Page 326 - Clinical Anatomy

ECA5 7/18/06 6:51 PM Page 311

The surface anatomy and surface markings of the head 311

Table 4◊Derivatives of the branchial system (note the 5th arch disappears).

External Internal
Arch Nerve Visceral cleft pouch Floor Cartilage Muscle Artery
I V Lower face External Eustachian Antr 2/3 Meckel’s, Muscles of Disappears
auditory tube, tongue incus and mastication,
meatus middle ear malleus antr belly
and Spheno- digastric, tensor
mastoid mandibular palati, tensor
antrum ligament tympani
II VII Grows Palatine Contributes Stapes, Muscles of Disappears
down to tonsil to antr styloid, facial
cover tongue stylohyoid expression,
remaining Thyroid lig, upper postr belly
clefts to forms as body and digastric,
form skin outgrowth lesser horn stylohyoid,
of neck between I of hyoid stapedius
and II
III IX Thymus, Postr 1/3 Greater Stylopharyngeus Common
inferior tongue horn and and
parathyroid lower part internal
of body of carotids
hyoid
IV X Superior Thyroid Muscles of R—
(superior parathyroid cartilage pharynx, larynx subclavian,
laryngeal) and palate L—
aortic arch
VI X Outgrowth Cricoid Pulmonary
(inferior of lung cartilage A. and
laryngeal) buds ductus
arteriosus

The surface anatomy and surface

markings of the head

Many of the important landmarks of the skull are readily felt (see Figs 222,
223). Revise on your own skull the position of: the external occipital protuber-
ance (the apex of this is termed the inion), the nasion, which is the depression
between the two supraorbital margins, and the glabella, which is the ridge
above the nasion. Feel the sharp edge of the lateral margin of the orbit
which is formed by the frontal process of the zygomatic bone; behind the
zygomatic bone is the zygomatic arch with the superficial temporal artery
crossing its posterior extremity and forming a convenient pulse which the
anaesthetist can reach. Rather less easily felt is the jugal point, the junction
between the zygomatic bone and the zygomatic process of the frontal bone;
it is the mass of bone encountered by the finger running forward along the