The skull constitutes the bony framework of the head. This bony box contains the brain, it ends at the level of the spine. The skull is made up of eight bones, joined together by joints called sutures.

The skull consists of a total of twenty-two bones divided into two groups: the bones of the skull and the bones of the face. The bones of the skull proper are eight in number.

The skull is a bony box that has an ovoid shape. The term skull comes, etymologically, from the Latin term cranium meaning “skull”, itself borrowed from the Greek word skull. It contains the brain and ends at the level of the spine. It is made up of a total of twenty-two bones (not counting the hearing ossicles), including eight bones which constitute the skull itself and fourteen bones for the face.

The skull therefore rests on the upper part of the spine. It is formed, more precisely of:

• four even bones: the two temporal bones and the two parietal bones;
• four odd bones: that constitute the frontal, the occipital (this one contains the hole which makes it possible to communicate with the spinal column), the sphenoid (placed at the base of the skull) and the ethmoid forming the floor of the nasal cavities. 

These bones are joined together by joints called sutures.

The front

The anterior part of the skull, called the forehead, is formed by the frontal bone. This contains the roof of the eye sockets, as well as most of the anterior cranial fossa.

Parietal bones

Most of the lateral and upper regions of the skull cavity are made up of the two parietal bones. The protrusions and depressions they include promote the passage of blood vessels that will irrigate the dura, a tissue covering the brain.

the temporaux

At the temple, the two temporal bones constitute the lower and lateral parts of the skull. The temple is the region of the skull that surrounds the ear.

Os occipital

The occipital bone constitutes the posterior part of the head: it is thus made up of the most important part of the posterior cranial fossa.

the sphenoid

The sphenoid bone has a wedge shape. It forms the cornerstone of the base of the skull. Indeed, it articulates with all the bones of the skull and keeps them in place. In fact, it articulates forward with the frontal bone as well as the ethmoid bone, laterally with the temporal bones, and posteriorly with the occipital bone.

the ethmoids

The ethmoid bone, so named for its resemblance to a sieve, thus has the appearance of a sponge. It is a delicate bone of the cranial fossa. The riddled lamina of this ethmoid bone forms the roof of the cavity of the nose.

The function of the bones of the skull is to protect the brain. In addition, they also make it possible to stabilize the position of the brain, blood and lymphatic vessels, through the meninges which are connected to their internal face. In addition, the outer faces of the bones of the skull serve as an insert for the muscles that allow movement of the different parts of the head.

Furthermore, the external faces of the bones of the skull also participate in facial expression, via the insertion zones that they contain for the muscles at the origin of this expression. These different bones that make up the skull as well as the face also have the function of supporting and protecting the sense organs such as those of:

• vision ;
• touch;
• of the gustation; 
• olfaction;
• hearing;
• and balance.

In addition, the skull has foramina, which are rounded places of passage, as well as cracks: these allow blood vessels and nerves to pass through.

Several anomalies and pathologies can affect the skull, mainly:

Skull fractures

Certain traumas can cause lesions in the skull, consisting of fractures or sometimes cracks, which are less serious lesions. A skull fracture is a broken bone surrounding the brain. Fractures may or may not be associated with brain damage.

Symptoms of a skull fracture can include pain and, with some types of fractures, fluid leaks through the nose or ears, sometimes bruising behind the ears or around the eyes.

Skull fractures can be caused by lesions that pierce the skin, which are then open lesions, or which do not pierce it, and then they are closed lesions.

Bone pathologies

Tumors 

Either benign or malignant, tumors of the skull bone can appear and these tumors or pseudotumors are most often discovered incidentally. In fact, in the vast majority of cases they turn out to be benign. They sometimes also correspond to anatomical variants.

Paget’s disease

It is a chronic bone disease of the skeleton. Areas of bone tissue face pathological remodeling. This causes hypertrophy, as well as weakening of the bone. In fact, as bone resorption and formation increase, the bones become thicker than normal, but also more fragile.

This pathology is most often asymptomatic but pain can sometimes occur and hypertrophy can appear in the bones, as well as a deformation. Sometimes the pain can be deep and intensify overnight.

Skull fractures

Most skull fractures require simple observation in the hospital and do not need any specific treatment. However, surgery may, in some cases, allow the removal of foreign bodies and / or replace the fragments of the skull. Also, people with seizures need anticonvulsants.

Bone tumors

Most non-cancerous bone tumors are removed with surgery or curettage. Usually, they do not reappear. As for malignant tumors, they will generally be treated with a treatment based on surgery as well as chemotherapy and radiotherapy.

Paget’s disease

The treatment of this disease consists first of all in treating the pain as well as the complications. In asymptomatic patients, it is sometimes unnecessary to treat. 

In addition, drug molecules can help slow the progression of the disease, mainly diphosphonates: these molecules inhibit bone turnover. Sometimes an injection of calcitonin can be given but it is only used when other medicines cannot be given.

Finally, patients should avoid excessive bed rest to prevent hypercalcemia. In addition, the bone being renewed quickly, it is necessary to ensure an adequate supply of calcium and vitamins D. A supplementation of vitamins D and calcium is therefore sometimes necessary, in order to avoid bone weakening.

Skull fractures

A densitometry examination will allow the diagnosis of skull fracture. Indeed, doctors are led to suspect a skull fracture depending on the circumstances, the symptoms and the clinical examination of patients who have been confronted with a head trauma.

The best method to confirm the diagnosis of skull fracture remains computed tomography (CT), to be preferred over magnetic resonance imaging (MRI). In fact, x-rays of the skull are rarely helpful in people who have had a head injury.

Bone tumors

The analysis of tumor lesions in the bone of the skull combines clinical criteria, such as age, sex or the traumatic or surgical context, with characteristics of the appearance of the tumor.

The radiological assessment is based on the scanner and MRI. The scanner thus allows an in-depth analysis of changes in the architecture of the bone. As for the MRI, it makes it possible to look for an invasion of the subcutaneous tissues. In addition, it also allows an analysis of the tissue nature. Finally, confirmation by biopsy may be necessary in some cases.

Paget’s disease

This pathology is frequently discovered by chance, especially during X-ray examinations or blood tests carried out for other reasons. The diagnosis can also be suspected in connection with the symptoms and the clinical examination.

The diagnosis of Paget’s disease is based on several examinations:

• the x-ray will show the characteristic abnormalities of Paget’s disease;
• laboratory tests will give the level of alkaline phosphatase, an enzyme involved in the formation of bone cells, calcium and phosphate in the blood;
• bone scintigraphy to identify which bones are affected.

Discovered in northern Chad in July 2001, Toumaï’s skull is dated 6,9 to 7,2 million years ago. Its cranial capacity has been estimated between 360 and 370 cm3, or equivalent to that of chimpanzees. In addition to the morphology of its premolars and molars, with thicker enamel than chimpanzees, and its relatively shortened face, it is indeed the base of its skull that has demonstrated that this hominid does indeed belong to the human branch, and not to that of chimpanzees. or gorillas.

Indeed, the base of this skull discovered by Ahounta Djimdoumalbaye (member of the Franco-Chadian Paleoanthropological Mission, or MPFT, directed by Michel Brunet) presents an occipital hole in a position already very anterior. In addition, its occipital face is very inclined backwards. The name “Toumaï”, which means “hope of life” in the Goran language, was given by the President of the Republic of Chad.