A human skull is a bone framework that has twenty three bones in its composition. They perform the function of protecting the brain from various injuries. The skull is a component of the skeletal system and musculoskeletal system. It consists of the brain and facial departments that perform certain functions. Each department has an outer and inner base.
What makes the base of the skull?
It is formed with the help of the orbital and nasal parts of the frontal bone, small and large wings, ethmoid bone and platelets, pyramids of the temporal and body main bones, lateral parts and lower parts of the scales of the occipital bone.
The base of the skull, the photo of which you see, has such a structure that its individual bones are partially connected by sutures or layers of cartilage tissue. They are called synchondrosis.
Departments and openings
The outer base of the skull is divided into departments and has various protrusions and holes through which the nerves and blood vessels pass. The posterior region is the location of the external occipital protrusion. The crest of the nape goes down from him. A large aperture of the nape is located in front of the scales. On the sides, it is limited to the occipital bone, and in front, the sphenoid. The sublingual nerve has a condylar canal passing under the processes of the occiput, behind which there is a fossa that passes into an unstable canal.
Not far from the large occipital foramen of the base of the skull, closer to the front, there is the pharyngeal tubercle, and the mastoid has a hole with the corresponding name, which is the exit site of the facial nerve, and the styloid process.
The lower surface of the rocky part has a jugular fossa and an opening with the same name. Cranial nerves pass through it. An external jugular vein emerges from this opening of the base of the skull . In front of it is a sleepy canal with an external opening, and a ragged one is located near the top of the rocky part.
The pterygoid canal passes just before the root of the pterygoid processes and opens into the fossa. The oval and spinous openings are located on the sphenoid bone. The openings of the nasal cavity are called choans. They are located in front of the ragged. Between the outer plate of the pterygoid process and the lower part of the surface of the large wing located on the sphenoid bone, there is a temporal fossa.
The posterior sections of the bone palate have openings of the same name that lead into the canals. Incisors have cells, behind which there is an incisal opening.
Structure
A skull is a cavity formed by tightly connected bones, in which organs important for human life are located: the brain of the head, the initial sections of the respiratory and digestive systems and sensory organs. In the skull, there is a vault, or roof, and a base, which is external and internal. The outer base of the skull is formed with the participation of its lower surfaces - the brain and facial sections, which are divided into anterior, posterior and middle.
The front part originates from the incisors and captures the posterior edge of the palatine bones formed by horizontal plates, which are connected in front with the processes of the palate of the upper jaw, forming a bone sky. In its space, the formation of the incisal fossa occurs, from which the incisal canal begins. It leads to the lower passages of the nose. The structure of the base of the skull is such that a seam extends in the middle of the bony palate, and palatal openings: small and large, lead to the canal.
The middle section is occupied by the space between the sky and the large occipital foramen, its front edge. Lateral borders pass along the external auditory canal up to the mastoid process. The outer base of the skull has two openings that open into the nasal cavity.
The posterior region is located between the anterior margin of the occipital large opening and the external occipital protuberance.
Front department
It consists of paired and unpaired bones. The first prevail. They are represented by the upper jaw, nasal, zygomatic, lacrimal and palatine bones, lower concha. The second - ethmoid bone, opener, hyoid bone, lower jaw. The bones of the base of the skull, which make up the facial section, have a huge effect on all senses, the respiratory and digestive systems.
Durable skull allow areas filled with air. They have unpaired bones. In addition, air is involved in providing thermal insulation. Such cavities are in the sphenoid, frontal, ethmoid, temporal bones and upper jaw.
A special role in the human body is assigned to the hyoid arched bone located between the larynx and the lower part of the jaw and connected to the cranial bones by ligaments and muscles. With its help, the formation of the body and paired horns occurs, from which the styloid processes go.
The upper bones of the base of the skull are flat and are plates filled with bone substance. In its cells are the brain and blood vessels through which blood circulates. Brains and grooves of the brain are formed due to irregularities of some bones of the skull.
Brain skull
It protects the brain from damage and is its protective framework. The cerebral region of the skull is above the facial and has the shape of an ellipse. Its volume is 1500 cm. It consists of paired, parietal and temporal, bones, and unpaired - occipital, sphenoid and frontal. The latter consists of two scales, the bow. She is airy. Here, the formation of the forehead and frontal tubercles takes place, due to which the walls of the orbits, the nasal cavity, and the fossa on the temples and in the front are formed. With the help of the parietal bone arches are formed, and with the help of the occipital bone , the base of the skull, a photo of which is presented to your attention.
The paired bone is a complex airborne temporal part. It carries out the formation of the cranial vault; hearing organs are contained in it. This bone forms a pyramid with a tympanum and inner ear.
Sphenoid bone
It is located where the base of the skull, in its very center. The sphenoid bone has a body with processes extending from it with the corresponding name, with large and small wings. The body has six surfaces that perform certain functions. These are front, back, top, bottom and two side.
At the base of the large wing there are holes of round, oval and spinous shape. There are four wing surfaces, which are called the temporal, maxillary, orbital and cerebral. Arterial grooves and impressions are located on them. The medial side of the small wing has an inclined process. The space between the large and small wings is occupied by the superior orbital fissure.
Occipital bone
It consists of basilar, lateral parts and scales. When they are connected, a large hole is formed, which is called the occipital. The lower surface of the lateral part is provided with a condyle, over which the sublingual canal is located. Behind it is a fossa with a condylar canal at the bottom.
The center of the outer surface of the scales has an occipital protrusion. A crest with the same name goes down from it.
Frontal bone
The outer base of the skull occupies most of the arch and has a frontal bone, which includes the nasal, orbital parts and frontal scales. The nasal part in front and on the sides is limited by the ethmoid notch, which separates the right and left eye sockets. The front part of the frontal part in the middle has a line that goes into the nasal spine. On both sides of it (horizontally) is the sinus aperture of the frontal part of the skull.
Functional features of the skull
Being a complex bone organ, the skull performs the following functions:
- It protects the brain, all senses from damage.
- The cranial bones connect the chewing, facial and cervical muscles.
- Participates in the speech process, and with the help of the jaws and air sinuses, sound is formed.
- The skull plays a large role in the digestive system, namely: with the help of the jaws, a chewing function is carried out and the oral cavity is limited.
Human Skull Base: Formation
In a newborn child, the jaw bones are flat, they are a collection of a huge number of bone beams without a clearly defined organization. Between them is loose connective tissue. There is no compact bone in the peripheral zones, it is replaced by the periosteum, represented by a thick layer.
Over time, the merging of the sticks occurs. A continuous compact plate is formed: first on the sides, then in the frontal and distal parts of the jaw. The size of the facial bones is increasing. Of great importance in the growth of facial bones is the base of the skull. The anatomy of their structure is such that the anterior cranial fossa is lengthened by sutures that separate the frontal and ethmoid, the last and main bones.
Growth ends at 10-11 years of human life. Subsequently, the frontal bone is pneumatized, and bone formation occurs on the external surface. In girls, this happens before 13 years old, and in boys - up to 14. With the growth of the base of the skull, the angle between the cranial fossa decreases: the posterior and anterior. This explains that the vertical size of a person's face prevails over the horizontal.
Features of the structure of the skull: sexual and age
All bones of the skull begin to develop from the membranous stage, then comes the cartilage and the final bone. The facial bones in their development pass the middle stage. A feature of the structure of the skull in a newborn child is the presence of residues of the membranous skull - fontanelles, which are front, back and side.
On the front fontanel (the largest) you can observe respiratory movements, intracranial pressure (if it increases, the fontanel swells), dehydration of the baby's body (in case of disease, the fontanel sinks).
The posterior fontanel is smaller and quickly overgrows. In a full-term newborn, most often there are no lateral fontanelles that are present in prematurely born children. But they are overgrown by 2-3 years of life.
The second feature is that both the inner and outer surfaces of the base of the skull have cartilaginous layers that are located between the individual parts of the bones.
The third feature. In newborns, the sinuses, processes, bumps, jaws are not developed, teeth are missing.
The formation of skull sutures occurs by 3-5 years of human life. In general, he finishes growing in 25-30 years.
The skull is distinguished by gender, but this is not significant. Age-related changes can spread to the entire base of the skull. The anatomy of its structure is such that the ridges and bone substance of the spongy structure begin to dissolve, the cranial bones become light and fragile. The shape of the skull can change under the influence of mechanical factors.