the skyscraper Bulk keeps on concrete support and steel beams. Wings of a huge air bus fasten powerful rasporkami and longerons. And our body keeps on an internal skeleton - a skeleton.
Without a skeleton our body would be shapeless weight of muscles, blood vessels and an internal. But elastic, firm bones form the strong skeleton supporting all other parts of a body. Working together with muscles, the skeleton allows to us full freedom to run, jump and be bent every which way.
The Skeleton of the person consists approximately of 206 separate bones connected by various joints. Depending on carried out function at each bone the size and the form - from a powerful femur in length to 50 sm to tiny, size about a flea, 2,6 mm stremechka in an ear.
Skeletal bones share on 4 basic groups. The oblong, slightly bent long bones are capable to maintain the big loadings. These are bones of feet, hands and fingers. Short - for example, carpal in brushes of hands and predpljusnevye in anklebones - are wide and thick. Wrong bones as it is clear from the name, neodinakovy in the sizes and the form. These are face bones and backs. Vitals are protected by flat bones - edges, a skull and shovels.
Muscles and bones
To bones are attached 500 with superfluous the muscles named the skeletal. Each muscle both ends fastens to a bone a cone-shaped sinew similar to a cord. At movement muscles are reduced and tighten bones. Muscles and bones together form one of the major systems of an organism - skeletno-muscular.
Mobility to a skeleton is given by articulate joints between bones. In some joints of a bone are strongly connected with each other by zigzag seams and seem to single whole. We will tell, big tazovaja the bone consists of three accrete bones - podvzdoshnoj above, lobkovoj below in front and sciatic below behind, there, where buttocks. At babies and children they still keep some mobility, but with the years grow together firmly. Other joints are more mobile, but to a miscellaneous. For example, the largest knee joint is similar to a door loop, allowing a shin to be bent back, but not forward or in the parties. The same loops, only less, it is possible to name and joints of fingers.
In a place where the foot incorporates to a basin, the spherical joint is located. The spherical top of a hip is drowned in vertluzhnoj to a hollow tazovoj bones, freely moving forward, back and to the parties. The hand is in the same way connected to a shoulder.
The Ridge or a spine column consists of 26 separate vertebras connected among themselves by a chain of joints. Each vertebra is only a little displaced in relation to neighbours, but, together taken, these displacement give to a backbone flexibility. Differently, you can bend forward, back and in both parties. The head is connected to a backbone other type of a joint. In the skull basis there are two bugorka. Coinciding with two cavities in the first vertebra, they allow to incline a head forward and back. This vertebra still name atlantom by name the Greek god holding all world on the shoulders. Koltseobraznyj the first vertebra is planted on a bone shoot of the second or axial vertebra. This cylindrical joint allows to turn a head in both parties. The elbow joint similar on a structure operates forearm rotation.
Perhaps, flat joints in which one surface slides on another are is most easier arranged. So some carpal bones are connected a patella to the bottom end of a femur and among themselves.
Sedlovidnyj a joint allows bones, without rotating, to move in two directions. So it is connected pjast a thumb to carpal bones that allows it to move across a palm. Without such opposed finger it would be difficult to us to take subjects.
In a typical joint adjoining surfaces of bones are covered by a brilliant, smooth cartilage similar to a small pillow. The joint is placed in a flexible bag, or sinovialnuju a membrane which develops slippery sinovialnuju a liquid. This liquid similar to a syrup greases a cartilage approximately the same as lubricating oil in mechanisms. A cartilage and sinovialnaja a liquid protect from deterioration rubbing the friend about the friend of a bone.
In inactive intervertebral joints (except a joint between atlantom and an axial vertebra) between bones are available elastic hrjashchevye layers. If the layer is displaced and restrains a nerve, there is a disease state which name disk displacement.
Each mobile joint is surrounded by sheaves - strong elastic plaits which are attached by both ends to bones. They do not allow bones to leave for natural limits of movements, threatening with a stretching, rupture or a dislocation.
we Will count bones
In a head 29 bones are. The uppermost - a dome-shaped skull - consists of strongly accrete 8 bones forming a receptacle for a brain. Add to them 14 obverse bones, on 3 in each ear and the bottom jaw. To facilitate a skull, the nature has provided in it some the cavities filled with air, or bosoms.
The Backbone consists of 26 bones - 7 cervical vertebras, 12 chest and 5 wide strong lumbar vertebras in the bottom third. The unique large bone - krestets - is located between tazovymi bones and generated from 5 accrete vertebras. The lowermost vertebra - kopchik, or human "§тюё=" - there is no time it was generated from 4 accrete vertebras.
The Thorax consists of 25 bones. From each party at us on 12 long bent edges, and in the center - a flat breast. Behind an edge are connected to chest vertebras, and in front of 10 top pairs edges are connected by cartilages to a breast.
In the shoulders located over them, and also in hands and palms 64 bones - about third of total number are. On either side of there are clavicles and shovels. Then there is a long humeral bone and two bones of a forearm - elbow and beam. It is a lot of stones in a palm: 8 carpal, 5 pjastnyh, 2 phalanxes in a thumb and on 3 phalanxes in other four.
The Basin, feet and stops consist of 62 bones - one more thirds of all skeleton. From both parties are located tazovye bones. Two tazovye bones and kresttsovaja a backbone part form the strong ring named a basin. Then there are two femurs, patellae over knee joints, and even more low - big and small bertsovye bones. In each anklebone on 7 predpljusnevyh bones. In stops, as well as in palms, too many small stones: on 5 pljusnevyh, 2 phalanxes in a thumb and on 3 phalanxes in other four.
the Internal structure
Live bones not so dry, white and fragile, as at museum skeletons. The live bone has grayish colour and is covered by an elastic film nadkostnitsy which fabric is penetrated by blood vessels and nerves.
Monolithic at first sight the bone actually has porous structure. Under nadkostnitsej disappears firm korkovyj a layer. On a cross-section cut of a bone you will see in korkovom a layer drawing from set of small circles. In these longitudinal gaversovyh channels there are blood vessels and the nerves originating in nadkostnitse. In gleams, or lacunas, between channels there are microscopic cages osteotsity of which the firm bone fabric consists.
More low korkovogo there is the easy porous layer similar to a sponge. It often name a spongy layer, but actually it firm. At last, in the center there is a marrow - the major krovetvornyj body of our organism.
As it is surprising for so firm fabric, the bone on one third consists of water. The rest is basically the fiber named collagen, and such minerals, as phosphorus and calcium. Collagen does a bone strong and hardy, forming a structural basis for the minerals giving to it hardness and elasticity.
New bones instead of old
Bones, as well as other parts of a body, continuously change and in due course wear out. In the course of time the organism deletes an old bone fabric and increases new, reacting to loadings. Differently, in those parts of a body which are subject to the raised loadings, bones change. We will tell, at equestrians on hips and in buttocks new bones can even grow.
The Bones which are not testing physical activities, gradually weaken. At inactive or confined to by an illness of bed of the person of a bone considerably weaken. About the same problems trap cosmonauts after long stay in space as absence of gravitation reduces loading by a skeleton.
At insignificant blows and concussions the bone is capable to be compressed and, without breaking, slightly to cave in. At the moment of a jump huge pressure falls upon bones of feet. The femur maintains the loading equivalent to weight of a hippopotamus, on everyone cm 2 . Our bones are perfectly adapted for usual loadings if not to subject them "эхяЁхфѕёью=Ёхээ№ь" to deformations. However awkward movement or falling happens enough for crisis or a bone crack.
Merging of bones
The Doctor should set immediately into place bone fragments as healing processes begin immediately after crisis. At first between fragments large clots of blood are formed. In some days the blood-groove deletes mineral substances from sharp fragments, leaving soft and elastic collagenic fibres. In the meantime, blood clots sprout a dense network of the fibres binding together broken fragments. Into this network get osteotsity, gradually forming a new firm bone fabric. Approximately in three weeks the gleam between fragments fills a soft, bone outgrowth rich with calcium. This so-called bone callosity gradually hardens and turns to the present bone. The next months and years all outgrowths or keen edges on a crisis place smooth out, and the bone becomes as new.
That who suffers illnesses of a marrow, it is possible to do changes. At first their own marrow collapses special preparations or an irradiation. Then the marrow taken from a breast or a basin of the healthy donor, is entered into veins of the patient.
Unekotoryh of people of finiteness are bent in the most unexpected directions, and often them name owners of double joints. Actually, about any double joints instead of habitual one is not present also speech. Simply their joints differ special mobility.
If you lived in the Middle Ages and suffered from strong headaches, doctors would decide that you are afflicted with an evil ghost, and, to relieve you of an illness, would make cranial trepanation. Differently, to you would drill an aperture in a skull to give vent to an evil ghost.