Page 327 - Clinical Anatomy

ECA5 7/18/06 6:51 PM Page 312

312 The head and neck

upper border of the zygomatic arch, and it is a surface marking for the
middle meningeal artery (vide infra). The anterior edge of the mastoid is
easily palpable but its posterior aspect and its tip are rather obscured by the
insertion of the sternocleidomastoid.
The whole of the superficial surface of the mandible is palpable apart
from its coronoid process. The condyloid process can be felt by a finger placed
immediately in front of, or within, the external auditory meatus while the
mouth is opened and closed.
When the teeth are clenched, masseter and the temporalis can be felt con-
tracting respectively over the ramus of the mandible and above the zygo-
matic arch. The parotid duct can be rolled over the tensed masseter and its
orifice seen within the mouth at the level of the 2nd upper molar tooth.
The pulsation of the facial artery can be felt as it crosses the lower margin
of the body of the mandible immediately in front of the masseter and again
opposite the angle of the mouth. In the latter situation, if the cheek is
gripped lightly with the finger placed within the mouth and the thumb
placed on the skin surface, the pulse will be felt a little more than a centime-
tre from the angle of the mouth.
A line drawn vertically between the first and second premolar teeth
passes through the mental foramen, the infraorbital foramen and the supra-
orbital notch. Through these three orifices, lying in plumb-line, pass
branches from each of the divisions of the trigeminal nerve, respectively,
the mental branch of the inferior alveolar nerve (V″′), the infra-orbital nerve
(V″) and the supra-orbital nerve (V′).
The middle meningeal artery can be represented by a line drawn upwards
and somewhat forwards from a point along the zygomatic arch, two
fingers’ breadths behind the jugal point. The posterior branch of this artery
passes backwards a thumb’s breadth above, and roughly parallel to, the
zygomatic arch.
The central sulcus of the cerebrum corresponds to a line drawn down-
wards and forwards from a point 1cm behind the midpoint between the
nasion and the inion.

The scalp

The soft tissues of the scalp are arranged in five layers (Fig. 221), which may
be remembered thus:
◊◊◊◊S—skin;
◊◊◊◊C—connective tissue;
◊◊◊◊A—aponeurosis;
◊◊◊◊L—loose connective tissue;
◊◊◊◊P—periosteum.
Each of these layers has features of practical importance.
The skin of the scalp is richly supplied with sebaceous glands and is the
commonest site in the body for sebaceous cysts.