The skull is a skeletal element of the head. It distinguishes the facial (visceral) and brain sections. The latter has a cavity. It houses the brain.
General information
The facial section is represented by the skeleton of the face, the initial segments of the respiratory tract and the digestive tube. It also contains palatine, lacrimal, nasal, zygomatic elements, vomer and ethmoid bone (the anatomy of this segment will be discussed later). It should be said that the latter lies partially in the department. In the brain part, parietal, frontal, wedge-shaped, occipital, temporal elements are distinguished. There is also a part of the ethmoid bone. In this department, the base and roof (vault) of the skull are distinguished. The brain and facial parts of the skull are connected motionlessly, except for the lower jaw. It articulates movably with the help of a joint with the bones of the temple.
Brain Area
The vault contains flat bones. These include the scales of the temporal and occipital, as well as the frontal and parietal elements. Flat bones consist of plates of compact substance (internal and external), between which lies a spongy bone structure (diploe). Connection of elementsthe roof is carried out by means of seams. At the base of the skull - the lower part - is the occipital foramen. It connects the cavity with the spinal canal. There are also openings for nerves and blood vessels. The pyramids of the temporal elements act as the lateral bones of the base. They contain departments of the organs of balance and hearing. Allocate the inner and outer sides of the base of the skull. The first is divided into posterior, middle and anterior central pits. They contain different parts of the brain. In the central part, in the middle pit, there is a Turkish saddle. It contains the pituitary gland. On the outside of the base, to the sides of the foramen magnum, are two condyles. They are involved in the formation of the atlantooccipital joint.
Facial
The upper jaw is represented by a paired bone. Inside it is the maxillary sinus. By means of the corresponding segments, the walls of the nasal cavity, eye sockets, and hard palate are formed. On the lateral side is the pterygopalatine fossa. It communicates with the oral, cranial and nasal cavities, the orbit. The infratemporal and temporal fossae are also present on the same surface. The cavities of the maxillary, frontal and sphenoid elements, as well as cells of the ethmoid bone, open into the nasal section. The articulation of the lower jaw is carried out by the temporomandibular joints. Next, consider what the ethmoid bone is.
Anatomy, location
This element serves to separate the cranial and nasal cavities. The ethmoid bone, the photo of which is presented in the article, isunpaired. The segment has a shape close to cubic. The element also has a cellular structure. This is the reason for the name. The segment is located between the sphenoid (behind), the frontal bones and the upper jaw (along the bottom). The element runs along the midline. The ethmoid bone is present in the anterior zone of the base of the brain region and the facial part. It is involved in the formation of the nasal cavity and eye sockets. There is a plate in the segment. Labyrinths are located on the sides of it. They are covered from the outside by vertically located orbital surfaces (right and left).
Ethmoid plate of ethmoid bone
This element is the top of the segment. It is located in the ethmoid notch in the frontal bone. The plate is involved in the formation of the bottom in the anterior cranial fossa. The entire surface of the element is occupied by holes. In appearance, it resembles a sieve, from where, in fact, its name comes from. Olfactory nerves (the first pair of cranial nerves) run through these openings into the cranial cavity. There is a cockscomb in the midline above the plate. In the anterior direction, it continues with a paired process - the wing. These parts, together with the frontal bone, which lies in front, delimit the blind opening. In some way, the continuation of the ridge is a perpendicular surface. It has an irregular pentagonal shape. It is directed downward towards the nasal cavity. In this zone, the plate, located vertically, participates in the formation of the upper region of the septum.
Maze
This is a paired formation. It consists of the ethmoid sinuses (air-filled cavities that communicate with each other and with the nose area). To the right and left at the top, the labyrinth looks like it is suspended. The medial surface of the formation is oriented to the nasal cavity and is separated from the perpendicular plate by means of a vertical narrow slit. She, in turn, is in the sagittal (vertical) plane. From the lateral side, the labyrinths are covered with a thin and smooth plate. It is part of the medial surface of the orbit.
Conchas
From the medial side, the cells are covered with curved thin bone plates. They represent the middle and superior conchas of the nose. The lower edge of each hangs freely into the gap. It passes between the perpendicular plate and the labyrinth. The upper section of each shell is attached to the medial surface of the holes of the labyrinth. From above, respectively, the upper shell is attached, just below it and a little anteriorly, the middle one passes. In some cases, a third element is also found. It is called the "highest shell" and is rather weakly expressed. Between the middle and upper shells lies the nasal passage. It is represented by a narrow gap. The middle course is located under the curved side of the corresponding turbinate. It is limited from below by the upper section of the inferior concha of the nose. On its posterior edge there is a hook-shaped process, curved downwards. It articulates on the skull with the ethmoid process extending from the lower shell. Behind this formation protrudes intomedium stroke large bubble. This is one of the largest cavities that the ethmoid bone includes. Behind and above, between the large vesicle and the uncinate process, a gap is visible in front and below. It has the shape of a funnel. Through this gap, the communication of the frontal sinus and the middle nasal passage is carried out. This is the normal anatomy of the ethmoid bone.
Joint types
The structure of the ethmoid bone involves connection with several elements of the skull. In particular, there are joints with the following segments:
- Opener. The ethmoid bone is connected to this element by the upper section of the anterior edge.
- Upper jaw. The articulation is carried out by the outer side of the lateral masses with the crest of the frontal process and the inferolateral zone with the posterior portion of the inner edge on the orbital surface.
- Frontal bone. The connection occurs by adjoining the front edge of the perpendicular element to the nasal spike. Also, the half cells in the lateral regions and the horizontal plate articulate with the half cells in the cribriform notch. There is a seam in this section.
- Sphenoid bone. The rear edge of the horizontal plate adjoins with a trellised spike. A flexible connection is formed in this section. The posterior edge of the vertical plate articulates with the crest. There is a seam at this point. The posterior margins in the lateral masses are adjacent to the pre-outer sides of the segment. This forms a seam.
- The palatine bone. The articulation is carried out at the level of the triangle by the lower side of the lateral masses.
- Nasal bones. The articulation makes the leading edge of the vertical segment.
- A lacrimal bone. This connection involves the lateral surface of the masses of the same name.
- The cartilaginous part of the nasal septum. The connection is made by the bottom-front side of the vertical plate.
- The lower conch of the nose. The ethmoid bone articulates with it through the junction of the uncinate process in the middle cavity to the branch from the inferior turbinate.
Formation
The ethmoid bone is of cartilaginous (secondary) origin. It develops with four nuclei of their cartilage in the nasal capsule. One of the original elements is present in the vertical plate, cockscomb and lateral masses. Ossification extends first to the turbinates. After the process affects the cribriform plate. After birth, six months later, ossification of the orbital surface is noted, and after 2 years - the cockscomb. The process concerns the vertical plate only at the age of 6-8 years. The openings of the labyrinth are permanently established by the age of 12-14.
Damage
Due to the fact that the structure of the ethmoid bone is porous, the segment is very susceptible to injury. Often, fractures occur in an accident, with a fall, a fight, an anterior-ascending blow to the nose. Fragments of bone can freely move through the cribriform plate, in fact, into the cranial cavity. This can provoke liquorrhea (liquor ingress)to the nose area. The resulting communication of the cranial and nasal cavities provokes severe, difficult to eliminate infections of the central nervous system. The ethmoid bone has a close relationship with the olfactory nerve. If the element is damaged, the sensitivity to odors may worsen or disappear completely.
