Skull, lat. cranium is the skeleton of the head. It performs two essential tasks. It is he who is the receptacle and protector of the brain and such sense organs as sight, hearing, smell, taste and balance. The initial links of the respiratory and digestive systems rely on it. As a rule, the bones of the skull anatomy in Latin describes for correct perception around the world.
The structure of the skull
The relief of the skull is quite complex. Bone receptacles contain not only the brain, but also a number of basic sense organs; nerves and various vessels pass through it through special channels and openings. It consists of 23 bones, while 8 of them are paired, and 7 are unpaired. Among them there are flat, spongy and mixed bones of the skull, anatomy also takes into account their connections, since together they create a single whole.
The human anatomy of the bones of the skull is divided into two groups: the brain and the facial section. Each has its own tasks and features. The brain skull (lat. Cranium celebrate) is larger and is located above the facial (cranium viscerale). Mobile throughout the skull is only the lower jaw.
Let's considerbrain bones. Anatomy highlights the occipital, frontal, sphenoid, ethmoid, single temporal and parietal paired bones, as well as their connections.
The composition of the facial skull is distinguished:
- bones of the masticatory apparatus - the lower and upper jaws, with the upper one referring to paired bones;
- the bones that make up the nasal and oral cavities and orbits, namely the single vomer and the hyoid and paired palatine, nasal, lacrimal, zygomatic bones and the inferior nasal concha.
Connection of bones
It is necessary to consider the bones of the skull and their connections. Human anatomy studies them both individually and in combination. Most of the bones of the skull are connected motionless. The only exception is the movable lower jaw and the hyoid bone attached to the muscles and ligaments.
The seams connecting all the components together are very diverse. The facial and cranial bones are characterized mainly by serrated, scaly and flat sutures. At the base of the skull, the joints are often temporary or permanent cartilage, the so-called synchondrosis. The sutures are named after the bones they connect (stony-occipital, sphenoid-frontal) or from the location and shape (lambdoid, sagittal).
Cerebral skull
Let's take a closer look at the bones of the cerebral skull: the skeleton and bone joints. This part can be divided into two more important parts: the base (Latin basis) and the vault (Latin calvaria), which is sometimes called the roof of the skull.
The feature of the vault isthe fact that in its bones one can distinguish between the inner and outer plates with the spongy substance of the diploe between them. The diploe contains many diploic canals with diploic veins. The smooth outer plate has a periosteum. The inner plate is thinner and more fragile, and the role of the periosteum for it is performed by the hard shell of the brain. It is worth noting that in case of injuries, a fracture of the inner plate can occur without damaging the outer one.
The periosteum only in the area of the sutures has the most dense connection with the bones, and in other places the connection is looser, so there is a subperiosteal space within the bone. In these places, sometimes hematomas or even abscesses occur.
In addition, the anatomy divides the bones of the skull into air-bearing and non-air-bearing. In the medulla, the air bones include the frontal, sphenoid, ethmoid, and temporal bones. They were named so for the presence of cavities filled with air and lined with a mucous membrane.
There are also holes in the skull intended for the passage of emissary veins. They connect the external veins with the diploic and venous sinuses that run in the dura mater. The largest in the brain skull are the mastoid and parietal foramen.
Description of the structure of the main bones of the brain skull
Each bone of the skull consists of several parts that have their own characteristics and shape, can be supplemented by protrusions, processes, tubercles, notches, holes, grooves, sinuses and more. The anatomical atlas most fully represents all the bones of the head.
The bones of the vault
frontal bone(lat. os frontale) in its structure consists of the nasal and orbital parts and the frontal scales. Is unpaired. It makes up the anterior part of the arch and is involved in the formation of the anterior cranial fossa and orbits.
The occipital bone (lat. os occipitale) is unpaired, located in the back of the skull. It is divided into the basilar part, the occipital scales and two lateral parts. These components cover a large opening called the occipital (Latin foramen magnum).
The parietal paired bone (lat. os parientale) forms the upper lateral sections in the cranial vault. Behind, these paired bones are connected to each other along the sagittal edge. The remaining edges are called frontal, scaly and occipital.
Foundation bones
Temporal paired bone (lat. os temporale) is placed on the side wall of the base of the skull. Behind it is the occipital bone, and in front - the sphenoid. This bone is divided into a pyramid (stony), scaly and tympanic parts. It is here that the organs of balance and hearing are located.
Several vessels and cranial nerves pass through the temporal bone. A number of channels are provided for them: carotid, facial, tympanic, carotid-tympanic, tympanic strings, mastoid, musculo-tubal, internal auditory canal, cochlear tubule and vestibule water supply.
The sphenoid bone (lat. os sphenoidale) is located in the center of the base of the skull, is necessary for the formation of its lateral sections, and also forms a rowpits and cavities. Is unpaired. It consists of large and small wings, body and pterygoid processes.
The ethmoid bone (lat. os ethmoidale) is involved in the formation of the orbit and nasal cavity. It is divided into a lattice and perpendicular plate and lattice labyrinths. Olfactory nerve fibers pass through the lamina cribrosa. In the lattice labyrinth there are lattice cells filled with air, there are also nasal passages and exits to the sinuses.
Facial bones in general
There are more bones in the facial skull than in the brain. There are 15 of them here. The hyoid bone, vomer, and lower jaw are unpaired. The remaining bones are paired: the lower nasal concha, nasal, zygomatic, lacrimal, palatine and upper jaw. Of these, only the upper jaw belongs to the air bones, which have a cavity with a mucous membrane and air.
These bones generally make up the front part. The anatomy of the skull considers the structure, functions of not just individual bones, but their combination. In the facial skull, eye sockets, oral and nasal cavities can be distinguished, where important organs, jaws are located. The walls of the cavities have holes and crevices for the passage of nerves and blood vessels, and also with their help the cavities communicate with each other.
Facial skull: important openings
Paired eye sockets are designed to be located in their cavities of the eyeballs with muscles, lacrimal glands and other formations. Important are the visual, nasolacrimal, alveolar and infraorbital canals, superior and inferior orbitalfissures, anterior and posterior ethmoid, zygomatic-orbital and supraorbital foramen.
In the nasal cavity, a pear-shaped aperture, choanae, nasolacrimal and incisive canals, sphenopalatine and nasal openings and openings of the cribriform plate are distinguished. The large palatine and incisive canals, the large and small palatine openings are located in the oral cavity.
Also in the structure of the facial skull, it is necessary to note the presence of nasal passages (lower, middle and upper), as well as the sphenoid and frontal sinuses.
Description of the structure of the main facial bones
The upper jaw (Latin maxilla) refers to paired bones. Consists of the body and the zygomatic, frontal, palatine and alveolar processes.
The palatine bone (lat. os palatinum), being a steam room, is involved in the formation of the pterygopalatine fossa, hard palate and orbit. It is divided into horizontal and vertical plates and three processes: sphenoid, orbital and pyramidal.
The inferior nasal concha (lat. concha nasalis inferior), in fact, is a thin plate, curved in a special way. It is equipped with three processes along the upper edge: lacrimal, ethmoid and maxillary. This is a paired bone.
Vomer (lat. vomer) is a bone plate necessary for the formation of a bony nasal septum. The bone is unpaired.
The nasal bone (lat. os nasale) is necessary for the formation of the bony back of the nose and the formation of a pear-shaped aperture. This bone is paired.
The zygomatic bone (lat. os zygomaticum) is important for strengthening the facial skull, with itshelp connect the temporal, frontal and maxillary bones. She is a couple. Divided into lateral, orbital and temporal surfaces.
The lacrimal bone (lat. os lacrimale) for the medial wall of the orbit is the anterior part. This is a twin bone. It has a posterior lacrimal crest and lacrimal trough.
Special facial bones
Next, consider the bones of the skull, the anatomy of which is somewhat different from all the others.
The lower jaw (Latin mandibula) is an unpaired bone. It is she who is the only bone of the skull that is mobile. It consists of three parts: the body and 2 branches.
The hyoid bone (lat. os hyoideum) is unpaired, located in the front of the neck, on one side of it is the lower jaw, and on the other - the larynx. It is divided into a curved body and paired processes - large and small horns. This bone is attached to the skull by muscles and ligaments, and it also connects to the larynx.
Stages of skull development
Even if the tests on the anatomy of the skull bones are considered from the point of view of an adult, it is necessary to know about the formation of the skull. Before taking on its final form, the skull goes through two more temporary stages. At first it is membranous, then cartilaginous, and only then comes the bone stage. In this case, the stages gradually flow into one another. All three stages pass through the bones of the base of the skull and part of the facial bones, the rest of the membranous immediately become bone. At the same time, not all bone, but only part of it, can have a cartilaginous model, and the rest is formeddirectly from connective tissue without cartilage.
The beginning of the membranous stage is considered the end of the 2nd week of embryonic development, and from the 2nd month the cartilage begins. Ossification of each department occurs at different times. First, the center of ossification appears, then from this point the process spreads in depth and over the surface. For example, on day 39 of intrauterine development, a center appears in the lower jaw, ossification of the occipital bone in its basilar part begins on day 65.
Final formation
In this case, the ossification centers merge after birth, and here the anatomy describes the bones of the skull with less accuracy, since this can be purely individual. For some areas, this occurs in early childhood: the temporal - up to a year, the occipital and lower jaw - from a year to four. Some bones, such as the zygomatic, complete the process from 6 to 16 years, and the hyoid from 25 to 30 years. In connection with this development of the skull, it can be said that the number of skull bones in a newborn is greater, since over time several of these elements merge into one final bone.
Some cartilage formations stay like this forever. These include the cartilages of the septum and wings of the nose and small cartilages located at the base of the skull.
