2 Skull

Orientation and general presentation (Figs 2.1 & 2.2)

The skull is a large, hollow, bony structure comprising several fused bones. (Note: The jaw is not part of the skull and is therefore described in a separate chapter.) Numerous palpable protuberances are present on the skull. The orbit (1) shows a sharp supraorbital edge (2) with a small supraorbital notch (SSN). The infraorbital foramen (SIF) is below the orbit. The center of the glabella (SGL) protuberance is located above a depression, i.e. the nasion (SNA) (or sellion) found at the intersection of both supraorbital edges. The anterior nasal spine (SNS) is located below the nostril cavities. Each zygomatic arch (SZR) is located on one of the lateral aspects of the skull, and runs horizontally towards the orbit. Each zygomatic arch shows palpable upper (3) and lower (4) edges, and a large anterior aspect supporting a vertical branch. The area between the horizontal and vertical branches of the SZR shows a sharp angle, the zygomatic angle (SZA). The mastoid process (SMP) is located at the posterolateral aspect of the skull. A large protuberance called the external occipital protuberance (SOP) is observable at the posterior aspect of the occiput at the intersection of both right and left superior nuchal lines (5).

Figure 2.1 Skull (3D model).

A Anterior view. B Lateral view. C Posterolateral view.

Figure 2.2 Skull (anatomic specimen).

A Posterior view. B Lateral view. C Anterolateral view. D Anterior view.

Skull – external Occipital Protuberance (SOP)[M] H|Anim

Landmark SOP

Large protuberance located at the posterior aspect of the occipital bone (see Figs 2.1 & 2.2).

The palpator stands behind the sitting

Place one finger on each trapezius muscle. Follow both muscles up to their insertions on the skull (yellow arrows).

A bony protuberance is located between these insertions.

The apex of this protuberance is the point to locate.

Manual palpation tip

• For better localization of the trapezius muscles, ask the subject to perform an active head extension.

• Then, to facilitate palpation, ask the subject to relax and put his or her head in slight extension to relax the trapezius muscles.

Observe the posterior aspect of the skull. The SOP landmark is located in the inferior third on a usually well developed protuberance. Select the apex of the latter.

Skull – Zygomatic aRch (SZR)[R,L]

Landmark SZR

Each zygomatic arch is located laterally on the skull and runs horizontally (see Figs 2.1 & 2.2). The angle between both the horizontal branch and the vertical branch of the arch is selected.

The palpator stands behind the sitting subject.

The zygomatic bone is delimited by the dotted blue line on this image (see also virtual palpation below).

Locate the upper edge of the horizontal branch of the zygomatic arch.

Glide forwards (green arrow) until the posterior edge of the vertical branch is reached.

Rotate the pulp of your finger slightly anteriorly, and select the angle between both branches.

Observe the skull from a lateral view. Locate the upper edge of the horizontal branch and the posterior edge of the vertical branch of the zygomatic arch. Select the angle between both edges.

Skull – Zygomatic Angle (SZA)[R,L]

Landmark SZA

The zygomatic bone shows a relatively sharp angle, located below the inferior edge of the orbit (see Figs 2.1 & 2.2).

The palpator stands next to the sitting subject.

The zygomatic bone is delimited by the dotted blue line on this image (see also virtual palpation below).

Gently pinch the horizontal branch of the zygomatic arch between thumb (on the zygomatic lower edge) and forefinger (on the zygomatic upper edge). Both fingers then follow the horizontal branch forwards until the widest section of the bone is reached; the index path remains horizontal (orange arrow), while the thumb path is inclined downwards (green arrow).

Now the pulp of the thumb should be on the zygomatic angle.

The point to locate is at the apex of the angle.

Manual palpation tip

• The apex is relatively sharp and may be located deep in the soft tissue, depending on the development of the subject’s cheeks.

NOTE

During manual palpation, the forefinger is on SZR (see p. 11).

Observe the skull from a lateral view. Follow the lower edge of the horizontal branch of the zygomatic arch forwards until the angle is found. Select the center of the angle.

Rotate (approx. 90°) backwards and make sure the center of the angle has been selected.

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