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TIIE SKULL FROM THE SIDE (norma later...

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Originally appearing in Volume V25, Page 197 of the 1911 Encyclopedia Britannica.
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TIIE SKULL FROM THE SIDE (norma lateralis). On looking at the accompanying ,figure (fig.'s) it will be seen that the calvaria or brain Fr, Frontal bone. Pa, Parietal. SO, Supra-occipital. Sq, Squamous-temporal. MT,Mastoid-temporal. Ty, Tympanic. St, Styloid-temporal. As, All-sphenoid. E, Os planum of ethmoid. L, Lachrymal. N, Nasal. case forms all the upper part, while the face is below the anterior half. Taking the' ealvaria first the side view of the frontal bone (fig, 2, Fr) is seen extending back as far as the coronal suture (cs). Just above Fr is an' elevation on each side, the frontal eminence, better seen in female than in male skulls. The junction between the frontal and malar (Ma) at the outer margin of the orbit has already been referred to as the external angular process and is an important 2.—Profile of the Skull. Mx, Superior maxilla. Ma, Malar. Mn, Mandible. bh, Basi-hyal. th, Thyro-hyal. ch, Cerato-hyal. em, External meatus. cs, Coronal suture. ls, Lambdoidal suture. ss, Squamous suture. landmark for measurements, and from it a curved line (the temporal Crest) runs back crossing the coronal suture to reach the parietal bone (Pa, fig. 2); as it runs back this line divides into two. Below the crossing of the temporal crest the coronal suture is less serrated than above, and here it becomes obliterated first. The quadrilateral outline of the parietal bone is seen as well as its articulations; above it touches its fellow of the opposite side; in front, the frontal (Fr) ; below the great wing of the sphenoid or alisphenoid (As), the squamous part of the temporal or squamosal (Sq) and the mastoid part of the temporal (MT), while behind it articulates with the supra-occipital (SO), through the lambdoid suture (Is). All four angles of the parietal are points of special interest ; the anterosuperior angle or bregma has been already noticed, and it will be seen to lie nearly above the ear opening or external auditory meatus in the temporal bone (em). The antero-inferior angle where the frontal, parietal and alisphenoid meet is the pterion and is the site of an occasional Wormian bone (epipteric). The posterior superior angle is the lambda and will be better seen on the norma occipitalis, while the posterior inferior angle, where the parietal, supra-occipital, and mastoid temporal bones meet, is known as the asterion and marks the lateral sinus within the cranium. A little above and behind the middle of the parietal bone, and just above the superior temporal crest, is the parietal eminence where ossification starts. The squamous part of the temporal bone overlaps the parietal at the squamous suture, while from its lower part the zygomatic process projects forward to articulate with the malar. At the root of this process is the glenoid cavity where the condyle of the lower jaw articulates, and just behind this the external auditory meatus is seen (em). Behind this again the mastoid temporal is prolonged down into a nipple-shaped swelling, the mastoid process (MT), containing air cells and only found in the adult human skull, while just in front of the external auditory meatus is the styloid process (St), connected with the hyoid bone by the stylo-hyoid ligament (clotted). In the side view of the face the nasal and maxillary bones are seen, and from this point of view it will be noticed that just below the nasal aperture the maxillae, where they join, are produced forward into a little spur, the anterior nasal spine, which is a purely human characteristic. At the side of the maxilla the malar or jugal (Ma) bone is placed, and its lozenge-shaped outline is apparent; it forms the anterior part of the zygomatic arch. When the mandible is disarticulated and removed the posterior part of the maxilla is seen, and behind it the external pterygoid plate of the sphenoid. Between these two bones there is a vertical slit-like opening into a cave, the spheno-maxillary fossa, which communicates with the orbit through the spheno-maxillary fissure, with the nasal cavity through the spheno- palatine foramen, with the cranial cavity through the foramen rotundum, and with the mouth through the posterior palatine canal, as well as having other smaller openings. The side view of the mandible or lower jaw shows the body, already seen from in front, and the ramus projecting up from the back part of it at an angle of from i Io° to 120° in the adult. Before the teeth come and after they are lost theangle is greater. The point just above ch (fig. 2) is known as the angle of the jaw. At the upper part of the ramus are two projections; the most anterior is the coronoid process for the attachment of the temporal muscle, while posteriorly is the condyle which articulates with the glenoid cavity of the temporal hone.
End of Article: TIIE SKULL FROM THE SIDE (norma lateralis)
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