Skull: anatomy of the most complex part of the human skeleton

March 1, 2019

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The human spine is the basis of the musculoskeletal system. At the same time, it not only performs a supporting function and provides the ability to walk upright, but also represents a fairly flexible axis of the body, which is achieved due to the mobility of the vast majority of its individual parts. In this case, the anterior part of the spine participates in the formation of the walls of the thoracic and abdominal cavities. But one of its most important functions is to ensure the safety of the spinal cord that runs inside it.

Features of the structure of the spine

The human spine is formed by 31-34 vertebrae lying on top of each other, between the bodies of which there are peculiar cartilaginous formations - intervertebral discs. In addition, adjacent vertebrae are connected to each other by joints and ligaments. In general, in the spine one can distinguish 122 joints of different sizes and structures, 365 ligaments and 26 cartilaginous joints, but there are only 52 true joints.

Most vertebrae have a similar structure. They have:

• body - the main part of the vertebra, which is a spongy bone close to a cylindrical shape;
• arch - a semicircular shaped bone structure located at the back of the vertebral body and attached to it by two legs;
• articular, transverse and spinous processes - have different lengths and extend from the vertebral arch, forming the spinal canal together with the body and arch, and the articular processes of adjacent vertebrae form true joints, called facet or facet joints.

Spongy bone is a special type of bone tissue that is highly durable. Inside, it has a system of bone crossbars diverging in different directions, which ensures its increased resistance to multidirectional loads.

Formed by the posterior part of the vertebral bodies, arches and processes, the vertebral foramina clearly coincide with each other and create a single spinal canal, where the spinal cord is located, conventionally divided into segments. On average, in an adult, its cross-sectional area is about 2.2-3.2 cm2, but in the cervical and lumbar regions it has a triangular shape, while in the thoracic region it is round.

At the level of each vertebra, spinal roots extend in pairs from the corresponding segments of the spinal cord. They pass through natural openings formed by the processes of the vertebrae. Blood vessels providing nutrition to the spinal cord are also located here.

Changing the position of the spine is carried out with the help of muscles attached to the vertebral bodies. It is thanks to their contraction that the body bends, and relaxation leads to the restoration of the normal position of the vertebrae.

Sections of the spine and structural features of the vertebrae

The spine is divided into 5 sections: cervical, thoracic, lumbar, sacral and coccygeal. At the same time, no matter how strange it may be, in fact, in different people, the spine can be formed by a different number of vertebrae. This:

• 7 cervical vertebrae – C1-C7;
• 12 chest – T1—T12;
• 5 lumbar – L1-L5;
• 5 sacral – S1-S5;
• 2-5 coccygeal.

The sacral and coccygeal vertebrae are connected motionlessly.

The cervical spine has the greatest mobility. It has 2 vertebrae, the structure of which is very different from the rest, since they must ensure the connection of the spinal column with the bone structures of the head, and also create the opportunity for turns and tilts of the head. The thoracic region is the least mobile. It has direct connections with the ribs, which provokes the appearance of corresponding anatomical features of the vertebrae of this section. Overall, it provides organ protection and support to the body. The lumbar spine is distinguished by massive vertebrae that bear the main weight of the body. The sacrum, formed by 5 fused vertebrae, helps maintain the vertical position of the body and takes part in distributing the load. The last part of the spine, the coccyx, serves as the attachment point for ligaments and other anatomical structures.

There are also developmental anomalies in which there is a change in the number of vertebrae. Normally, during embryonic development, the 25th vertebra should fuse with the sacrum. But sometimes this does not happen, which leads to the formation of the 6th lumbar vertebra. In such cases, they speak of the presence of lumbarization. There are also opposite cases, when not only the 25th, but also the 24th vertebrae fuses with the sacrum. As a result, 4 vertebrae remain in the lumbar region, while the sacrum is formed by the 6th. This is called sacralization.

The vertebrae of different parts of the spinal column have different sizes and shapes, but all of them are covered on the front, back and sides with a thin layer of dense tissue, perforated by vascular canals. The cervical vertebrae are the smallest, while the first of them, the atlas, has no body at all. As the serial number increases, the size of the vertebral bodies increases and reaches a maximum in the lumbar region. The fused sacral vertebrae bear the entire weight of the upper body and connect the spine to the pelvic bones and lower limbs. The coccygeal vertebrae are the remnants of a rudimentary tail and are small bone formations that have extremely poorly developed bodies and are completely devoid of arches.

Normally, the height of the vertebral bodies is the same over the entire area, with the exception of the 5th lumbar vertebra (L5), the body of which is wedge-shaped.

The spinous processes present in almost all vertebrae, tiledly covering each other, extend from them at different angles in different parts of the spine. Thus, in the cervical and lumbar regions they are located almost horizontally, and at the mid-thoracic level, which corresponds to 5-9 thoracic vertebrae, they are located at rather sharp angles. At the same time, the processes of the upper and lower thoracic vertebrae occupy an intermediate position.

The spinous processes, as well as the transverse ones, are the base to which the ligaments and muscles that move the vertebrae are attached. The articular processes of adjacent vertebrae form facet joints. They create the ability to bend the spine back and forth.

Thus, the vertebral bodies are connected by intervertebral discs, and the arches are connected by intervertebral joints and ligaments. The anatomical complex formed by the intervertebral disc, two adjacent intervertebral joints and ligaments is called the spinal motion segment. In each individual segment, the mobility of the spine is small, but the simultaneous movement of many segments provides a sufficient level of flexibility and mobility of the spine in different directions.

Normally, the spine has 4 physiological curves, which provide a weakening of shocks and concussions of the spine during movement. Thanks to this, they do not reach the skull and ensure the safety of the brain. There are:

• cervical lordosis;
• thoracic kyphosis;
• lumbar lordosis;
• sacrococcygeal kyphosis.

Lordosis is a curvature of the spine that is convex toward the front of the body, and kyphosis is a curve in the opposite direction.

Due to the presence of physiological curves, the human spine has an S-shape. But normally they should be smooth and not exceed permissible values. The presence of pronounced angles or the location of the spinous processes at different distances from each other is a sign of a pathological increase in kyphosis or lordosis. In the lateral or frontal plane, any bends or tilts should normally be absent.

Moreover, the degree of physiological bending is not a constant value even for an absolutely healthy person. The fact is that the angle of inclination depends on the age of the person. Thus, a child is born already having physiological curves of the spine, but they are much less pronounced. The degree of their manifestation directly depends on the age of the child.

In a horizontal position of the body, physiological bends straighten out a little, and in a vertical position they are more pronounced. Therefore, in the morning after sleep, the length of the spine increases slightly, the curves are less pronounced, and in the evening the situation changes. Moreover, when the load increases, the magnitude of the bends increases proportional to the applied load.

All vertebrae are different sizes. Moreover, their width and height progressively increase with distance from the head. The dimensions of the intervertebral discs correspond to the vertebral bodies and are present between almost all of them. Such a cartilaginous layer, which acts as a shock absorber and ensures mobility of the spine, is absent only between the 1st and 2nd cervical vertebrae, i.e., the atlas and axis, as well as in the sacrum and coccyx.

There are a total of 23 intervertebral discs in the adult human body. Each of them has a pulpous nucleus, called the pulposus, and a surrounding tough fibrous membrane, called the annulus fibrosus. The intervertebral disc passes into a fairly thin plate of hyaline cartilage, which covers the bone surface.

Ligamentous apparatus

The spine is equipped with a powerful ligamentous apparatus formed by a large number of different ligaments. The main ones are:

• The anterior longitudinal ligament is formed by fibers and bundles of different lengths, which are firmly attached to the vertebral bodies and much more loosely to the corresponding intervertebral discs. It runs along the anterior and lateral surfaces of the vertebral bodies. This ligament originates from the occipital bone and passes through the entire spinal canal up to the 1st sacral vertebra.
• The posterior longitudinal ligament also originates from the occipital bone and covers the posterior surface of the vertebral bodies down to the lower part of the sacral canal. Its thickness is greater than that of the anterior similar ligament, and at the same time it is more elastic due to the presence of a larger number of elastic fibers. Unlike the anterior one, it firmly fuses with the intervertebral discs, but is more loosely attached to the bony bodies of the vertebrae. Therefore, in places of contact with cartilaginous plates it is thicker in cross section, and at the point of attachment to the vertebrae it takes on the appearance of a narrow strip. The lateral parts of the posterior longitudinal ligament form a thin membrane that delimits the venous plexuses of the vertebral bodies from the dura mater of the spinal cord, thereby protecting the spinal cord from compression.
• Ligamentum flavum – located between the vertebral arches, closing the gaps and forming the spinal canal. They are formed from elastic fibers, but with age they tend to become denser, that is, ossify. The ligamentum flavum resists excessive forward flexion and extension of the spine.

There are also interspinous, intertransverse and supraspinous ligaments that connect the corresponding processes. But the legs of the arches are not connected by ligaments, which is why intervertebral foramina are formed, through which the spinal roots and blood vessels emerge.

Connection of the spine to the skull

The spinal column is connected to the skull through:

• paired atlanto-occipital joints;
• median atlantoaxial joints;
• lateral atlantoaxial joints.

The atlanto-occipital joints are formed at the point of contact of the protruding parts (condyles) of the occipital bone with the upper articular fossae of the 1st vertebra of the cervical spine, called the atlas. Both atlanto-occipital joints are surrounded by wide articular capsules and strengthened by 2 membranes: anterior and posterior. These joints have physiological restrictions on mobility: flexion up to 20°, extension not exceeding 30°, head tilt to the side within 15-20°.

By the way, it is through the posterior atlanto-occipital membranes, which are wider, that the vertebral arteries, which are responsible for the blood supply to the vertebrobasilar area of ​​the brain, pass.

The median atlantoaxial joint has a cylindrical shape and includes 2 separate joints, which are formed by the posterior and anterior articular surfaces of the tooth of the 2nd cervical vertebra, a fossa on the posterior side of the arch of the 1st cervical vertebra, and a fossa on the anterior surface of the transverse ligament. Both tooth joints have separate articular cavities and capsules. The vertebral tooth is connected to the foramen magnum by a corresponding ligament, at the same time it has 2 strong pterygoid ligaments, which begin on its lateral surfaces and are attached to the condyle of the occipital bone, thereby preventing excessive rotation of the head. Therefore, rotations in the joint are only possible by 30-40° in each direction.

The lateral atlantoaxial joint is a paired combined multiaxial low-moving joint, the formation of which involves the lower articular fossa of the C1 vertebra and the upper articular surfaces of the axial vertebra. Each joint has a separate capsule and is additionally strengthened by the cruciate ligament of the atlas. It originates from the apex of the tooth and ends at the front of the foramen magnum.

Structure of the skull: anatomy of bone joints and joints

The vast majority of the skull bones are connected using fixed sutures. Facial bone formations adjacent to each other form flat joints, invisible under the thin cover of the muscle tissue. And the temporal bone, connecting with the parietal, gives rise to the scaly suture.

There are only 3 serrated sutures in the anatomy of the skull:

• coronary, formed by the parietal and frontal bones;
• sagittal, located between the two parietal bones;
• lambdoid, located between the occipital and parietal bones.

The only movable joint of the skull is the mandibular joint. The lower jaw can perform movements in different planes: rise and fall, move to the right/left and forward/backward. Thanks to this mobility, a person can not only chew food thoroughly, but also maintain articulate speech.

Age characteristics

With age, the shape and structure of the skull changes. Thus, in newborn babies, the facial region is almost 8 times smaller than the brain, so the head may look disproportionate and large. The baby's jaws are usually underdeveloped and have no teeth, because he does not yet have the need to chew solid food.

The bones of the skull of infants do not articulate tightly, due to which the head can slightly change shape and shrink as it passes through the birth canal. This feature protects newborns from birth injuries and helps maintain normal intracranial pressure. At the interosseous sutures they have noticeable membranous areas - fontanelles. The largest, the anterior fontanelle, occupies a central position at the junction of the sagittal and coronal sutures. It usually heals by the age of two. Other fontanelles are less voluminous: the occipital, two sphenoid and mastoid membranes are not palpable by 2–3 months.

Anatomy of the skull

changes not only in infancy - formation usually takes place in 3 stages:

1. Predominant growth in height, strengthening of bones and hardening of sutures - from birth to 7 years;
2. The period of relative rest is from 7 to 14 years;
3. The growth of the facial part of the skull is from 14 to 20–25 years, depending on puberty.

A short excursion into the anatomy of the skull allows us to clearly see that the head is an extremely complex structure, the condition of which directly affects the health of the brain, and therefore most vital functions. With the slightest injury, most of the damage is taken by the bones, but their strength is not unlimited - with a strong impact, fractures and bruises are possible, the consequences of which can be irreversible. Therefore, under any circumstances, the skull should be properly protected and protected from injury and other damage.

Spinal cord

The spinal cord is one of the parts of the central nervous system. It is a long, delicate cylindrical cord, slightly flattened from front to back, from which the nerve roots branch. It is the spinal cord that is responsible for transmitting bioelectric impulses from the brain to every organ and muscle and vice versa. It is responsible for the functioning of the sense organs, contraction when the bladder is filled, relaxation of the sphincters of the rectum and urethra, regulation of the functioning of the heart muscle, lungs, etc.

The spinal cord is located inside the spinal canal, and its length in an adult is 45 cm in men and 41-42 cm in women. Moreover, the weight of such an anatomical structure, which is so important for the human body, does not exceed 34-38 g. Thus, the length of the spinal cord is less than the length of the spinal canal. It starts from the medulla oblongata, which is the lower part of the brain, and thins out at the level of 1 lumbar vertebra (L1), forming the conus medullaris. The so-called filum terminale departs from it, the lower part of which consists of the spinal membranes and is ultimately attached to the 2nd coccygeal vertebra.

In men, the apex of the conical point of the spinal cord is localized on the border of the lower edge of L1, and in women - in the middle of L2. From this moment on, the spinal canal is occupied by the lumbosacral roots, extending from the last segments of the spinal cord, which forms a large nerve formation - the cauda equina. Its constituent nerve roots emerge at an angle of 45° from the corresponding intervertebral foramina.

In newborn children, the spinal cord ends at the level of L3, but by the age of 3, its cone is already at the same level as in adults.

The spinal cord is divided by longitudinal grooves into two halves: anterior and posterior. Its central part is formed by gray matter, and the outer layers are formed by white matter. In the central part of the spinal cord there is a canal that contains cerebrospinal fluid. It communicates with the fourth ventricle of the brain. In adults, this canal is closed in some parts or along the entire length of the spinal cord. Gray matter is formed by the bodies of neurons, i.e., nerve cells, and in cross section resembles a butterfly in shape. As a result, it contains:

• The anterior horns contain motor neurons, also called motoneurons. Like any other neurons, they have long processes (axons) and short branches (dendrites). The axons of motor neurons transmit impulses to the skeletal muscles of the arms, legs and torso, provoking their contraction.
• Posterior horns - the bodies of interneurons are located here, which connect sensory neurons with motor neurons, and also take part in the transmission of information to other parts of the central nervous system.
• Lateral horns - neurons that create the centers of the sympathetic nervous system are localized in them.

On average, the diameter of the spinal cord is 10 mm, but in the region of the cervical and lumbar spine it increases. In these places, so-called thickenings of the spinal cord are formed, which is explained by the influence of the functions of the arms and legs. Therefore, in the cervical spine its transverse size is 10-14 mm, in the thoracic spine - 10-11 mm, and in the lumbar spine - 12-15 mm.

The spinal cord is bathed in cerebrospinal fluid, or cerebrospinal fluid. It is designed to act as a shock absorber and protect it from various damages. In this case, the cerebrospinal fluid is the most filtered blood, devoid of red blood cells, but saturated with proteins and electrolytes, the vast majority of which are sodium and chlorine. Thanks to this, it is completely transparent. Liquor is formed in the ventricles of the brain at a rate of approximately 0.5 liters per day, although on average its volume in the canal does not exceed 130-150 ml. Therefore, even with significant losses of cerebrospinal fluid, its losses are quickly compensated by the body. A small part of the cerebrospinal fluid is absorbed by the blood and lymphatic vessels of the spinal cord.

Spinal cord membranes

The spinal cord is surrounded by 3 membranes: the hard outer membrane, the arachnoid membrane, separated from the first by the subdural space, and the internal one, called the pia mater. The latter is adjacent directly to the spinal cord and is separated from the membrane occupying the middle position by the subarachnoid space. Each of the spinal membranes has its own structural features and performs specific functions.

Thus, the hard shell is a kind of connective tissue case for this sensitive and important nervous structure, densely intertwined with blood vessels and nerves. It consists of collagen fibers and has 2 layers, the outer one fits tightly to the bone structures of the spine and, in fact, forms the periosteum, and the inner one forms the dural sac of the spinal cord. The dura mater is additionally strengthened by multiple bundles of connective tissue, which connect it to the posterior longitudinal ligament, and in the lower parts of the spine they form the filum terminale (filum terminale of the spinal cord), which is ultimately attached to the periosteum of the coccyx. The hard shell has different thickness in different areas, which ranges from 0.5 to 2 mm. It reliably protects the spinal cord from most external influences and runs from the foramen magnum down to 2-3 sacral vertebrae, i.e., it covers the delicate spinal cord along its entire length.

In addition, this shell has cone-shaped protrusions. They are designed to form a protective layer for the nerve roots extending at the level of all vertebrae, and therefore exit with them into the intervertebral foramina.

The dura mater is delimited from the wall of the spinal canal by the epidural space. It contains fatty tissue, spinal nerves and numerous blood vessels responsible for the blood supply to the vertebrae and spinal cord.

The subdural space mentioned above separates the dura mater and the arachnoid membrane of the spinal cord. Essentially, it is a narrow gap filled with thin bundles of connective tissue fibers. In this case, the subdural space ends blindly at the S2 level, but has a free connection with a similar space inside the cranium.

The arachnoid membrane is a delicate, transparent anatomical structure formed by multiple trabeculae (cords), which does not have a rigid fixation system with the dura spinal membrane. They are connected to each other only at the intervertebral foramina.

The arachnoid membrane is separated from the soft membrane by a subarachnoid (subarachnoid) space in which cerebrospinal fluid circulates, and also connective tissue cords pass that unite these membranes with each other. The subarachnoid space communicates with the fourth ventricle of the brain, which ensures continuous circulation of cerebrospinal fluid.

The third membrane of the spinal cord is located in the closest proximity to it and has many blood vessels that provide blood delivery to the spinal cord. It is connected to the arachnoid membrane by a significant number of connective tissue bundles.

Spinal roots

As already mentioned, the entire spinal cord is divided into segments. Moreover, it is shorter than the spinal canal, so there is a discrepancy between the serial number of its segments and the positions of the vertebrae. Thus, the upper cervical segments fully correspond to the position of the vertebral bodies. A shift in numbering is already observed in the lower cervical and thoracic segments. They are one vertebra higher than the corresponding vertebrae. In the central part of the thoracic spine, this difference already increases by two vertebrae, and in the lower part - by 3. Therefore, it turns out that the lumbar segments of the spinal cord are at the level of the bodies of the 10th and 11th thoracic vertebrae, and the sacral and coccygeal segments correspond to 12 thoracic and 1 lumbar vertebrae. But the spinal roots always exit through the intervertebral foramina at the level of the discs corresponding in number.

A pair of nerve roots depart from each spinal segment: anterior and posterior. There are 31 pairs in total. They originate from the lateral surface of the spinal cord and penetrate the dural sac, which forms a protective sheath for them. When leaving it, the spinal roots pass through the hard shell, which has special protrusions in the form of funnel-shaped pockets designed specifically for them. Thanks to this, the spinal roots can bend physiologically, but there is no risk of folding or stretching.

Each dural funnel-shaped recess has 2 openings through which the anterior and posterior nerve roots pass. Moreover, they are delimited by parts of the hard and arachnoid membranes. They are firmly fused with the roots, so leakage of cerebrospinal fluid beyond the subarachnoid space is excluded.

The anterior and posterior roots unite at the level of the intervertebral foramina, forming the spinal nerves. But the posterior intervertebral foramen thickens, forming the so-called ganglion. The anterior and posterior roots join together immediately after the ganglion to form the spinal nerve. Each has several branches:

• Posterior – responsible for innervation of deep muscles, skin of the back and neck.
• Anterior - takes part in the formation of the cervical, brachial, lumbar and sacral plexuses. In this case, the anterior branches of the thoracic nerves form the intercostal nerves.
• Meningeal - ensures the transmission of bioelectric impulses to the dura mater of the spinal cord, as it returns to the spinal canal through the vertebral foramina.

Defects of the bones of the skull

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Defects in the bones of the cranial vault can occur as a result of traumatic effects, inflammation, surgical interventions for tumor and tumor-like lesions of the marrow bones or brain, vascular pathology of the cranial cavity, epileptic lesions, and also have a congenital origin. Their presence is accompanied by cosmetic inconveniences and, as a rule, clinical manifestations of the so-called “trepanned skull” syndrome, including local or diffuse headaches, various neuropsychiatric disorders, neurological symptoms in the form of cerebral symptoms, epileptic seizures, pyramidal, extrapyramidal, sensory, motor and speech disorders.

The majority of the above defects do not recover on their own; their replacement requires surgery using implantation and/or transplantation materials. The use for these purposes of various types of grafts of auto-, allo- and xenogeneic origin, implantation materials based on plastics, titanium, ceramics, hydroxyapatite, etc., which do not exhibit a lag effect during loading and unloading [1-5, 13-25] does not may satisfy the needs of patients and clinicians due to their resorbability or foreign body-like behavior.

The Research Institute of Medical Materials and Implants with Shape Memory (Tomsk) has developed designs and implantation materials based on titanium nickelide, which are currently widely used in many branches of medicine [6-11]. Due to biocompatibility, in particular, superelastic hysteresis behavior under conditions of alternating deformation, such implants, after being placed in tissue defects, do not reject, interact harmoniously with recipient tissues, and due to growth through the mesh and porous structures of biological tissues form an organotypic regenerate united with the implantation material [12] .

Based on numerous clinical experiences in the use of titanium nickelide in medicine, as well as the results of our own experimental studies, a technology for replacing defects in the bones of the cranial vault has been developed, which consists of the following. Hydropreparation of tissues was performed in the projection of the bone defect. The tissue was dissected to a compact layer along the edge of the defect for a length of up to half or more of the perimeter, 0.5-1.0 cm away from the bone edge, with partial excision of scars, movement and rotation of skin flaps or without them. The skin-aponeurotic flap including the periosteum (if present) was separated from the dura mater over the entire area of ​​the defect, exposing the compact layer of the sides opposite to the incision by the previously indicated amount. The meningeal scar was dissected and/or partially excised, its fusion with the edges of the bone defect and limited mobility of the brain were eliminated. A superelastic four-layer mesh knitted thin-profile implant, repeating the configuration of a bone defect, made from a nickel-titanium thread 40 microns thick by double weaving with a cell size of 200-250 × 300-350 microns (Fig. 1), was placed on the bone edges of the defect between the periosteum and the hard bone. the meninges without tension with an external overlap of 0.5-1.0 cm, the latter was fixed around the perimeter of the defect with mini staples made of titanium nickelide with a shape memory effect in the form of an open ring, having dimensions in the open state: main length - 6.3 mm, legs - 3.5 mm, made of wire with a diameter of 0.8 mm. In cases where it was necessary to restore the shape of the skull, one, two or more thin-profile plates made of porous titanium nickelide were used as a frame, repeating the shape of the skull, of appropriate length, width 10-15 mm, thickness 0.3 mm, laid subperiosteally on top of the mesh structure. In order to optimize reparative osteogenesis, the two upper layers of the mesh implant material were saturated with osteogenic tissue grown in the thickness of the iliac crest, containing low-differentiated cellular elements of mesenchymal origin. The wound was sutured and drained within 12-48 hours.

According to the developed technology, 18 patients, persons of both sexes with defects of the frontal, temporal and parietal bones of traumatic origin, aged from 17 to 60 years, were surgically treated. The intervention was performed 4 months or more after the injury. Preoperative examination included the use of traditional clinical and laboratory methods with the study of computerized x-ray studies of the skull. Attention was paid to the presence or absence of neurological symptoms, in particular epileptic seizures. The results were assessed on the basis of clinical dynamic observations and radiological studies at 1, 2, 4, 6, 12 or more months after surgical treatment.

In all patients, the postoperative period was favorable, no significant complications were observed, and wound healing was primary. Within 2-4 months after the intervention in the area of ​​former defects, a gradual decrease in tissue prolapse during palpation and an increase in their density were observed, which by the end of 4 months reached the level of compact bone tissue. By this time, the clinical manifestations characteristic of the “trepanation skull” syndrome were completely or significantly eliminated. X-ray in all cases revealed a complete restoration of the shape of the skull; the implantation material was determined in the form of moderate darkening, mainly in the area of ​​overlap of the former defect. In the long term (12-36 months), the patients did not show any special complaints, and satisfactory cosmetic and functional results were obtained. Phenomena such as cutting through the implant material through soft tissue or migration of the installed structure were not observed.

The use of super-elastic thin-profile mesh implants based on titanium nickelide in combination with lamellar porous titanium nickelide makes it possible to fully restore the lost bone structures of the cranial vault with high efficiency. Due to their biocompatibility with body tissues, the implantation materials used were not rejected after being placed in the defect area and grew with connective tissues from the recipient areas, forming a single connective tissue regenerate. Osteogenic tissue containing low-differentiated cellular elements of mesenchymal origin, possessing the properties of interstitial and appositional growth, anaerobic glycolysis, ensured optimization of reparative osteogenesis.

It should be noted that favorable conditions for the formation of organotypic native tissues in the area of ​​tissue defects of the cranial vault were facilitated by adequate physical and mechanical characteristics of the mesh implantation material used: a given level of plasticity, strength and elasticity; correspondence of hysteresis properties to the behavior of biological tissues; cycle resistance to bending deformations; high corrosion resistance in biological environments; optimal spacing between adjacent threads, i.e. cell size. The thread from which the knitted material is made is a composite structure, including a core of nanostructured monolithic titanium nickelide and a micro-porous surface layer (5-10 microns) of titanium oxide, which is combined with the plasticity of the fibers, viscoelasticity of deformation due to changes in the phase structure of nickelide during deformation titanium and the displacement of the loop structure over a wide area of ​​quasi-plastic deformation determines the high plasticity of the material as a whole, which is necessary when manipulating it in the specific and cramped conditions of a surgical operation. The capillary properties and high degree of wettability inherent in the implantation material make it possible to saturate it with osteogenic tissues, threads with antimicrobial solutions by soaking and use it in conditions of an infected wound surface.

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16. Modern materials used to close skull bone defects / V.V. Stupak [and others] // Modern problems of science and education. 2021. No. 4.; URL: https://science-education.ru/ru/article/view?id=26626.
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Blood vessels

The blood supply to the spine is realized through fairly large arteries that pass either in close proximity to the vertebral bodies or along them. The arteries of the cervical vertebral bodies originate from the subclavian artery, the thoracic vertebrae are supplied by the intercostal arteries, and the lumbar vertebrae are supplied by the lumbar arteries. As a result, the spine is actively supplied with blood at all levels, and the pressure in the vessels is at fairly high levels. But if the bone structures have a direct blood supply, then the intervertebral discs are deprived of this. Their nutrition is carried out through the diffusion of substances during compression/straightening of the disc during physical activity.

The lumbar and intercostal arteries are located along the anterolateral surfaces of the vertebral bodies. In the area of ​​the intervertebral natural foramina, posterior branches branch off from them, which are responsible for feeding the soft tissues of the back and dorsal parts of the vertebrae. In turn, spinal branches depart from them, which deepen into the spinal canal, where the blood vessels are again divided into 2 branches: anterior and posterior. The anterior branch is larger in size and is located transversely to the anterior part of the vertebral body, and on the posterior surface it unites with a similar vessel on the opposite side of the body. The posterior branch extends along the posterolateral surface of the spinal canal and connects with a similar artery on the opposite side.

Thus, the spinal arteries form an anastomotic network that covers the entire spinal canal and has transverse and longitudinal branches. Numerous vessels responsible for feeding the vertebral bodies and spinal cord are diverted from it. The arteries penetrate into the vertebral bodies near the midline, but they do not pass into the intervertebral discs.

The spinal cord has 3 blood supply basins:

• Cervicothoracic, where the first 4 segments are fed from the anterior spinal artery, formed by the fusion of 2 vertebral arteries, the next 5 segments have absolutely independent nutrition, and the blood supply is provided by 2-4 large radicular-spinal arteries, branching from the vertebral arteries, the ascending and deep cervical arteries.
• The intermediate (middle) thoracic basin, including segments T3-T8, is supplied exclusively by one single artery located at level 5 or 6 of the thoracic root. Due to such anatomical features, there is a high risk of developing severe ischemic lesions in this part of the spinal cord.
• Lower thoracic and lumbosacral basin - blood supply is provided by one large anterior radicular artery.

As for the venous system, the spine has 4 venous plexuses: 2 external, localized on the anterior surface of the vertebral bodies behind the arches, and 2 internal. The largest venous plexus is the anterior intravertebral plexus. Its large vertical trunks are interconnected by transverse branches. It is firmly fixed to the periosteum along the posterior surface of the vertebrae by a large number of jumpers. The posterior venous intravertebral plexus can easily move because it does not have strong connections with the vertebral bodies. But at the same time, all 4 venous plexuses of the spine are closely interconnected by numerous vessels that penetrate the vertebral bodies, as well as the yellow ligaments. In general, they form a single whole and extend from the base of the skull to the tailbone.

Venous blood is drained through the system of the superior and inferior vena cava, into which it enters from the vertebral, intercostal, lumbar and sacral veins. All intervertebral veins exit through the corresponding openings of the spine. At the same time, they are firmly attached to the periosteum of the bony edges of the foramina.

The spinal cord itself has 2 venous blood outflow systems: anterior and posterior. In this case, the veins of the surface of the organ are united by a large anastomotic network. Therefore, if it is necessary to ligate one or more veins, the likelihood of developing spinal disorders is close to zero.

Structure of the skull

1. parietal bone;
2. coronal suture;
3. frontal tubercle;
4. temporal surface of the greater wing of the sphenoid bone;
5. orbital plate of the ethmoid bone;
6. lacrimal bone;
7. nasal bone;
8. temporal fossa;
9. anterior nasal spine;
10. body of the maxillary bone;
11. lower jaw;
12. cheekbone;
13. zygomatic arch;
14. styloid process;
15. condylar process of the mandible;
16. mastoid;
17. external auditory canal;
18. lambdoid suture;
19. occipital bone scales;
20. superior temporal line;
21. squamous part of the temporal bone.

1. coronal suture;
2. parietal bone;
3. orbital part of the frontal bone;
4. orbital surface of the greater wing of the sphenoid bone;
5. cheekbone;
6. inferior nasal concha;
7. maxillary bone;
8. chin protuberance of the lower jaw;
9. nasal cavity;
10. vomer;
11. perpendicular plate of the ethmoid bone;
12. orbital surface of the maxillary bone;
13. inferior orbital fissure;
14. lacrimal bone;
15. orbital plate of the ethmoid bone;
16. superior orbital fissure;
17. squamous part of the temporal bone;
18. zygomatic process of the frontal bone;
19. visual channel;
20. nasal bone;
21. frontal tubercle

The structure of the human skull develops around the growing brain from mesenchyme, which gives rise to connective tissue (membranous stage); cartilage then develops at the base of the skull. At the beginning of the 3rd month of intrauterine life, the base of the skull and the capsule (container) of the organs of smell, vision and hearing are cartilaginous. The lateral walls and vault of the cerebral part of the skull, bypassing the cartilaginous stage of development, begin to ossify already at the end of the 2nd month of intrauterine life. The individual parts of the bones are subsequently combined into a single bone; for example, the occipital bone is formed from four parts. From the mesenchyme surrounding the head end of the primary intestine, between the gill pouches, cartilaginous gill arches develop. The formation of the facial part of the skull is associated with them.

Age and gender characteristics of the spine

The length of the spinal column in newborns does not exceed 40% of the total height. But during the first 2 years of life, its length almost doubles. All this time, all parts of the spine are growing at a high speed, but mainly in width. From 1.5 to 3 years, the growth rate decreases, especially in the cervical and upper thoracic regions. At about 3 years of age, active growth of the lumbar and lower thoracic spine begins. From 5 to 10 years, a phase of smooth, uniform growth in all parameters begins, followed by a phase of active growth, lasting from 10 to 17 years. After this, the growth of the cervical and thoracic regions slows down, but the growth of the lumbar region accelerates. The entire process of development of the spinal column is completed at 23-25 ​​years of age.

Thus, in an adult man, the length of the spine is on average 60-75 cm, and in a woman - 60-65 cm. Over the years, degenerative changes occur in the intervertebral discs, they flatten and cease to fully cope with their functions, and physiological bends increase. As a result, not only various diseases arise, but also the length of the spinal column decreases in old age by about 5 cm or more.

Thoracic kyphosis and lumbar lordosis are more pronounced in women than in men.

Thus, the human spine has a complex structure, a dense network of nerves and blood vessels. This largely explains the difficulty of performing surgical interventions on it and the possible risks. Therefore, today all efforts are aimed at finding the least invasive methods of performing operations that involve minimal tissue trauma, which sharply reduces the likelihood of developing complications of varying severity.

Asymmetry of the human face, head and skull

September 30, 2010 - Thursday

In living nature, as in the material world in general, there are neither absolutely symmetrical nor absolutely asymmetrical objects. This principle of the structure of matter concerns all its components: space, energy, physics, chemistry, biology, cell, atom, electron, quantum. In any object there is always a unity of symmetry and asymmetry.

Humans, like vertebrates, have bilateral symmetry of the body in the form of paired organs or the presence of right and left halves of single parts and organs. But the biological principle of bilateral symmetry of living organisms does not manifest itself with mathematical precision due to uneven development or function, and is expressed in the form of a predominance in the size of one of the halves. A striking example of asymmetry is right- and left-handedness.

There are over twenty-five theories of the origin of asymmetry - from the influence of the Coriolis motion of the Earth, to the influence of temporary factors or professional habits.

In humans, asymmetries manifest themselves in the form of morphological (structure, size, proportions, etc.) and functional differences: motor (movement), sensory (vision, hearing, touch, smell) and mental.

Morphological asymmetries of the skull are noted already in the intrauterine state, and functional ones (in the form of right- and left-handedness) - in children 4-9 months old, when voluntary, purposeful movements appear in them. This type of asymmetry is associated with the functional asymmetry of the cerebral hemispheres and is unique to humans. In animals, the percentage of “right-footed” and “left-footed” is the same.

The magnitude of asymmetry clearly correlates with the degree of functional activity of the elements of the human body - more active and mobile parts of the body exhibit greater asymmetry. Thus, the upper limbs of a person are more asymmetrical compared to the lower ones, and the lower jaw, as a moving part of the face, is characterized by greater asymmetry compared to the fixed upper jaw. These facts indicate the functional orientation of asymmetry.

Morphological and functional changes that occur due to various internal and external reasons create one-sided differences in facial shape, which, within the limits of physiological asymmetry, are an expression of individual personality characteristics.

The conventional boundary between individual (physiological) asymmetry and the initial stage of pathological (requiring correction) is difficult to determine in practice, especially since the soft tissues of the face hide uneven development of the facial skeleton until a certain time. Variations in the structure of the human skull and face, which exceed the natural differences in the right and left halves in significant quantities, are considered deformations. The conventional limits of this difference are considered to be 3-5 degrees (in angular values) and 2-3 mm. (in linear).

The fact of asymmetry in the external structure of the human face and body was known to ancient artists and sculptors of the ancient world, and was used by them to add expressiveness and spirituality to their works.

However, not at all times asymmetry in the fine arts was recognized as the rule. It is known that the Greeks achieved such success in proportioning the body that different masters could create the same sculpture from two separate halves. When these halves were connected, they suited each other so well that they seemed to be the work of the same sculptor.

Advocates of asymmetry believed that it enlivens the face, gives it greater charm, expressiveness, originality and beauty.

The asymmetry of the face of the Venus de Milo statue, created by an ancient Greek sculptor, is expressed by the displacement of the nose to the right of the midline, in a higher position of the left auricle and left eye socket, and a smaller distance from the midline of the left eye socket than the right. Meanwhile, supporters of symmetry criticized the asymmetry of the forms of this generally accepted standard of female beauty, believing that Venus's face would be much more beautiful if it were symmetrical.

Extensive studies carried out on several thousand skulls by the Parisian ophthalmologist Liebreich found that the asymmetry is mainly reflected in the fact that the right zygomatic bone and the lower half of the upper jaw are shifted to the right, as a result of which the lower edge of the orbit on the right has a more transverse direction, and on the left it is more sloping posteriorly; the right canine fossa is deeper and narrower; the teeth of the upper jaw, as well as the lower part of the nasal septum, are shifted to the right. It is noted that the left half of the skull is larger than the right.

Evidence for the presence of asymmetry in a normal human face comes from a method of creating an image of the same face from two left and two right halves. Thus, two additional portraits are created with absolute symmetry, but significantly different from the original and they should be considered paradoxical (Fig. 1).

Numerous measurements of facial parameters in men and women have shown that the right half, compared to the left, has more pronounced transverse dimensions, which gives the face rougher, more masculine features inherent in the male sex. The left half of the face has more pronounced longitudinal dimensions, without rough lateral outlines, which gives it softness, smooth lines and femininity. This fact explains the predominant desire of females to pose in front of artists with the left side of their faces, and males with the right.

It is wrong to consider facial symmetry an indispensable condition for its beauty. To assess the beauty of a face, what is important is the combination of features and slight asymmetry, which is inherent in persons of all nationalities and does not detract from the merits of the portrait. With good reason we can say that there is not a single face with absolute symmetry of the right and left halves.

Thus, the fact of facial asymmetry, expressed by the disparity of the right and left halves, one of which, as a rule, is wider and higher, the other narrower and lower, is generally accepted. The reason for this asymmetry, in most cases, is the unevenness of the elements of the bone skull, and on the face its intensification is explained by the specificity of facial expressions (physiological asymmetry). Its manifestations have a natural character: if one half is taller, then it is also narrower. In this case, the eyebrow is located higher than on the opposite, wider half of the face, and the palpebral fissure is larger. The nasolabial fold on this side of the face is more pronounced and straighter. The right half of the face, as a rule, is larger than the left, stands out more sharply, and expresses masculinity. The left half is generally softer, reflecting femininity. The usual asymmetrical smile on the face is curved towards the wide half. When the eyebrows are unevenly displaced, the eyebrow on the narrow side of the face rises more actively and higher.

The facial asymmetry inherent in humans is explained by differences in innervation and is manifested by the peculiarities of facial expressions. Functional asymmetry of the face depends on the functional asymmetry of the brain and is expressed in right-handed people by more active expressiveness of the left-sided facial muscles (when half-smiling, as a rule, the left half of the mouth stretches, and when winking, the left eye works). However, criminologists have found that with a one-sided smile, predominantly the wider half of the face is involved, and the usual raising of one eyebrow is carried out on the narrower side of the face. Chewing food (with healthy teeth) is carried out by the functionally dominant side. In the speech act, the right half of the mouth is more active in 86% of right-handers and 67% of left-handers.

All human asymmetries are divided into static (proportions, size, weight, volume, etc.) and functional: motor (motor), sensory (sensitive) and mental (sensory).

Among facial asymmetries, in addition to organic ones, two types are considered and have practical significance. The first is the unequal ability of the halves of the face to reflect a person’s emotional state. There is no consensus on this issue. Some researchers believe that in most people the right half of the face is superior to the left in expressiveness and is more similar to the entire face than the left. Others (and the majority of them) recognize the left half of the face as more emotional, and photographs composed only of the left halves were recognized by all professional experts as more emotional, more energetic, and active. Right-sided photographs were rated as weaker, softer, and more positive.

The left half of the face of left-handed people looks more cheerful when smiling than the right half, which is relatively sad when calm. Right-handed people rated their faces sadder and happier in photographs taken of their right halves.

The second type of facial asymmetry relates to eye movements that have a sensory-motor function.

When thinking about issues that require verbal comprehension and thinking or mathematical, logical operations, most people's eyes are directed to the right. When performing visual-spatial and musical tasks and perceiving music, rhythmic sounds of nature - to the left.

Emotional appeals to subjects more often cause left-sided eye movement, and positive emotions – to the right; fear - to the left. People with predominant right-sided eye movements are more likely to specialize in the exact sciences and use adjectives less in their answers. Lateral eye movements do not occur if the question is simple or already prepared for the person.

The leading eye is the first to direct its gaze to the object, the second (non-dominant) directs the visual axis to the fixation point of the leading eye; in the dominant eye, the accommodation mechanism is activated earlier.

The leading (in terms of aiming ability) right eye is more often observed in right-handed people, and the left eye is observed in 40% of left-handed people. Right-handers with the right dominant eye have better orientation than right-handers with the left dominant eye.

Functional asymmetry also applies to hearing, as a means of human communication through speech. The predominance of the left ear, when examined with an audiometer, is noted in 50% of people, the right - in 7%, and in 43% of cases they are equivalent. The advantage of the right ear in distinguishing speech sounds is called the “right ear effect”, and the “left ear effect” is manifested in a better perception of non-speech sounds - musical, rhythmic and intonation, as well as emotional speech (joy, grief, anger, fear, declaration of love and etc.).

Due to a number of biological, national, historical, geographical and social factors, each person's face is individually expressive. Of the billions of people living on Earth, you cannot meet exactly the same faces. Even stable racial and national facial parameters acquire certain variations in combinational characteristics. Under the influence of mental processes, facial reactions occur, differing in different dynamism.

The unique diversity of faces and their qualitative specificity have long attracted the attention of artists and sculptors, who are able to “read” the emotional state by facial expression. A sculpture, portrait, description of a face in works of art always testify to the degree of talent of the author, reflecting his ability to correctly notice, perceive and record facial expressions. Leonardo da Vinci, thanks to his knowledge of anatomy, brilliantly guessed the connection between a person’s emotional state and the nature of his facial expressions. The doctor is united with artists by a constant readiness to monitor the shades of facial expression. Responsibility for the patient’s life obliges him to see not only the external shape, but also the direction of the lines, the size of the parts, the projection of natural openings on the face and other factors. The nuances of facial expressions, eye expression, and violation of proportions in the facial ensemble deserve detailed analysis and special study.

The ability to geometrically measure, display and model objects of material space makes it possible to explain the origin of bilateral asymmetry in organic forms and the formation of imagery in objects of living nature.

The question of the dominant direction of facial asymmetry is still debated. There is also no unity on the question of which parts of the face show the greatest and which the least asymmetry. However, the inequality of the right and left halves of the face in reflecting emotional states has been proven.

Researchers morphologically divide the face into three zones, each of which is assigned one of three characteristic features. The forehead and expression of the eyes are capable of reflecting intelligence; the middle of the face (the area of ​​the nose and lips with rich facial expressions) demonstrates a sensual state, and the lower third of the face (chin) expresses will, energy and activity. There is an opinion that the right half of the face reflects the mind, and the left is an expression of emotions. There is a better development of facial muscles and greater expressiveness of facial movements of the right half of the face in right-handed people, and the left half in left-handed people. In criminology, there is a concept of biological facial dissymmetry. The right type has a higher and narrower right side of the face and a wider and lower left side. The left type is characterized by inverse relationships.

The different meaning (aesthetic, functional, psychological and physiognomic) and perception of the right and left halves of the face explains the predominant desire of females to pose in front of artists and photographers with the left side of the face, and for males with the right. We tested this fact on 820 portraits (320 female and 500 male) of the most famous masters of painting before the beginning of the twentieth century. In 65% of cases, female faces are presented on the left side, and only in 35% - on the right side; men, respectively - in 55% of the right, and the left - in 45%. Some striking illustrations include the following portraits: “La Gioconda” and “Madonna Litta” by Leonardo da Vinci; "Flora" and "Self-Portrait with Saskia" by Rembrandt; "Portrait of a Young Woman" and "Equestrian Portrait of Charles V" by Titian; “Head of Grace” and “Birth of Venus” by Botticelli; "Sistine Madonna" by Raphael; "Portrait of a Woman with Blonde Hair" by Rubens; “Portrait of a Stranger” by Kramskoy; “The Spinner” and “The Lacemaker” by Tropinin”; “Portrait of Pope Innocent X” by Velazquez; “Portrait of A.S. Pushkin” by Kiprensky; “Girl with Peaches” by Serov.

Thus, in the visual arts there is a manifestation of facial asymmetry, as a reflection of natural beauty, tenderness and charm in women, on the one hand, and inner strength, perseverance and courage in men, on the other.