THE HUMAN SKELETON 
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2. Special Features. 
(a) External. 
Ridges, Processes, etc. —Superciliary arches, zygomatic arches, 
postorbital bars, temporal ridges, external occipital protuberance 
and crest (cf. lambdoidal ridge in those mammalian skulls in 
which the temporal ridges meet), alveolar ridges of upper and 
lower jaws, and the types of teeth which they bear (cf. human 
dentition with that of other mammals), pterygoid processes and 
hamuli, styloid processes, mastoid processes, occipital condyles; 
on the lower jaw note also the coronoid processes, the condyloid 
processes, the angles of the jaw, and the mental protuberance. 
Fossae. —Orbital, temporal, nasal, and mandibular (for articu¬ 
lation with lower jaw). 
Foramina, Fissures, etc. —Supraorbital, infraorbital, and 
mental foramina, for the exit of the terminal portions of the three 
branches of the trigeminal nerve; mandibular foramen for the 
entrance into the mandibular canal of the third branch of the 
trigeminal nerve; piriform opening (anterior nares), choanae 
(posterior nares), larger and smaller palatine foramina; lacrimal 
foramen; optic foramen, superior orbital fissure, inferior orbital 
fissure, foramen rotundum, foramen ovale, lacerated foramen, 
semicanal of auditory tube (Eustachian tube), carotid canal, 
jugular foramen, hypoglossal canal, condyloid canal, occipital 
foramen; external acoustic meatus, stylomastoid foramen, mas¬ 
toid foramen (or foramina). All of these are paired except the 
occipital foramen. 
( b ) Internal (within cranial cavity). 
Use for this purpose a horizontally sawn skull. Note the 
structure of the bones of the cranium as shown by the cut edges. 
In the roof of the cranial cavity note the grooves for the veins 
and arteries, and granular foveolae. 
In the floor of the cranial cavity note: 
Ridges and Processes. —Crista galli, clinoid processes, and 
prominent ridges separating anterior, middle, and posterior 
cranial fossae. 
Fossae. —Anterior cranial, middle cranial, posterior cranial; 
sella turcica; grooves for veins and arteries. 
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