breakdown of biopolymers, fat metabolism, the synthesis of amylase and maltase.
Calcium enhances the permeability of, in particular, their membranes. This is very important for transport various substances and maintaining homeostasis - the constancy of the internal environment of the body.
Healthy foods
As you can see, a lack of calcium in the body can lead to serious disruption of its functioning. Every day a child should consume about 600 mg of this substance, an adult - 1000 mg. And for pregnant and breastfeeding women, this figure must be increased by one and a half to two times.
What foods are rich in calcium? First of all, these are a variety of dairy products: kefir, fermented baked milk, sour cream, cottage cheese ... And the leader among them are hard types of cheeses. And it's not even about the amount of calcium, but about its form. These products contain milk sugar - lactose, which promotes better absorption of this chemical element. The amount of calcium also depends on the fat content. The lower this indicator, the more it is in the dairy product.
Rich in calcium and vegetables. These are spinach, broccoli, cabbage and cauliflower. The most valuable nuts are almonds and Brazilian nuts. A real storehouse of calcium is poppy and sesame seeds. They are good to eat both unprocessed and as milk.
Eating food also contributes to the increase in calcium levels. wheat bran and baking from whole grain flour, soy cheese and milk, parsley leaves, dill, basil and mustard.
Dangerous symptoms
How to understand that calcium in the body is not enough for its normal development? External manifestations of this are weakness, irritability, fatigue, dryness. skin, fragility of the nail plate. With a serious lack of calcium, teeth decay, cramps, pain and numbness of the extremities, impaired blood clotting, decreased immunity, tachycardia, cataract development, and a tendency to frequent bone fractures are observed. In such cases, it is necessary to donate blood and, if necessary, start therapy.
So, the hardness is given to the bones by their mineral components. First of all, these are salts, which include calcium, magnesium and phosphorus.
The structure and functions of the human skeletal system
The structure, chemical composition and physical properties of bones
Each bone of a living person is a complex organ: it occupies a fixed position in the body, has a certain shape and structure, and performs its inherent function.
All types of tissues take part in bone formation, but the main place is occupied by bone tissue. Cartilage covers only the articular surfaces of the bones, outside the bone is covered by the periosteum, inside is the bone marrow.
Bone contains adipose tissue, blood and lymph vessels, and nerves. The structural features of the bone tissue determine the most important feature of the bone - its mechanical strength. The strength of the bone can be compared with the strength of metal, for example, the tibia, which is part of the skeleton of the lower limbs, placed vertically, is able to withstand a load of almost two tons in weight.
Great importance for the strength of bones has their chemical composition. Living bone contains 50% water, 12.5% organic protein substances (ossins and ossemucoid), 21.8% inorganic minerals (mainly calcium phosphate) and 15.7% fat.
Mineral substances give the bones hardness, and organic - elasticity and flexibility.
Bone plate systems are formed from bone tissue. If the bone plates fit tightly to each other, then it turns out to be dense, or compact, bone substance. If the bone bars are loosely located, forming cells, then a spongy bone substance. The ratio of compact and spongy substances in different bones depends on their functional value... The bones, which perform the functions of support and movement, contain more compact matter. It should be remembered that both in the compact and in the cancellous substance, the bone crossbeams are not randomly arranged, but strictly regular along the lines of compression and extension forces, i.e. in the direction of impact on the bone of force loads.
Outside, the bone is covered with a thin but dense connective tissue sheath - periosteum... The periosteum contains a large number of nerves and blood vessels that supply bone tissue. There are also bone-forming cells (osteoblasts), which determine the growth of bone in thickness and the fusion of bone fragments in fractures. On the surface of the bones in the places of muscle attachment, roughness, tubercles, ridges are formed, the location and degree of development of which is determined by motor loads. In men, they are more pronounced than in women, and in people who go in for sports, they are more pronounced than in those who do not.
The bones that make up the skeleton also differ in shape. There are 4 types of bones: long or tubular, short, flat or wide, mixed. Tubular bones are part of the skeleton of the limbs (femur and humerus, bones of the forearm, lower leg, etc.) Each tubular bone has a middle long part ( diaphysis) and two extended articular ends ( pineal glands). In childhood, cartilage is located between the diaphysis and the pineal gland, and in adults, these cartilages are replaced by bone tissue. The diaphysis of the tubular bone consists of a compact bone substance. Inside the diaphysis there is a bone marrow cavity filled with yellow bone marrow. The epiphyses are formed by a cancellous bone substance, in the cells of which there is a red bone marrow.
Red bone marrow is a very important hematopoietic organ. It consists of a thin network of connective tissue fibers, in which a large number of red and white blood cells mature. These cells are, as it were, washed out by the blood stream and spread throughout the body.
In the embryonic period of development and in the early childhood the bone marrow cavities of the diaphysis of long tubular bones are also filled with red bone marrow. Over time, it undergoes fatty degeneration and turns into yellow bone marrow.
During the entire period of growth and development, between the diaphysis and the epiphysis of tubular bones there is a cartilaginous layer, the so-called epiphyseal cartilage, due to which the bone grows in length. Complete replacement of this cartilage with bone occurs in women by the age of 18-20, and in men by the age of 23-25. From this time on, the growth of the skeleton, which means that the growth of a person stops.
Another group is short bones, built like the epiphyses of long tubular bones. Such bones (vertebrae, sternum, bones of the wrist and tarsus, etc.) consist mainly of cancellous bone substance and are covered only on the outside with a thin layer of compact bone substance.
Flat bones formed of two plates of compact bone substance, between which there is a spongy substance. These bones perform mainly a protective function, limiting their wide surfaces to cavities (parietal, pelvic, etc.). Some bones contain air cavities inside, they are called air cavities (frontal bone, maxillary, ethmoid, etc.).
Mixed bones differ in a variety of structures, for example, the zygomatic and nasal bones, the mandibular bone.
Connecting bones
There are two main types of bone connection: continuous and discontinuous. When continuous At the junction, the bones are connected to each other by a continuous layer of cartilaginous or fibrous connective tissue, which allows only a slight displacement of the bones, and even then not always. It is completely absent if the layer is replaced by bone tissue, for example, when the sacral vertebrae are fused into a single bone - the sacrum. The immobility of the bones of the cerebral skull is achieved by the fact that the numerous protrusions of one bone enter the corresponding grooves of the other. this connection of bones is called seam.
Small mobility is achieved by elastic cartilaginous pads, inside which there is a cavity filled with a gelatinous mass. Such spacers are found between the individual vertebrae. when squeezed, for example, when the muscles of the spine contract, the cartilage pads are compressed and the vertebrae are slightly closer to each other. For the same reason, when a person lies with relaxed muscles, his body is slightly longer than when standing. When flexing to the side, the muscles contract only on one side of the spine, so the cartilage pads on the flexion side are compressed and on the opposite side they are stretched. Thus, the vertebrae, especially in the lumbar and neck regions, can tilt relative to each other. The entire spine has a significant range of motion and can bend forward, backward, and to the sides. When walking, running, jumping, the layers of elastic cartilage act as springs, softening sharp shocks and protecting the body from concussion. This is of particular importance for the preservation of the delicate tissue of the spinal cord and brain.
The connection of bones is called discontinuous or joint if there is a narrow gap between them. Each joint is surrounded by a bursa of very dense connective tissue. There are strong and elastic ligaments in the thickness of the bag and around it. the edges of the bag, together with the ligaments, adhere to the bones at some distance from their contacting surfaces and hermetically close the joint cavity. The contacting, or articular, surfaces of the bones are covered with a layer of cartilaginous tissue, which significantly reduces friction between the bones and thereby facilitates their movement. Friction is also reduced by fluid, which is constantly released on the inner surface of the bag and acts as a lubricant. When the bag is stretched, negative pressure is formed in the joint cavity. It prevents the separation of bones and gives the joint extraordinary strength. If the bag is punctured, then air will enter inside and no negative pressure will be created. Therefore, the joint with the punctured pouch is less strong. As a result of excessive loads on the joint, it may be damaged: sprain or rupture of ligaments, displacement of the articulating ends of the bones ( joint dislocation).
The articular surfaces of bones vary in shape. Accordingly, the joints are subdivided into spherical, elliptical, cylindrical, block-shaped, saddle-shaped and flat. The shape of the articular surfaces determines the range and direction of movements that occur around three axes. Distinguish between uniaxial, biaxial and triaxial joints. Uniaxial allow movement only around one axis, in other words, in one plane (for example, flexion and extension between the bones of the fingers), biaxial- around two axes, or in two mutually perpendicular planes (for example, the joint between the radius and the wrist). Triaxial (multi-axle) the joints provide movement in all directions - flexion and extension, abduction and rotation (for example, the shoulder joint).
There is also a transitional type of bone connection - half-joints... There is no joint capsule in the semi-joints, but there is cartilaginous tissue between the bones (for example, the cartilaginous junction of the pubic bones).
Skeleton structure
In the human skeleton, four sections are distinguished: the skeleton of the head (skull), the skeleton of the body, the skeleton of the upper and lower extremities.
Torso skeleton includes the spine ( vertebral column), sternum and ribs. The spine is a kind of axis of the body. Top end it connects to the skull, the lower one - to the bones of the pelvis. The spine consists of 33-34 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, fused into a single bone - the sacrum, and 4-5 coccygeal. In the vertebra, a massive body is distinguished in front, and in the back - an arc with several processes, some of which serve to attach muscles, and others to connect with neighboring vertebrae. The spinal cord is located in the vertebral canal, formed by the holes between the body and the arch of the vertebrae.
The vertebrae of the cervical, thoracic and lumbar regions are interconnected by intervertebral cartilage, ligaments and joints. The range of motion between the two vertebrae is small, but in general, these parts of the spine have significant mobility.
The sacral and coccygeal parts of the spine are formed by fused vertebrae, and therefore this part of the spine is practically motionless.
The human spine has four bends: two directed by the bulge anteriorly, they are called lordosis (cervical and lumbar), the other two - bulge posteriorly, they are called kyphosis(thoracic and sacral).
The curvatures of the spine are distinctive feature a person associated with an upright position of the body. Thanks to these bends, the center of gravity of the standing person's body is shifted back and is on a plumb line between the soles of the feet, closer to the heels. This position of the center of gravity maintains balance and greatly facilitates walking on two legs. Curves make the spine more elastic and flexible. When walking, running, jumping and all kinds of sudden movements, it springs and thereby protects the body from shock.
The rib cage forms the bony base of the chest cavity. It protects the heart, lungs, liver and serves as an attachment point for the respiratory and upper limb muscles. The rib cage consists of the sternum, 12 pairs of ribs connected to the back of the spinal column.
Thoracic vertebrae - component chest. From each thoracic vertebra there is one pair of ribs movably connected to it.
The front ends of the 10 upper pairs of ribs are connected with the sternum, or the sternum, with the help of cartilage, and the cartilages of the 8th, 9th, 10th pairs of ribs grow together and join the cartilages of the 7th pair, 11th and 12th the first couples do not reach the sternum and end freely.
Head skeleton, or skull, consists of the facial and cerebral parts. The cerebral skull forms a large cavity in which the brain is located. The composition of the cerebral skull includes the following bones: frontal, two parietal, occipital, two temporal, main ethmoid.
The facial skull includes the upper and lower jaws, zygomatic bones, palatine bones, vomer, nasal bones, inferior turbinates and lacrimal bones.
The joints of the skull bones are mostly continuous and are made with sutures. There is only one discontinuous movable joint - the temporomandibular joint.
Upper limb skeleton consists of the bones of the shoulder girdle, formed by the scapula and the clavicle, and the bones of the free upper limb, in which the humerus is distinguished, which is movably connected to the scapula; forearm, consisting of two bones - the ulna and the radius; a hand, which includes the small bones of the wrist, five long bones of the metacarpus and phalanges of the fingers (two in the thumb, three in the others).
Lower limb skeleton consists of the bones of the pelvic girdle and bones of the free lower limb. The girdle of the lower extremities or the pelvic girdle is formed by the sacrum and two pelvic bones fixedly connected to it, which are also fixedly connected to each other in front. In the lower extremities are distinguished: thigh; two bones of the lower leg - tibia and tibia; foot, consisting of the bones of the tarsus, metatarsus and phalanges of the fingers.
The thigh forms with the tibia knee-joint, to which a small bone adjoins in front - the patella, which protects the knee joint from damage.
Bone system development
In the process of prenatal and postnatal development, the child's skeletal system undergoes complex transformations. The skeleton of a child differs from that of an adult in size, proportions, structure and chemical composition of bones. The formation of the skeleton begins from the middle of the 2nd month of embryogenesis and continues up to 18-25 years of postnatal life.
Initially, in the embryo, the entire skeleton consists of cartilaginous tissue. In the future, the cartilaginous tissue is destroyed, and in its place bone tissue is formed, i.e. ossification of the skeleton occurs. However, most of the bones of the cerebral and facial skull appear in place of the compacted primary connective tissue, i.e. without prior cartilage formation.
The development of bone tissue is preceded by a rapid multiplication of cells of the primary connective tissue, which begin to intensively produce the intercellular substance characteristic of bone tissue. These cells are called osteoblasts, i.e. bone formers, and the shell covering the bone from the outside is periosteum... The ossification process is not completed by the time of birth, therefore, there are many more cartilages in the skeleton of a newborn child, and the bone itself is significantly different in chemical composition from the bone of an adult. At the first stages of postnatal ontogenesis, it contains a lot of organic matter, does not have strength and is easily bent under the influence of unfavorable external influences: narrow shoes, improper position of the child in the crib or on the hands, etc. Intensive thickening of the walls and an increase in their mechanical strength lasts up to 6-7 years. Then, until the age of 14, the thickness of the compact layer practically does not change, and after 14 and up to 18 years, there is an increase in bone strength again.
Different bones grow differently. Flat bones, as, for example, most of the bones of the brain and facial skull, increase in size by the imposition of new bone tissue both on the surface (growth in thickness) and along the edges. Otherwise they grow longer than the limbs. First, bone tissue forms in the middle of the diaphysis, both on its surface and inside the cartilage. Ossification gradually spreads to the entire diaphysis; much later, islets of bone tissue appear in the pineal glands. However, on the border between the diaphysis and the pineal gland, an interlayer of cartilaginous tissue remains. From the side of the diaphysis, this layer undergoes partial destruction and replacement with bone tissue, but does not disappear, since at the same time new cells are formed in it. As a result, the distance between the pineal glands increases, in other words, the bone grows in length. With ossification of the cartilaginous layer, the growth of the bone in length becomes impossible.
The final ossification of the skeleton is completed in women at 17-21 years old, in men at 19-25 years old. Bones of different parts of the skeleton ossify at different times. For example, ossification of the spine ends by the age of 20-25, and of the tip vertebrae - even by the age of 30; ossification of the hand ends at 6-7 years, ossification of the carpal bones at 16-17 years; bones of the lower extremities - by about 20 years. In this regard, the tense subtle handmade can disrupt the development of the bones of the hand, and wearing uncomfortable shoes can lead to deformation of the foot.
The spine of a newborn is characterized by the absence of any bends and is characterized by extreme flexibility. By the age of 3-4, he acquires all four bends that are observed in an adult. At 3 months, cervical lordosis appears, at 6 months - thoracic kyphosis, by the 1st year - lumbar lordosis. The last to form is sacral kyphosis. However, until the age of 12, the child's spine remains elastic and the bends of the spine are poorly fixed, which easily leads to its curvature in unfavorable developmental conditions. An increase in the growth rate of the spine is observed in primary school age, at 7-9 years, and with the onset of puberty. After 14 years, the spine practically does not grow. By the age of 12-13, the chest already significantly resembles the chest of an adult.
The pelvic bones grow together at the age of 7-8, and from the age of 9, gender differences are formed in the structure of the pelvis in girls and boys. In general, the structure of the pelvis approaches an adult by the age of 14-16, from that moment the pelvis is able to withstand significant loads.
The skeleton of the head undergoes significant changes. In a newborn child, the flat bones of the cerebral skull are not yet in contact with each other throughout their entire length. The gap between the frontal and parietal bones is especially large - frontal or large fontanelle... It gradually overgrows by the end of the 1st, the beginning of the 2nd year of life. The gap between the occipital and two parietal bones ( small fontanelle) overgrows during the first months of a child's life, and more often - to his birth.
Even minor bruises on areas of the infant's head that are not protected by bone can lead to dangerous damage to the meninges and the brain itself. Therefore, special care must be taken when handling a baby during the first months of life, for example, when bathing or swaddling.
In children at an early age, the cerebral part of the skull is more developed than the facial one. With age, especially from 13-14 years old, the facial region grows more vigorously and begins to prevail over the brain. In a newborn, the volume of the cerebral section of the skull is 6 times greater than the facial one, and in an adult it is 2-2.5 times.
Head growth is observed at all stages of a child's development; it occurs most intensively during puberty.
The chemical composition of bones
Bones are composed of organic, inorganic (mineral) substances and water. In childhood and adolescence, the content of organic matter in bones exceeds the amount of mineral matter; in old age, the amount of organic matter decreases. Bones contain the bulk of the minerals found in the body. Their excess is deposited in the skeleton. With a lack of minerals, the body replenishes them from the bones. Consequently, the skeleton is involved in the exchange of mineral substances in the human body.
Bones are strong and resilient. The elasticity of bones depends on the amount of organic matter. Therefore, in children and young people it is more than in old age. If the bone is decalcified by keeping it in an acid solution for some time, then all minerals are removed. This bone can be tied into a knot.
Bone strength is very high. It is 5 times higher than that of reinforced concrete. If you ignite a bone on a fire, then all organic matter will be destroyed, and the mineral will remain. Such a bone retains its shape and the location of the bone plates, but loses its elasticity and becomes fragile. Minerals provide strength to bones. By old age, human bones become fragile, their elasticity decreases. Therefore, they are more prone to fractures.
Bone growth
In the early stages of development of the human embryo, its skeleton consists of connective tissue. Then it becomes cartilaginous. The skeleton of a newborn is not entirely made up of bone. As the child grows, the cartilage of the skeleton is replaced by bone tissue and the bones grow in length and thickness. Some bones do not go through the cartilaginous stage, such as the bones of the skull.
The growth of bones in thickness occurs due to the bone-forming cells of the periosteum. At the same time, the bone tissue is absorbed on the inner surface of the compact substance and the volume of the bone cavity increases. The bone grows in length due to cartilaginous growth plates located between the body and the epiphyses of the bone. The cells of the cartilaginous growth plates form bone tissue and the body of the bone lengthens.
Some bones are laid in the human embryo from several parts, subsequently forming one bone. So, complete ossification of the pelvic bone occurs by 14-16 years, and tubular - at 18-25 years. The development of the skeleton and growth stops in men at the age of 20-25, and in women at the age of 18-21. During the development of the human skeleton, not all cartilage is replaced by bone tissue. The ends of the ribs, part of the skeleton of the nose, remain cartilaginous in an adult. The surfaces of the epiphyses of the bones are covered with cartilage.
"Human Anatomy and Physiology", M.S. Milovzorova
The system of organs of support and movement - the musculoskeletal system - is a skeleton, consisting of bones and their joints, and muscles. Muscles are an active part of the musculoskeletal system. Muscle contractions move the bones of the skeleton. With the help of muscles, a person can remain motionless for a long time, holding often very complex choreographic poses. The total number of muscles in a person is about 600. They ...
Bones are made of hard bone tissue. Bone cells are located at a distance from one another and are connected by numerous processes. The bulk of the bone tissue is the intercellular substance. Osteons and insertion plates located between them consist of it. Bone cells are located between the bone plates. The intercellular substance contains organic matter and is impregnated with mineral salts, which give it strength. Bone tissue refers to ...
Each human bone is a complex organ: it occupies a certain position in the body, has its own shape and structure, and performs its inherent function. All types of tissues are involved in bone formation, but bone tissue predominates.
General characteristics of human bones
Cartilage covers only the articular surfaces of the bone, the outside of the bone is covered by the periosteum, and the bone marrow is located inside. Bone contains adipose tissue, blood and lymph vessels, and nerves.
Bone possesses high mechanical properties, its strength can be compared with the strength of metal. The chemical composition of human living bone contains: 50% water, 12.5% organic substances of a protein nature (ossein), 21.8% inorganic substances (mainly calcium phosphate) and 15.7% fat.
Types of bones by shape divided into:
- Tubular (long - shoulder, femoral, etc.; short - phalanges of the fingers);
- flat (frontal, parietal, scapula, etc.);
- spongy (ribs, vertebrae);
- mixed (wedge-shaped, zygomatic, lower jaw).
Human bone structure
The main structural unit of bone tissue is osteon, which is visible through a microscope at low magnification. Each osteon contains from 5 to 20 concentrically located bone plates. They resemble cylinders inserted into each other. Each plate consists of intercellular substance and cells (osteoblasts, osteocytes, osteoclasts). In the center of the osteon there is a channel - the osteon channel; vessels pass through it. Intercalated bone plates are located between adjacent osteons.
Bone tissue is formed by osteoblasts releasing the intercellular substance and walled up in it, they turn into osteocytes - process cells, incapable of mitosis, with weakly expressed organelles. Accordingly, the formed bone contains mainly osteocytes, and osteoblasts are found only in areas of growth and regeneration of bone tissue.
The largest number of osteoblasts is located in the periosteum - a thin but dense connective tissue plate containing many blood vessels, nerve and lymph endings. The periosteum provides bone growth in thickness and bone nutrition.
Osteoclasts contain a large number of lysosomes and are able to secrete enzymes, which can explain their dissolution of bone substance. These cells are involved in bone destruction. In pathological conditions in the bone tissue, their number increases sharply.
Osteoclasts are also important in the process of bone development: in the process of building the final shape of the bone, they destroy calcified cartilage and even newly formed bone, "correcting" its primary shape.
Bone structure: compact and spongy substance
On the cut, thin sections of the bone, two of its structures are distinguished - compact substance(bone plates are densely and orderly), located superficially, and spongy substance(bone elements are loosely located), lying inside the bone.
Such a structure of bones fully complies with the basic principle of structural mechanics - with the least material consumption and great ease to ensure the maximum strength of the structure. This is confirmed by the fact that the location of the tubular systems and the main bone beams corresponds to the direction of action of the forces of compression, tension and twisting.
The structure of bones is a dynamic reactive system that changes throughout a person's life. It is known that in people engaged in heavy physical labor, the compact layer of bone reaches a relatively high development. Depending on the change in the load on individual parts of the body, the location of the bone beams and the structure of the bone as a whole can change.
Connecting human bones
All bone connections can be divided into two groups:
- Continuous connections earlier in development in phylogeny, immobile or inactive in function;
- interrupted connections, later in development and more flexible in function.
Between these forms there is a transitional - from continuous to discontinuous or vice versa - half-joint.
The continuous connection of bones is carried out by means of connective tissue, cartilage and bone tissue (bone of the skull itself). A discontinuous bone joint, or joint, is a younger bone joint formation. All joints have a common structural plan, including the articular cavity, the articular capsule and the articular surfaces.
Articular cavity It stands out conditionally, since normally there is no void between the articular capsule and the articular ends of the bones, but there is fluid.
Joint bag covers the articular surfaces of the bones, forming a hermetic capsule. The bursa consists of two layers, the outer layer of which passes into the periosteum. The inner layer releases fluid into the joint cavity, which plays the role of a lubricant, providing free sliding of the articular surfaces.
Types of joints
The articular surfaces of the articulating bones are covered with articular cartilage. The smooth surface of the articular cartilage facilitates movement in the joints. The articular surfaces are very diverse in shape and size, they are usually compared with geometric shapes. Hence and the name of the joints by shape: spherical (shoulder), elliptical (radial-carpal), cylindrical (radial-ulnar), etc.
Since the movements of the articulating links are performed around one, two or many axes, joints are also usually divided by the number of axes of rotation into multiaxial (spherical), biaxial (elliptical, saddle-shaped) and uniaxial (cylindrical, block-shaped).
Depending on the the number of articulating bones joints are divided into simple, in which two bones are connected, and complex, in which more than two bones are articulated.