The core of the earth. Norm of formation of the nucleus of ossification of the fetal hip joints Formation of the nucleus
Japanese scientists believe they have identified the "lost element" in the Earth's core. They have been looking for this element for many decades, believing that it makes up a significant part of the center of our planet after iron and nickel. Now, having recreated the conditions of high temperatures and pressures deep in the bowels of the planet, scientists have established through experiments that the most likely candidate is silicon.
This discovery could help us better understand how our world was formed.
Lead researcher Eiji Otani from Tohoku University said: "We believe that silicon is a major element - about 5% by weight of the Earth's inner core may be silicon dissolved in iron-nickel alloys."
The innermost part of the Earth is believed to be a solid ball with a radius of 1200 km. It is too deep to be explored directly, so instead scientists study how seismic waves pass through the area and reveal compositional data.
The inner core is mostly composed of iron, which accounts for 85% of the weight, and nickel, which accounts for about 10% of the core. To find the unknown 5% of the core, Eiji Ohtani and his team created alloys of iron and nickel and mixed them with silicon. They then exposed them to the enormous pressures and temperatures that occur in the inner core.
Scientists found that this mixture matches what seismic data showed about the Earth's interior. Professor Ohtani says further work is needed to confirm the presence of silicon and not rule out the presence of other elements.
Core formation
Commenting on the study, Professor Simon Redfern from the University of Cambridge in the UK says: “These difficult experiments are very interesting because they provide a window into the interior of the Earth as it was just after the formation of the core 4.5 billion years ago, when the core was just beginning to separate from the solids. parts of the Earth. But other recent work also points to an important role for oxygen in the nucleus."
He says knowing what's in the core will help scientists better understand the conditions that existed during Earth's formation. In particular, was there a lot of oxygen then, or was it limited? If the Earth's core had been rich in silicon four-plus billion years ago, the rest of the planet would have been relatively rich in oxygen. If not, oxygen was sucked into the core, and the surrounding solid mantle was poor in this element.
“In some ways, these two options represent viable alternatives, depending on the conditions prevailing on Earth at the time the core formed. The new work adds depth to our understanding, but I am confident that this is not the last word in this story."
In the process of evolution, they underwent a number of changes. The appearance of new organelles was preceded by transformations in the atmosphere and lithosphere of the young planet. One of the significant acquisitions was the cell nucleus. Eukaryotic organisms received, thanks to the presence of separate organelles, significant advantages over prokaryotes and quickly began to dominate.
The cell nucleus, the structure and functions of which differ slightly in different tissues and organs, has made it possible to improve the quality of RNA biosynthesis and the transmission of hereditary information.
Origin
To date, there are two main hypotheses about the formation of a eukaryotic cell. According to the symbiotic theory, organelles (such as flagella or mitochondria) were once separate prokaryotic organisms. The ancestors of modern eukaryotes absorbed them. As a result, a symbiotic organism was formed.
The nucleus was formed as a result of protrusion into the cytoplasmic region and was a necessary acquisition on the way to the cell’s development of a new method of nutrition, phagocytosis. The capture of food was accompanied by an increase in the degree of cytoplasmic mobility. Genophores, which were the genetic material of a prokaryotic cell and attached to the walls, fell into a zone of strong “current” and needed protection. As a result, a deep invagination of a section of the membrane containing attached genophores was formed. This hypothesis is supported by the fact that the nuclear membrane is inextricably linked with the cytoplasmic membrane of the cell.
There is another version of the development of events. According to the viral hypothesis of the origin of the nucleus, it was formed as a result of infection of an ancient archaeal cell. A DNA virus penetrated into it and gradually gained complete control over life processes. Scientists who consider this theory more correct provide a lot of arguments in its favor. However, to date there is no comprehensive evidence for any of the existing hypotheses.
One or more
Most modern eukaryotic cells have a nucleus. The vast majority of them contain only one such organelle. There are, however, cells that have lost their nucleus due to certain functional features. These include, for example, red blood cells. There are also cells with two (ciliates) and even several nuclei.
Structure of the cell nucleus
Regardless of the characteristics of the organism, the structure of the nucleus is characterized by a set of typical organelles. It is separated from the internal space of the cell by a double membrane. Its internal and external layers merge in some places, forming pores. Their function is to exchange substances between the cytoplasm and the nucleus.
The space of the organelle is filled with karyoplasm, also called nuclear juice or nucleoplasm. It houses chromatin and the nucleolus. Sometimes the last of the named organelles of the cell nucleus is not present in a single copy. In some organisms, on the contrary, nucleoli are absent.
Membrane
The nuclear envelope is formed by lipids and consists of two layers: outer and inner. Essentially, this is the same cell membrane. The nucleus communicates with the channels of the endoplasmic reticulum through the perinuclear space, a cavity formed by two layers of the membrane.
The outer and inner membranes have their own structural features, but in general they are quite similar.
Closest to the cytoplasm
The outer layer passes into the membrane of the endoplasmic reticulum. Its main difference from the latter is a significantly higher concentration of proteins in the structure. The membrane, in direct contact with the cytoplasm of the cell, is covered with a layer of ribosomes on the outside. It is connected to the inner membrane by numerous pores, which are rather large protein complexes.
Inner layer
The membrane facing the cell nucleus, unlike the outer one, is smooth and not covered with ribosomes. It limits the karyoplasm. A characteristic feature of the inner membrane is the layer of nuclear lamina lining it on the side in contact with the nucleoplasm. This specific protein structure maintains the shape of the shell, is involved in the regulation of gene expression, and also facilitates the attachment of chromatin to the nuclear membrane.
Metabolism
The interaction between the nucleus and the cytoplasm occurs through They are quite complex structures formed by 30 proteins. The number of pores on one core may vary. It depends on the type of cell, organ and organism. Thus, in humans, the cell nucleus can have from 3 to 5 thousand pores; in some frogs it reaches 50,000.
The main function of pores is the exchange of substances between the nucleus and the rest of the cell. Some molecules penetrate through pores passively, without additional energy expenditure. They are small in size. Transporting large molecules and supramolecular complexes requires the expenditure of a certain amount of energy.
RNA molecules synthesized in the nucleus enter the cell from the karyoplasm. In the opposite direction, proteins necessary for intranuclear processes are transported.
Nucleoplasm
The structure of nuclear sap changes depending on the state of the cell. There are two of them - stationary and arising during the period of division. The first is characteristic of interphase (time between divisions). At the same time, nuclear juice is distinguished by a uniform distribution of nucleic acids and unstructured DNA molecules. During this period, the hereditary material exists in the form of chromatin. The division of the cell nucleus is accompanied by the transformation of chromatin into chromosomes. At this time, the structure of the karyoplasm changes: the genetic material acquires a certain structure, the nuclear membrane is destroyed, and the karyoplasm mixes with the cytoplasm.
Chromosomes
The main functions of the nucleoprotein structures of chromatin transformed during division are the storage, implementation and transmission of hereditary information contained in the cell nucleus. Chromosomes are characterized by a specific shape: they are divided into parts or arms by a primary constriction, also called the coelomere. Based on their location, three types of chromosomes are distinguished:
- rod-shaped or acrocentric: they are characterized by the placement of the coelomere almost at the end, one arm is very small;
- multi-armed or submetacentric have shoulders of unequal length;
- equilateral or metacentric.
The set of chromosomes in a cell is called a karyotype. For each type it is fixed. In this case, different cells of the same organism can contain a diploid (double) or haploid (single) set. The first option is typical for somatic cells, which mainly make up the body. The haploid set is the privilege of germ cells. Human somatic cells contain 46 chromosomes, sex cells - 23.
The chromosomes of the diploid set are in pairs. Identical nucleoprotein structures included in a pair are called allelic. They have the same structure and perform the same functions.
The structural unit of chromosomes is the gene. It is a section of a DNA molecule that codes for a specific protein.
Nucleolus
The cell nucleus has one more organelle - the nucleolus. It is not separated from the karyoplasm by a membrane, but it is easy to notice when examining the cell using a microscope. Some nuclei may have multiple nucleoli. There are also those in which such organelles are completely absent.
The shape of the nucleolus resembles a sphere and is quite small in size. It contains various proteins. The main function of the nucleolus is the synthesis of ribosomal RNA and the ribosomes themselves. They are necessary to create polypeptide chains. Nucleoli are formed around special regions of the genome. They are called nucleolar organizers. This contains the ribosomal RNA genes. The nucleolus, among other things, is the place with the highest concentration of protein in the cell. Some proteins are necessary to perform organelle functions.
The nucleolus consists of two components: granular and fibrillar. The first represents the maturing ribosomal subunits. In the fibrillar center, the granular component surrounds the fibrillar component, located in the center of the nucleolus.
Cell nucleus and its functions
The role played by the nucleus is inextricably linked with its structure. The internal structures of the organelle jointly implement the most important processes in the cell. Genetic information is located here, which determines the structure and functions of the cell. The nucleus is responsible for the storage and transmission of hereditary information, which occurs during mitosis and meiosis. In the first case, the daughter cell receives a set of genes identical to the mother's. As a result of meiosis, germ cells with a haploid set of chromosomes are formed.
Another equally important function of the nucleus is the regulation of intracellular processes. It is carried out as a result of control of the synthesis of proteins responsible for the structure and functioning of cellular elements.
The effect on protein synthesis has another expression. The nucleus, controlling the processes inside the cell, unites all its organelles into a single system with a well-functioning operating mechanism. Failures in it usually lead to cell death.
Finally, the nucleus is the site of synthesis of ribosomal subunits, which are responsible for the formation of the same protein from amino acids. Ribosomes are essential in the process of transcription.
It is a more perfect structure than the prokaryotic one. The emergence of organelles with their own membrane has made it possible to increase the efficiency of intracellular processes. The formation of a nucleus surrounded by a double lipid shell played a very important role in this evolution. Membrane protection allowed ancient single-celled organisms to develop new ways of life. Among them was phagocytosis, which, according to one version, led to the emergence of a symbiotic organism, which later became the progenitor of the modern eukaryotic cell with all its characteristic organelles. The cell nucleus, structure and functions of some new structures made it possible to use oxygen in metabolism. The consequence of this was a fundamental change in the Earth's biosphere; the foundation was laid for the formation and development of multicellular organisms. Today, eukaryotic organisms, which include humans, dominate the planet, and there is no sign of changes in this regard.
An alloy with an admixture of other siderophile elements. The estimated temperature in the center of the Earth's core reaches 5000? C, density - about 12.5 t/m?, pressure - up to 361 GPa. The mass of the earth's core is 1,932? 10 24 kg.
There is very little data about the core - all information was obtained by indirect geophysical or geochemical methods, samples of the core material are not available, and it is unlikely that they will be obtained in the near future.
1. History of the study
One of the first to suggest the existence of a region of increased density inside the Earth was Henry Cavendish, who calculated the mass and average density of the Earth and found that it was significantly greater than that characteristic of rocks exposed on the Earth’s surface.
The existence of the core was proven last year by the German seismologist E. Wichert due to the presence of the so-called “seismic shadow” effect. years, following a sharp jump in the speed of longitudinal seismic waves, the American geophysicist Beno Gutenberg determined the depth of its surface - 2900 km.
Founder of geochemistry V. M. Goldschmidt (German) Victor Moritz Goldschmidt ) proposed that the core was formed by gravitational differentiation of the primordial Earth during the accretion period or at later periods. An alternative hypothesis that the iron core was formed in the protoplanetary cloud was developed by the German scientist A. Eiken (), the American scientist E. Orovan and the Soviet scientist A. P. Vinogradov ( - 70s).
4. Mechanism for constantly updating the internal core
A number of studies in recent years have shown anomalous properties of the earth's core - it was found that seismic waves cross the eastern hemisphere of the core faster than the western. Classical models suggest that the inner core of our planet is a symmetrical, homogeneous and practically stable formation, which slowly grows due to the solidification of the material of the outer core. However, the inner core is a fairly dynamic structure.
A group of researchers from Joseph Fourier universities Universit? Joseph Fourier ) And Lyon (fr. Universit? de Lyon) put forward the assumption that the inner core of the Earth is constantly
The condition of the musculoskeletal system and the hip joint are closely interrelated. The process of ossification of the hip joints occurs gradually in humans and is completed at the age of 20 years. The focus of bone tissue formation appears during the period of intrauterine development. At this time, the fetus begins to form a hip joint.
If the baby is premature and is born prematurely, by the time of birth the nuclei in the joints will be small. This deviation can also occur in full-term infants; they also often exhibit the absence of ossification nuclei. In most cases, this is a pathology that affects the development of the musculoskeletal system. If the nuclei do not develop during the first year of a baby’s life, the full functioning of his hip joints is at risk.
Types of pathologies of the nuclei of the hip joint
The health status of the newborn is the main criterion for determining in which case slow nuclear development is normal and in which it is pathology. If the child does not have a dislocation in this area, then in this case the delayed development of the nuclei is not assessed as a dangerous pathology. When the normal functioning of the hip joints is not disrupted, but the nuclei develop slowly, this is also not a dangerous process. When the baby has impaired functioning of the musculoskeletal system, there is a dislocation in this area and both of these phenomena arose due to the absence of ossification nuclei, the pathology is dangerous. It harms the child’s health and disrupts the growth, formation, and functioning of the joints located in this area.
We must immediately clarify: this pathology of the bone hip joints occurs mainly in newborn babies and in children whose age is no more than a year. The condition of the musculoskeletal system directly depends on the intrauterine development of the child. When a woman is 3-5 months pregnant, the baby begins to lay down bone tissue, which will become the basis of its limbs. Ossification nuclei are the key to the normal development of the child’s musculoskeletal system. At the time of birth, they increase to a diameter of 3-6 millimeters. When the ossification nuclei reach this value, this is an indication that the bones and tissue of the fetus are developing normally. If the baby is born full-term, this fact will also have a positive effect on the further development of the musculoskeletal system.
However, in medical practice there are many cases when full-term children who developed normally in the womb experience problems with the development of the hip joint. Due to a number of reasons not yet completely known to science, they simply do not have such nuclei. This occurs in 3-10% of babies.
The time norm for the development of the ossification nucleus is not the same for everyone, as are some signs of the formation of these tissues. There are often cases when the nuclei do not develop in the fetus until the woman is 8 months pregnant, and this process slows down the formation of the tissues themselves. Then, without the influence of any external factors, the baby’s hip joint begins to dynamically develop.
In such cases, at the 8th month of pregnancy, the nuclei reach a normal size, no different in structure and shape from those that were formed in other children when their mothers were 3-5 months pregnant. And in the state of tissues that are delayed in development, no deviations are noted in this area.
Factors provoking ossification
As the child develops, the hip joint enlarges. A similar process occurs with nuclei. There are a number of negative factors that can cause a delay in their increase, that is, cause ossification. It should be noted: the same reasons negatively affect the growth of the hip joint.
Every second child who has rickets suffers from ossification, because it causes a catastrophic lack of nutrients in the tissues. Vitamins and microelements are not received in the required volume by muscle tissue, ligaments, tendons, and bones.
If the baby has dysplasia and the hip joint suffers, it will negatively affect the formation of nuclei. Most often, they develop slowly in children who are bottle-fed. It weakens the child’s immunity and does not have a beneficial effect on their tissues.
The main symptoms of dysplasia in children are:
- asymmetry of skin folds;
- restriction in hip abduction;
- clicking symptom (sliding symptom);
- external rotation of the hip;
- relative shortening of the limb.
The health status of both parents is often the main cause of hip joint pathologies in the baby. A special role in this process is played by the health of the mother, which is reflected in the nuclei. Medical studies show that if parents have diabetes, such a nucleus in the child will develop slowly. In such a child, the hip joint will begin to form much more slowly than in peers. In such situations, a set of measures aimed at stimulating and developing the musculoskeletal system is required. Such help is needed by many children whose parents suffer from thyroid diseases. The nucleus in such children develops slowly. In parallel with this process, there are signs of metabolic disorders that inhibit the development of the hip joint. All this affects the formation of the main tissues in the pelvic area.
An important factor influencing the health of the unborn child and the development of his hip joint is how the woman’s pregnancy proceeded. The nuclei may be absent or develop slowly in pelvic, transverse, or breech presentations of the fetus.
Pathologies in this area often arise due to the incorrect position of the growing baby in the mother's womb. The fetal nucleus may not begin to form due to a lack of vitamins E, B and microelements necessary for this process in the mother’s body: calcium, phosphorus, iodine, iron. All this affects the development of the baby. Hormonal imbalances, multiple pregnancies, viral and infectious diseases of the mother, and the presence of gynecological problems during pregnancy are all reasons why the nucleus will not develop.
An important point is the genetic predisposition to diseases of the hip joint. A number of pathologies in this area can be inherited. Premature birth and unfavorable environmental factors also affect how the nucleus is formed. But, as scientific research shows, in every fifth case such a malfunction is due to genetic reasons.
An equally dangerous factor is the underdevelopment of the spine and spinal cord in the mother. This also affects the condition of the baby’s musculoskeletal system. Increased uterine tone does not go unnoticed for the development of the fetus; it can often provoke disturbances in the development of the child’s musculoskeletal system.
Hypertonicity of the uterus in some cases can be the root cause of the fact that the nucleus does not form or develops slowly.
First steps to help a child
In the first year of life, the child’s hip joint should stabilize. The neck of the femur gradually ossifies. At the same time, its ligamentous apparatus is strengthened, and its head is centralized. The acetabulum must reduce the angle of inclination so that the baby’s musculoskeletal system can function normally.
The ossification nucleus is especially actively formed from the 4-6th month of a child’s life; at 5-6 years old, it increases on average 10 times in a child. At 14-17 years old, cartilage will be replaced by bone. The femoral neck will continue to grow until the age of 20, by which time the femoral joint will have formed and there will be bone in place of the cartilage.
If it has not developed correctly all this time, the head of the femur will not be able to stay in the socket of the hip joint, which is a sign of dysplasia. In order to prevent pathology in this area, it is necessary to immediately consult a doctor at the slightest disturbance in their formation in a child. If the hip joint has pathology associated with nuclear development, ultrasound will detect it. To identify it, sonographic research methods are also used. An X-ray examination of the pelvis may often be required. For this purpose, the X-ray is taken in a direct projection. It allows doctors to receive the most accurate information about the presence or absence of pathology.
There are special orthopedic devices to ensure that a child’s hip joint develops normally. When there is a delay in the development of its head, orthopedists prescribe treatment and prevention of rickets. In such cases, doctors prescribe wearing a special splint. It is effectively strengthened by electrophoresis and massage. Sea salt baths and paraffin baths help stabilize the hip joint.
If the baby has ossification, parents should definitely take care that his hip joint does not get damaged. It is strictly forbidden to sit or stand a child until the hip joint is strengthened and stabilized.
Prevention for mothers
Even if there is a family predisposition to ossification and dysplasia of the hip joint, there is always a chance to prevent the disease. Properly taken preventive measures will protect the developing hip joint of the fetus. It all starts with nutrition. During pregnancy, a woman should receive all the necessary vitamins and microelements. They will participate in the formation of all the joints of her unborn child. At the slightest sign of vitamin deficiency in your baby, you should immediately consult a doctor. Vitamin deficiency, like rickets, negatively affects the baby’s musculoskeletal system.
During breastfeeding, a woman should receive a balanced diet so that the baby’s hip joint receives all the necessary minerals and trace elements. In order for the musculoskeletal system to develop normally, a child from 7 months should receive a diet consisting of additional food products. Walking in the fresh air, massage, exercise, and hardening the baby are useful for the development of the musculoskeletal system. However, all these procedures must be agreed upon with the attending physician, who will help you choose a set of measures for the development of the hip joint.
In the autumn-winter period, for prevention, the baby will definitely need to take vitamin D, which is necessary for its normal functioning and growth.
Recently, the hypothesis of the formation of the Earth's core from metallized silicates as a result of gravitational convection has gained popularity, which proceeds from the fact that the existence of a liquid core, denser than the mantle, means that intensive differentiation of the primary substance of the Earth and all substances occurs (or occurred). those heavier than the substance of the outer core must sink into it, and all substances lighter than the primary substance of the Earth must rise into the outer layers. However, as follows from the calculations of V.N. Zharkov and V.A. Magnitsky (1970), the process of differentiation of the Earth’s matter can occur only if there is a region where the separation of matter with different densities occurs. Differentiation of any rock by density is possible only after its effective liquefaction. This means that approximately a few tens of percent to half the volume of the rock should be melted. At a lower liquid concentration, the majority of particles are unable to move in a solid medium, and their speed of movement in the gravity field is low. Thus, this hypothesis does not find an explanation for the preliminary melting of the Earth’s substance, but only declares it. Moreover, due to the established solid nature of the lower mantle, convection of matter through the entire shell of the Earth cannot occur.
It should be borne in mind that V. Ramsey's calculations, which allow the metallization of silicates, have not been confirmed experimentally and contradict the temperatures calculated by other researchers at the core boundary. As V.N. Zharkov and V.A. Magnitsky showed in 1970, the hypothesis of metallization of silicates cannot be accepted for the following reasons: a) in experiments with powerful shock waves, most silicates were compressed to pressures much higher than the pressure at the boundary of the earth core (1.4-10 21 Pa), but the corresponding phase transition was not detected; even if this transition is “slow”, then it still had to happen, since the factor determining the disequilibrium AVAp (AV - volume jump, Ap - transfer) is so great that it will practically “zero out” any finite transition time; b) metallization of silicates under the conditions of the earth’s core cannot be accompanied by a decrease in volume by approximately two times, as required by geophysical data; c) the properties of iron (according to laboratory data) are very close to the properties of the earth’s core (according to geophysical data), which makes it possible to assume a substantially iron composition of the core with the addition of some fairly common light elements (for example, silicon).
Finally, the assumption of such significant pressures at great depths of the Earth (of the order of 1.5-10 11 Pa) is geologically completely unjustified, since all calculations about the increase in pressure with depth are based on the hydrostatic law, i.e. on the assumption that there are no lateral pressures does not exist and that the upper layers press on the lower ones with their full weight. The fact that this assumption does not correspond to reality follows even from the fact of the existence of super-deep mines and wells and, in particular, the Kola super-deep (the “vault” effect). The binding energy in the crystal lattice at relatively low temperatures is sufficient to withstand pressure from all sides of n-10 11 Pa, which was pointed out in 1930 by P. N. Chirvinsky and V. K. Cherkas, according to whose data it follows, that if individual zones of the Earth (geosphere) at great depths have hardened, then there will be no pressure gradient at all, and the geospheres of the Earth in this case are similar to steel spheres. The conclusion about the absence of ultra-high pressures within, in particular, the lower mantle was reached in 1968 by V. A. Magnitsky, and in 1969 by F. Staei. We can speak with certainty about hydrostatic pressure only in relation to the outer core, since it is in a plastic state, but the pressure of the plastic core on the solid inner core cannot exceed 1.5-10 11 Pa, and therefore the hypothesis of metallized silicates is not confirmed and from these positions.
