Cranial bones (skull): how many are there and what are they called?

The brain is one of the most important organs of the human body, governing the functioning of other body systems. Being protected is essential for survival.

Fortunately, we have different protection mechanisms, one of which is a tough bone covering that surrounds it. We are talking about the skull, which is composed of different cranial bones.

Bone protection of the brain: the skull

When talking about the skull, usually imagine all the bones that are part of the head. This consideration is not entirely correct, since the skull as such is technically the bone structure that covers the brain. The rest of the bones, like those of the jaw, are part of the facial skeleton.

However, given its use as a synonym for the set of bones of the head, it is sometimes distinguished between neurocranium, which would be the skull itself, which protects the brain) and viscerocranial (which would include the bone structure that shapes the face and of which the bones of the ear, the nostrils, the eye socket, the nasal cavity and the set of bones that form the jaw are part of).

In general, both neurocranial and viscerocranial are solidly joined, considering that the border between one and the other marks the ear canal and the upper part of the eye socket

The adult human skull, in its meaning as neurocranial, is a set of eight welded bones and joined together throughout the development by hardened connective tissue. Its main function is the protection of the brain and allow a basic structure in which part of the facial musculature can adhere, in addition to providing a stable position to the blood vessels, cranial nerves and the brain itself. Also the skull can be divided into cranial vault and skull base.

Cranial bone

Bones that make up the skull

As we have seen, the skull or neurocranium is formed by a total of eight bones joined and welded along the development of the individual in what are called sutures. All of them have different openings and holes through the blood vessels and nerves.

Below are the different bones that are part of the skull, as well as some of its substructures.

Frontal bone

This bone is placed on and protects the frontal lobe. It allows shaping the forehead and reaches the upper part of the vault of the eye or supraorbital margin, being a point of union between neurocranial and viscerocranial. Its joins with the parietal bones by the coronary suture, and with the nasal bones by the frontonasal suture.

Parietal bones

It is the largest bones in the skull, which form most of the upper and lateral region of the skull. It is connected with the frontal by the coronary suture, with the parietal by the squamous sutures and with the occipital by the lambdoid suture. Both parietals are joined together by the sagittal suture.

Temporary bones

Two bones each located under one of the parietals and attached to them by squamous sutures. These irregular bones can be divided into three zones: the squamous one that is located around the squamous suture, the mastoid that refers to the part closest to the jaw in which several muscles of the neck and neck are located. and the stone that is located in deeper regions, forming part of the base of the skull and having the middle and inner ear inside. There is also a tympanic region, which surrounds the ear canal.

Occipital bone

This bone mostly configures the base of the skull, the foramen magnum or hole in which the brain and spinal cord connect. It protects part of the occipital and temporal lobe, the cerebellum and the brain stem. It has several bumps and ridges that connect with the vertebrae. It is connected with the parietal by the lambdoid suture and with the temporal by the occipitomastoid suture.

Sphenoid

This butterfly or bat-shaped bone is located in an area at the height of the temple, connecting with the frontal, temporal and occipital bones. It goes from side to side of the skull, horizontally, and is composed of body and major, minor wings and pterygoid process. In the first one you can find the Turkish chair, a structure that surrounds and protects the pituitary gland. The major wings are part of the dorsal wall of the ocular orbit, while the minor wings are part of the medial part. Keeps the rest of the skull bones together and connected.

Ethmoid

The bone known as ethmoids is located between the sphenoid and the nasal bone, participating in the formation of the eye orbits and the nostrils, acting as the roof of the second (specifically the part called the screened sheet) and floor of the first, as well as of separation between both (of this the lateral masses of the ethmoides are in charge).

This bone connects with the meninges through the crista galli. It has numerous cavities called esmoidal cells.

Viscerocranial bones

Although the bones of the skull are properly the previous ones, it must be taken into account that there are other bones in the structure of the head beyond them, those corresponding to the viscerocranium. In this case we can find a total of 14 bones, which together with the previous 8 make up the 22 that on average has the head of an adult human (to which it is possible to add those of the ear).

Below you can see them listed, each person possessing two of each of the following except the vomer and jaw (the latter being the only movable bone structure).

  • Jaw
  • Maxillary bones
  • Nasal bones
  • Tear bones
  • Vomer
  • Turrets
  • Palatine bones
  • Zygomatic bones (cheekbones)

In addition to these, within the viscerocranium we can also find the internal ossicles of the ear that allow the reverberation of the sound to the cloquea: hammer, anvil and stirrup.