Clinical Anatomy of the European Hamster 
In the European hamster, the pectoraHs muscu- 
lature consists of the superficial pectoralis (m. pec- 
toralis superficialis) and the pectoralis profundus 
(m. pectoralis profundus) muscles. A cranial de- 
scending {pars descendens) part and a caudal trans- 
verse {pars transversus) part of the former can be 
distinguished. The deep pectoral is covered by the 
superficial pectoral. Since the caudal part of the 
latter muscle is very thin, it is very difficult to sepa- 
rate the two muscles at this point (Figs. 3-7, 3-8). 
At the thoracic aperture {apertura thoracis cra- 
nialis), each cranial vena cava divides into a sub- 
clavian vein {v. subclavta), an external jugular vein 
{v. jugularis externa) and internal jugular vein {u. 
jugularis interna). The external jugular vein 
emerges into the cervical region between the clavicle 
and the pectoral and sternocephalic muscles; it 
then extends lateral to the sternocephalic and clei- 
docephalic muscles until it reaches the head. The 
internal jugular vein turns medially and runs with 
the common carotid artery along the trachea to- 
wards the head. The right subclavian artery, which 
originated from the brachiocephalic trunk in the 
ventral part of the cranial mediastinum, passes 
dorsal to the right external jugular vein at the level 
of the thoracic aperture. The right common carotid 
artery, also originating from the brachiocephalic 
trunk, and the left common carotid artery, arising 
directly from the aortic arch (Figs. 3-10, 3-11, 
4-18) in the cranioventral mediastinum, both divide 
at the level of the larynx, giving rise to the external 
and internal carotid arteries of either side. 
The cranial cervical ganglion {ganglion cervicale 
craniale) of the sympathetic trunk {truncus sympa- 
thicus) is dorsolateral to the thyroid gland. The 
vagus and sympathetic nerves run together in the 
neck as the vagosympathetic trunk {truncus vago- 
sympathicus) (Fig. 3-11) ventrolateral to the com- 
mon carotid artery, but separate before entering 
the thoracic cavity. Adjacent to the cranial thoracic 
aperture and ventrolateral to the edge of the longus 
colli muscle, the stellate ganglion {ganglion stell- 
atum) and the middle cervical ganglion {ganglion 
cervicale medium) of the sympathetic trunk are 
located. TTie sympathetic trunk runs ventrolateral 
to the longus colli to the caudal end of that muscle; 
then it is dorsolateral to the vertebral column. The 
sympathetic trunk and the cervical ganglia are only 
visible histologically. However, the vagosympa- 
thetic trunk in the cervical area and the vagus nerve 
in the thoracic cavity are visible under low power 
magnification. 
3.3 PHARYNX 
Caudal to the oral cavity is the pharynx, the 
chamber common to the respiratory and digestive 
systems. The pharynx is divided into three parts, 
the nasal part {pars nasalis) rostrodorsally, the 
oral portion {pars oralis) rostroventrally, and the 
laryngeal portion {pars laryngea) caudally. The 
oropharynx extends 6 mm from the entrance to the 
pharynx {aditus pharyngis) to the epiglottis {val- 
lecula epiglottica) and is floored by the tongue (Figs. 
2-3, 2-4). The soft palate separates the oropharynx 
from the nasopharynx, which lies between the cho- 
ana and the epiglottis. The laryngeal portion is 
continuous posteriorly with the esophagus. 
The epiglottis projects into the dorsal pharyngeal 
space and lies with its cranioventral surface on the 
free caudal edge of the soft palate {velum palati- 
num). Ventral to the free edge, the pharyngeal 
cavity is closed by the epiglottis. The epiglottis 
guides the swallowed food down the pharyngeal 
furrow which lies lateral to the aryepiglottic fold 
{plica ary epiglottica). The free crest of the soft 
palate continues bilaterally along the pharyngeal 
walls, forming the palatopharyngeal arch {arcus 
palatopharyngeus) which attaches the pharynx to 
the esophagus. 
3.4 LYMPHATIC SYSTEM OF NECK 
AND ADJACENT THORACIC 
REGION 
Tonsils are neither macroscopically recog- 
nizable nor histologically demonstrable. The man- 
dibular lymph center {lymphocentrum mandibu- 
lare) is a cluster of four lymph nodes in the laryngeal 
region. It lies rostral, dorsal and lateral to the large 
complex consisting of the mandibular and sublin- 
gual glands (Fig. 3-12). Usually, two of the lymph 
nodes {Inn. mandibulares rostrales) are embedded 
in adipose tissue in front of the salivary glands. In 
general, the lymph nodes can be seen only with a 
magnifying glass, but in some animals the nodes are 
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