Scull. Features of bone formations of the brain and facial parts of the skull

Inner base of the skullbasis cranii interna, has a concave, uneven surface, reflecting the complex topography of the lower surface of the brain. It is divided into three cranial fossae: anterior, middle and posterior.

Anterior cranial fossa, fossa cranii anterior, formed by the orbital parts of the frontal bones, on which cerebral elevations and finger-like impressions are well defined. In the center, the fossa is deepened and filled with a cribriform plate of the ethmoid bone, through the openings of which the olfactory nerves (1st pair) pass. In the middle of the cribriform plate the cock's comb rises; in front of it are the foramen cecum and the frontal crest.

Middle cranial fossa, fossa cranii media, much deeper than the anterior one, its walls are formed by the body and large wings of the sphenoid bone, the anterior surface of the pyramids, and the scaly part of the temporal bones. In the middle cranial fossa, a central part and lateral parts can be distinguished.

On the lateral surface of the body of the sphenoid bone there is a well-defined carotid groove, and near the apex of the pyramid a ragged foramen of irregular shape is visible. Here, between the lesser wing, the greater wing and the body of the sphenoid bone, the superior orbital fissure is located, fissura orblalis superior, through which the oculomotor nerve (III pair), trochlear nerve (IV pair), abducens (VI pair) and ophthalmic (first branch of the V pair) nerves pass into the orbit. Posterior to the superior orbital fissure there is a round foramen for the passage of the maxillary nerve (second branch of the V pair), then an oval foramen for the mandibular nerve (third branch of the V pair).

At the posterior edge of the greater wing lies the foramen spinosum for the passage of the middle meningeal artery into the skull. On the anterior surface of the pyramid of the temporal bone, on a relatively small area, there is a trigeminal depression, a cleft of the greater petrosal nerve canal, a groove of the greater petrosal nerve, and a cleft of the lesser petrosal nerve canal.

nerve, groove of the lesser petrosal nerve, roof of the tympanic cavity and arcuate eminence.

Posterior cranial fossa, fossa cranii posterior, the deepest. The occipital bone, the posterior surfaces of the pyramids and the inner surface of the mastoid processes of the right and left temporal bones take part in its formation. The fossa is complemented by a small part of the body of the sphenoid bone (in front) and the posteroinferior angles of the parietal bones - from the sides. In the center of the fossa there is a large occipital foramen, in front of it there is a slope, clivus, formed by the fused bodies of the sphenoid and occipital bones in an adult.

The internal auditory foramen (right and left) opens into the posterior cranial fossa on each side, leading into the internal auditory canal, in the depths of which the facial canal for the facial nerve (VII pair) originates. The vestibular-cochlear nerve (VIII pair) emerges from the internal auditory opening.

It is impossible not to note two more paired large formations: the jugular foramen, through which the glossopharyngeal (IX pair), vagus (X pair) and accessory (XI pair) nerves pass, and the hypoglossal canal for the nerve of the same name (XII pair). In addition to the nerves, the internal jugular vein leaves the cranial cavity through the jugular foramen, into which the sigmoid sinus continues, lying in the groove of the same name. The boundary between the vault and the inner base of the skull in the region of the posterior cranial fossa is the groove of the transverse sinus, which passes on each side into the groove of the sigmoid sinus.

Inner base of the skull

Internal base of the skull (basis cranii interna). Top view. 1st orbital part of the frontal bone; 2-cock febe; 3-cribriform plate.; 4-visual channel; 5-pituitary fossa; 6-back saddle. 7-round hole; 8-oval hole; 9-ragged hole; 10-spinous foramen; 11-internal auditory opening; 12-jugular foramen; 13-hyoid and canal; 14-lambdoid suture; 15-slope; 16-sulcus of the transverse sinus; 17-internal occipital protrusion; 18-large (occipital) foramen; 19-occipital scales; 20-sulcus of the sigmoid sinus; 21-pyramid (stony part) of the temporal bone; 22-squamosal part of the temporal bone; 23-large wing of the sphenoid bone; 24-lesser wing of the sphenoid bone;

In some places of the skull there are bone thickenings, or buttresses, through which chewing pressure is transmitted to the cranial vault. Between these buttresses are thinner bony formations called weak points. Fractures are more common in these areas. Thickenings are observed on both the upper and lower jaws. On upper jaw There are 4 buttresses (Fig. 1).

Frontonasal buttress rests below on the alveolar elevations in the canine area, at the top it continues in the form of a reinforced plate of the frontal process of the upper jaw, reaching the nasal part of the frontal bone. The right and left buttresses in the area of the nasal part of the frontal bone are strengthened by transversely located bone ridges in the form of brow arches. This buttress balances the upward pressure developed by the canines.

Alveolar-zygomatic buttress comes from the alveolar eminence of the 1st and 2nd molars, goes up along the zygomaticalveolar ridge to the zygomatic bone, which redistributes pressure: posteriorly - on the zygomatic process of the temporal bone, from above - on the zygomatic process of the frontal bone, inwardly - on the zygomatic process and infraorbital margin maxilla, towards the frontonasal buttress. The alveolar-zygomatic buttress is the most pronounced and balances the force developed by the chewing teeth in the direction from bottom to top, from front to back and from outside to inside.

Pterygopalatine buttress starts from the alveolar eminence of the molars and the tubercle of the upper jaw, goes upward, where it is strengthened by the pterygoid process of the sphenoid bone and the perpendicular plate of the palatine bone. This buttress balances the force developed by the molars from bottom to top and from back to front.

Palatal buttress formed by the palatine processes of the upper jaw and horizontal plates of the palatine bone, connecting the right and left alveolar arches in the transverse direction. This buttress balances the force developed during chewing in the transverse direction.

In general, there are 2 buttresses on the lower jaw:

1) alveolar (heads upward to the alveolar cells);

2) ascending (goes up the branch of the lower jaw to the neck and head).

From here, chewing pressure is transmitted to the mandibular fossa of the temporal bone.

On the inner base of the skull, just as in the facial region, there are a number of buttresses that absorb loads and form the walls of the cranial fossae (see Fig. 1, g).

Weak spots in the skull bones (thin areas, holes, crevices) determine the direction of fractures.

On the internal base of the skull (Fig. 5) there are:

anterior, middle and posterior cranial fossae.

In the anterior cranial fossa:

The most anteriorly located are the veins coming from the nasal cavity and flowing into the superior sagittal sinus. Through these veins, infection from the facial part of the head can pass into the cranial cavity:

Posterior to the foramen cecum are the perforated plate and the branches of the first pair of cranial nerves passing through it.

Fig.5. Inner base of the skull:

1 - cockscomb; 2 - perforated plate of the ethmoid bone; 3 - optic nerve panel;
4 - oval hole; 5 - stony-scaly gap; 6 – jugular foramen; 7 - foramen magnum; 8 - internal occipital crest; 9 - internal occipital protrusion; 10 - groove of the transverse sinus; 11- mastoid foramen; 12 - groove of the sigmoid sinus; 13 - groove of the superior petrosal sinus; 14 - cleft of the greater petrosal nerve; 15 - cleft of the lesser petrosal nerve; 16 - back of the sella turcica; 17 - spinous foramen; 18 - Turkish saddle;
19 - round hole; 20 - large wing of the sphenoid (main) bone; 21 - small wing of the sphenoid (main) bone.

In the middle cranial fossa:

The openings communicating with neighboring areas are located mainly in the sphenoid bone.

The most anterior is the optic canal, which contains: the 2nd pair of cranial nerves, the ophthalmic artery, and a branch of the carotid artery. The following pass through the superior orbital fissure: the 3rd, 4th, 6th pairs of cranial nerves and the first branch of the trigeminal nerve;

Posterior to the superior orbital fissure lies the foramen rotundum, which passes through the maxillary nerve, the 2nd branch of the trigeminal nerve;

Posterior and outward from the foramen ovale is a small foramen spinosum, which serves for the passage of the middle meningeal artery;

The next hole is ragged, where the internal carotid artery passes;

On the side of it, the carotid canal opens, the internal carotid artery.

Posterior cranial fossa:

The posterior cranial fossa contains the cerebellum, medulla oblongata, and the Varalian pons.

In the center is the foramen magnum, where the medulla oblongata with membranes and arteries passes;

On the posterior surface of the pyramid is the internal auditory opening, where the facial and auditory nerves pass. In the anterior section it passes the 9th, 10th, 11th pairs of cranial nerves, and in the posterior section the internal jugular vein

Thus, the bones of the base of the skull have unequal thickness and strength, many holes, channels, and crevices. In skull injuries, these features contribute to fractures.

Fractures of the base of the skull can easily cause damage to the nerves and blood vessels in the area.

For fractures of the base of the skull in the area anterior fossa There is bleeding from the nose, ears, and when the membranes rupture, there is a leakage of cerebrospinal fluid. Bleeding from the nasopharynx, hemorrhages into the orbital cavity, and bulging eyes also occur. When the cavernous sinus and internal carotid artery are damaged, pulsating bulging eyes, paralysis of the abducens nerve and a symptom of “spectacles” in the orbital area are observed.

For fractures in the area middle cranial fossa with damage to the pyramid of the temporal bone, bleeding and liquorrhea from the ear and symptoms of damage to the cranial nerves are observed.

External base of the skull(Fig. 6).

On the outer base of the skull, between the styloid and mastoid processes, the stylomastoid foramen (foramen stylomastoideum) opens, through which the branches of the facial nerve emerge. Inward from the temporomandibular joint there is a petrotympanic fissure (fissure petrotympanica), through which a thin branch of the facial nerve emerges - the chorda tympani. Anterior to the jugular foramen on the outer base of the skull is the opening of the carotid artery canal, to which the internal carotid artery is attached.

Inner surface of the base of the skull, basis cranii interna, is divided into three fossae, of which the cerebrum is located in the anterior and middle, and the cerebellum in the posterior. The border between the anterior and middle fossae is the posterior edges of the small wings of the sphenoid bone, and between the middle and posterior fossae is the upper edge of the pyramids of the temporal bones.

Anterior cranial fossa, fossa cranii anterior, is formed by the orbital parts of the frontal bone, the ethmoidal plate of the ethmoid bone lying in the recess, the lesser wings and part of the body of the sphenoid bone. The frontal lobes of the cerebral hemispheres are located in the anterior cranial fossa. On the sides of the crista galli there are laminae cribrosae, through which the olfactory nerves pass, nn. olfactorii (I pair) from the nasal cavity and a. ethmoidalis anterior (from a. ophthalmica) accompanied by the vein and nerve of the same name (from the first branch of the trigeminal nerve).

Middle cranial fossa, fossa cranii media, deeper than the anterior one. It consists of a middle part, formed by the upper surface of the body of the sphenoid bone (the area of the sella turcica), and two lateral ones. They are formed by the large wings of the sphenoid bone, the anterior surfaces of the pyramids and partly by the scales of the temporal bones. The central part of the middle fossa is occupied by the pituitary gland, and the lateral parts by the temporal lobes of the hemispheres. Cleredi from the sella turcica, in the sulcus chiasmatis, is the optic chiasm, chiasma opticum. On the sides of the sella turcica lie the most important sinuses of the dura mater in practical terms - cavernous, sinus cavernosus, into which the superior and inferior ophthalmic veins flow.

Middle cranial fossa communicates with the orbit through the optic canal, canalis opticus, and the superior orbital fissure, fissura orbitalis superior. The optic nerve passes through the canal, n. opticus (II pair), and ophthalmic artery, a. ophthalmica (from the internal carotid artery), and through the gap - the oculomotor nerve, n. oculomotorius (III pair), trochlear, n. trochlearis (IV pair), abducens, n. abducens (VI pair) and ophthalmic, n. ophthalmicus, nerves and ophthalmic veins.

Middle cranial fossa communicates through the round foramen, foramen rotundum, where the maxillary nerve passes, n. maxillaris (II branch of the trigeminal nerve), with the pterygopalatine fossa. It is connected to the infratemporal fossa through the oval foramen, foramen ovale, where the mandibular nerve passes, n. mandibularis (III branch of the trigeminal nerve), and the spinous, foramen spinosum, where the middle meningeal artery passes, a. meningea media. At the top of the pyramid there is an irregularly shaped hole - foramen lacerum, in the area of which there is an internal opening of the carotid canal, from where the internal carotid artery enters the cranial cavity, a. carotis interna.

Internal base of the skull (basis cranii interna)

Inner base of the skull(basis cranii interna).

Top view.

1st orbital part of the frontal bone;
2-cock febe;
3-cribriform plate.;
4-visual channel;
5-pituitary fossa;
6-back saddle.
7-round hole;
8-oval hole;
9-ragged hole;
10-spinous foramen;
11-internal auditory opening;
12-jugular foramen;
13-hyoid and canal;
14-lambdoid suture;
15-slope;
16-sulcus of the transverse sinus;
17-internal occipital protrusion;
18-large (occipital) foramen;
19-occipital scales;
20-sulcus of the sigmoid sinus;
21-pyramid (stony part) of the temporal bone;
22-squamosal part of the temporal bone;
23-large wing of the sphenoid bone;
24-lesser wing of the sphenoid bone;

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Internal base of the skull (basis cranii interna) represents an uneven concave surface in which three cranial fossae are distinguished: anterior, middle and posterior (Fig. 1).

Anterior cranial fossa (fossa cranii anterior) formed by the nasal and orbital parts of the frontal bone, the lesser wings of the sphenoid bone, and the ethmoidal plate of the ethmoid bone. The olfactory filaments of the first pair of cranial nerves pass through the holes in the plate. In the middle of it rises cockscomb, in front of which is located blind hole. Visible on the orbital processes of the frontal bone cerebral eminences and depressions of the gyri, from the fit of the grooves and convolutions of the brain.

Middle cranial fossa (fossa cranii media) formed by the sphenoid and temporal bones. It is delimited from the anterior cranial fossa by the posterior edge of the lesser wings, and from the posterior by the upper edge of the pyramid of the temporal bone and the dorsum of the sella turcica. The middle cranial fossa consists of three parts: two lateral and a central one. The central part is formed by the sella turcica, at the bottom of which there is a pituitary fossa - a place for the pituitary gland. Anterior to it are the tubercle of the sella and precross groove, continuing into the optic canal, through which the second pair of cranial nerves exits the orbit. The carotid groove runs along the lateral surface of the body of the sphenoid bone. Posteriorly and inferiorly from it there is torn hole, next to which at the apex of the pyramid of the temporal bone opens internal carotid aperture.

On the anterior surface of the pyramid of the temporal bone is trigeminal depression: Here under the dura mater lies the trigeminal ganglion. Posterior to the depression along the anterior surface of the pyramid there are grooves leading into small canal clefts And greater petrosal nerves, located even further arched eminence And roof of the tympanic cavity.

Rice. 1. Internal base of the skull: a - anatomical formations of the internal base of the skull: 1 - blind foramen; 2 - cockscomb; 3 - orbital part of the frontal bone; 4 - anterior cranial fossa; 5 - pre-cross groove; 6 - tubercle of the saddle; 7 - visual channel; 8 - pituitary fossa; 9 - large wing of the sphenoid bone; 10 - round hole; 11 - oval hole; 12 — torn hole; 13 - foramen spinosum; 14 - stony-occipital fissure; 15 - internal auditory opening; 16 - groove of the inferior petrosal sinus; 17—jugular foramen; 18— canal of the hypoglossal nerve; 19 - large hole; 20 - occipital scales; 21 - internal occipital crest; 22 - posterior cranial fossa; 23 - condylar canal; 24 - groove of the sigmoid sinus; 25 - groove of the superior petrosal sinus; 26 - stony-scaly fissure; 27 - slope; 28 - middle cranial fossa; 29 — wedge-shaped fissure; 30 - trigeminal depression; 31 - sphenoid-occipital synchondrosis; 32 — back of the saddle; 33 - carotid groove; 34 — lesser wing of the sphenoid bone; 35 - wedge-shaped eminence; 36 - cribriform plate

b — details of the structure of the middle cranial fossa: 1 — wedge-shaped eminence; 2 - pre-cross groove; 3 - visual channel; 4 - anterior inclined process; 5 - superior orbital fissure; 6 - round hole; 7 - tubercle of the saddle; 8 - carotid groove; 9 - foramen spinosum; 10 - cleft and groove of the lesser petrosal nerve; 11 — roof of the tympanic cavity; 12 — arcuate elevation; 13 - groove of the superior petrosal sinus; 14 - oval hole; 15 - torn hole; 16 - posterior inclined process; 17 — back of the saddle; 18 - pituitary fossa; 19 - cleft and groove of the greater petrosal nerve; 20 - trigeminal depression; 21 - apex of the pyramid of the temporal bone; 22 - large wing of the sphenoid bone; 23 - lesser wing of the sphenoid bone

At the base of the large wings there are three openings (from front to back): round, oval and spinous. The maxillary nerve passes through the foramen rotundum into the pterygopalatine fossa, the mandibular nerve passes through the oval foramen into the infratemporal fossa, and the middle meningeal artery passes through the spinous foramen into the middle cranial fossa. In the anterolateral sections of the middle cranial fossa, between the small and large wings, there is superior orbital fissure (fissura orbitalis superior), through which the III, IV, VI cranial nerves and the optic nerve pass.

Posterior cranial fossa (fossa cranii posterior) formed by the occipital bone, the posterior surface of the pyramid, the body of the sphenoid bone and partially the parietal bone. This fossa is deeper than the anterior and middle ones. At its center lies big hole. Anterior to it is the slope (clivus), formed by the body of the sphenoid and basilar part of the occipital bone. Behind and above the large hole is located internal occipital protuberance, to the sides from which it goes transverse sinus groove. It continues in sigmoid sinus groove, leading to jugular foramen. On the posterior-inferior surface of the pyramid one can see internal auditory opening, where the facial nerve enters and where the vestibulocochlear nerve exits. Between the lateral part of the body of the occipital bone and the medial edge of the pyramid there is groove of the inferior petrosal sinus (sulcus sinus petrosi inferioris). In the posterior cranial fossa, to the side of the foramen magnum, lie the cerebellar hemispheres, and on the clivus are the medulla oblongata and the pons.

At the border of the brain and facial skull there are pits that are very important in practical terms: temporal, infratemporal and pterygopalatine (Fig. 2).

Temporal fossa (fossa temporalis) bounded above and behind by the temporal line, externally by the zygomatic arch, below by the infratemporal crest of the greater wing of the sphenoid bone, and in front by the zygomatic bone. The temporalis muscle lies in the temporal fossa.

Infratemporal fossa (fossa infratemporalis) bounded above by the infratemporal surface of the greater wing of the sphenoid bone and the temporal scales, medially by the lateral plate of the pterygoid process, anteriorly by the infratemporal surface of the upper jaw and partially by the temporal surface of the zygomatic bone, laterally by the zygomatic arch and the ramus of the mandible. The infratemporal fossa communicates with the orbit through the inferior orbital fissure, through pterygomaxillary fissure (fissura pterygomaxillaris)- with the pterygopalatine fossa and through the spinous and foramen ovale - with the middle cranial fossa.

Pterygopalatine fossa (fossa pterygopalatina) limited in front tubercle of the maxilla, medially - by the perpendicular plate of the palatine bone, behind - by the anterior edge of the pterygoid process, above - by the maxillary surface of the greater wing of the sphenoid bone (see Fig. 2). Through the pterygomaxillary fissure, this fossa opens from the outside into the infratemporal fossa. Through the pterygoid canal it communicates with the region of the foramen lacerum, through the foramen rotundum - with the middle cranial fossa, through sphenopalatine foramen (foramen sphenopalatinum)- with the nasal cavity, through the lower orbital fissure - with the orbit and through the greater palatine canal - with the oral cavity.

Rice. 2. Temporal, infratemporal and pterygopalatine fossa:

a — position of the temporal fossa;

b — temporal, infratemporal and pterygopalatine fossa (zygomatic arch removed): 1 — temporal surface of the greater wing of the sphenoid bone; 2 - infratemporal crest; 3 - lateral plate of the pterygoid process; 4 - hook of the medial plate of the pterygoid process; 5 - external auditory opening; 6 - mandibular fossa; 7 - articular tubercle; 8 - styloid process; 9 - spine of the sphenoid bone; 10 - perpendicular plate of the palatine bone; 11—sphenopalatine foramen; 12— posterior superior alveolar openings; 13 - tubercle of the upper jaw; 14 - inferior orbital fissure; 15 — entrance to the pterygopalatine fossa; 16 - borders of the infratemporal fossa

Human anatomy S.S. Mikhailov, A.V. Chukbar, A.G. Tsybulkin