CHAPTER TWO 
ANATOMY OF THE HEAD 
2.1 BONES OF THE SKULL 
The skull of the European hamster accounts for 
approximately a fifth of the length of the body (Fig. 
2-1). The skull includes two bone assemblies, 
neurocranial and facial, which partly overlap. The 
neurocranium (cranium) encloses the brain, while 
the facial skeleton (Jacies) encloses the nasal, para- 
nasal and oral cavities, including the mandible. 
The soft tissue over the neurocranium, includes 
the skin, superficial fascia and m. cervicoauricu- 
laris with its aponeurosis. The skin is among the 
deepest in the body and attaches firmly to the apo- 
neurosis via the superficial fascia, the freely movable 
skin carrying the aponeurosis with it. The loose 
subaponeurotic connective tissue and the perios- 
teum to which it attaches underneath are easily torn 
from the skull, except at the sutures, and are sites 
of freely spreading effusions, sometimes indicative 
of subcranial or submeningeal neoplasms. 
2.2 FACIAL SKELETON 
The facial skeleton (Fig. 2-2) invests the nasal 
and paranasal cavities (cavum nasi, sinus parana- 
sales) as far as the nasopharynx {pharynx, pars 
nasalis), extending between the choanae and the 
epiglottis, and the oral cavity {cavum oris) as far as 
the oropharynx {pharynx, pars oralis), extending 
between the soft palate {palatum molle) and the 
hyoid bone {os hyoideum) (Figs. 2-3, 2-4, 2-5). 
2.3 NASAL CAVITY 
The nasal cavity {cavum nasi) is separated from 
the braincase by the ethmoid bone {os ethmoides) 
(Fig. 2-6). The roof of the nasal cavity {dorsum 
nasi) includes the paired nasal {os nasale) and 
frontal {as frontale) bones (Figs. 2-2, 2-6, 2-7). 
The lateral wall is composed of incisive or premax- 
illary {os incisivum), maxillary {maxilla) and cau- 
dally the palatine {os palatinum) bones (Figs. 2-2, 
2-7). The base of the nasal cavity, the ventral sur- 
face of which is the bony roof of the oral cavity, is 
formed by the horizontal laminae of the incisive, 
maxillary and palatine bones (Figs. 2-6, 2-8). The 
incisive duct {ductus incisivus) perforates the bony 
base of the nasal cavity through the palatine fissure 
{Jissura palatina) in the incisive and maxillary 
bones (Fig. 2-8.). 
The interior of the nasal cavity is best studied in 
serial section (Figs. 2-9 to 2-37). The nasal cavity 
extends from the nostrils to the choanae and is bi- 
sected by a principally cartilaginous median septum 
{septum nasi) (Figs. 2-9 to 2-20, 2-29 to 2-33) 
(Reznik and Reznik-Schiiller, 1974). The cavity is 
filled with epithelium disposed in a highly elabo- 
rated pattern, borne by thin bony processes, the 
turbinal scrolls {turbinalia) or nasal conchae (Figs. 
2-10 to 2-20, 2-29, 2-33). Dorsal and ventral 
nasal conchae are attached to the lateral walls of the 
nasal cavity (Figs. 2-3, 2-4). The dorsal nasal con- 
cha {concha nasalis dorsalis) (termed nasoturbinal 
by various authors) attaches to the nasal bone; the 
ventral nasal concha {concha nasalis ventralis) (also 
called maxilloturbinal) attaches to the maxillary 
bone. The conchae curl inward to shape the scrolls, 
whose overhang forms the recesses of various 
lengths which ultimately communicate with the 
nasal cavity. In this species the conchae extend 
about 8 mm caudally into the lumen of the nasal 
cavity. The ventral concha, partially situated above 
the nasolacrimal duct {ductus nasolacrimalis) (Fig. 
2-13) is shorter than the dorsal concha and bears 
no mucosal fold, unlike the Syrian golden hamster 
(Schwarzeand Michel, 1959-60; Och, 1959). 
More complicated than the conchal apparatus is 
a second group of projections in the ethmoid region, 
the ethmoturbinals (ethmoturbinalia) (Figs. 2-3, 
2-4, 2-6). They are lined almost entirely by olfac- 
tory epithelium (Fig. 2-38) and are disposed in two 
rows, termed endoturbinals {endoturbinalia) and 
ectoturbinals {ectoturbinalia) (Figs. 2-16 to 2-20, 
2-31 to 2-33). This hamster has four endoturbinals 
and three ectoturbinals (Reznik and Reznik- 
Schiiller, 1974); similar counts are reported for 
rats (Kelemen and Sargent, 1946; Vidic and Gre- 
ditzer, 1971; Giddens, et al., 1971), mice (Kele- 
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