The human skull

The skull has been a very powerful symbol in human cultures, whether to commemorate ancestors or as a warning of our mortality. In the more practical world of artistic anatomy, the skull is the hard bone structure that gives form to the head.

Skulls, and the muscles and features built upon them, vary greatly, across ethnicities, the sexes and individuals, but the basic structures are the same for everybody. Realist artists need to study the skull’s parts and how the muscles fit over them, and understand how these underlying structures define people’s heads and faces as we see them. Anyone who has seen forensic reconstructions of faces of long dead people or even Neanderthals, based upon skulls alone, will have an idea of the importance of variations in the bony architecture in defining the individual features. Some people have wide heads, some have narrow heads; some people have prominent cheekbones; some have large protruding chins whereas others have hardly any chin at all. These facial characteristics are rooted in the individual’s skull.

Here we shall look just at the skull, and follow up with a look at the head muscles. We will explore in due course how to draw convincing heads of men, women and children of various ages and types – but first things first. If someone has, for example, a steep forehead, or high cheekbones, or a receding chin, you need to grasp that it is their skull that defines those features.

I will try to cover the most important aspects here, but if you want to study the skull and muscles in detail, you should get hold of a good book of artistic anatomy. There are plenty to choose from and they cover similar ground. (My personal recommendation is Classic Human Anatomy by Valerie L. Winslow.)

The skull has two main parts: 1) the cranium and 2) the mandible, or separable jaw bone. The mandible is the only bone in the skull that moves, for example when you’re chewing or talking. The skull is composed of 22 bones, not including the teeth. Almost all of them are fused together with sutures: rigid, fibrous joints found only in the cranium, which look a bit like stitches.

Here are two digital paintings of mine, a front view and a side view. (The squiggly lines that look like cracks are the sutures where different bones join up.) You should draw or paint these views of the skull too. If possible your subject should be a real skull, not another artist’s interpretation of one.

For what it’s worth you can see these two views without the annotations in my DeviantArt gallery here.

Major bones of the skull

The cranium

The cranium, which houses the brain, is made of eight fused bones.

The forehead and the tops of the eye sockets are formed by the frontal bone; this has prominences above the eye sockets called frontal eminences which give the forehead its form. At the back of the frontal bone on either side is a ridge known as the superior temporal line or temple line (marked red on the painting), which marks an important change from the front plane to the side plane of the skull. It sometimes creates a noticeable ‘corner’ on the forehead.

Top view of the cranium

The upper side walls and rear roof of the skull are formed by the parietal bones, which meet in the middle on top of the skull. The temporal line arches back across the parietals, marking a distinction between the side and roof of the skull. Viewed from the top, the skull is broader at the back, with prominences on either side known as parietal eminences.

The lower side walls of the cranium, in the region of the ears, are formed by the temporal bones. There is a large, shallow depression in the side wall, called the temporal fossa, where the temporalis jaw muscle attaches.

Projecting from either temporal bone is a ridge called the zygomatic process of the temporal bone, which links with the facial zygomatic bone to form a kind of bridge called the zygomatic arch; there is a gap between this arch and the side of the skull. The head of the jawbone fits into a hollow beneath this arch. Behind that is the auditory meatus or ear hole, leading into the ear canal of the fleshy ear. Bulging behind this hole is the large mastoid process, a point of attachment for several neck muscles.

The sphenoid bone helps to form the floor of the cranium. Part of it appears in the side walls between the temporal and frontal bones, at the temple (the area behind the eye and above the cheekbone).

The occipital bone is the lower back wall of the cranium and forms a bulge at the back of the head. Its bottom rests on the spinal column at two knob-like protuberances called occipital condyles that permit rocking movements, e.g. when we nod. There is a ridge on the underside called the occipital protuberance which is an important landmark between the back of the head and the neck, and an attachment point for neck muscles.

The face

The facial region of the skull is made of 14 bones, including the lower jaw, and serve as the foundation for the facial muscles and sense organs.

Along the upper rims of the orbits (eye sockets) are the superciliary crests which form the brow ridge. Stephen Rogers Peck (Atlas of Human Anatomy for the Artist) describes this as like “a stretched-out letter M above the eyes”. Above the nose the ridges are separated by a wedgelike area called the glabella, below which there is an indentation where the frontal bone meets the top of the two nasal bones, known as the root of the nose. The nasal bones project from under this wedge, creating a bridge for the fleshy nose.

The zygomatic bones (cheekbones) fasten to the upper jaw and create a prominence in the cheek. From the top, a spur rises to the zygomatic process of the frontal bone, forming the outer rim of the orbit. Another spur turns toward the nose, helping form the lower rim of the orbit. The rear of the zygomatic bone joins up with the ridge of the temporal bone to help form the zygomatic arch.

The maxilla bones form the upper jaw and provide the upper dental arch for the upper teeth. They join at the front, at the base of the nasal cavity, to form the protruding nasal spine.

The mandible

The mandible (lower jawbone), shaped like a horseshoe, is the only bone in the skull that moves: it can drop down to open the mouth and close up again, but it can also move forward and back and from side to side. It provides the dental arch for the lower teeth. There is a projection at the chin called the mental protuberance (Latin mentum, chin). Small lumps on either side known as mental tubercles give squareness to the chin.

On either side of the jaw, a broad blade called the ramus juts upwards, dividing into two. The front spur is the coronoid process, which attaches to the temporalis muscle for chewing. The back spur is the condyloid process, which articulates with the temporal bone via a hinge joint. The rear ‘corner’ of the jaw is the angle of the mandible. This is noticeable on people with angular jaws and is very important in defining the jaw line.

My digital drawing above illustrates the relationship between the skull and the surface features of the head and face.

On the image I have included the horseshoe-shaped hyoid bone, a bone in the neck between the chin and the thyroid cartilage. When at rest this small bone sits level with the bottom of the mandible. The hyoid, which helps us move our tongue and swallow, is unique as it is connected to other bones only by muscles and ligaments.

The teeth

People often expose their teeth, for example when laughing or snarling, so artists need to be familiar with their locations and forms. The teeth nestle in the upper dental arch (the maxilla) and the lower dental arch (the mandible), which are shaped like horseshoes. There are various kinds of teeth, which vary according to what they are for. People usually have thirty-two teeth, though they may have lost some, and the teeth vary a lot in their forms and spacing, as well as how they affect the surface forms of the face – if someone has lost all their teeth, e.g. through age, their jaw may collapse a bit inwards.

The chisel-shaped front teeth are the incisors and used for biting. There are four on either arch: the two upper middle ones are the largest, and the others are similar sized. Next in row are the canines (or cuspids), one on either side, which are fang-like and used to tear food. After those are two wedge-like premolars (or bicuspids), followed by three boxy molars used to crush and grind.

Variations in the skull

Art books, simplifying for the sake of teaching, often present us with an ‘average skull’ – usually of an adult white male. Heck, I did it myself above. Of course, every individual skull is unique. But there are particular tendencies based upon age, sex and ethnicity.

Age

The form of the skull varies a lot according to the person’s age. As infants, our faces are more compact, then expand as we grow up. We are at our best in our twenties. As an adult ages, his or her facial bones wither and become more compact again. The jawbone gets thinner and recedes.

Sex

Unsurprisingly there are differences between male and female skulls. Male skulls tend to be larger, heavier and thicker – more ‘robust’ – than female ones, with a squarer jaw and chin. The male superciliary arch is more prominent and the mastoid process is larger. The female frontal bone is more vertical than the male’s; her bones in general are smoother and more rounded.

Ethnicity

People of different ethnicities vary in their skin colour, features and build, so naturally this is reflected in their skulls. Here are a few points:

Sub-Saharan African: Tend to have more facial projection at the mouth, and wider noses. The orbits are rectangular; the nasal cavity is short and wide; the maxillae project a bit more forwards (prognathous); the teeth are large; the mastoid process is wide.
East Asian: The orbits are circular; the cheekbones are projecting.
European: Tend to have flat profiles and narrow faces. The orbits are sloping; the nasal cavity is long and narrow; the maxillae are less projecting; the mastoid process is narrow and pointed.
Native American: Tend to have wide faces. The orbits are rounded; the cheekbones are large and prominent; the nasal cavity is medium-sized; the teeth are large; the mastoid process has a small secondary projection.

The characteristics outlined above are subtle: for this reason even forensic anthropologists talk only in terms of a skull being ‘consistent with’ a certain ancestry. It’s worth remembering that there is more variation between individual members of an ethnic group than there is between the groups. Despite their diversity, healthy skulls are also all basically the same.

What to do

The bones are the framework of the head, and even the facial features relate to the bones, not the flesh. Therefore it is important to observe and draw the skull from a variety of angles until you have memorised its forms. Norman Rockwell recalled:

I had an art teacher years ago (George Bridgman) who made us draw hundreds of skulls in all positions. I felt he was overdoing it at the time, but now I realised what a wonderful lesson he taught us. Whenever I draw a head, I instinctively feel the skull structure beneath.
(Cited by Gary Faigin in The Artist’s Complete Guide to Facial Expression)

Book-learning (like this article) is all very well, but the only way to learn to draw skulls is to draw them. Ideally, get hold of a skull, and know what sort it is: what age, sex, etc. Fortunately a replica is fine! If you don’t have one available, you could try drawing from an online 3D scan such as this one (an adult male). Now draw it from a variety of angles. They don’t have to be beautifully realised paintings – quick sketches are fine. The point is to learn the skull. Observe carefully, respond honestly, and remember what you’ve learnt.

If you spend three minutes on each sketch, you can fill a sheet with ten skulls in half an hour. That’s twenty in an hour. Forty in just a couple of hours. Imagine how much better prepped you will be for drawing the human head when you’ve sketched forty skulls at multiple angles!

As an example here are some studies of my own (though not three-minute ones). Yours don’t have to look like mine. Chances are, yours will be better.

A good exercise is to find images of skulls and trace them, either with tracing paper or, if you work digitally, as an opaque layer in your drawing software. Practice adding planes or faces to your tracings.