Occipital tubercles: variants of norm and pathology. The structure of the human occipital bone and possible injuries Features of the occipital bone
The human skull is made up of many small and large bones. For example, in its lower back there is an occipital bone. She does not have her own pair, but this does not prevent her from creating the wall of the cranium and the cranial vault, as well as the base. If you look at it, you will understand that it is almost perfect, because both the left and right parts are absolutely symmetrical. The occipital bone does not form on its own. It can be considered the result of combining several bones. In many animals, the components of the occipital bone can develop separately from each other. From this we can assume that it is created from at least four parts, which finally turn into a single whole only after 3 or even 6 years of life. The closest neighbors of such a complex bone can be considered the parietal, temporal bones, as well as the first cervical vertebra, which has long been officially called the atlas. The part that faces outward has a convex shape, but inside it is noticeably concave. If you turn your gaze to the bottom of the occipital bone, you can see the foramen magnum with the naked eye. It serves as a connective for the cranial cavity and spinal canal. It can be divided into several parts, or rather into four. These are the occipital scales, lateral in the amount of two pieces and basilar.
The basilar part of the trip to the quadrangle, but at the same time it is rather short and thick. The back is not burdened by the neighborhood. Perhaps that is why its edge is only slightly pointed, but you will not see any roughness here either. Thus, this part creates a border for the foramen magnum. Now for the front. It also has thickenings, but unlike the back, it is not smooth, but with flaws. With it, the body of the sphenoid bone is able to join the occipital part of the skull, and cartilage serves as a connective tissue, which creates sphenoid-occipital synchondrosis. Upon reaching the age of fourteen, this cartilage develops into bone tissue. And the result is a single bone. The upper part is directed towards the cranial cavity. It does not have any roughness, but there is a slight concavity.
The lateral part has a pair. They are located behind and gradually pass into the scales of the occipital bone. Its lower part is decorated with an elliptical eminence or occipital condyle. At its base, a canal was found through which the hypoglossal nerve passes. Going a little back behind the condyle, you can find the jugular notch. Together with another notch, but already the pyramids of the temporal bone, they form the jugular foramen. The jugular notch has a process of the same name. Its outer part is decorated with the paramastoid process. It is in this part that the rectus lateral muscle of the head connects to the occipital part. Literally a millimeter from the jugular notch is the groove of the sigmoid cone. It is considered part of the temporal bone groove, or rather its continuation. But the smooth jugular tubercle is located almost in the middle.
The occipital bone has scales, which is an integumentary bone. At the same time, it is a plate that is quite convex on the outside and strongly concave on the inside. Outside, the scales are not at all smooth, and you can even say embossed. And all due to the fact that ligaments and even muscles are attached to it. The very center of the outer surface is occupied by the occipital protrusion. You can find it yourself by slightly feeling the skeleton of the head in the back of the head. From this protrusion on the sides diverge upper lines. Interestingly, they do not go in a straight line, but along a curved one. Slightly above them, but parallel to them, you can find the highest protruding lines. This protrusion was another start for the occipital crest. But you can find its end at the posterior edge of the foramen magnum, and it should be exactly in the middle. From the median line on the ridge, the protruding lines diverge, which run parallel to the upper ones. Thus, there is a fastening of the muscles. Directly on the occipital bone and the attachment of the muscles ends with the help of the surface of the occipital scales and the upper nuchal lines. The inner part of the occipital bone completely repeats the pattern of the brain, as well as the shell that protects it. Because of this relief, the bone is divided by two ridges that intersect at right angles. As a result, we get four parts, or, as doctors call them, pits. The ledge is not only outside, but also inside. You can find it in the brain part of the scales. It is here that the cruciform elevation is located, and already on it is the ledge itself. Several grooves of the transverse sinus originate from the cruciate eminence. The sagittal crest goes up, the internal occipital crest goes down. He, in turn, goes to the posterior semicircle of the foramen magnum.
The occipital bone is prone to injury, which can lead to serious consequences. In most cases, if the injury reaches the foramen magnum, then it is very likely that the spinal cord will be destroyed, as well as the nerves and blood vessels.
Occipital bone, os occipitale, forms the posterior and lower walls of the cranium, participating simultaneously in the vault of the skull and at its base. Accordingly, it (being a mixed bone) ossifies both as an integumentary bone on the soil of the connective tissue (upper part of the occipital scale), as well as on the soil of cartilage (the rest of the bone). In humans, it is the result of the fusion of several bones that exist independently in some animals. Therefore, it consists of 4 parts that are laid down separately, fusing into a single bone only at the age of 3-6 years. These parts, which close the large occipital foramen, foramen magnum (the place where the spinal cord passes into the oblong from the spinal canal into the cranial cavity), are as follows: in front - the basilar part, pars basilaris, on the sides - the lateral parts, partes laterales, and behind - the occipital scales, squama occipitalis. The upper part of the scale, wedged between the parietal bones, ossifies separately and often remains separated by a transverse suture for life, which is also a reflection of the existence in some animals of an independent interparietal bone, os interparietale, as it is called in humans.
The occipital scales, squama occipitalis, as an integumentary bone, has the form of a plate, convex on the outside and concave on the inside. Its external relief is due to the attachment of muscles and ligaments. So, in the center of the outer surface is the external occipital protrusion, protuberantia occipitalis externa (the place where the ossification point appears). From the protrusion, it runs laterally on each side along a curved line - the upper protruding line, linea nuchае superior. A little higher, a less noticeable one is found - linea nuchae suprema (the highest). From the occipital protrusion down to the posterior edge of the foramen magnum, the external occipital crest, crista occipitalis externa, runs along the midline. From the middle of the ridge to the sides go lower and different lines, lipae nuchae inferiores.
The relief of the inner surface is due to the shape of the brain and the attachment of its membranes, as a result of which this surface is divided by means of two ridges crossing at right angles into four pits; both of these crests together form a cruciform eminence, eminentia cruciformis, and at the place of their intersection, an internal occipital protrusion, protuberantia occipitalis interna. The lower half of the longitudinal crest is sharper and is called crista occipitalis interna, while the upper and both halves (often right) of the transverse crest are provided with well-defined grooves: sagittal, sulcus sinus sagittalis superioris, and transverse, sulcus sinus transversi (traces of adjoining venous sinuses of the same name). Each of the lateral parts, partes laterales, is involved in the connection of the skull with the spinal column, therefore, on its lower surface it carries the occipital condyle, condylus occipitalis - the place of articulation with the atlas.
Approximately near the middle of the condylus occipitalis, the hypoglossal canal of the canalis hypoglossalis passes through the bone. On the upper surface of the pars lateralis is sulcus sinus sigmoidei (a trace of the venous sinus of the same name). The basilar part, pars basilaris, fuses with the sphenoid bone by the age of 18, forming a single bone in the center of the skull base os basilare. On the upper surface of this bone is a clivus, fused from two parts, on which the medulla oblongata and the brain bridge lie. On the lower surface, the pharyngeal tubercle, tuberculum pharyngeum, protrudes, to which the fibrous membrane of the pharynx is attached.
frontal bone, os frontale, unpaired, participates in the formation of the cranial vault and refers to its integumentary bones, developing on the basis of connective tissue. In addition, it is associated with the sense organs (smell and vision). According to this dual function, it consists of two departments: vertical - scales, squama frontalis, and horizontal. The latter, according to the relation to the organs of vision and smell, is divided into a steam room orbital part, pars orbitalis, and unpaired nasal, pars nasalis. As a result, 4 parts are distinguished in the frontal bone:
1. frontal scales, squama frontalis, like any integumentary bone, has the form of a plate, convex on the outside and concave on the inside. It ossifies from two ossification points, noticeable even in an adult on outer surface, facies externa, in the form of two frontal tubercles, tubera frontalia. These bumps are expressed only in humans in connection with the development of the brain. They are absent not only in great apes, but even in extinct forms of man. The lower edge of the scale is called supraorbital, margo supraorbitalis. Approximately on the border between the inner and middle thirds of this region, there is supraorbital notchincisura supraorbitalis(sometimes turns into foramen supraorbital), the place of passage of the same name arteries and nerve. Immediately above the supraorbital margin, prominently varying in size and extent of the eminence is noticeable - brow ridges, arcus superciliares, which pass medially along the midline into a more or less elevated platform, glabella(glabella). It is a reference point when comparing the skulls of modern man with fossils.
The outer end of the supraorbital margin extends into zygomatic process, processus zygomaticus connecting with the zygomatic bone. From this process goes up a clearly visible temporal line,linea temporalis, which limits temporal surface scales, facies temporalis. On inner surface, facies interna, runs along the midline from the posterior edge furrow, sulcus sinus sagittalis superioris, which goes down to frontal ridgecrista frontalis. These formations are the attachment of the dura mater.
Near the midline, pits of granulations of the arachnoid membrane (outgrowths of the arachnoid membrane of the brain) are noticeable.
2 and 3. Orbital parts, partes orbitals, represent two horizontally arranged plates, which, with their lower concave surface, face the orbit, the upper one - into the cranial cavity, and are connected with the sphenoid bone with their posterior edge.
On the upper cerebral surface there are traces of the brain - finger-like impressions, impressiones digitatae.
bottom surface, facies orbitalis, forms the upper wall of the orbit and bears traces of adhering eye accessories; y zygomatic process - lacrimal fossa, fossa glandulae lacrimalis, near incisura supraorbitalis - fovea trochlearis and small thorn, spina trochlearis where cartilage attaches block (trochlea) for the tendon of one of the muscles of the eye. Both orbital parts are separated from each other tenderloin, incisura ethmoidalis, filled on the whole skull with an ethmoid bone.
4. bow , pars nasalis, occupies the anterior part of the lattice notch along the midline; visible here scallop, crista, which ends with an acute awn - spina nasalis involved in the formation of the nasal septum.
On the sides of the scallop are pits that serve as the upper wall for the cells of the ethmoid bone; anterior to them there is a hole leading to frontal sinus, sinus frontalis, - a cavity that is located in the thickness of the bone behind the superciliary arch, the size of which varies greatly. The frontal sinus, which contains air, is usually divided septumseptum sinuum frontalium.
In some cases, there are additional frontal sinuses behind or between the main ones. The frontal bone in its form is the most characteristic of all the bones of the skull for a person. In the most ancient hominids (as well as the Great Apes), it was sharply tilted back, forming a sloping, "running back" forehead. Behind the orbital constriction, it sharply divided into the scales of the orbital parts. Along the edge of the eye sockets, from one zygomatic process to the other, a continuous thick ridge ran. In modern man, the roller has sharply decreased, so that only the superciliary arches remain of it.
According to the development of the brain, the scales straightened and took a vertical position, at the same time the frontal tubercles developed, as a result of which the forehead from sloping became convex, giving the skull a characteristic appearance.
Frontal bone. Front view. 1. Frontal scales; 2. Frontal tubercle; 3. Glabella (glabella); 4. Zygomatic process; 5. Supraorbital margin; 6. Nasal part (frontal bone); 7. Nasal spine; 8. Frontal notch; 9. Superciliary arch; 10. Supraorbital foramen; 11. Temporal line. Frontal bone. Back view. 1. Parietal edge; 2. Groove of the superior sagittal sinus; 3. Frontal crest; 4. Zygomatic process; 5. Finger-like impressions; 6. Blind hole; 7. Bow; 8. Orbital part; 9. Brain elevations; 10. Arterial furrows; 11. Frontal scales.
Occipital bone, os occipitale, forms the posterior and lower walls of the cranium, participating simultaneously in the vault of the skull and at its base. Accordingly, it (being a mixed bone) ossifies both as an integumentary bone on the soil of the connective tissue (upper part of the occipital scales), as well as on the soil of cartilage (the rest of the bone). In humans, it is the result of the fusion of several bones that exist independently in some animals. Therefore, it consists of 4 parts that are laid down separately, fusing into a single bone only at the age of 3-6 years. These parts that close the big foramen magnum, foramen magnum(the place of transition of the spinal cord to the oblong from the spinal canal to the cranial cavity), the following: in front - basilar part, pars basilaris, on both sides - lateral parts, partes laterales, and behind - occipital scale, squamaoccipitalis. The upper part of the scales, wedged between the parietal bones, ossifies separately and often remains separated by a transverse suture for life, which is also a reflection of the existence of an independent interparietal bone, os interparietale as u call her y person.
Occipital scales, squama occipitalis, as the integumentary bone has the form of a plate, convex on the outside and concave on the inside. Its external relief is due to the attachment of muscles and ligaments. So, in the center of the outer surface is external occipital protuberance, protuberantia occipitalis externa(the place where the ossification point appears). From the protrusion laterally goes on each side along a curved line - top notch line,linea nuchae superior. A little higher there is a less noticeable - highest line,linea nuchae suprema. From the occipital protrusion down to the posterior edge of the foramen magnum runs along the midline external occipital crest, Crista occipitalis externa. From the middle of the ridge to the sides go lower cut lines, lineae nuchae inferiores. The relief of the inner surface is due to the shape of the brain and the attachment of its membranes, as a result of which this surface is divided by means of two ridges crossing at right angles into four pits; both of these ridges together form cruciformelevation, eminentia cruciformis, a at the place of their intersection - internal occipital protuberance, protuberantia occipitalis interna. The lower half of the longitudinal ridge is sharper and is called crista occipitalis interna, the upper and both halves (usually right) of the transverse are provided with well-defined furrows: sagittal, sulcus sinus sagittalis superioris, And transverse, sulcus sinus transversi(traces of adjoining of the venous sinuses of the same name).
Occipital bone. Back view. 1. The highest cut line; 2. External occipital protrusion; 3. Top notch line; 4. Lower nuchal line; 5. Condylar canal; 6. Occipital condyle; 7. Intra-jugular process; 8. Pharyngeal tubercle; 9. Basilar (main) part; 10. Lateral part; 11. Jugular notch; 12. Jugular process; 13. Condylar fossa; 14. Foramen magnum; 15. Vynaya surface (platform); 16. External occipital crest; 17. Occipital scales.
Occipital bone. Front view. 1. Groove of the superior sagittal sinus; 2. Scales of the occipital bone; 3. Internal occipital protrusion; 4. Internal occipital crest; 5. Large foramen magnum; 6. Groove of the sigmoid sinus; 7. Muscular canal; 8. Furrow of the lower stony sinus; 9. Skat; 10. Basilar part; 11. Lateral part; 12. Jugular notch; 13. Jugular tubercle; 14. Jugular process; 15. Inferior occipital fossa; 16. Groove of the transverse sinus; 17. Superior occipital fossa.
Each of lateral parts, partes laterales, participates in the connection of the skull with the spinal column, therefore, on its lower surface it carries occipital condyle, condylus occipitalis- place of articulation with the atlas. Approximately around the middle condylus occipitalis passes through the bone hypoglossal canalcanalis hypoglossalis. On the top surface pars lateralis located sulcus sinus sigmoidei(a trace of the venous sinus of the same name).
Basilar part, pars basilaris, by the age of 18 fuses with the sphenoid bone, forming a single bone in the center of the base of the skull os basilare. On the upper surface of this bone is located merged from two parts slope, clivus on which the medulla oblongata and the pons of the brain lie. On the bottom surface protrudes pharyngeal tubercle, tuberculum pharyngeum to which the fibrous membrane of the pharynx is attached.
Ethmoid bone
Ethmoid bone is part of the anterior part of the base of the brain skull, as well as the facial part of the skull, participating in the formation of the walls of the orbits and nasal cavity. In the ethmoid bone, a horizontally located ethmoid plate is distinguished, from which a perpendicular plate extends downward along the midline. On the sides of it are lattice labyrinths, which are closed from the outside by vertically (sagittally) located right and left orbital plates.
Lattice plate represents the upper part of the ethmoid bone; located in the ethmoid notch of the frontal bone and is involved in the formation of the bottom of the anterior cranial fossa. The entire plate is perforated with holes and resembles a sieve (hence its name). Olfactory nerves (1 pair of cranial nerves) pass through these openings into the cranial cavity. Above the lattice plate, along the midline, a cockscomb rises. Anteriorly, it continues into a paired process - the wing of the cockscomb. These processes, together with the frontal bone lying in front, limit the blind opening of the frontal bone.
Perpendicular plate irregular pentagonal shape. It is, as it were, a continuation of the cockscomb downwards, into the nasal cavity. In the nasal cavity, the perpendicular plate, located sagittally, participates in the formation of the upper part of the nasal septum.
lattice maze- pair education. It consists of bone air-carrying lattice cells communicating with each other and with the nasal cavity. The lattice labyrinth at the top right and left of the perpendicular plate is, as it were, suspended at the ends of the lattice plate. The medial surface of the ethmoid labyrinths faces the nasal cavity and is separated from the perpendicular plate by a narrow vertical slit located in the sagittal plane. On the medial side, the ethmoid cells are covered by two thin curved bone plates - the superior and middle turbinates. The upper part of each shell is attached to the medial wall of the labyrinth cells, and the lower edge hangs freely into the gap between the labyrinth and the perpendicular plate. The superior nasal concha is attached at the top, below it and somewhat anteriorly is the middle nasal concha, sometimes there is a weakly expressed third - the highest nasal concha. Between the upper nasal concha and the middle one there is a narrow gap - the upper nasal passage. Under the curved edge of the middle turbinate is the middle nasal passage, which is bounded from below by the upper edge of the inferior turbinate. The middle turbinate at its posterior end has a hook-shaped process, which, on the whole skull, connects with the ethmoid process of the inferior turbinate. Behind the uncinate process, a large ethmoid vesicle protrudes into the middle nasal passage - one of the largest cells of the ethmoid labyrinth. Between the large ethmoid vesicle behind and above and the uncinate process below and in front, a funnel-shaped gap is visible - the ethmoid funnel. Through this funnel, the frontal sinus communicates with the middle nasal passage.
On the lateral side, the ethmoid labyrinths are covered with a smooth thin plate, which is part of the medial wall of the orbit, the orbital plate.
Variants and anomalies.
Frontal bone. In about 10% of cases, the frontal bone consists of two parts, the frontal suture is preserved between them, sutura frontlis (sutura metopica). The size of the frontal sinus varies, very rarely the sinus is absent.
Occipital bone. The upper part of the occipital scale, in whole or in part, can be separated from the rest of the occipital bone by a transverse suture. As a result, a special triangular-shaped bone stands out - the interparietal bone, os in- terparietdle.
Ethmoid bone. The shape and size of the cells of the ethmoid bone is very variable. The highest nasal concha is often found, concha nasdlis suprema.
The occipital bone (os occipitale) (Fig. 59) is unpaired, located in the posterior part of the brain skull and consists of four parts located around a large hole (foramen magnum) (Fig. 60, 61, 62) in the anteroinferior section of the outer surface.
The main, or basilar, part (pars basilaris) (Fig. 60, 61) lies anterior to the external opening. In childhood, it connects to the sphenoid bone with the help of cartilage and forms a wedge-occipital synchondrosis (synchondrosis sphenooccipitalis), and in adolescence (after 18-20 years) the cartilage is replaced by bone tissue and the bones grow together. The upper inner surface of the basilar part, facing the cranial cavity, is slightly concave and smooth. It contains part of the brain stem. At the outer edge there is a groove of the lower petrosal sinus (sulcus sinus petrosi inferior) (Fig. 61), adjacent to the posterior surface of the petrous part of the temporal bone. The lower outer surface is convex and rough. In the center of it is the pharyngeal tubercle (tuberculum pharyngeum) (Fig. 60).
Lateral, or lateral, part (pars lateralis) (Fig. 60, 61) steam room, has an elongated shape. On its lower outer surface is an elliptical articular process - the occipital condyle (condylus occipitalis) (Fig. 60). Each condyle has an articular surface, through which it articulates with the I cervical vertebra. Behind the articular process is the condylar fossa (fossa condylaris) (Fig. 60) with the non-permanent condylar canal (canalis condylaris) lying in it (Fig. 60, 61). At the base, the condyle is pierced by the hypoglossal canal (canalis hypoglossi). On the lateral edge is the jugular notch (incisura jugularis) (Fig. 60), which, combined with the same notch of the temporal bone, forms the jugular foramen (foramen jugulare). The jugular vein, glossopharyngeal, accessory and vagus nerves pass through this opening. On the posterior edge of the jugular notch is a small protrusion called the jugular process (processus intrajugularis) (Fig. 60). Behind him, along the inner surface of the skull, there is a wide groove of the sigmoid sinus (sulcus sinus sigmoidei) (Fig. 61, 65), which has an arcuate shape and is a continuation of the temporal bone groove of the same name. Anterior to it, on the upper surface of the lateral part, there is a smooth, gently sloping jugular tubercle (tuberculum jugulare) (Fig. 61).
The most massive part of the occipital bone is the occipital scales (squama occipitalis) (Fig. 60, 61, 62), located behind the large occipital foramen and taking part in the formation of the base and vault of the skull. In the center, on the outer surface of the occipital scales, there is an external occipital protrusion (protuberantia occipittalis externa) (Fig. 60), which is easily palpable through the skin. From the external occipital protrusion to the large occipital foramen, the external occipital crest (crista occipitalis externa) is directed (Fig. 60). Paired upper and lower nuchal lines (linea nuchae superiores et inferiores) (Fig. 60) depart from the external occipital crest on both sides, which are a trace of muscle attachment. The upper protruding lines are at the level of the outer protrusion, and the lower ones are at the level of the middle of the outer ridge. On the inner surface, in the center of the cruciform eminence (eminentia cruciformis), there is an internal occipital protrusion (protuberantia occipittalis interna) (Fig. 61). Down from it, up to the large occipital foramen, the internal occipital crest (crista occipitalis interna) descends (Fig. 61). A wide flat groove of the transverse sinus (sulcus sinus transversi) is directed to both sides of the cruciform eminence (Fig. 61); the furrow of the superior sagittal sinus (sulcus sinus sagittalis superioris) goes vertically upwards (Fig. 61).
The occipital bone is connected to the sphenoid, temporal and parietal bones.
The sphenoid bone (os sphenoidale) (Fig. 59) is unpaired, located in the center of the base of the skull. In the sphenoid bone, which has a complex shape, the body, small wings, large wings and pterygoid processes are distinguished.
The body of the sphenoid bone (corpus ossis sphenoidalis) has a cubic shape, six surfaces are distinguished in it. The upper surface of the body faces the cranial cavity and has a depression called the Turkish saddle (sella turcica), in the center of which is the pituitary fossa (fossa hypophysialis) with the lower appendage of the brain, the pituitary gland, lying in it. In front, the Turkish saddle is limited by the tubercle of the saddle (tuberculum sellae) (Fig. 62), and behind it by the back of the saddle (dorsum sellae). The posterior surface of the body of the sphenoid bone is connected to the basilar part of the occipital bone. On the front surface there are two openings leading to the airy sphenoid sinus (sinus sphenoidalis) and called the aperture of the sphenoid sinus (apertura sinus sphenoidalis) (Fig. 63). The sinus is finally formed after 7 years inside the body of the sphenoid bone and is a paired cavity separated by the septum of the sphenoid sinuses (septum sinuum sphenoidalium), which emerges on the front surface in the form of a sphenoid ridge (crista sphenoidalis) (Fig. 63). The lower section of the crest is pointed and is a wedge-shaped beak (rostrum sphenoidale) (Fig. 63), wedged between the wings of the vomer (alae vomeris), which is attached to the lower surface of the body of the sphenoid bone.
Small wings (alae minores) (Fig. 62, 63) of the sphenoid bone are directed in both directions from the anteroposterior corners of the body and represent two triangular plates. At the base, the small wings are pierced by the optic canal (canalis opticus) (Fig. 62), which contains the optic nerve and the ophthalmic artery. The upper surface of the small wings faces the cranial cavity, and the lower surface takes part in the formation of the upper wall of the orbit.
Large wings (alae majores) (Fig. 62, 63) of the sphenoid bone move away from the side surfaces of the body, heading outward. At the base of the large wings there is a round hole (foramen rotundum) (Fig. 62, 63), then an oval (foramen ovale) (Fig. 62), through which the branches of the trigeminal nerve pass, and outwards and backwards (in the region of the wing angle ) there is a spinous opening (foramen spinosum) (Fig. 62), passing the artery that feeds the hard shell of the brain. The inner, cerebral, surface (facies cerebralis) is concave, and the outer one is convex and consists of two parts: the orbital surface (facies orbitalis) (Fig. 62), which is involved in the formation of the walls of the orbit, and the temporal surface (facies temporalis) (Fig. 63) involved in the formation of the wall of the temporal fossa. Large and small wings limit the upper orbital fissure (fissura orbitalis superior) (Fig. 62, 63), through which blood vessels and nerves enter the orbit.
Pterygoid processes (processus pterygoidei) (Fig. 63) depart from the junction of large wings with the body and go down. Each process is formed by the outer and inner plates, fused in front, and diverging behind and limiting the pterygoid fossa (fossa pterygoidea).
The inner medial plate of the pterygoid process (lamina medialis processus pterygoideus) (Fig. 63) takes part in the formation of the nasal cavity and ends with a pterygoid hook (hamulus pterygoideus) (Fig. 63). The outer lateral plate of the pterygoid process (lamina lateralis processus pterygoideus) (Fig. 63) is wider, but less long. Its outer surface faces the infratemporal fossa (fossa infratemporalis). At the base, each pterygoid process is pierced by the pterygoid canal (canalis pterygoideus) (Fig. 63), through which the vessels and nerves pass.
The sphenoid bone is connected to all the bones of the brain skull.
The temporal bone (os temporale) (Fig. 59) is paired, takes part in the formation of the base of the skull, lateral wall and arch. It contains the organ of hearing and balance (see the "Sense Organs" section), the internal carotid artery, part of the sigmoid venous sinus, the vestibulocochlear and facial nerves, the trigeminal ganglion, the branches of the vagus and glossopharyngeal nerves. In addition, connecting with the lower jaw, the temporal bone serves as a support for the masticatory apparatus. It is divided into three parts: stony, scaly and drum.
The stony part (pars petrosa) (Fig. 65) has the shape of a tripartite pyramid, the top of which is facing anteriorly and medially, and the base, which passes into the mastoid process (processus mastoideus), is posteriorly and laterally. On the smooth front surface of the stony part (facies anterior partis petrosae), near the top of the pyramid, there is a wide depression, which is the site of the adjoining trigeminal nerve, the trigeminal depression (impressio trigemini), and almost at the base of the pyramid there is an arcuate elevation (eminentia arcuata) (Fig. 65), formed by the upper semicircular canal of the inner ear lying under it. The front surface is separated from the inner stony-scaly fissure (fissura petrosquamosa) (Fig. 64, 66). Between the gap and the arcuate elevation is a vast platform - the tympanic roof (tegmen tympani) (Fig. 65), under which lies the tympanic cavity of the middle ear. Almost in the center of the posterior surface of the stony part (facies posterior partis petrosae), the internal auditory opening (porus acusticus internus) (Fig. 65) is noticeable, heading into the internal auditory meatus. Vessels, facial and vestibulocochlear nerves pass through it. Above and lateral to the internal auditory opening is the subarc fossa (fossa subarcuata) (Fig. 65), into which the process of the dura mater penetrates. Even more lateral to the opening is the external opening of the vestibule aqueduct (apertura externa aquaeductus vestibuli) (Fig. 65), through which the endolymphatic duct exits the cavity of the inner ear. In the center of the rough lower surface (facies inferior partis petrosae) there is an opening leading to the carotid canal (canalis caroticus), and behind it is the jugular fossa (fossa jugularis) (Fig. 66). Lateral to the jugular fossa, a long styloid process (processus styloideus) (Fig. 64, 65, 66), which is the point of origin of muscles and ligaments, protrudes downward and anteriorly. At the base of this process is the stylomastoid foramen (foramen stylomastoideum) (Fig. 66, 67), through which the facial nerve emerges from the cranial cavity. The mastoid process (processus mastoideus) (Fig. 64, 66), which is a continuation of the base of the stony part, serves as an attachment point for the sternocleidomastoid muscle.
On the medial side, the mastoid process is limited by the mastoid notch (incisura mastoidea) (Fig. 66), and along its inner, cerebral side, there is an S-shaped groove of the sigmoid sinus (sulcus sinus sigmoidei) (Fig. 65), from which to the outer surface of the skull leads mastoid opening (foramen mastoideum) (Fig. 65), relating to non-permanent venous graduates. Inside the mastoid process there are air cavities - mastoid cells (cellulae mastoideae) (Fig. 67), communicating with the middle ear cavity through the mastoid cave (antrium mastoideum) (Fig. 67).
The scaly part (pars squamosa) (Fig. 64, 65) has the shape of an oval plate, which is located almost vertically. The outer temporal surface (facies temporalis) is slightly rough and slightly convex, participates in the formation of the temporal fossa (fossa temporalis), which is the starting point of the temporal muscle. The inner cerebral surface (facies cerebralis) is concave, with traces of adjacent convolutions and arteries: digital depressions, cerebral eminences and arterial grooves. Anterior to the external auditory canal, the zygomatic process (processus zygomaticus) rises sideways and forward (Fig. 64, 65, 66), which, connecting with the temporal process, forms the zygomatic arch (arcus zygomaticus). At the base of the process, on the outer surface of the scaly part, there is a mandibular fossa (fossa mandibularis) (Fig. 64, 66), which provides a connection with the lower jaw, which is limited in front by the articular tubercle (tuberculum articularae) (Fig. 64, 66).
The tympanic part (pars tympanica) (Fig. 64) is fused with the mastoid process and the squamous part, it is a thin plate that limits the external auditory opening and the external auditory meatus in front, behind and below.
The temporal bone contains several canals:
- carotid canal (canalis caroticus) (Fig. 67), in which lies the internal carotid artery. It starts from the outer opening on the lower surface of the rocky part, goes vertically upwards, then, gently curving, passes horizontally and exits at the top of the pyramid;
- facial canal (canalis facialis) (Fig. 67), in which the facial nerve is located. It begins in the internal auditory meatus, goes horizontally forward to the middle of the anterior surface of the petrous part, where, turning at a right angle to the side and passing into the posterior part of the medial wall of the tympanic cavity, it goes vertically down and opens with a stylomastoid opening;
- the muscular-tubal canal (canalis musculotubarius) (Fig. 66) is divided by a septum into two parts: the semi-canal of the muscle that strains the eardrum (semicanalis m. tensoris tympani) (Fig. 67), and the semi-canal of the auditory tube (semicanalis tubae auditivae) (Fig. . 67), connecting the tympanic cavity with the pharyngeal cavity. The canal opens with an external opening lying between the anterior end of the petrous part and the scales of the occipital bone, and ends in the tympanic cavity.
The temporal bone is connected to the occipital, parietal and sphenoid bones.
The parietal bone (os parietale) (Fig. 59) is paired, flat, has a quadrangular shape and takes part in the formation of the upper and lateral parts of the cranial vault.
The outer surface (facies externa) of the parietal bone is smooth and convex. The place of its greatest convexity is called the parietal tubercle (tuber parietale) (Fig. 68). Below the hillock are the upper temporal line (linea temporalis superior) (Fig. 68), which is the site of attachment of the temporal fascia, and the lower temporal line (linea temporalis inferior) (Fig. 68), which serves as the site of attachment of the temporal muscle.
The inner, cerebral, surface (facies interna) is concave, with a characteristic relief of the adjacent brain, the so-called digital impressions (impressiones digitatae) (Fig. 71) and tree-like branching arterial grooves (sulci arteriosi) (Fig. 69, 71).
Four edges are distinguished in the bone. The anterior frontal edge (margo frontalis) (Fig. 68, 69) is connected to the frontal bone. Rear occipital margin (margo occipitalis) (Fig. 68, 69) - with the occipital bone. The upper swept, or sagittal, edge (margo sagittalis) (Fig. 68, 69) is connected to the same edge of the other parietal bone. The lower squamous edge (margo squamosus) (Fig. 68, 69) is covered in front by the large wing of the sphenoid bone, a little further by the scales of the temporal bone, and behind it is connected to the teeth and mastoid process of the temporal bone.
Also, according to the edges, four corners are distinguished: frontal (angulus frontalis) (Fig. 68, 69), occipital (angulus occipitalis) (Fig. 68, 69), wedge-shaped (angulus sphenoidalis) (Fig. 68, 69) and mastoid (angulus mastoideus ) (Fig. 68, 69).
The frontal bone (os frontale) (Fig. 59) is unpaired, participates in the formation of the anterior part of the vault and base of the skull, eye sockets, temporal fossa and nasal cavity. Three parts are distinguished in it: the frontal scales, the orbital part and the nasal part.
Frontal scales (squama frontalis) (Fig. 70) is directed vertically and backwards. The outer surface (facies externa) is convex and smooth. From below, the frontal scales end with a pointed supraorbital margin (margo supraorbitalis) (Fig. 70, 72), in the medial part of which there is an supraorbital notch (incisura supraorbitalis) (Fig. 70), containing the vessels and nerves of the same name. The lateral section of the supraorbital margin ends with a triangular zygomatic process (processus zygomaticus) (Fig. 70, 71), which connects to the frontal process of the zygomatic bone. Behind and upward from the zygomatic process, an arcuate temporal line (linea temporalis) (Fig. 70) passes, separating the outer surface of the frontal scale from its temporal surface. The temporal surface (facies temporalis) (Fig. 70) is involved in the formation of the temporal fossa. Above the supraorbital margin on each side is the superciliary arch (arcus superciliaris) (Fig. 70), which is an arcuate elevation. Between and slightly above the superciliary arches is a flat, smooth area - the glabella (glabella) (Fig. 70). Above each arc there is a rounded elevation - frontal tubercle (tuber frontale) (Fig. 70). The inner surface (facies interna) of the frontal scales is concave, with characteristic indentations from the convolutions of the brain and arteries. The groove of the superior sagittal sinus (sulcus sinus sagittalis superioris) (Fig. 71) runs along the center of the inner surface, the edges of which in the lower section are combined into the frontal scallop (crista frontalis) (Fig. 71).
The orbital part (pars orbitalis) (Fig. 71) is steam room, takes part in the formation of the upper wall of the orbit and has the form of a horizontally located triangular plate. The lower orbital surface (facies orbitalis) (Fig. 72) is smooth and convex, facing the cavity of the orbit. At the base of the zygomatic process in its lateral section is the fossa of the lacrimal gland (fossa glandulae lacrimalis) (Fig. 72). The medial part of the orbital surface contains a trochlear fossa (fovea trochlearis) (Fig. 72), in which lies the trochlear spine (spina trochlearis) (Fig. 72). The upper cerebral surface is convex, with a characteristic relief.
The nasal part (pars nasalis) (Fig. 70) of the frontal bone in an arc surrounds the ethmoid notch (incisura ethmoidalis) (Fig. 72) and contains pits that articulate with the cells of the labyrinths of the ethmoid bone. In the anterior section there is a descending nasal spine (spina nasalis) (Fig. 70, 71, 72). In the thickness of the nasal part lies the frontal sinus (sinus frontalis), which is a paired cavity separated by a septum, belonging to the air-bearing paranasal sinuses.
The frontal bone is connected to the sphenoid, ethmoid and parietal bones.
The ethmoid bone (os ethmoidale) is unpaired, participates in the formation of the base of the skull, the orbit and the nasal cavity. It consists of two parts: a lattice, or horizontal, plate and a perpendicular, or vertical, plate.
Ethmoid plate (lamina cribosa) (Fig. 73, 74, 75) is located in the ethmoid notch of the frontal bone. On both sides of it is a lattice labyrinth (labyrinthus ethmoidalis) (Fig. 73), consisting of air-bearing lattice cells (cellulae ethmoidales) (Fig. 73, 74, 75). On the inner surface of the ethmoid labyrinth there are two curved processes: the upper (concha nasalis superior) (Fig. 74) and the middle (concha nasalis media) (Fig. 74, 75) nasal conchas.
Perpendicular plate (lamina perpendicularis) (Fig. 73, 74, 75) is involved in the formation of the septum of the nasal cavity. Its upper part ends with a cockscomb (crista galli) (Fig. 73, 75), to which a large sickle-shaped process of the dura mater is attached.
The occipital bone, os occipitalae, is unpaired, making up the back of the base and roof of the skull. It distinguishes four parts: the main, pars basilaris, two lateral, partes laterales, and scales, squama. In a child, these parts are separate bones connected by cartilage. On the 3rd - 6th year of life, the cartilage ossifies and they fuse together into one bone. All these parts join together to form a large opening, the foramen magnum. In this case, the scales lie behind this hole, the main part is in front, and the lateral ones are on the sides. The scales are mainly involved in the formation of the posterior part of the skull roof, and the main and lateral parts are the base of the skull.
The main part of the occipital bone has the shape of a wedge, the base of which is turned forward to the sphenoid bone, and the tip is posterior, limiting the large opening in front. In the main part, five surfaces are distinguished, of which the upper and lower are connected behind at the anterior edge of the occipital foramen. The anterior surface is connected by the sphenoid bone until the age of 18 - 20 with the help of cartilage, which subsequently ossifies. The upper surface - slope, clivus, is concave in the form of a groove, which is located in the sagittal direction. The medulla oblongata, pons, blood vessels and nerves are adjacent to the slope. In the middle of the lower surface is the pharyngeal tubercle, tuberculum pharyngeum, to which the initial part of the pharynx is attached. On the sides of the pharyngeal tubercle, two transverse ridges extend from each side, of which m is attached to the anterior one. longus capitis, and to the back - m. rectus capitis anterior. Lateral rough surfaces of the main part are connected by means of cartilage to the petrous part of the temporal bone. On their upper surface, near the lateral edge, there is a small groove of the lower petrosal sinus, sulcus sinus petrosi inferioris. It is in contact with a similar groove in the petrous part of the temporal bone and serves as a place to which the inferior petrosal venous sinus of the dura is adjacent.
The lateral part is located on both sides of the foramen magnum and connects the main part to the scales. Its medial edge faces the foramen magnum, the lateral edge faces the temporal bone. The lateral edge carries the jugular notch, incisura jugularis, which, with the corresponding notch of the temporal bone, limits the jugular foramen. The intrajugular process, processus intrajugularis, located along the edge of the notch of the occipital bone, divides the opening into anterior and posterior. The internal jugular vein passes in the anterior, and the IX, X, IX pairs of cranial nerves pass in the posterior. The back of the jugular notch is limited by the base of the jugular process, processus jugularis, which faces the cranial cavity. Behind and inside of the jugular process on the inner surface of the lateral part is a deep groove of the transverse sinus, sulcus sinus transverse. In the anterior part of the lateral part, on the border with the main part, there is a jugular tubercle, tuberculum jugulare, and on the lower surface there is an occipital condyle, condylus occipitalis, with which the skull articulates with the I cervical vertebra. The condyles, according to the shape of the upper articular surface of the atlas, form oblong ridges with convex oval articular surfaces. Behind each condyle there is a condylar fossa, fossa condylaris, at the bottom of which there is a visible opening of the outlet canal connecting the veins of the meninges with the external veins of the head. This hole is absent in half of the cases on both sides or on one side. Its width is highly variable. The base of the occipital condyle is pierced by the hypoglossal nerve canal, canalis hypoglossi.
The occipital scales, squama oscipitalis, are triangular in shape, curved, its base facing the occipital foramen, the apex facing the parietal bones. The upper edge of the scales is connected by the parietal bones through a lambdoid suture, and the lower edge is connected to the mastoid parts of the temporal bones. In this regard, the upper edge of the scales is called lambdoid, margo lambdoideus, and the lower edge is mastoid, margo mastoideus. The outer surface of the scales is convex, in its middle there is an external occipital protrusion, protuberantia occipitalis externa, from which the external occipital crest, crista occipitalis externa, descends vertically down towards the occipital foramen, intersecting in pairs with two nuchal lines, lineae nuchae superior et inferior. In some cases, the highest nuchal line, lineae nuchae suprema, is also noted. Muscles and ligaments are attached to these lines. The inner surface of the occipital scale is concave, forming in the center an internal occipital protrusion, protuberantia occipitalis interna, which is the center of the cruciform eminence, eminentia cruciformis. This elevation divides the inner surface of the scale into four separate depressions. The occipital lobes of the brain adjoin the two upper ones, and the hemispheres of the cerebellum adjoin the two lower ones.
Ossification. It begins at the beginning of the 3rd month of intrauterine development, when islands of ossification appear both in the cartilaginous and connective tissue parts of the occipital bone. In the cartilaginous part, five ossification points arise, of which one is located in the main part, two in the lateral parts, and two in the cartilaginous part of the scale. Two ossification points appear in the connective tissue upper part of the scale. By the end of the 3rd month, the fusion of the upper and lower sections of the scales occurs; in the 3rd-6th year, the main part, lateral parts and scales grow together.
