Skull as a whole

The skull has a complex relief on both the inner and outer surfaces, which is due to the location of the brain, sensory organs, the presence of numerous openings and channels for the passage of blood vessels and nerves in its bone receptacles.

All bones of the skull, except the lower jaw and the hyoid bone, are immovably and firmly connected to each other by means of dentate, flat, scaly joints in the region of the cranial and facial arch, as well as permanent and temporary cartilaginous joints (synchondrosis) at the base of the skull. The names of the joints and synchondrosis come from the names of the connecting bones (for example, the wedge-frontal suture, the stony-occipital suture). Some stitches are called by their location, shape or direction (sagittal suture, lambdoid suture).

When examining the skull from above (norma verticalis), a vault or roof, skull, bottom (norma basilaris) is visible - the base of the skull, in the front (norma facialis) - the facial skull, behind (norma occipitalis) - the occipital part, from the sides (norma lateralis) a series of depressions (pits), bounded by various bones.

The brain of the skull

The upper part of the cerebral skull in connection with its shape is called the vault, or roof, of the skull. The lower part of the skull serves as the base. The boundary between the arch and the base on the outer surface of the skull is a conditional line that passes through the outer occipital protrusion, then along the upper ear line to the base of the mastoid process, over the external auditory opening, at the base of the malar bone of the temporal bone and along the trailing crest of the large wing of the sphenoid bone. This line rises up to the zygomatic process of the frontal bone and along the supraorbital margin reaches the nasophilic suture. The boundary between the vault and the base on the inner surface of the skull is not determined. Only in the posterior part of this boundary can be drawn along the sulcus of the transverse sinus, corresponding to the upper nasal line on the external side of the occipital bone.

The cranial vault (calvaria) is formed by the scales of the frontal bone, the parietal bones, the scales of the occipital and temporal bones, the lateral sections of the large wings of the sphenoid bone. The sagittal suture (sutura sagittalis) is formed on the outer surface of the cranial vault along the median line , formed by the union of the sagittal margins of the parietal bones. Perpendicular to it on the border of the frontal scales with parietal bones in the frontal plane is the coronal suture (sutura coronalis). Between the parietal bones and the occipital scales is a lambdoid suture (sutura lambdoidea), similar in shape to the Greek letter "lambda". On the lateral surface of the cranial vault on each side between the scales of the temporal and parietal bones there is a scaly suture (sutura squamosa), as well as serrated suturae (suturae serratae) between other adjacent bones.

In the anterior parts of the cranial vault there is a convex part - the forehead (frons), formed by the scales of the frontal bone. On the sides are visible frontal tubercles, above the eye sockets are the superciliary arches, and in the middle - a small area - glabella. On the upper side of the cranial vault are parietal knolls. Below each hillock there is an arcuate upper temporal line (linea temporalis superior), the place of attachment of the temporal fascia. Below this line is a more pronounced lower temporal line (linea temporalis inferior) - the place of the beginning of the temporal muscle. On the anterolateral side of the skull are two pits - temporal and transverse.

The temporal fossa (fossa temporalis) is bounded at the top by the lower temporal line, at the bottom - by the platemoral crest of the large wing of the sphenoid bone. From the lateral side, the temporal fossa is limited by the zygomatic arch (arcus zygomaticus), in front - the temporal surface of the malar bone. The hip comb separates the temporal fovea from the temporal fossa.

The subordinate fossa (fossa infratemporalis) is clearly visible when viewed from the side of the skull. The upper wall of the inframammary fossa is the lower surface of the large wing of the sphenoid bone. The medial wall is formed by the lateral plate of the pterygoid process of this bone. The anterior wall is limited by the tubercle of the upper jaw and partly by the malar bone. There is no lateral and lower walls in the pedicle fossa. From the front this fovea communicates with the orbit via the inferior orbital fissure (fissura orbitalis inferior), medially through the pterygo-mandibular fissure with the pterygopalatine fossa. The entrance to the pterygoid palatine is located in the anterior regions of the inframammary fossa.

The pterygo-palatine fossa (fossa pterygopalatina) is confined in the front by a tubercle of the maxilla, posteriorly by the base of the pterygoid process of the sphenoid bone, medial perpendicular plate of the palatine bone. The lateral wall of the pterygo-palatine fossa has no, on this side it communicates with the pteryphalic fossa. In the pterygoid palatine, 5 holes are opened. This fossa is medially mediated with the nasal cavity through the wedge-palatine foramen (foramen sphenopalatinum), with the middle cranial fovea at the top and back - by means of a round hole. Behind the pterygopalatine fossa has a communication with the region of the torn aperture of the skull with the help of a pterygoid canal. With the eye socket, the fossa is communicating through the lower orbital fissure, and with the oral cavity through the large palatal canal. Through these and other openings pass blood vessels, cranial nerves and their branches.

Seams (sagittal, coronal, lambdoid, scaly) are visible on the inner (cerebral) surface of the cranial vault, finger-like impressions are impressions of the brains of the large brain, and narrow arterial and venous furrows (sulci arteriosi and venosi) are the places of adherence of the arteries and veins.

Near the sagittal suture are the dimples of granulations (foveolae granulares), formed by protrusion of the arachnoid membrane of the brain.

The base of the skull can also be viewed from two positions: from the outside (from below) - the outer base of the skull and from the inside (after the horizontal cutting is made at the level of the border with the arch) - the inner base.

The external base of the skull (basis cranu externa) in the anterior part is covered with facial bones. The posterior part of the base of the skull is formed by the outer surfaces of the occipital, temporal and wedge-shaped bones. Numerous holes are visible here, through which the arteries, veins, nerves pass through the living person. Almost in the center of the posterior section there is a large (occipital) opening , and on the sides it is the occipital condyles. Behind each condyle is a condylar fossa with an irregular hole - condylar canal. Through the base of each condyle passes the sublingual canal. The posterior part of the base of the skull is confined to the front by the outer occipital protrusion with the upper, outward line leaving it to the right and to the left. Ahead of the large (occipital) opening is the basilar part of the occipital bone with a pharyngeal tubercle, it passes into the body of the sphenoid bone. On each side of the occipital bone, the lower surface of the pyramid of the temporal bone is visible, on which the external opening of the canal channel is located, the musculoskeletal channel, the jugular fossa and the jugular notch. The latter, together with the jugular cutting of the occipital bone, forms a jugular opening, a styloid process, a mastoid process, and a stylo- sacroid opening between them. To the pyramid of the temporal bone from the lateral side adjoins the drum part of the temporal bone surrounding the external auditory aperture. Behind the drum part is separated from the mastoid process by means of a tympanic-mastoid fissure. On the posterior medial side of the mastoid process are mastoid fillet and a furrow of the occipital artery.

In the lower part of the scaly part of the temporal bone, the mandibular fossa is visible, forming the temporomandibular joint with the condylar process of the lower jaw. Ahead of this fossa is an articular tubercle. Between the stony and scaly parts of the temporal bone is the posterior part of the large wing of the sphenoid bone. A clear and oval hole is clearly seen here. The pyramid of the temporal bone is separated from the occipital bone by the stony-occipital slit (fissura petrooccipitalis), and from the large wing of the sphenoid bone is the wedge-stony fissure (fissura sphenopetrosa). On the lower surface of the outer base of the skull you can see a hole with uneven edges - a lacerated hole (foramen lacerum), which is located between the tip of the pyramid, the occipital body and the large wing of the sphenoid bones.

The inner base of the skull (the base cranii interna) has a concave uneven surface reflecting the complex relief of the lower surface of the brain. Three cranial fossae are distinguished at the inner base of the skull: anterior, middle and posterior. Anterior cranial fossa from the middle separates the posterior edge of small wings and the tubercle of the Turkish saddle of the sphenoid bone. Borders between the middle and posterior fossae are the upper edge of the pyramids of the temporal bones and the back of the Turkish saddle of the sphenoid bone. When examining the inner base of the skull, numerous openings are visible for the passage of arteries, veins, nerves.

The anterior cranial fossa (fossa cranii anterior) is formed by the orbital parts of the frontal bones, as well as the latticed plate of the latticed bone, through the holes of which the fibers of the olfactory nerves pass (I pair). In the middle of the trellis plate a cock's crest rises, in front of which there is a blind hole.

The middle cranial fossa (fossa cranii media) is much deeper than the anterior. It is formed by the body and large wings of the sphenoid bone, the anterior surface of the pyramids and the scaly parts of the temporal bones. The central part of the pit is occupied by a Turkish saddle. In it, the pituitary fossa is distinguished, anterior to which is the pre-cross groove (sulcus prehiasmatis) leading to the right and left visual channels through which the optic nerves pass (II pair). On the lateral surface of the body of the sphenoid bone, the carotid furrow is visible, and near the apex of the pyramid there is an irregularly torn opening. Between the small wing, the large wing and the body of the sphenoid bone, there is the upper orbital fissure (fissura orbitalis superior), through which the oculomotor (III pair) passes into the orbit, the block (IV pair), the verve (VI pair) and the optic nerve (the first branch V pair). Behind the upper glenoid aperture there is a circular opening serving for the passage of the maxillary nerve (the second branch of the V pair), then an oval for the mandibular nerve (the third branch of the V pair). At the rear edge of the large wing there is a spinous hole for passage into the skull of the middle meningeal artery. On the anterior surface of the pyramid of the temporal bone there are the trigeminal depression, the cleft of the canal of the large stony nerve, the groove of the large stony nerve, the cleft of the small stony nerve channel, the roof of the tympanic cavity, and the arcuate elevation.

The posterior cranial fossa (fossa cranii posterior) is the deepest. It is formed by the occipital bone, the posterior surfaces of the pyramids and the inner surface of the mastoid processes of the right and left temporal bones. The body of the sphenoid bone (in front) and the posterior corners of the parietal bones (from the sides) supplement the fossa. In the center of the fovea there is a large (occipital) hole, in front of it there is a clavus formed by the joints of the wedge-shaped and occipital bones in the adult person, on which the bridge (brain) and oblong brain lie. Behind the large (occipital) opening on the median line is the inner occipital crest. In the posterior cranial fossa on either side, an inner auditory opening opens (right and left) leading into the internal auditory meatus. In the depth of this opening, the facial channel for the passage of the facial nerve (VII pair) begins. From the inner auditory aperture comes the pre-cochlear nerve (VIII pair).

In the depth of the posterior cranial fossa, two large pairs of large formations are visible: the jugular hole through which the lingual-pharyngeal (IX pair), the wandering (X) and additional (XI pair) nerves, and the sublingual canal for the eponymous nerve (XII pair).

Through the jugular opening, the inner jugular vein emerges from the cavity of the skull, into which passes the sigmoid sinus, which lies in the furrow of the same name.

[1], [2], [3], [4], [5], [6]