The human skull is a significant component of the musculoskeletal system. The set of bones of the head is a skeleton that determines its shape and serves as a receptacle 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 his bones, including facial and chewing muscles. It is customary to distinguish between the following sections of the human skull: facial and cerebral, but this separation is as arbitrary as the division into the arch and base. Most cranial bones are characterized by a complex irregular shape. They are connected to each other using various 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.
Human Skull Anatomy: Brain
This department 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 is located above the front. The superior cranial bones are smooth (outside) and flat. They are relatively thin, but strong plates in which the bone marrow is located. The human skull, the photo of which is presented below, is a complex and perfect structure, each element of which has its own function.
Front department
As for the facial section, it includes paired maxillary and zygomatic bones, unpaired mandibular, palatine, ethmoid, hyoid and lacrimal bones, the vomer, the nasal bone and the lower 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 the thermal insulation of the organs inside. These bones form the walls of the oral and nasal cavities, as well as the orbits. 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's seclet changes. It is known that in infants the ratio between the facial and brain sections is not at all the same as in adults: the second is significantly predominant. The skull of the newborn is smooth, the connecting seams are elastic. Moreover, between the bones of the arch there are areas of connective tissue, or fontanelles. They make it possible to displace parts of the cranium during labor 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 and facial parts are formed, milk teeth are replaced by molars. Up to 13 years, the arch and base of the skull grow evenly and not quickly. Then comes the turn of the frontal and facial departments. After 13 years, gender differences begin to manifest. 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 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, seams begin to overgrow. In the elderly, there is a decrease in the elasticity and strength of the bones (including the head), deformation of the facial section occurs (primarily due to tooth loss and worsening of chewing functions). The skull of a person whose photo can be seen below belongs to the old man, and this is immediately clear.
Arch and base
The brain part of the skull consists of two unequal parts. The border between them runs just below the line going from the infraorbital region to the zygomatic process. It coincides with the sphenoid-zygomatic suture, then passes from the top of the external auditory opening and reaches the occipital protrusion. Visually, the arch and base of the skull do not have a clear boundary, so this division is arbitrary.
Anything above this uneven border line is called a roof or roof. The arch is formed by the parietal and frontal bones, as well as the scales of the occipital and temporal bones. All components of the arch are flat.
The base is the lower part of the skull. In its center is a large hole. Through it, the cranial cavity connects to the spinal canal. There are numerous exits 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). A hemispherical occipital bone fits behind them. It consists of several flat parts, which at the age of 3-6 years completely merge into one. Between them is a large hole. Strictly speaking, the base of the skull includes only the basilar part and the anterior part of the scales of the occipital bone.
Another important constituent of the base is the sphenoid bone. It connects with the zygomatic bones, the vomer and the lacrimal bone, and in addition to the already mentioned occipital and temporal ones.
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. The sphenoid is connected with the scales of the occipital bone by a synchronous dose.
Base inside
The surface of the inner base is uneven, concave, divided by peculiar elevations. She repeats the relief of the brain. Internal the base of the skull includes three fossae: posterior, middle and anterior. The first of them is the most deep and roomy. It is formed by parts of the occipital, sphenoid, parietal bones, as well as the posterior surface of the pyramid. In the posterior cranial fossa there is a circular opening, from which the internal occipital crest extends to the occipital protrusion.
The bottom of the middle fossa are: sphenoid bone, scaly surfaces of the temporal bones and the anterior surface of the pyramid. In the middle is the so-called Turkish saddle, which houses the pituitary gland. Sleepy furrows fit the base of the Turkish saddle. The lateral sections of the middle fossa are the deepest, they contain several holes intended for nerves (including the optic nerves).
As for the anterior part of the base, it is formed by the small 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 cocks ridge.
Outside surface
What does the base of the skull look like on the outside? Firstly, its anterior section (in which a bone palate is distinguished, limited by teeth and alveolar maxillary processes) is hidden by the bones of the face. Secondly, the posterior base is formed by the temporal, occipital and sphenoid bones. It contains a variety of holes designed for passage of blood vessels and nerves. The central part of the base is occupied by a large occipital foramen, on the sides of which the condyles of the same name protrude. They are connected to the cervical spine. The styloid and mastoid processes, the pterygoid process of the sphenoid bone and numerous openings (jugular, styloid mast) and channels are also located on the outer surface of the base.
Injuries
Base of skull, fortunately, not as vulnerable as a vault. Damage to this part is relatively rare, but has serious 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 effects, the temporal bone is damaged. Fractures of the base are accompanied by cerebrospinal fluid (expiration of cerebrospinal fluid from the ears or nose), bleeding.
If the anterior cranial fossa is damaged, bruising in the eye area is formed, if the middle is bruising in the area of the mastoid process. In addition to cerebrospinal fluid and bleeding, with a fracture of the base, hearing loss, loss of taste, paralysis and nerve damage can be observed.
Injuries to the base of the skull lead, at best, to curvature of the spine, at worst, to complete paralysis (since as a result of them the connection between the central nervous system and the brain is broken). People who have experienced fractures of this kind often suffer from meningitis.