Topographic craniology. Inner base of the skull

The human skull is the bone base of the head, consisting of twenty-three bones, in addition to which there are three paired bones that are located in the cavity of the middle ear. The base of the skull consists of that part of it that is below the face that runs in front at the border of the infraorbital region, behind the frontal bone, in particular, its zygomatic process, and the infratemporal crest of the bone in the form of a wedge, the upper border of the external auditory canyon, as well as to external protrusion of the occiput. Allocate external and. Today we will consider the inner foundation. But before proceeding to the study of this issue, we will consider what structure and functions the skull has, as well as its shape.

Forms and functions of the skull

The human skull performs several functions:

Protective, which is characterized by the ability to protect the human brain and sensory organs from various damages;

Support, which consists in the ability to accommodate the brain and the initial sections of the respiratory and digestive systems;

Motor, characterized by articulation with the spinal column.

The human skull can be represented by one of the forms: standard (cranial index), acrocephaly (tower shape) and craniosynostosis (fusion of the sutures of the cranial vault).

To better navigate the anatomy of the skull, consider in more detail.

External base of the skull

So it is customary to call that which is turned down and is closed in front by the bones of the face, and behind the outer base is formed by the bone palate, processes in the form of wings, medial plates, which limit the choanae separated by the vomer. Behind the pterygoid processes, the base is formed by a bone in the form of a wedge, the lower part of the pyramid, the tympanic part, and also the anterior part of the occipital bone. Outdoor skull base, anatomical atlas will tell you its location, it has three parts: front, middle and back. Let's consider each of them in more detail.

The back section of the base of the outer

The vault of the nasopharynx is located in the posterior section, which is limited by the pharynx. A fascia is attached to the base of the skull, having a direction from the pharyngeal tubercle to the side, in front of the carotid canal of the temple bone pyramid to the lower jaw. In the posterior part of the base there is a large occipital fissure and emissaries that connect the sinuses of the dura mater with the plexus of the suboccipital veins, the vertebral vein and the subclavian artery.

Anterior section of the base of the outer

There are gaps here, through which nerves and blood vessels pass. The largest openings, the role of which is very important, are located along the border, which connects the awl-mastoid fissure and the incisive opening. The base section, which is located in front, includes the bone palate with the incisive and large palatine canals. Choanae go back from the nasal cavity.

The middle section of the outer base

This area includes a torn gap, which is located between bones such as the temporal, occipital and sphenoid. There is also a jugular mouth located between the occipital bone and the temporal. In the same area, such cracks as wedge-stony and occipital are located.

Inner surface of the base of the skull

The base of the skull on the inside contains three fossae: anterior, middle and posterior. In its location, the anterior fossa is above the middle one. And this, in turn, fit over the back. The large brain is located in the first two fossae, the cerebellum is located in the posterior fossa. The demarcations between the pits are presented in the form of the edges of the sphenoid bone, which are located behind, as well as the upper level of the pyramids of the bones of the temple. AT the internal base of the skull is the surface of the skull, which is concave and has irregularities, it repeats the structure of the brain that is adjacent to it. Let's consider its structure in more detail.

Anterior fossa of the skull

The anterior cranial fossa is the deepest. It is formed by the edges of the wings of the bone in the form of a wedge and a protrusion that is located between the visual mouths. The frontal sinuses adjoin this fossa in front, and below there are recesses of the ethmoid bone, nasal cavity and sinus. Anterior to the cockscomb is a blind ostium through which a small vein follows, which unites the superior sagittal sinus with the nasal veins. On both edges of the ethmoid bone there are olfactory bulbs, where the olfactory nerves come through the plate from the nasal cavity. Arteries, nerves and veins also pass through the ethmoid bone, which provide the membrane of the brain of the anterior fossa. AT internal base of the skull involves the placement of the frontal lobes of the large hemispheres of the human brain in this pit.

Middle cranial fossa

The middle cranial fossa is separated from the posterior one with the help of the Turkish saddle and the tops of the pyramids of the bones of the temple. In the middle of the fossa there is a Turkish saddle, which is covered with a diaphragm, which has a gap through which a recess appears, which has an end in the form of a cerebral appendage. On the diaphragm in front of the funnel is the intersection of the optic nerves, on the sides of which there are the so-called siphons of the carotid arteries. From them, in turn, the ophthalmic arteries move away, they, together with the optic nerves, pass into the visual gorges. So, it involves the placement in the middle fossa of the cavernous sinus, which is located away from the Turkish saddle. In this place, the carotid internal artery passes and above the carotid artery in the walls of the sinuses there are nerves: trigeminal, cranial and oculomotor. They pass through the upper mouth into the orbit. On the side of these nerves are the veins of the eye sockets and the eyeball, which then go into the cavernous sinus. Behind the Turkish saddle on the vagus nerve between the sheets of one of the three meninges is the motor nerve. Its branches go through the cracks of the round and oval forms of the cranial fossa, which is located in the middle. Behind the form there is a spinous gap, through which the anterior artery of the dura mater passes into the cranial cavity. It also suggests the presence on both sides of the Turkish saddle in the fossa, which is located in the middle, cerebral. In front of the inner part of the bone of the temple, which has the shape of a pyramid, there is a cavity of the middle ear, an intra-ear cavity and a cavity in the mastoid process of the temporal bone.

Posterior cranial fossa

The posterior cranial fossa houses the cerebellum, medulla oblongata, and pons. In front of the fossa on an inclined surface there is a bridge, the main artery with all branches. In are the plexus of veins and petrosal sinuses. All are interconnected. The posterior fossa is almost entirely occupied by the cerebellum, on top and on the sides of it there are sinuses: sigmoid and transverse. The cranial cavity and the posterior fossa are separated by the cerebellar tenon, through which the brain passes. Consider what role it has.

Behind the pyramid of the temple bone is the auditory mouth, through which the facial, auditory nerves and the membranous labyrinth pass. Below the auditory canyon, the glossopharyngeal, accessory nerves, vagus, and also the jugular vein pass through the torn fissure. If you look in the atlas below, you can see that the hypoglossal nerve and its canal, as well as the plexus of veins, pass through the mouth of the hypoglossal nerve. In the middle of the posterior fossa is a large occipital fissure through which the medulla oblongata and its membranes, the arteries of the spine and the spinal nerve root extend. Along the edge of the groove of the sigmoid sinus, several mouths open into the fossa, which is located behind, which let the emissary veins and the meningeal branch of the occipital artery pass. Mouths and fissures that connect the posterior fossa with other areas are located in its anterior parts. Thus, they are presented in three types: front, middle and back.

Finally…

It is impossible to study the features of the shape and structure of the human skull without analyzing its functions, just as it is impossible to imagine the functions of any organ without comprehending its structure. Knowledge of the anatomy of the skull in medicine is undeniable. This science uses modern diagnostic methods. The structure of the skull was known through inspection, dissection, study, and other things. Today we have the opportunity to study the external and thanks to the medical atlases that were created many years ago. This knowledge is of particular importance in the medical sciences, since it makes it possible to investigate the anomalies in the development of the skull, the structure of the veins and vessels of the brain. The study of the anatomy of the skull is especially important for neurosurgeons, traumatologists and maxillofacial surgeons. Knowledge helps them to make the correct diagnosis and prescribe proper treatment in case of various defects or diseases. And this, in turn, can save a person's life.

We now know what the human scull. Anatomy of the internal base of the skull considered when studying at medical universities. The base is a concave surface that repeats the structure of the brain. It contains many channels and holes and consists of three pits. The inner base of the skull is the surface of the skull where the frontal lobes of the cerebral hemispheres are located, as well as the cerebellum, medulla oblongata and pons. Also located here are arteries, vessels, nerves. All of them play a huge role in the normal functioning of the human body.

The inner base of the skull (basis cranii interna) has a concave, uneven surface corresponding to the shape of the base of the brain. It has three cranial fossae: anterior, middle, and posterior. The posterior edges of the small wings (ala minor) and the tubercle of the Turkish saddle of the sphenoid bone (tuberculum sellae turcicae ossis sphenoidalis) separate the anterior cranial fossa (fossa cranii anterior) from the middle one (fossa cranii media).

The boundary between the middle and posterior cranial fossae ( fossa cranii posterior) are the upper edges of the pyramids of the temporal bones (margines superiores partis petrosae) and the back of the Turkish saddle of the sphenoid bone.

When examining the internal base of the skull, numerous openings for the passage of arteries, veins, and nerves are visible here.

1. Anterior cranial fossa (fossa cranii anterior) is formed by the orbital parts of the frontal bone ( pars orbitalis ossis frontalis), on which the cerebral eminences and finger-like impressions are well expressed, and the ethmoid plate of the ethmoid bone (lamina cribrosa ossis ethmoidalis), through the openings of which numerous bundles of olfactory nerve fibers pass. In the center of the cribriform plate, a cockscomb (crista galli) rises, in front of which there is a blind hole (Moran's hole, foramen caecum), surrounded by pterygoid processes of the cockscomb of the ethmoid bone and legs of the frontal crest (Morand Sauveur Francois, 1697-1773) - French surgeon and anatomist), and the frontal crest.

Near the cockscomb of the ethmoid bone there is Palfin sinus - a space connecting with the frontal and ethmoid cells (Palfyn Jean (Palfyn Jean, 1650-1730) - French doctor and anatomist).

2. Middle cranial fossa (fossa cranii media) is much deeper than the anterior fossa. The walls of the middle fossa are formed body and greater wings of the sphenoid bone (corpus et alae majores ossis sphenoidalis), the anterior surface of the pyramids and the squamous part of the temporal bones (facies anterior partis petrosae et pars squamosa ossis temporalis). In the middle cranial fossa, the central part and lateral sections can be distinguished. The central part is occupied by the Turkish saddle with its pituitary fossa. At the bottom of the pituitary fossa of the body of the sphenoid bone, there may be a non-permanent formation (found in 0.3% of adults) - the Landucert canal (syn.: craniopharyngeal canal, canalis craniofaryngealis). It penetrates through the body of the sphenoid bone and opens on its lower surface (near the junction of the vomer wings) with a “pharyngeal” opening.

The canal contains a continuation of the hard shell of the brain in the form of a fibrous sleeve containing connective tissue and blood vessels (veins) (Landuzert Fedor Pavlovich (1833-1889) - professor at the St. Petersburg Medical and Surgical Academy).

Anterior to the pituitary fossa, a chiasm furrow is visible ( sulcus hiasmatis) leading to the right and left visual channels (canalis opticus) through which the optic nerves pass. On the lateral surface of the body of the sphenoid bone there is a well-defined carotid groove (sulcus caroticus), and near the top of the pyramid, an irregularly shaped ragged hole (foramen lacerum) is visible. Here, between the small and large wings and the body of the sphenoid bone, there is an upper orbital fissure (fissura orbitalis superior), through which the oculomotor, trochlear and ophthalmic nerves pass into the orbit. Posterior to the superior orbital fissure is a round foramen for the passage of the maxillary nerve, then an oval foramen for the mandibular nerve.

At the posterior edge of the large wing of the sphenoid bone, a spinous foramen is visible through which the middle meningeal artery passes into the skull. On the anterior surface of the pyramid of the temporal bone there is a trigeminal impression (impressio trigemini) - the Meckel fossa (Meckel Johan Friederich (senior), 1724-1774) - a German anatomist), lateral to it is a cleft canal of the large stony nerve ( hiatus canalis nervi petrosi majoris) - Tarenian hole - a hole on the anterior surface of the pyramid of the temporal bone, through which the large stony nerve exits, and the groove of the stony nerve (Tarin Pierre (1725-1761) - French doctor and anatomist). Even more lateral and anteriorly there is a cleft (hole) of the canal of the small stony nerve and a furrow of the small stony nerve.

Lateral and posterior to these formations are visible roof of the tympanic cavity (tegmen tympani) and arcuate eminence (eminentia arcuata). Between the carotid canal and the trigeminal node - the Gasser node (syn. trigeminal ganglion, ganglion trigeminale) on the pyramid of the temporal bone is Gruber's notch (syn.: jugular notch, inciscura jugularis), covered with a thin bone plate (Gasser Johann Laurentius, 1723 -1769) - an Austrian doctor and anatomist; Gruber Ventseslav Leopoldovich (Gruber W.L., 1814-1890) - an Austrian anatomist who worked in Russia). In the pyramid of the temporal bone, under the dura mater of the brain, there is a canal formed by it and the furrow of the inferior petrosal sinus Dorello channel - a channel through which the inferior petrosal sinus, vessels and abducens nerve pass, heading to the cavernous sinus (Dorello Paolo, born in 1872 .) - Italian anatomist). In the area of ​​​​the apex of the pyramid of the temporal bone is the Prenseto tubercle - an elevation to which the superior stony sinus adjoins (Princeteau Laurent (Princeteau Laurent, 1858-1932) - French doctor and anatomist).

The topographic and anatomical landmark for surgical interventions on the labyrinth, less often on the cerebellum, is the Trautmann triangle - an area of ​​\u200b\u200bthe skull, bounded behind by the sigmoid sinus of the dura mater, in front - by the posterior semicircular canal of the inner ear, from above - by the upper edge of the petrous part of the temporal bone (Trautmann Moritz ( Trautmann Moritz F., 1832-1902) - German surgeon).

3. Posterior cranial fossa (fossa cranii posterior) is the deepest. It is formed by the occipital bone, the posterior surface of the pyramids and the inner surface of the mastoid processes of the right and left temporal bones, as well as the posterior part of the body of the sphenoid bone and the posteroinferior angles of the parietal bones. In the center of the fossa there is a large (occipital) opening, in front of it is the Blumenbach slope (syn. slope of the skull, clivus), formed by the bodies of the sphenoid and occipital bones fused in an adult, on which lie the bridge (of the brain) and the medulla oblongata (Blumenbach Johann ( Blumenbach Johann Friedrich, 1752-1840) - German physician and anatomist, zoologist and anthropologist).

An additional bone can be located between the bodies of the occipital and sphenoid bones - Albrecht's bone(Albrecht Karl Martin Paul (1851-1894) - German anatomist). In the posterior edge of the large opening of the occipital bone in the course of development, a Kerkring-ga bone is distinguished - the ossification point of the occipital bone (Kerckring Theodor (Kerckring Theodor, 1640-1693) - a Dutch doctor and anatomist).

Behind the large (occipital) foramen along the midline are located internal occipital crest (crista occipitalis interna) and cruciform elevation (eminentia cruciformis). On the back surface of the pyramid, on each side, one can see the internal auditory opening (porus acusticus in tern us), leading to the internal auditory canal (meatus acusticus internus). In its depth, the facial canal begins, in which the facial nerve passes. The vestibulocochlear nerve emerges from the internal auditory opening. At the bottom of the posterior cranial fossa behind the pyramids is a paired jugular foramen (foramen jugulare), through which the glossopharyngeal, vagus and accessory nerves pass, and medially from it is the hypoglossal canal for the nerve of the same name. Through the jugular foramen, the internal jugular vein also exits the cranial cavity, into which the sigmoid sinus continues, lying in the sulcus of the same name.

On the surface of the cranial vault, 3 cm posteriorly and above the upper edge of the external auditory canal, there is a Keen point, which is a topographic and anatomical landmark when puncturing the lower horn of the lateral ventricle of the brain (Keen William Williams, 1837-1932) - American surgeon).

On the inner base of the skull, in the region of the posterior cranial fossa, there is Mouret's zone - an area of ​​\u200b\u200bthe skull bounded from above by the lower stony sinus of the hard shell of the brain, from behind - by the transverse sinus, in front and from the inside - by the internal auditory canal on the pyramid of the temporal bone; this area is a zone of frequent localization of cerebellar abscesses.

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 (sulcus sinus transversi), passing on each side into the groove of the sigmoid sinus (sulcus sinus sigmoidei).

Educational video of the anatomy of the internal base of the skull (basis cranii interna)

The bones of the skull, connecting with each other, form a large number of cavities, depressions and pits.

On the brain skull, its upper part is distinguished - the roof of the skull and the lower part - the base of the skull.

The roof of the skull is composed of the parietal bones, partly the frontal, occipital and temporal bones. The base of the skull is formed by the orbital parts of the frontal bone, ethmoid, sphenoid, temporal, and occipital bones.

Having separated the roof of the skull, one can study the inner base of the skull, which is divided into three cranial fossae: anterior, middle and posterior. The anterior cranial fossa is formed by the orbital part of the frontal bone, the ethmoid plate of the ethmoid bone, and the lesser wings of the sphenoid bone; the middle cranial fossa is predominantly the cerebral surface of the large wings of the sphenoid bone, the upper surface of its body, as well as the anterior surface of the temporal bone pyramid; the posterior cranial fossa is the occipital bone and the posterior surface of the petrous part of the temporal bone.

In the anterior cranial fossa are the frontal lobes of the cerebral hemispheres, in the middle - the temporal lobes, in the back - the cerebellum, bridge and medulla oblongata. Each hole has a number of holes. The anterior cranial fossa has holes in the cribriform plate that communicate it with the nasal cavity. From the middle cranial fossa, the superior orbital fissure and optic canal lead into the orbital cavity; a round opening leads into the pterygopalatine fossa and through it into the orbit; the oval and spinous foramen communicate the middle cranial fossa with the outer base of the skull. In the posterior cranial fossa there are several openings: a large (occipital), which communicates the cranial cavity with the spinal canal; jugular, leading to the outer surface of the base of the skull, and internal auditory, leading to the inner ear.

Looking at the skull from below, one can see that the base of the skull in its anterior section is covered by the bones of the face, which form the bony palate, consisting of the palatine processes of the upper jaws and the palatine bones. In the middle and posterior sections, the base of the skull is formed by the lower surfaces of the sphenoid, occipital, and temporal bones. They have a large number of foramina, in particular the jugular foramen between the occipital and temporal bones and the lacerated foramen between the petrosal part of the temporal bone and the sphenoid bone.

The largest topographic and anatomical formations of the facial skull are the orbit, nasal and oral cavities.

The eye socket has the shape of a tetrahedral pyramid. Its medial wall is formed by the frontal process of the upper jaw, the lacrimal bone, the orbital plate of the ethmoid bone, and partly by the body of the sphenoid bone; the upper wall is the orbital part of the frontal bone, small wings of the sphenoid bone; lateral wall - large wings of the sphenoid bone and zygomatic bone; the lower wall is the upper surface of the body of the upper jaw. The orbit communicates with the cranial cavity through the superior orbital fissure and the optic canal; with the nasal - through the nasolacrimal canal formed by the lacrimal bone, the frontal process of the upper jaw and the lower nasal concha; with the infratemporal and pterygopalatine fossae - with the help of the lower orbital fissure, which is located between the large wings of the sphenoid bone and the body of the upper jaw.

The nasal cavity has upper, lower and side walls. It is separated by a bony septum located in the median plane. The septum is formed by the perpendicular plate of the ethmoid bone and the vomer. The upper wall of the nasal cavity is formed by the ethmoid plate of the ethmoid bone, as well as the nasal and frontal bones; the lower wall is the palatine process of the upper jaw and the horizontal plate of the palatine bone; lateral walls - the upper jaw, the lacrimal and ethmoid bones, the inferior nasal concha, the perpendicular plate of the palatine bone and the medial surface of the pterygoid process of the sphenoid bone. The anterior opening of the nasal cavity, called the pear-shaped opening, communicates it with the environment; the posterior openings, the choanae, face the outer base of the skull and communicate the nasal cavity with the pharyngeal cavity.

The nasal cavity on the right and left is subdivided by the turbinates located on its lateral wall into three passages: lower, middle and upper. All of them are connected to each other by a common nasal passage located on the sides of the nasal septum. The nasal cavity communicates with the cavity of the skull, orbit, nasal and oral cavities, with the airways. The upper nasal passage communicates with the cranial cavity through the holes of the ethmoid plate of the ethmoid bone, the middle one - with the sinus of the upper jaw, with cells of the ethmoid bone and with the frontal sinus. Behind, at the level of the superior nasal concha, the sinus of the sphenoid bone opens into the nasal cavity. The inferior nasal passage communicates with the orbital cavity through the nasolacrimal canal. The nasal cavity also communicates with the pterygopalatine fossa through the sphenopalatine foramen and with the oral cavity through the incisive foramen.

The oral cavity is limited by bony walls only from above, in front and from the sides. Its upper wall is formed by the bony palate, composed of the palatine processes of the right and left upper jaws and the horizontal plates of the palatine bones; the lateral and anterior walls are formed by the lower jaw and the alveolar processes of the upper jaws. The oral cavity communicates through the incisal opening with the nasal cavity, and through the large palatine canal - with the pterygo-palatine fossa.

On the lateral surface of the skull are the pterygopalatine, infratemporal, and temporal fossae.

The pterygopalatine fossa is located between the bones of the facial and cerebral skulls and is bounded in front by the body of the upper jaw, on the medial side by the palatine bone, behind by the pterygoid process of the sphenoid bone, and from above by the body of this bone. It communicates with the nasal cavity, with the middle cranial fossa, with a ragged foramen, eye socket, and oral cavity. The pterygopalatine fossa does not have a lateral wall and passes outwards into the infratemporal fossa.

The infratemporal fossa is located behind the body of the upper jaw, inward from the zygomatic bone and zygomatic arch, and externally from the pterygoid process of the sphenoid bone. It forms part of the outer base of the brain skull. It is separated from the temporal fossa by the infratemporal crest.

The temporal fossa is a flat depression in which the temporalis muscle lies. The temporal surface of the large wings of the sphenoid bone, the scales of the temporal bone, and partly the parietal and frontal bones participate in the formation of the temporal fossa.

Scull formed by paired and unpaired bones, firmly connected with sutures. It serves as a receptacle and support for vital organs. In the cavities formed by the bones of the skull, the brain is located, as well as the organs of vision, hearing, balance, smell, taste, which are the most important sense organs. Through numerous holes in the bones of the base of the skull, the cranial nerves exit, and the arteries that feed them pass to the brain and other organs. The skull consists of two sections: brain and facial. The area in which the brain is located is called brain skull. The second section, which forms the bone base of the face, the initial parts of the digestive and respiratory systems, is called facial skull.

Rice. The structure of the human skull (side view): 1 - parietal bone, 2 - coronal suture, 3 - frontal bone, 4 - sphenoid bone, 5 - ethmoid bone, 6 - lacrimal bone, 7 - nasal bone, 8 - temporal fossa, 9 - anterior nasal bone, 10 - upper jaw, 11 - lower jaw, 12 - zygomatic bone, 13 - zygomatic arch, 14 - styloid process, 15 - condylar process, 16 - mastoid process, 17 - external auditory canal, 18 - lamdoid suture, 19 - occipital bone, 20 - temporal lines, 21 - temporal bone. The structure of the human skull (front view): 1 - coronal suture, 2 - parietal bone, 3 - orbital part of the frontal bone, 4 - sphenoid bone, 5 - zygomatic bone, 6 - inferior nasal concha, 7 - upper jaw, 8 - chin protrusion of the lower jaw, 9 - nasal cavity, 10 - vomer, 11 - ethmoid bone, 12 - upper jaw, 13 - lower orbital fissure, 14 - lacrimal bone, 15 - ethmoid bone, 16 - superior orbital fissure, 17 - temporal bone, 18 - zygomatic process of the frontal bone, 19 - optic canal, 20 - nasal bone, 21 - scales of the frontal bone.

The cerebral region of the skull of adults is formed by the frontal, sphenoid, occipital, parietal, temporal and ethmoid bones. frontal bone unpaired in adults. It forms the anterior part of the brain skull and the upper wall of the orbits. The following parts are distinguished in it: frontal scales, orbital and nasal parts. In the thickness of the bone there is a frontal sinus that communicates with the nasal cavity. Sphenoid bone located in the center of the base of the skull. It has a complex shape and consists of a body from which three pairs of processes extend: large wings, small wings and pterygoid processes. In the body of the bone there is a sinus (sphenoid), which also communicates with the nasal cavity. Occipital bone forms the posterior-lower part of the brain skull. It distinguishes the main part, lateral masses and occipital scales. All these parts surround a large occipital foramen, through which the brain is connected to the spinal cord. Parietal bone steam room, forms the upper lateral part of the cranial vault. It is a quadrangular plate, convex outward and concave from the inside. Ethmoid bone unpaired, participates in the formation of the walls of the orbits and nasal cavity. The following parts are distinguished in it: a horizontally located lattice plate with numerous small holes; a perpendicular plate involved in the division of the nasal cavity into the right and left halves; ethmoid labyrinths with upper and middle turbinates forming the side walls of the nasal cavity. Temporal bone steam room. It is involved in the formation of a joint with the lower jaw. In the temporal bone, a pyramid, tympanic and squamous parts are distinguished. A sound-perceiving apparatus is placed inside the pyramid, as well as a vestibular apparatus that detects changes in the position of the body in space. In the pyramid of the temporal bone is the cavity of the middle ear - the tympanic cavity with the auditory ossicles located in it and miniature muscles acting on them. On the lateral surface of the temporal bone there is a hole in the external auditory meatus. The temporal bone is pierced by several canals in which nerves and blood vessels pass (carotid canal for the internal carotid artery, canal of the facial nerve, etc.). The facial part of the skull. The bones of the facial part of the skull are located under the brain. A significant part of the facial skull is occupied by the skeleton of the chewing apparatus, represented by the upper and lower jaws. upper jaw - a paired bone involved in the formation of the lower wall of the orbit, the side wall of the nasal cavity, the hard palate, the opening of the nose. In the upper jaw, a body and four processes are distinguished: frontal, zygomatic, palatine and alveolar, bearing alveoli for the upper teeth. Lower jaw - the unpaired bone is the only movable bone of the skull, which, connecting with the temporal bones, forms the temporomandibular joints. At the lower jaw, a curved body with alveoli for the lower teeth, coronoid processes for attaching one of the chewing muscles (temporal) and articular processes are isolated. The rest, the so-called small bones of the face (paired palatine, inferior nasal concha, nasal, lacrimal, zygomatic, and unpaired vomer) are small in size and are part of the walls of the orbits, nasal and oral cavities. The bones of the skull also include an arcuately curved hyoid bone, which has paired processes - the upper and lower horns. Joints of the bones of the skull. All bones of the skull, with the exception of the lower jaw and hyoid bone, are fixedly connected to each other with sutures. For ease of study, the upper part of the brain skull is distinguished - vault, or skull roof, and the lower part base of skull. Skull roof bones connected by continuous fibrous connections - seams, bones of the base of the skull form cartilaginous joints - synchondrosis. The frontal, parietal, and occipital bones form serrated sutures; the bones of the facial skull are connected using flat, harmonious sutures. The temporal bone is connected to the parietal and sphenoid bones with a scaly suture. In adulthood, at the base of the skull, cartilaginous joints are replaced by bone tissue - adjacent bones fuse with each other. The lower jaw forms a pair with the temporal bone temporomandibular joint. The articular process of the lower jaw and the articular surface on the temporal bone participate in the formation of this joint. This joint is ellipsoid in shape, complex in structure, combined in function. Inside the joint there is an intra-articular disc, fused along the periphery with the joint capsule and dividing the articular cavity into two floors: upper and lower. The temporomandibular joint performs the following movements: lowering and raising the lower jaw, moving the jaw to the sides, moving the lower jaw back and forth. The skull has a complex relief of both the outer and inner surfaces, due to the location in its bone cavities of the brain (cranial cavity), organs of vision (eye sockets), smell (nasal cavity), taste (mouth cavity), hearing and balance (tympanic cavity). and labyrinths of the inner ear). In the front of the skull are eye sockets, in the formation of which the upper jaws, frontal, zygomatic, sphenoid and other bones participate. Above the eye sockets is the anterior surface of the frontal bone with superciliary arches. Between the eye sockets is the bony dorsum of the nose, formed by the nasal bones, and below is the anterior opening (aperture) of the nasal cavity. Even lower, arcuate alveolar processes of fused maxillary bones and lower jaw with teeth located in the alveoli are visible. nasal cavity, which is the bone skeleton of the beginning of the respiratory tract, has an inlet (aperture) in front, and two outlets in the back - choanae. The upper wall of the nasal cavity is formed by the nasal bones, the ethmoid plate of the ethmoid bone, the body of the sphenoid bone and the frontal bone. The lower wall is represented by the upper surface of the bony palate. On the side surfaces formed by the maxillary and other bones, three curved plates are visible - the upper, middle and lower nasal conchas. On the lateral surface of the skull is visible zygomatic arch, which connects the zygomatic bone anteriorly to the temporal bone posteriorly and external auditory meatus with the mastoid process located behind it directed downwards. Above the zygomatic arch is a recess - temporal fossa, where the temporal muscle originates, and below the arc - deep infratemporal fossa, as well as processes of the lower jaw. In the back of the skull, the external occipital protrusion protrudes posteriorly. Inferior surface of the skull has a complex terrain. Ahead is solid sky, bounded in front and on the sides by an alveolar arch with upper teeth. Behind and above the hard palate are visible choanae - posterior openings of the nasal cavity, communicating this cavity with the pharynx. On the lower surface of the occipital bone there are two condyles for connection with the I cervical vertebra, and between them - large foramen magnum. On the sides of the occipital bone, a complex relief of the lower surface of the temporal bones is visible with openings for the passage of nerves and blood vessels, the articular fossa and anterior to it a tubercle for articulation with the articular processes of the lower jaw. Inner surface of the base of the skull has a relief corresponding to the lower surface of the brain. Three cranial fossae are visible here - anterior, middle and posterior. In the anterior cranial fossa, formed by the frontal and ethmoid bones, the frontal lobes of the brain are located. The middle cranial fossa is formed by the sphenoid and temporal bones. It contains the temporal lobes of the brain, and in the pituitary fossa - the pituitary gland. In the posterior cranial fossa, bounded by the occipital and temporal bones, are the cerebellum and the occipital lobes of the brain. The inner base of the skull, basis cranii interna, has a concave, uneven surface, reflecting the complex relief of the lower surface of the brain (Fig. 50). It is divided into three cranial fossae: anterior, middle and posterior. The posterior edge of the small wings and the tubercle of the Turkish saddle of the sphenoid bone separate the anterior cranial fossa from the middle one. The border between the middle and posterior cranial fossae runs along the upper edge of the pyramids of the temporal bones and the back of the Turkish saddle of the sphenoid bone. Numerous openings for the passage of arteries, veins, and nerves are visible on the inner base of the skull.
The anterior cranial fossa, fossa cranii anterior, is formed by the orbital parts of the frontal bones, on which the cerebral eminences and finger-like impressions are well expressed. In the center, the fossa is deepened and is made by a cribriform plate of the ethmoid bone, through the holes of which the olfactory nerves (I pair) pass (see Fig. 50). A cockscomb rises in the middle of the lattice plate; in front of it are the blind opening and the frontal crest.
The middle cranial fossa, fossa cranii media, is 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 squamous part of the temporal bones (see Fig. 50). In the middle cranial fossa, the central part and lateral parts can be distinguished. The central part is occupied by the Turkish saddle, in it is the pituitary fossa. Anterior to the latter there is a precross groove, sulcus prehiasmatis, leading to the right and left visual canals, through which the optic nerves (II pair) pass. On the lateral surface of the body of the sphenoid bone there is a well-defined carotid groove, and near the top of the pyramid, an irregularly shaped ragged hole is visible. Here, between the small wing, the large wing and the body of the sphenoid bone, there is the upper orbital fissure, fissiira orbitdlis superior, through which the oculomotor nerve (III pair), trochlear (IV pair), abducent (VI pair) and ophthalmic (first branch V) pass into the orbit. pairs) nerves. Behind the superior orbital fissure is a round opening that serves to pass the maxillary nerve (the second branch of the V pair), then the oval opening for the mandibular nerve (the third branch of the V pair).
At the posterior edge of the large wing lies a spinous opening for passage into the skull of the middle meningeal artery. On the anterior surface of the pyramid of the temporal bone, on a relatively small area, there are a trigeminal depression, a cleft of the canal of the large stony nerve, a furrow of the large stony nerve, a cleft of the canal of the small stony nerve, a furrow of the small stony nerve, a roof of the tympanic cavity and an arcuate elevation.
The posterior cranial fossa, fossa cranii posterior, is 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 supplemented by a small part of the body of the sphenoid bone (in front) and the posterior lower corners of the parietal bones, from the sides (see Fig. 50). In the center of the fossa there is a large occipital foramen, in front of it is a slope, cliuus, formed by the bodies of the sphenoid and occipital bones fused in an adult. Behind the foramen magnum in the midline is the internal occipital crest, reaching a cruciform eminence. The (right and left) internal auditory opening opens into the posterior cranial fossa on each side, leading to the internal auditory meatus, in the depth of which the facial canal for the facial nerve (VII pair) originates. The vestibulocochlear nerve (VIII pair) emerges from the internal auditory opening.
It should be noted two more paired large formations:
the jugular opening 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 exits the cranial cavity through the jugular foramen, into which the sigmoid sinus continues, lying in the sulcus 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 basis cranii interna, has a concave, uneven surface, reflecting the complex relief 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 the cerebral eminences and finger-like impressions are well expressed. In the center, the fossa is deepened and is made by a cribriform plate of the ethmoid bone, through the openings of which the olfactory nerves (I pair) pass.

A cockscomb rises in the middle of the lattice plate; in front of it are the blind opening 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 squamous part of the temporal bones. In the middle cranial fossa, the 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 top of the pyramid, an irregularly shaped ragged hole is visible.

Here, between the lesser wing, the greater wing, and the body of the sphenoid bone, there is the superior orbital fissure, fissura orblalis superior, through which the oculomotor nerve (III pair), trochlear (IV pair), abducens (VI pair) and ophthalmic (first branch V) pass into the orbit. pairs) nerves.

Behind the superior orbital fissure is a round opening that serves to pass the maxillary nerve (the second branch of the V pair), then the oval opening for the mandibular nerve (the third branch of the V pair).

At the posterior edge of the large wing lies a spinous opening for passage into the skull of the middle meningeal artery.

On the anterior surface of the pyramid of the temporal bone, on a relatively small area, there are a trigeminal depression, a cleft of the canal of the large stony nerve, a furrow of the large stony nerve, a cleft of the canal of the small stony nerve, a furrow of the small stony nerve, a roof of the tympanic cavity and an arcuate elevation.

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 supplemented by a small part of the body of the sphenoid bone (in front) and the posterior lower corners of the parietal bones - from the sides. In the center of the fossa there is a large occipital foramen, in front of it is a slope, clivus, formed by the bodies of the sphenoid and occipital bones fused in an adult.

The (right and left) internal auditory opening opens into the posterior cranial fossa on each side, leading to the internal auditory meatus, in the depth of which the facial canal for the facial nerve (VII pair) originates. The vestibulocochlear nerve (VIII pair) emerges from the internal auditory opening.

It is impossible not to note two more paired large formations: the jugular opening 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 exits the cranial cavity through the jugular foramen, into which the sigmoid sinus continues, lying in the sulcus 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.