This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The region of the temple is on the side of the head as far forward as the eye and as low as the zygoma and infratemporal crest. The floor of the temporal fossa is formed by the posterior portion of the frontal and anterior portion of the parietal bones as high as the temporal ridge, the outer surface of the greater wing of the sphenoid, and the squamous portion of the temporal bone. These four bones meet to form the region of the pterion (see p. 39 and 42). The anterior edge of the temporal bone overlaps and is superficial to the posterior edge of the sphenoid. The anterior edge of the parietal overlies the posterior edge of the frontal. The upper edges of the temporal and sphenoid overlap the lower edges of the frontal and parietal bones. That the temporal region of the skull is distinctly weaker than other regions is due to the thinness of the bones, and the reason that fractures here are exceptionally dangerous is on account of the middle meningeal artery running through a canal in the bone in this region; so that in cases of fracture the artery is torn and hemorrhage occurs above the dura, which causes compression of the brain (Fig. 56).
The infratemporal crest (crista infratemporalis) or pterygoid ridge separates the temporal region above from the pterygoid region below. It is an important landmark in operating on the Gasserian ganglion.
A spot two centimetres behind the external angular process and slightly above its level marks the anterior extremity of the fissure of Sylvius. In trephining in the temporal region no diploe is found in the bones, so that extreme care is necessary to avoid wounding the dura mater. The trephine may be placed 4 cm. (1 1/2 in-) behind the external angular process and 4.5 cm. (1 3/4 in.) above the zygoma to strike the middle meningeal artery. This will be level with or a little above the highest part of the edge of the orbit.
Fig. 56. - Frontal and temporal regions of an adult skull.
This is the dense fascia covering the temporal muscle; it is formed as follows: The pericranium as it comes down from the vault of the skull and reaches the temporal ridge passes under and gives attachment to the temporal muscle. The temporal fascia consists of two distinct sheets of fascia, the superficial one from the superior temporal ridge being attached to the zygoma below and to the malar bone in front; the deeper layer from the inferior temporal ridge covers the temporal muscle, and a short distance above the zygoma divides into two layers, one of which is attached to the outer edge, and the other to its inner edge. The upper or superficial layer of the temporal fascia leaves the bone at the superior temporal ridge and is attached .below to the top of the zygoma, blending near the bone with the layer beneath. This is a distinct layer though not always readily demonstrable in dissections. Between the layers above the zygoma is some fat and the orbital branch of the middle temporal artery. Anteriorly the temporal fascia is attached to the posterior border of the malar bone and the temporal ridge of the frontal. The temporal fascia is tough and dense and gives attachment by its under surface to the temporal muscle. Abscess occurring under the temporal fascia, therefore, does not tend to come to the surface, but sinks downward. It is prevented from making its exit on the face below the zygoma by the parotid gland and masseter muscle, so it passes inward to the pterygoid region and may point in the throat or go down into the neck.
The occipitofrontal aponeurosis, or galea aponeurotica as it approaches the side of the head becomes thinner and passes down to insert into the top of the zygoma so that in the temporal region the layers are as follows: Skin, superficial fascia, galea aponeurotica, two layers of the temporal fascia, temporal muscle, an indistinct periosteum, and bone. Immediately above the zygoma we have the deep layer of the temporal fascia dividing instead of a single layer as is the case higher up. The temporal fossa contains considerable fat which disappears in serious illnesses. Disfiguring depressions are also left in this region after operations involving the temporal muscle.
The temporal artery begins opposite the neck of the lower jaw, then passes over the temporomaxillary articulation, lying on its capsule, thence over the zygoma about a centimetre in front of the ear. It lies on the temporal fascia and about 4 cm. above the zygoma divides into an anterior and posterior branch. The course of the temporal artery and its anterior branch is usually quite conspicuous in old people and affords a ready means of ascertaining whether or not the arteries possess the calcareous deposits characteristic of atheroma. The location of the artery in front of the ear should be remembered, as the pulse is readily felt there in the administration of anaesthetics. In certain angiomas of the scalp the blood supply may be diminished by ligating the vessel at that point. 1 he te?nporal muscle receives blood from the middle temporal artery which comes from the temporal and perforates the temporal fascia just above the zygoma, and from the anterior and posterior temporal branches of the internal maxillary. The temporal fossa is frequently the seat of operations to expose the Gasserian ganglion and the bleeding from these various temporal arteries contributes to their gravity. The auriculotemporal nerve lies slightly posterior to the artery and the vein in front of it. They are not important.
Fig. 57. - Transverse coronal section in the region of the temple, showing the various layers.