Skull, lat. cranium is the skeleton of the head. He performs two crucial tasks. It is he who is the receptacle and protector of the brain and such sensory organs as vision, hearing, smell, taste and balance. The initial links of the respiratory and digestive systems are based on it. Typically, anatomy in Latin describes skull bones for proper perception around the world.
Skull structure
The relief of the skull is quite complex. In bone containers, not only the brain is located, but also a number of the main sensory organs, through it through special channels and holes pass the nerves and various vessels. 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, the anatomy takes into account their connections, as they together create a single whole.
The human anatomy of the bones of the skull is divided into two groups: the brain and facial. Each has its own tasks and features. The brain skull (lat.cranium celebrate) is larger and located above the facial (cranium viscerale). Only the lower jaw is mobile throughout the skull.
Consider the bones of the brain skull. Anatomy distinguishes the occipital, frontal, sphenoid, ethmoid, single temporal and parietal paired bones, as well as their joints.
As part of the facial skull, there are:
- bones of the chewing apparatus - the lower and upper jaw, and the upper one refers to paired bones;
- bones that make up the nasal and oral cavity and orbits, namely the single opener and hyoid and paired palatine, nasal, lacrimal, zygomatic bones and lower nasal concha.
Bone joint
It is necessary to consider the bones of the skull and their joints. Human anatomy studies them both individually and in combination. Most 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 bones of the cranial vault are mostly dentate, scaly, and flat. At the base of the skull, the joints are often temporary or permanent cartilage, the so-called synchondrosis. Sutures have names formed from the bones that they connect (stony-occipital, sphenoid-frontal) or from the location and shape (lambdoid, sagittal).
Brain skull
Let us consider in more detail the bones of the brain skull: the skeleton and bone joints. This part can be divided into two more important parts: the base (lat. Basis) and the arch (lat. Calvaria), which is sometimes called the roof of the skull.
A feature of the arch is that in its bones it is possible to distinguish between the inner and outer plates with a spongy substance diploe between them. Diploea contains many diploic channels with diploic veins. The smooth outer plate has a periosteum. The inner plate is thinner and more fragile, and the hard shell of the brain plays the role of the periosteum for it. It is worth noting that with injuries, a fracture of the inner plate can occur without damage to the outer one.
The periosteum only in the area of sutures has the most dense connection with the bones, and in other places the connection is more loose, therefore, within the bone there is a subperiosteal space. In these places, sometimes hematomas or even ulcers occur.
In addition, the anatomy divides the bones of the skull into airy and non-airy. In the medulla, the frontal, sphenoid, ethmoid, and temporal are referred to the airways. They were called so for the presence of cavities filled with air and lined with mucous membranes.
There are holes in the skull designed for the passage of emissary veins. They connect the external veins with the diploic and venous sinuses passing in the hard shell of the brain. 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 with protrusions, processes, tubercles, notches, holes, grooves, sinuses and more. Most fully represents all the bones of the head anatomical atlas.
Arch bones
The frontal bone (lat. Os frontale) in its structure consists of the nasal and orbital parts and frontal scales. It is unpaired. It forms the front 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 posterior lower part of the skull. It is divided into the basilar part, the occipital scale and two lateral parts. These components cover a large opening, called the occipital (lat. Foramen magnum).
The parietal paired bone (lat.os parientale) forms in the cranial vault the upper lateral sections. Behind these paired bones along the sagittal edge are connected to each other. The remaining edges are called frontal, scaly and occipital.
Base bones
The temporal paired bone (lat. Os temporale) is located on the side wall of the base of the skull. The occipital bone is located behind it, and the sphenoid in front. This bone is divided into a pyramid (stony), scaly and drum 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 strum, mastoid, muscular-tubal, internal auditory meatus, cochlear tubule, and vestibule.
The sphenoid bone (lat. Os sphenoidale) is located in the center of the base of the skull, it is necessary for the formation of its lateral departments, and also forms a series of pits and cavities. It 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 trellised and perpendicular plate and trellised labyrinths. The olfactory nerve fibers go through the ethmoid plate. In the trellis labyrinth there are trellis cells filled with air, nasal passages pass there and exits to the sinuses are located.
Facial bones in general
There are more bones in the facial skull than in the brain. There are 15. There are unpaired hyoid bones, a vomer, a lower jaw. 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 having a cavity with a mucous membrane and air.
These bones generally make up the facial part. Considers the anatomy of the skull structure, functions not just individual bones, but their combination. In the facial skull, eye sockets, mouth and nose can be distinguished, where important organs, jaws are located. The walls of the cavities have openings and slots for the passage of nerves and blood vessels, and with their help, the cavities communicate with each other.
Facial skull: critical 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, the upper and lower orbital fissures, the anterior and posterior ethmoid, zygomatic and infraorbital foramen.
In the nasal cavity, a pear-shaped aperture, choanas, nasolacrimal and incisal canal, wedge-palatine and nasal openings and openings of the trellis are secreted. In the oral cavity there is a large palatine and incisal canal, a large and small palatine opening.
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 (lat. Maxilla) refers to the paired bones. It consists of the body and the zygomatic, frontal, palatine and alveolar processes.
The palatine bone (lat. Os palatinum), being a paired one, is involved in the formation of the pterygo-palatine fossa, the hard palate and the orbit. It is divided into horizontal and vertical plates and three processes: sphenoid, orbital and pyramidal.
The lower nasal concha (lat. Concha nasalis inferior), in fact, is a thin plate, in a special way curved. It is equipped with three processes along the upper edge: lacrimal, ethmoid, and maxillary. This is a pair of bones.
The vomer (Latin vomer) is a bone plate necessary for the formation of a bone 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 its help the temporal, frontal and maxillary bones are connected. She's a steam room. It is divided into lateral, orbital and temporal surfaces.
The lacrimal bone (Latin os lacrimale) for the medial wall of the orbit is the anterior part. This is a pair of bones. It has a posterior lacrimal crest and lacrimal groove.
Special facial bones
Next, we 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 the one side of it is the lower jaw, and on the other - the larynx. It is divided into a body curved by an arc 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.
Skull developmental stages
Even if skull anatomy tests are considered from an adult perspective, knowledge of skull formation is necessary. Before taking on its final appearance, the skull goes through two more time stages. At first it is membranous, then cartilaginous, and only then does the bone stage begin. In this case, the stages gradually flow into one another. All three stages go through the bones of the base of the skull and part of the facial, the rest of the membranes immediately become bone. At the same time, not the whole bone can have a cartilaginous model, but only a part of it, and the rest is formed immediately from the connective tissue without cartilage.
The beginning of the membranous stage is considered the end of 2 weeks of embryonic development, and cartilage begins already from 2 months. The ossification of each department occurs at different times. First, the center of ossification appears, then from this point the process spreads in depth and on the surface. For example, on the 39th day of intrauterine development, a center appears in the lower jaw, ossification of the occipital bone in its basilar part begins on the 65th day.
Final formation
In this case, the centers of ossification 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: temporal - up to a year, occipital and lower jaw - from one to four. Some bones, for example the cheekbones, 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 such elements merge into one final bone.
Some cartilaginous formations remain so forever. These include cartilage of the septum and wings of the nose and small cartilage located at the base of the skull.