The human skull is a characteristic part of the skeletal system that protects the brain, sense organs and other tissues within it. It is divided into the cerebral and facial parts. At an early stage of human development, it contains soft, flexible fontanels that ossify as the shape and size of the skull adjust to the brain.

Human skull(Latin cranium) is a durable structure made of bones that connect tightly (cartilage, ligaments, sutures) and with the help of temporomandibular joints. The solid, and at the same time light, to some extent flexible and quite complicated (full of numerous holes) structure of the skull can be admirable. It would certainly be called an outstanding engineering achievement if it were not for the fact that it is a work of nature.

Skull structure

The skull is divided into two functionally and developmentally different parts:

  • the skullsurrounding the brain;
  • the facial skeleton , which is used to receive food and air and protects the sensory organs.

The brain's part is made up of bones:

  • occipital;
  • wedge ;
  • frontal ;
  • rush ;
  • parietal(x2);
  • temporal(x2).

The facial part of the skull is made up of bones:

  • nasal ;
  • tear ;
  • blade ;
  • jaws ;
  • zygomatic ;
  • palatal ;
  • mandible;
  • gnykowa ;
  • auditory ossicles(hammers, anvils, stapes);
  • inferior turbinates .

The individual bones of the skull connect tightly and immobile with the help ofsynchondrosesandligaments . Only the lower jaw is suspended on the skull by means of an articular joint, which allows this structure the greatest range of motion. The connective tissue ligaments seen on the skull are sometimes calledsutures .

Considering the skull as a whole, you can also separate walls:

  • upper ;
  • lower ;
  • front ;
  • back ;
  • twoside .

Thickness of the walls of the skullit is smallest where the muscles adhere to it. It mainly concerns the temporal area and the lower occipital part. The thickness of the vault can vary considerably (2-8 mm). This is an individual relationship, and the thickest skulls may have walls three times as thick as those of the thinnest skulls.

In old age, osteitis can cause a significant thickening of the vault, even up to 2 cm, which also translates into a significant increase in the weight of the skull - even up to 500 g, while the norm ranges from 125-200 g. On the other hand, when the bone tissue of the parietal bones is atrophied, they can become even paper-thin and flex under pressure, which is most easily seen in cases of rickets or osteoporosis.

Skull functions

The skull bones owe their shape to pressure and the forces with which they are influenced by the chewing, neck and expression muscles. They also co-create the upper head joint and both temporomandibular joints.

The main functions of the skull, however, arestatic . The bones of the skull create spaces containing organs that require protection. The structure of these bones and the holes in them also enable the intake of food and air, and the functioning of the sense organs. The basic functions of the skull are:

  • skull cavity , which is responsible for the protection of the brain;
  • eye socket , which protects the eye;
  • bone labyrinththat surrounds the organs of hearing and body balance;
  • nasal cavity and its sinuses , which allow air circulation and protect the sense of smell;
  • Oral cavity through which it is possible to extract and grind food.

Skull mechanics

The high strength of the skull is due to the considerable ability of elastic deformation. Under the influence of lateral pressure, it can reduce its transverse dimension by as much as 3-4 mm, and after the pressure ceases, it returns to its original dimensions.The resilience of the skull is an important protective factor for the brain .

Additionally, the structure of the skull must meet the requirements of the masseter muscles, which exert the greatest force on it. The effect of the weight of the head itself and of other muscles that move the head is of less importance.

Skull fractures

Skull fractures are the result of mechanical injuries, most often caused by a fall or a blow to the head. Disruption of the cranial bones (and especially a dislocated fracture) can have far more serious consequences for the brain than the damage caused by shock ora different type of action of a mechanical force. How serious a skull fracture is depends largely on the type and location of the fracture. When the bones of the skull break but remain in place, the brain often remains intact.

Some skull fractures damage the veins or arteries that bleed into the space around the brain tissue. Blood can then pool between the brain and skull, causing an intracranial hematoma. Fractures, especially those on the back and bottom (base) of the skull, can even damage the meninges, the tissues that cover the brain. Bacterial and viral infections, which can occur as a result of an open fracture, pose an additional threat to the brain.

Fracture at the base of the skullmay herald the following symptoms:

  • cerebrospinal fluid leaking from the nose or ears(a clear fluid that flows through the surface of the brain between the meninges);
  • blood behind the eardrum(blood may leak from the ear if the eardrum ruptures);
  • bruises behind the ear or around the eyes(spectacle hematomas);
  • blood in the sinuses(especially if they are broken).

Brain injuryfrom fracture may result in the following symptoms:

  • persistent or increasingsleepiness and confusion ;
  • convulsions ;
  • vomiting;
  • severe headache;
  • paresis of a limb or limbs;
  • difficulties in recognizing people or surroundings ;
  • balance problems ;
  • trouble speaking or seeing ;
  • no coordination.

Bibliography

Bochenek A., Reicher M., "Human Anatomy", volume I, PZWL Medical Publishing, Warsaw 2012.

Category:

Anatomy