The human skull is the bony base of the head, consisting of twenty-three bones, in addition to which there are three paired bones that are located in the middle ear cavity. The base of the skull consists of the part below the face that extends anteriorly on the border of the infraorbital margin, 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 gorge, as well as the outer protrusion of the nape. The outer and inner base of the skull is distinguished . Today we look at the inner foundation. But before starting to study this issue, we will consider what structure and functions the skull has, as well as its shape.
Shapes and functions of the skull
The human skull performs several functions:
- protective, which is characterized by the ability to protect the human brain and sense organs from various injuries;
- supporting, consisting in the ability to accommodate the brain and the initial parts of the respiratory and digestive systems;
- motor, characterized by articulation with the spinal column.
A human skull can be represented in one of the forms: standard (cranial index), acrocephaly (tower shape) and craniosynostosis (fusion of sutures of the cranial vault).
In order to better navigate in the anatomy of the skull, let us consider in more detail the internal and external base of the skull .
The outer base of the skull
It is customary to call it that which is facing down and is closed in front by the bones of the face, and behind the outer base is formed by the bone sky, processes in the form of wings, medial plates, which limit the choanas separated by the opener. Behind the pterygoid processes, the base is formed by a wedge-shaped bone, the lower part of the pyramid, the tympanic section, and also the front part of the back of the head. The outer base of the skull, the anatomical atlas will tell its location, has three parts: front, middle and back. We consider each of them in more detail.
The back of the base of the outer
In the posterior section is the nasopharyngeal arch, which is limited to the pharynx. A fascia is attached to the base of the skull, with a direction from the pharyngeal tuber 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 vein of the vertebral and subclavian arteries.
Front section of the base of the outdoor
There are gaps here, nerves and blood vessels pass through them. The largest holes, the role of which is very important, are located along the border that connects the awl-mastoid fissure and the incisal opening. The base department, which is located in front, includes a bone sky with incisor and large palatine canals. Joans go back from the nasal cavity.
The middle section of the outer base
This area includes a ragged gap that 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.
The inner surface of the base of the skull
The base of the skull on the inside contains three pits: the front, middle and back. In its location, the anterior fossa is above the middle. And this, in turn, fit above the back. The large brain is located in the first two fossae, the cerebellum is located in the posterior fossa. The distinctions between the fossae are presented in the form of the edges of the sphenoid bone that are located behind, as well as the upper level of the pyramids of the bones of the temple. In the inner 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. Consider its structure in more detail.
Anterior fossa of the skull
The anterior cranial fossa is the deepest. It is formed by the faces of the wings of the bone in the form of a wedge and a protrusion that is between the visual mouths. Frontal sinuses adjoin this fossa in front, and below are the recesses of the ethmoid bone, nasal cavity and sinus. In front of the cockscomb, there is a blind mouth, through which a small vein follows, which combines the superior sagittal sinus with nasal veins. On both edges of the ethmoid bone there are olfactory bulbs, where the olfactory nerves fit 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. The inner 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 pit with the help of the Turkish saddle and the tops of the pyramids of the bones of the temple is separated from the back. In the middle of the fossa is the Turkish saddle, which is covered by a diaphragm having a slit through which a recess appears, which has an ending in the form of a brain appendage. On the diaphragm in front of the funnel there is a intersection of the optic nerves, on the sides of which there are so-called siphons of the carotid arteries. From them, in turn, the orbital arteries move away, they, together with the optic nerves, pass into the visual gorges. So, the inner surface of the base of the skull suggests placement in the middle fossa of the cavernous sinus, which is located away from the Turkish saddle. At this point, the carotid internal artery and the abducting nerve pass . Above the carotid artery, nerves are located in the walls of the sinuses: trigeminal, cranial and oculomotor. They pass through the upper mouth into the orbit. To the side of these nerves there are veins of the orbits and the eyeball, which then enter 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. There is a spinous fissure behind the oval- shaped opening ; through it, the anterior artery of the dura mater passes through the cranial cavity. The inner base of the skull suggests the presence on both sides of the Turkish saddle in the fossa, which is located in the middle, of the temporal lobes of the brain . In front of the inner part of the bone of the temple, which has the shape of a pyramid, a cavity of the middle ear, an aural cavity and a cavity in the mastoid process of the temporal bone are placed.
Fossa posterior cranial
The posterior cranial fossa houses the cerebellum, medulla oblongata, and the bridge. In front of the fossa on an inclined surface there is a bridge, the main artery with all branches. The plexus of veins and stony sinuses are located in the hard shell of the brain . All cranial fossae of the inner base of the skull are interconnected. The posterior fossa is almost entirely occupied by the cerebellum; on the top and sides of it there are sinuses: sigmoid and transverse. The cerebellar cavity and the posterior fossa are separated by a cerebellar tent through which the brain stem passes. Consider what the internal base of the skull has holes and their purpose and role.
Behind the pyramid of the bone of the temple is the auditory mouth, through which the facial, auditory nerves and the membranous labyrinth pass. Below the auditory gorge, the glossopharyngeal, accessory nerves, vagus, as well as the sinuses of the dura mater and jugular vein pass through the ragged gap. If you look below in the atlas, you can see that the hyoid nerve and its channel, as well as the plexus of veins, pass through the mouth of the hyoid nerve. In the middle of the posterior fossa there is a large occipital fissure, through which the medulla oblongata and its membranes, spinal arteries, and the spine root are laid. Along the edge of the sigmoid sinus groove into the fossa, which is located behind, several estuaries open that pass the emissary veins and the meningeal branch of the occipital artery. The mouths and crevices that connect the posterior fossa to other sites are located in its front parts. Thus, the cranial fossa of the inner base of the skull is presented in three forms: 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; in the same way, one cannot imagine the functions of any organ without comprehending its structure. The knowledge of skull anatomy in medicine is undeniable. This science uses modern diagnostic methods. The structure of the skull was known through examination, autopsy, examination and other things. Today we have the opportunity to study the outer and inner base of the skull thanks to medical atlases that were created many years ago. This knowledge is of particular importance in the medical sciences, since it makes it possible to study anomalies in the development of the skull, the structure of veins and blood vessels of the brain. Especially important is the study of skull anatomy 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.
Now we know what a human skull is. Anatomy of the inner base of the skull is 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 the bridge. There are also arteries, vessels, nerves. All of them play a huge role in the normal functioning of the human body.