HealthMedicine

Base of skull. Which bones form the base of the skull

The human skull is a significant component of the musculoskeletal system. The totality of the bones of the head is the framework 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 mimic and chewing muscles. It is customary to distinguish the following sections of the human skull: facial and cerebral, but this division is as arbitrary as the division into the vault and base. For most cranial bones, a complex irregular shape is characteristic. They are connected to each other by means of seams of various types. The only movable joint in the skeleton of the head is the temporomandibular joint, which participates in the process of chewing and speech.

Anatomy of the human skull: the brain department

This department has a spherical shape and contains a brain. The cranium is formed by unpaired (occipital, cuneate and frontal) and paired (temporal and parietal) bones. Its volume is about 1500 cm³. The brain department is located above the facial. The upper cranial bones are smooth (outside) and flat. They are relatively thin, but strong plates, in which the bone marrow is located. The skull of the person whose photo is presented below is a complex and perfect structure, each element of which has its own function.

The front department

As for the facial division, it includes paired maxillary and zygomatic bones, unpaired mandibular, palatine, latticed, sublingual and lacrimal bones, opener, nasal bone, and lower nasal concha. Teeth also appear as 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 isolation of the organs inside. These bones form the walls of the oral and nasal cavities, as well as orbits. Their structure and individual characteristics achieve a variety of facial features.

Features of growth

Anatomy of the human skull has long been studied, but still causes surprise. In the process of growing up, and then aging, the shape of the head sextape changes. It is known that in infants the relationship between the facial and cerebral divisions is not at all the same as in adults: the second predominates significantly. The skull of the newborn is smooth, the joints are elastic. Moreover, between the bones of the arch there are sites of connective tissue, or fontanelles. They make possible the displacement of parts of the skull during labor without damage to the brain. By the second year of life the fontanelles "close"; The head begins to increase dramatically in size. Approximately to seven years the back and front parts are formed, the milk teeth are replaced by the root ones. Up to 13 years, the vault and base of the skull grow evenly and not fast. Then comes the turn of the frontal and facial parts. After 13 years, sexual differences begin to appear. In boys, the skull becomes more elongated and embossed, the girls remain round and smooth. By the way, in women the volume of the brain department is less than that of men (since their skeleton is in principle inferior to the male in size).

A little more about the age features

The growth and development of the facial department lasts the longest, but after 20-25 years it also slows down. After reaching a man of 30 years of age, sutures begin to overgrow. In the elderly there is a decrease in the elasticity and strength of bones (including headaches), deformation of the facial part occurs (primarily due to loss of teeth and deterioration of masticatory functions). The skull of a man, whose photo can be seen below, belongs to the old man, and it is immediately clear.

Code and foundation

The brain of the skull consists of two unequal parts. The border between them runs just below the line running from the infraorbital margin to the zygomatic process. It coincides with the wedge-zygomatic suture, then passes from above the external auditory aperture and reaches the occipital protrusion. Visually, the vault and the base of the skull do not have a clear boundary, so this division is arbitrary.

Everything that is above this uneven boundary line is called a vault or a roof. The vault is formed by the parietal and frontal bones, as well as by the scales of the occipital and temporal bones. All the components of the vault are flat.

The bottom is the lower part of the skull. In its center there is a large hole. Through it, the cranial cavity is connected to the vertebral canal. There are also numerous outlets for nerves and vessels.

Which bones form the base of the skull

The lateral surfaces of the base are formed by paired temporal bones (more precisely, by their scales). Behind them is the occipital bone, which has a hemispherical shape. It consists of several flat parts, which at the age of 3-6 years fully fuse into one. Between them is a large hole. Strictly speaking, the base of the skull includes only the basilar part and the anterior section of the scales of the occipital bone.

Another important component of the base is the sphenoid bone. It joins with the zygomatic bones, the vomer and the teardrop, and besides 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 a beetle with spread wings. Its surface is uneven, bumpy, with numerous bulges, bends and holes. With scales of the occipital, the wedge-shaped joint is synchronously joined.

Foundation from the inside

The surface of the inner base is uneven, concave, divided by peculiar elevations. It 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 profound and capacious. It is formed by parts of the occipital, cuneate, parietal bones, as well as the back surface of the pyramid. In the posterior cranial fossa there is a circular aperture, from which an internal occipital ridge extends to the occipital protrusion.

The bottom of the middle fossa is: a sphenoid bone, scaly surfaces of the temporal bones and the front surfaces of the pyramid. In the middle there is a so-called Turkish saddle, in which the pituitary gland is located. Sleeping furrows fit the base of the Turkish saddle. The lateral sections of the middle fossa are the deepest, there are several holes in them, intended for the nerves (including the visual ones).

As for the front part of the base, it is formed by the small wings of the sphenoid bone, the orbital part of the frontal bone and the latticed bone. The protruding (central) part of the pit is called the cock's crest.

Outside surface

What does the base of the skull look like from the outside? First, its anterior section (in which the bony palate, limited by the teeth and alveolar maxillary processes, is distinguished) is hidden by the bones of the face. Secondly, the posterior part of the base is formed by the temporal, occipital and wedge-shaped 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 opening, with the same-sized condyles on either side. They are connected to the cervical spine. On the outer surface of the base are also located the subulate and mastoid processes, the pterygoid process of the sphenoid bone and numerous openings (jugular, silicose) and canals.

Injuries

Base of skull, Fortunately, it is not as vulnerable as the arch. Damage to this part is relatively rare, but has serious consequences. In most cases, they are caused by falls from a great height with a subsequent landing on the head or legs, accidents and impacts to the lower jaw and the base of the nose. Most often as a result of such influences, the temporal bone is damaged. Fractures of the base are accompanied by cerebrospinal fluid (the outflow of cerebrospinal fluid from the ears or from the nose), bleeding.

If the anterior cranial fossa is damaged, bruises in the eye area are formed, if the middle one - bruises in the region of the mastoid process. In addition to liquorrhea and bleeding, with fractures of the base, hearing loss, loss of taste sensations, paralysis and nerve damage can occur.

Injuries to the base of the skull lead at best to the curvature of the spine, at worst to complete paralysis (as a result of them the connection between the central nervous system and the brain is broken). People who have undergone fractures of this kind often suffer from meningitis.

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