The human skull is a significant component of the musculoskeletal system. The totality of the bones of the head is the frame that determines its shape and serves as a container for the brain and sensory organs. In addition, some elements of the respiratory and digestive systems are located in the skull. Numerous muscles are attached to its bones, including facial and chewing muscles. It is customary to distinguish between the following sections of the human skull: facial and cerebral, but this division is as arbitrary as the division into arch and base. Most cranial bones are characterized by a complex irregular shape. They are connected to each other with different types of seams. The only movable joint in the skeleton of the head is the temporomandibular joint, which is involved in the process of chewing and speech.
Anatomy of the human skull: brain region
This section has a spherical shape and contains the brain. The cranium is formed by unpaired (occipital, sphenoid and frontal) and paired (temporal and parietal) bones. Its volume is about 1500 cm³. The brain section is located above the facial. Upper cranial bones - smooth (outside) andflat. They are relatively thin but strong plates that contain the bone marrow. The skull of a person, the photo of which is presented below, is a complex and perfect structure, each element of which has its own function.
Facial
As for the facial region, it includes paired maxillary and zygomatic bones, unpaired mandibular, palatine, ethmoid, hyoid and lacrimal bones, vomer, nasal bone and inferior nasal concha. The teeth are also part of the facial skull. A characteristic feature of the unpaired bones of the department is the presence of air cavities in them, which serve for thermal insulation of the organs inside. These bones form the walls of the oral and nasal cavities, as well as the eye sockets. Their structure and individual characteristics achieve a variety of facial features.
Growth Features
The anatomy of the human skull has long been studied, but is still surprising. In the process of growing up, and then aging, the shape of the head seclet changes. It is known that in infants the ratio between the facial and brain regions is not at all the same as in adults: the second one significantly predominates. The skull of the newborn is smooth, the connecting sutures are elastic. Moreover, between the bones of the arch there are areas of connective tissue, or fontanelles. They make it possible to shift parts of the skull during childbirth without damaging the brain. By the second year of life, the fontanelles "close"; the head begins to increase sharply in size. By about seven years, the back andthe front part, milk teeth are replaced by molars. Until the age of 13, the vault and base of the skull grow evenly and slowly. Then comes the turn of the frontal and facial sections. After the age of 13, gender differences begin to appear. In boys, the skull becomes more elongated and embossed, in girls it remains rounded and smooth. By the way, in women the volume of the brain is smaller than in men (since their skeleton, in principle, is inferior to the male in size).
A little more about age-related features
The growth and development of the facial section lasts the longest, but after 20-25 years it also slows down. When a person reaches the age of 30, the seams begin to overgrow. In the elderly, there is a decrease in the elasticity and strength of bones (including the head), deformation of the facial region occurs (primarily due to loss of teeth and deterioration of chewing functions). The skull of the person seen below belongs to an old man, and this is immediately clear.
Vault and base
The medulla of the skull consists of two unequal parts. The border between them passes just below the line running from the infraorbital margin to the zygomatic process. It coincides with the sphenoid-zygomatic suture, then passes from above from the external auditory opening and reaches the occipital protuberance. Visually, the vault and base of the skull do not have a clear boundary, so this division is conditional.
Anything above this uneven boundary line is called a vault or roof. The arch is formed by the parietal and frontal bones, as well as the scales of the occipital and temporalbones. All components of the vault are flat.
The base is the lower part of the skull. There is a large hole in its center. Through it, the cranial cavity is connected to the spinal canal. There are also numerous outlets for nerves and blood vessels.
Which bones form the base of the skull
The lateral surfaces of the base are formed by paired temporal bones (more precisely, their scales). Behind them comes the occipital bone, which has a hemispherical shape. It consists of several flat parts, which at the age of 3-6 years are completely fused into one. There is a large hole between them. Strictly speaking, the base of the skull includes only the basilar portion and the anterior occipital squama.
Another important component of the base is the sphenoid bone. It connects with the zygomatic bones, vomer and lacrimal bone, and in addition to them - with the already mentioned occipital and temporal.
The sphenoid bone consists of large and small processes, wings and the body itself. It is symmetrical and resembles a butterfly or beetle with spread wings. Its surface is uneven, bumpy, with numerous bulges, bends and holes. With the scales of the occipital bone, the sphenoid is connected by synchrondosis.
Foundation from within
The surface of the inner base is uneven, concave, divided by peculiar elevations. She repeats the relief of the brain. Inner base of the skullincludes three fossae: posterior, middle and anterior. The first of them is the deepest and most spacious. It is formed by parts of the occipital, sphenoid, parietal bones, as well as the back surface of the pyramid. In the posterior cranial fossa there is a round opening from which the internal occipital crest extends to the occipital protuberance.
The bottom of the middle fossa is: the sphenoid bone, the squamous surfaces of the temporal bones and the anterior surfaces of the pyramid. In the middle is the so-called Turkish saddle, which houses the pituitary gland. Sleepy furrows approach the base of the Turkish saddle. The lateral sections of the middle fossa are the deepest, they contain several openings intended for nerves (including optic nerves).
As for the anterior part of the base, it is formed by the lesser wings of the sphenoid bone, the orbital part of the frontal bone and the ethmoid bone. The protruding (central) part of the fossa is called the cockscomb.
Outer surface
What does the base of the skull look like from the outside? Firstly, its anterior section (in which the bony palate is distinguished, limited by the teeth and alveolar maxillary processes) is hidden by the bones of the face. Secondly, the posterior part of the base is formed by the temporal, occipital and sphenoid bones. It contains a variety of openings designed for the passage of blood vessels and nerves. The central part of the base is occupied by a large occipital foramen, on the sides of which protrudecondyles of the same name. They are connected to the cervical spine. On the outer surface of the base are also located the styloid and mastoid processes, the pterygoid process of the sphenoid bone and numerous foramina (jugular, stylomastoid) and canals.
Injuries
The base of the skull, fortunately, is not as vulnerable as the vault. Damage to this part is relatively rare, but has severe consequences. In most cases, they are caused by falls from a great height followed by landing on the head or legs, road accidents and blows to the lower jaw and base of the nose. Most often, as a result of such impacts, the temporal bone is damaged. Fractures of the base are accompanied by liquorrhea (outflow of cerebrospinal fluid from the ears or nose), bleeding.
If the anterior cranial fossa is damaged, bruises form in the eye area, if the middle one - bruises in the mastoid process. In addition to liquorrhea and bleeding, base fractures can cause hearing loss, loss of taste, paralysis, and nerve damage.
Injuries to the base of the skull lead at best to a curvature of the spine, at worst to complete paralysis (because they disrupt the connection between the central nervous system and the brain). People who have suffered fractures of this kind often suffer from meningitis.
