The Temporal Line: There's a Kansas City That Isn't In Kansas

Now that we've covered basic head anatomy in The Head: Part One of Oh My Gosh, Who Knows?, we're ready to observe the individual bones and landmarks of the skull. The first rule of thumb to establish is that bony landmarks of the head tend to be more prominent and visible in adult males. This is especially evident in the superciliary crest (a.k.a. brow ridge), the mental protuberance (a.k.a chin bump), the zygomatic arch (the bony ridge along the cheek) and the temporal line, which we'll look at more closely today.

The temporal line runs along the side of the head across two separate bones-- the frontal bone, which forms the forehead, and the parietal bone, which, with its bilateral twin on the other side, forms the "roof" of the head. 

The temporal line's name can be a little confusing for those first learning about skull anatomy, because we also have a temporal bone (shown in blue below). But, just to keep you on your toes, the temporal line is not on the temporal bone. The temporal bone, which is also bilateral, lies lower down on the side of the head. It's the bone on which the external ear rests, and in which the delicate inner ear structures lie. It's quite an elaborate cranial bone, so we'll take time to look at it and its many surface features later.

This whole situation was summed up nicely by one of my anatomy students last spring. Several students were quizzing one another in preparation for an upcoming skull test, and as they reviewed the temporal line, one said, "the temporal line is not on the temporal bone-- kind of like there's a Kansas City that isn't in Kansas." Indeed!

So let's take a look at the structures involved:

The temporal line (shown in red dashes) is a subtle ridge that runs across the frontal bone (shown in green) and the parietal bone (shown in peach). The temporal bone is shown in blue, but the temporal line does not run across the temporal bone.

Several anatomical structures in this area of the head have all or part of the word temporal in their names. The temporal line, the temporal bone, the temporal fossa (which is the shallow depression on the side of the cranium), the temporalis muscle (a muscle that rests in the temporal fossa), the temporal lobe of the brain (which is the part of the brain that lies on the sides of the head), and several temporal arteries and veins (blood vessels that run through this area). The only of these that we can observe directly on the surface, though, are the temporal line and the temporalis muscle (which we can sometimes see moving when an individual is chewing.)

The slightly sunken area on the lateral skull, just below the temporal line, is known as the temporal fossa.

The temporalis muscle rests in the temporal fossa, just below the temporal line (shown with a red dashed line). The movement of this muscles can sometime be observed when the figure is chewing.

As you can probably guess, most of the temporal line is obscured by hair (unless, of course, the individual in question is losing said hair). At its anterior end, though, it often shows up on the sides of the forehead, where hair would not get in the way. This is one of the skull landmarks that seems to be more prominent on older males-- particularly the bad guys in comic books. (Google Professor X to see what I mean.)

If you look around a little bit, you should have no trouble seeing examples of the temporal line. Even on an individual with a full head of hair, look for a ridge on either side of the forehead, positioned at the same degree laterally as the outer edges of the orbits.

What did I say about older males? Just take a look at Fred Thompson's temporal line. And really, next time you see your dad, take a close look at his forehead. There's a very good chance you'll see at least part of his temporal line. Perhaps all of it, if he's losing his hair!

Older males do not, however, hold a monopoly on the temporal line, as this photo of a bald Britney will demonstrate. She has quite a few prominent skull landmarks, so we'll revisit this image soon. And you thought her abs were defined!

Uncle Fester can join the fun, too. Not much hair blocking this one.

Hey, even individuals sewn together from spare parts can have a temporal line. Dr. Frankenstein was clearly meticulous in his attention to head detail.

The great Oz has spoken! His temporal line rules all! It's prominent as well as quite elaborate. Enough so to have haunted me as a child, anyway. Did anyone else worry that this guy was going to show up in their closet when they were trying to fall asleep?

And finally...

Here is one last shot of the temporal line, this time on my pal Tim. This is from my book, The Figure Artist's Book of Anatomical Landmarks, for which Tim was kind enough to pose. Tim is an accomplished a capella singer, so be sure to check out his group Chicago Voice Exhange!

Well, I think we've about exhausted this topic. Next time we'll either cover more head landmarks, or possibly to finish up one of the other several areas we've begun. Until then, go out and look for some temporal lines! They're everywhere! Even Kansas City.

The Head: Part One of Oh My Gosh, Who Knows?

The human head is incredibly complex-- certainly too complex to try to write too much about it in one post. When I took gross anatomy in graduate school, we spent as much time dissecting the human head as we spent on the rest of the body. And for good reason. There's just a heck of a lot going on in there. On this blog, of course, we won't be discussing any of the deep structures, like the brain, the twelve cranial nerves, or the elaborate labrynth of cerebral blood vessels. But in this area of the body, even the surface landmarks are packed in. I would like very much to savor them one post at a time, but before we do this, we she should probably start with a head overview. 

The head differs a great deal from the rest of the body, even landmark-wise, because not much muscle shows here. There are muscles that obscure most of the skull, but they are very thin and flat and, as such, don't show much on the surface. Most of the facial muscles insert into the skin (as opposed to inserting on bone) because it's the skin that they move-- for the sake of facilitating facial expression. But most of the muscles themselves don't show up individually.

Sometimes we can see evidence of two cranial muscles, the temporalis muscle and the masseter muscle, because they contract a bit when we are chewing. The masseter, the thickest muscle on the skull, lies over a portion of the mandible, just anterior to the ear, and sometime even its striations can be seen during chewing. The wide temporalis muscle lies on the side of the head, just above the ear, and sometimes we can see it, too, flexing, when an individual is chewing or clenching. 

Movement of both the temporalis muscle and the masseter muscle can sometimes be seen when an individual is chewing. These are among the only muscles on the head that can be identified individually on the surface.

But other than these occasionally visible muscles, most of the head's prominent surface landmarks are bone. We'll cover each of these in future posts. But before we begin this, let's look at the basic structure of the skull.

The skull has two basic portions, the cranium and the facial region. These are good to keep in mind when drawing the head, because each has its own shape and the two together help define the form of the head. The cranium is the oval shaped, hollow portion of the skull that encases and protects the brain. It shaped somewhat like an egg and is tilted upward anteriorly. The facial region of the skull is the area on which the facial features (such as the eyes, nose, and mouth) rest. It's shaped like a mask and hangs off the front of the cranial egg shape. 

The image below shows a lateral view of the skull alone and with outlines of the cranial and facial regions. The cranium is shown in pink and the facial region is shown in blue.

The cranium is the egg shaped portion of the skull than encases and protects the brain. The cranial region of the skull is outlined in pink here. The facial region, outlined in blue, is the mask shaped portion of the skull. It's the area on which the facial features rest.

It's important to consider the shapes of both these regions when drawing the head. The region shapes may also be used to determine proper head proportions and to position the ear. When measuring any human head from its most anterior to its most posterior point, the halfway point almost always falls just behind the mandible and just in front of the ear. When drawing a head, placing a vertical line halfway back on it helps to properly position both the back edge of the mandible and the front edge the ear. This is demonstrated in the image below.

When divided in half from front to back, the halfway way point on the human head falls just posterior to the mandible and just anterior to the ear. This is helpful to know when placing an ear on a drawing of the head. The black lines here show the anterior and posterior halves of the head. The verticle strip of beige shows where tissue depth has been accounted for on the anterior side (since its greater here than on the posterior side.) The red line shows the placement of the ear behind the middle line.

In upcoming posts we will begin examining the individual bony landmarks of the skull more thoroughly. These include the superciliary crests, the zygomatic arch, the mental protuberance, the angle of the mandible, and the occipital protuberance, to name a few. This will take, well, who knows how long? But I don't mind! Do you?