Head and skull bones: anatomy, functions and features

The human head is much more than the place where the eyes, mouth and other organs responsible for much of our senses rest.

It is where many of the structures that carry out basic survival functions remain, and that are grouped in thehuman brain.

In this article we will see a summary about what are and how are the bonesof the head and specifically of the skull, the vault that protects our brain and that is divided into different parts that is not difficult to identify with the naked eye once the skin is removed.

What are the bones of the head?

It is necessary, first of all, to clarify that talking about the bones of the skull and the bones of the head are not the same. Technically, the concept of “skull” encompasses only the bones that cover the brain, while the rest of the bony elements that are in the human head are the facial skeleton.

However, as unofficially we often refer to the entire head as “skull”, more recently an alternative classification has begun to be used: on the one hand there would be the neurocranium, which is composed of the flattened bones that cover the brain, and on the other hand, the viscerocranium, with all the bones of very variable shapes that shape the face and serve as support for the mouth, eyes, nose, etc.

Respecting this last classification, in the next lines we will see which are the bones of the headdistinguishing between bones of the skull (or neurocranium) and bones of the viscerocranium.

Skull bones

The bones of the skull are several bones of flattened and somewhat curved shape, with a design reminiscent of a shield, which in adults are “wedged” together forming a shape similar to that of an ellipsoid, or a sphere flattened at the top.

In the first months of life, these bones are not fully joined together, leaving space between them; But with the passage to childhood, sutures are created, lines in which these bones are welded together, leaving as the only testimony of their edges some lines or fine cracks that show where one bone begins and where another ends.

This process by which the bones of the skull go from leaving several openings to creating a hermetically closed space has to do with the development of the brain: we are born with very large brains in relation to the rest of our body, so it is the rest of the body that has to develop more quickly in size to reach this part of thenervous system.

1. Frontal bone

As the name suggests, the frontal bone is located in the space occupied by the forehead, although it extends beyond: it begins at the top of the eye sockets and ends at the top of the head aligned with the temple. Its function is to protect the eyes and thefrontal lobes of the brain, which are located just below.

On the other hand, in the skull there is only one frontal bone, and not two constituting a pair distributed between the left side and the right side of the head.

2. Parietal bones

Unlike what happened with the previous skull bone, here we find a pair: two bones that maintain a symmetry relationship with each other, and that are just behind the frontal bone, occupying the area of the head that is around the crown (including the latter).

The function of this bone structure is to protect the part of the cortex below, that is, the parietal lobes and all the subcortical organs underneath.

3. Occipital bone

In this case we also find a single bone, as was the case with the front. It is in this case a bone with a very curved and concave shape, located behind the neck, and thatsurrounds a part of the brain below, that is, in an opposite direction to how the other two bones did.

The main functions of this cranial bone are to protect the cerebellum and occipital lobes, as well as the brainstem.

4. Temporal bones

These bones are located on the sides of the head, and unlike what happened with the previous ones, there is a considerable distance between these two halves.

These rigid structures cover most of the lateral areas of the skull, protecting the temporal lobes and brainstem, and supporting the ear (each of these bones has a large hole in its lower part, to allow sounds to reach the eardrums on each side.

5. Sphenoid bone

This bone has a butterfly shape reminiscent of that of the hip, and is located on the inner lower aspect of the skull, behind the eyes, nose and upper jaw.

It serves as support for certain parts of the brain (for example, the pituitary gland area) and also shapes the internal structure of the face. It is not divided into two halves, but is a single symmetrical piece.

6. Ethmoid bones

Unlike the previous bones, and especially the first 4,  this one has a very irregular and rough shape, full of cavities . Like the ethmoid, it consists of a single piece located in the inner part of the face, although it is just in front of the sphenoid and behind the nose.

Its main function is to give structure to the olfactory system, creating channels through which air can flow into the skull.

viscerocranium bones

Once we have seen the bones that form the neurocranium, let’s see what the bones of the head are.

1. Mandible

The jaw is a bone whose function is to allow a rigid body to move towards or exert pressure on the upper jaw, so that vocalization and chewing or bite are possible. On it rests the entire row of teeth in the lower part of the mouth.

2. Nasal bones

The nasal bones are made up of two small bones that arejoined in the middle of the face and protect the nose, as if it were a roof.

3. Zygomatic bone

These are the bones that are under the cheekbones, shaping them. They serve to keep in place some groups of muscles that participate in chewing, and at the same time give physical support to the eyes, forming a good part of the eye sockets.

4. Maxillary bone

The maxillary bone has a short and compact shape, and is located in the middle of the face, making it one of the most important bones of the viscerocranium, because it offers support to others. It is just above the top row of teeth, the roots of which go deep into this bone.

5. Lacrimal bones

These small bonesare located just behind the maxillary bone, at the height of the nose, and occupy a vertical space attached to the axis formed by the nostrils.

6. Vomiting

The vomer in a bone located between the inside of the face and the area just below the nose. It has the shape of a spearhead, and its outermost part is the base of the nasal septum in its deep part, out of sight. Thus, it is behind the maxilla.

7. Palatine bone

This is the head bone belonging to the viscerocranium thatis located deeper than the surface of the face. It is a continuation of the maxilla, supporting other bones and internal tissues.

8. Nasal turbinate

The nasal turbinate is a bone of porous or spongy consistency, and is in the nasal cavity, being the rigid support by which the outside air reaches this area through holes. Its function is to create a design that allows the constant entry of air into the nasal cavity, as well as being the support of tissues covered with nasal mucosa and blood vessels.

The ossicles of the middle ear, a special case

All the bones of the head that we have seen so far have the function of supporting other soft structures and other bones, or protecting certain soft structures. However, there is an exceptional case: that of the ossicles of the middle ear.

Located behind the eardrums of the eardrums, these small bones do not serve as support or protection, but are specialized in transmitting vibrations; The patterns of waves captured by the eardrum, so that this information reaches the inner ear, where this kind of data will be transformed into electrical signals that can travel to the brain through the auditory nerves.

This is an example of how evolution can create situations in which biological structures created in principle to satisfy a need can occupy a new type of function, provided that this increases the chances of survival and reproduction that the individual who carries these traits has.