The shape of the human skull in ogtogenesis undergoes significant changes. During prenatal development and in newly born children, the skull is more rounded, due to the fact that the brain in it is more developed and its placement requires a larger volume of the cranium. The shape of the skull changes as the teeth grow and the chewing muscles become fixed .
Species of facial bones
The skull has facial and cerebral regions. The border lies between the posterior and orbital margin. The bones of the skull are flat. They are connected by sutures, which enable the growth of all cranial bones. After their ossification, growth stops.
The facial section of the skull consists of the nasal and oral cavities. Unpaired include:
- ethmoid bone;
- opener
- hyoid bone.
From the pair stand out:
- upper jaw;
- nasal bone;
- incisor;
- tearful;
- zygomatic;
- pterygoid;
- palatine bone;
- lower jaw;
- nasal concha.
Let us consider in more detail all the bones of the facial skull.
Upper jaw
This bone is paired. It consists of a body and four processes. The maxillary sinus enters the body, which communicates with a wide cleft and nasal cavity. The body consists of the anterior, infratemporal, orbital and nasal surfaces.
Ahead, the surface has a concave shape. At its border is the infraorbital region, below which lies the infraorbital foramen with nerves and blood vessels. Under it is a depression in the form of a canine fossa. On the medial edge, the nasal notch is well defined, in which the anterior opening of the nasal cavity is noticeable. The lower edge protrudes and creates a nasal spine.
From the orbital surface, the lower orbital wall is created, having a triangular smooth concave shape. In the area of the medial edge, it borders on the lacrimal bone, the orbital plate and the process. In the posterior part, the border runs along the lower orbital fissure, from where the infraorbital groove begins. In front, it transforms into the infraorbital canal.
The temporal surface is created from the pterygo-palatine and temporal fossae. In front, it is delimited by the zygomatic process. A jugular tubercle is clearly distinguished on it, from where the alveolar holes originating pass into the corresponding channels. Through these channels, blood vessels and nerves directed towards molars function.
The surface of the nose is formed by a complex relief. It combines with the bone of the sky and the lower concha, passing into the upper part of the palatine process. On the surface, the maxillary cleft in the shape of a triangle is clearly visible. Ahead, a vertical groove is clearly pronounced, which is connected to the lower concha and the lacrimal bone.
Further, the bones of the facial skull continue with the frontal process, extending from the body of the upper jaw at the convergence of the nasal, anterior and orbital surfaces. At one end, the process reaches the nasal part of the frontal bone. On the lateral surface lies the lacrimal crest, passing into the infraorbital region, delimiting the lacrimal groove. On the medial surface of the appendix there is a trellised ridge connecting to the zygomatic bone.
The zygomatic process, leaving the jaw, also converges with the zygomatic bone.
The alveolar bone is a thick plate, concave on one side and convex on the other, extending from the jaw. Its lower edge is the alveolar arch with indentations (dental holes) for 8 upper teeth. The separation of the alveoli is provided by the presence of interalveolar septa. Outside, elevations stand out, especially pronounced in the area of the front teeth.
The process of the sky is a horizontal plate. It originates from the nasal surface, from where it passes into the alveolar process. Its surface is smooth from above and creates the lower wall of the nasal cavity. The medial margin carries an elevated ridge of the nose, which creates the palatine process, combining with the opener margin.
Its lower surface is rough, and palatine grooves stand out on the back. The medial edge is connected to the same process on the other hand, whereby a solid palate is created. The front edge contains a hole in the incisal canal, and the posterior one is combined with the palatine bone.
Palatine bone
The bones of the facial skull are paired and unpaired. The palatine bone is paired. It includes perpendicular and horizontal plates.
The horizontal plate has four corners. Together with the palatine processes, it makes up the bony palate. The horizontal plate below has a rough surface. The nasal surface, in contrast, is smooth. Along it and on the process of the upper jaw there is a nasal crest that passes into the nasal bone.
The perpendicular plate enters the wall of the nasal cavity. On its lateral surface there is a large furrow of the sky. It, together with the grooves of the upper jaw and the process of the sphenoid bone, creates a large canal of the sky. At its end is a hole. A pair of horizontal ridges is located on the medial surface of the plate: one is trellised, and the other is shell.
Orbital, pyramidal, and sphenoidal processes depart from the palatine bone of the facial part of the skull. The first passes laterally and forward, the second goes down, back and laterally at the junction of the plates, and the third passes back and medially, connecting to the sphenoid bone.
Opener
The opener represents the unpaired bones of the facial skull. This is a trapezoidal plate that is located in the nasal cavity and creates a septum. The upper back margin is thicker than other parts. It is divided in two, and in the formed groove passes the beak and crest of the sphenoid bone. The posterior margin separates the choans, the lower is connected by the crests of the nose with the palatine bone, and the front is in one part with the nasal septum, and in the other with the plate of the ethmoid bone.
Nasal bone
Paired bones of the facial skull are represented by the nasal bone, which creates the bone back. This is a thin plate with four corners, the upper edge of which is thicker and narrower than the lower. It is connected with the frontal bone, the lateral one with the frontal process, and the lower one, together with the base of the frontal process, is the border of the aperture of the nasal cavity. The front surface of the bone has a smooth surface, and the back is concave, with a trellised groove.
Lacrimal bone
These bones of the human facial skull are also paired. They are represented by a rather fragile quadrangular plate. With the help of it, the front wall of the orbit is formed. In front, it is combined with the frontal process, at the top with the edge of the frontal bone, and behind with the plate of the ethmoid bone, the beginning of which covers its medial surface. On the lateral surface there is a lacrimal crest with a lacrimal hook at the end. And in front is a tear groove.
Cheekbone
Another paired bone that combines the bones of the brain and facial skull. It is represented by the orbital, temporal and lateral surfaces, as well as the frontal and temporal processes.
The lateral surface has an irregular quadrangular shape, the orbital one forms the wall of the orbit and the infraorbital margin, and the temporal one forms part of the temporal fossa.
The frontal process moves up, and the temporal one down. The latter with the zygomatic process forms the zygomatic arch. The bone with the upper jaw is mounted on a jagged platform.
Lower jaw
This is the only mobile cranial bone. It is unpaired and consists of a horizontal body, as well as two vertical branches.
The body is curved in the shape of a horseshoe and has both an inner and an outer surface. Its lower edge is thickened and rounded, and the upper creates an alveolar part with dental alveoli, which are separated from each other by partitions.
In the front part there is a chin protrusion, expanding and turning into a chin tubercle. Behind there is a chin hole, beyond which comes the oblique line.
In the middle of the lower jaw , a chin spine stands out, on the sides of which there is an oblong 2-abdominal fossa. At the upper edge, not far from the dental alveoli, there is a hyoid fossa, under which a weak jaw-hyoid line originates. And under the line is the submandibular fossa.
The jaw branch is paired, it has front and rear edges, outer and inner surfaces. Chewing is found on the outside, and pterygoid tuberosity is found on the inside.
The branch ends with the anterior and posterior processes that extend upward. Between them there is a notch of the lower jaw. The anterior process is coronary, pointed at the top. The buccal crest is directed from its base to the molar. And the posterior process, condyle, ends with the head, which continues with the neck of the lower jaw.
Hyoid bone
The bones of the facial section of the human skull end with the hyoid bone, which is located on the neck between the larynx and the lower jaw. It includes the body and two processes in the form of large and small horns. The body of the bone is curved, with the front part convex and the back concave. Large horns extend to the sides, and small horns upward, laterally and backward. The hyoid bone is suspended from the cranial bones through muscles and ligaments. It is connected to the larynx.
Conclusion
When studying the bones of the facial skull, the anatomy attracts attention primarily due to the complex relief on the outer and inner surfaces, which is explained by the fact that there are the brain, nerve nodes and sensory organs.
The bones are motionless (except for the lower jaw). They are firmly fixed due to various sutures in the region of the skull and face, as well as using cartilage joints at the cranial base.