Zygomatic bone

“ Skull: Zygomatic arch broadly and squarely spreading anteriorly; temporal impressions uniting to form a low sagittal crest in adult males, but in adult females and in young males the impressions usually remain apart; shape of interparietal varying from subquadrate in young specimens to subtriangular or triangular in adults; in some young specimens the interparietal is reduced to a minute, ovoid bone.
Comparisons.—See comparisons in the accounts of other subspecies occurring in Kansas. ”

“ The lower facet of the zygoma anterior to the glenoid cavity gradually contracts in breadth, as it advances forward, and at the distance of three inches from the articular cavity the zygoma changes from a prismatic to a laminar form. It is at this point that the zygomatic suture commences, at the lower margin of the arch; whence it extends directly forwards for more than half its length, and then bends upwards at a right angle. ”

“ The neural spine and zygapophyses are as in the lumbar region. Projecting laterally from each sacral vertebra, forming a close, sutural joint with both centrum [57] and neural arch, is a heavy bone shaped like a truncated pyramid (4) ; the base of the pyramid is ankylosed with the ilium. These bones seem to be much thickened transverse processes, but since they are not completely fused with their respective vertebræ and are said to ossify separately they should probably be called sacral ribs. The two sacral vertebræ do not seem to be any more closely united than are any other two vertebræ. ”

“ Skull relatively broad interorbitally; zygoma broad and squared; cranium larger in all dimensions than in most other subspecies. Average and extreme measurements of 10 adults from 1 mi. S, 11 mi. W Zamora, 5400 ft., Michoacán, are: total length, 109.4 (102-121) ; length of body, 64.3 (58-72) ; length of tail, 44.9 (39-51) ; length of hind foot, 14.6 (14-15) ; occipitonasal length, 18.0 (17.5-18.6) ; zygomatic breadth, 9.4 (9.1-9.7) ; postpalatal length, 6.6 (6.2-7.2) ; least interorbital breadth, 3.5 (3.3-3.8) ; length of incisive foramina, 4.0 (3.8-4.2) ; length of rostrum, 6.2 (5.8-6.5) ”

“ To reach the foramen rotundum (second division) —a rather more difficult procedure—it is necessary to find the posterior border of the orbital process of the malar bone, prolonging this line downwards to the lower border of the zygoma and inserting the needle 1⁄2 cm. posterior to this point. The needle is pushed horizontally inwards and the point directed slightly upwards, the foramen being reached in the pterygo-maxillary fossa at a depth of about 3 cm. from the zygoma. ”

“ The disorder of growth is confined to those elements of the skeleton where a core of bone formed in cartilage comes to be encased in a sheath of bone formed beneath the periosteum. To indicate this abnormality the name _diaphysial aclasis_ has been employed by Arthur Keith at the suggestion of Morley Roberts.
Bones formed entirely in cartilage are exempt, namely, the tarsal and carpal bones, the epiphyses of the long bones, the sternum, and the bodies of the vertebrae. Bones formed entirely in membrane, that is, those of the face and of the cranial vault, are also exempt. ”

“ Such are the Sutures of the Skull-Bones.
Harmonia is the uniting of two Bones by a simple Line; as the Bone of the Cheek with that of the Jaw.
Gomphosis is a kind of close Articulation, which unites two Bones after the manner of Nails or Wooden Pins fixt in the Holes made to receive them: Such is that of the Teeth in their Sockets.
What is Symphysis?
Symphysis is the uniting of two Bones by the interposition of a Medium, which ties them very streight together, being also threefold: Such is the Connexion of the Knee-Pan or Whirl-Bone of the Knee, and the Omoplata or Shoulder-Blade. ”

“ Whitish basally, gradually blackening toward tip but interrupted by Ochraceous-Tawny, subapical zone 3 mm long; total length 14 to 16 mm; maximum width, 0.04 mm.
[Pg 341]
Skull.—Large and strong; nasals pointed posteriorly; supraorbital ridges moderately developed and extended caudad across anterior third of parietals; zygomatic arches strong; postorbital process of zygoma involving mostly squamosal; incisive foramen elongate and narrow (5 to 6.5 × 2.3 mm) with margins more or less parallel and raised to form ridges which extend posteriorly to within 3 mm of plane of premolars ”

“ Prominence of the zigoma or cheek-bone has been noted by many observers, especially in sexual offenders, among whom Marro found it in 30 per cent. as against 22 per cent. in normal persons. This recalls a remark made many years ago by Charles Kingsley: “I have generally seen with strong animal passion a tendency to high cheek-bone;” but he confines this generalisation to women, and to those who are dark-complexioned. Virchow believes that the large development of the jaws and the cheek-bones (to which powerful muscles are attached) is favoured by coarse and hard food through many generations. ”

“ The lateral aspect of the clavicle is prone to osteoporosis and is consistent with other bones containing a neural crest component (skull vault) being resistant to osteoporosis.
In conclusion, this study shows that genes associated with bone mass and mineral density are differentially expressed in functionally distinct skeletal sites. Our observations also demonstrate developmental gene expression-based “positional identity” in the adult skeleton. ”

“ On the dorsal side of the cartilage there is a projecting ridge composed mainly of a bone known as the pterotic, sometimes erroneously [Pg 596] called the squamosal, and continued in front by the sphenotic. The pterotic, or the cartilaginous region corresponding to it, always supplies the articular surface for the hyomandibular.
In the floor of the skull, in the region of the pituitary body, there is formed a basisphenoid; while in the lateral parts of the wall of this part of the cranium, there is a bone known as the alisphenoid. ”

“ Except among the Gibbons, the vertebral column shows in the sacral region indications of that curve—or concavity in the back between the two convexities of the neck and loins—which is one of the distinctive characters of the human skeleton. The processes for the interlocking of the vertebræ, which are large in the lower Anthropoids, are much reduced in the Man-like Apes, and become inconspicuous in Man.
The breast-bone is flat, and resembles that of Man, and, in all, except the Orang, is composed of two bones. The arm-bone is often shorter than the fore-arm. ”

“ Glycosaminoglycan (Gag) concentrations are higher in limb bone. Osteocyte density in the limb bone was decreased in OVX animals, which is consistent with OVX-induced decreases in other non-cranial skeletal sites [26] . However, the osteocyte density in skull bone was unaffected during growth in an ovarian estrogen-depleted animal. This is consistent with differential responses of regional skull and limb osteoblasts and the pattern of bone loss induced by menopausal hormonal changes. However, we can not preclude that any decrease is partly in response to ageing [27] . ”

“ The formation of new bone by the osteoblasts may be defective as a result of physiological conditions, such as old age and disease of a part, and defective formation is often associated with atrophy, or more strictly speaking, absorption, of the existing bone, as is well seen in the edentulous jaw and in the neck of the femur of a person advanced in years. Defective formation associated with atrophy is also illustrated in the bones of the lower limbs of persons who are unable to stand or walk, and in the distal portion of a bone which is the seat of an ununited fracture. ”

“ A large entry wound in the scalp was produced, while the defect in the skull was coarsely comminuted and was capable of admitting three fingers into a mass of pulped brain. Both brain matter and fragments of bone were found in the external wound, which was situated just anterior to the right parietal eminence. The bullet passed onwards through the base of the skull, crossing the external auditory meatus, fracturing the zygoma and probably the condyle of the mandible, and eventually lodged beneath the masseter muscle. Blood and brain matter escaped from the external auditory meatus. ”

“ F. The significance of the peculiar characters of massiveness and cranial flattening as presented by the Neanderthal type of skeleton continues to stimulate research. In addition to the scattered remarks already made on these subjects, two recently-published views demand special notice.
(i) Professor Keith has (1911) been much impressed with the exuberance of bone-formation, and the parts it affects in the disease known as Acromegaly. The disease seems dependent upon an excessive activity of processes regulated by a glandular body in the floor of the brain-case (the pituitary gland) . ”

“ Upper surface of the skull concave; its posterior and lateral edges raised into a very high and greatly compressed semicircular crest or wall (fig. 2) . Zygomatic processes of jugal bones thick and massive. Muzzle greatly elongated, broad at the base, and gradually tapering to the apex. Lower jaw exceedingly long and narrow, the symphysis being more than half the length. Vertebrae: C 7, D 11, L 8, Ca 24; total 50. Atlas, or first vertebra, free; all the other cervical vertebrae united by their bodies and spines into a single mass. ”

“ Where there are two parallel bones--as in the leg, for example--the growth of the diseased bone may be impaired, and the other continuing its normal growth becomes disproportionately long; less frequently the growth of the diseased bone is exaggerated, and it becomes the longer of the two. In either case, the longer bone becomes curved. An _obliquity_ of the bone may result when one half of the epiphysial cartilage is destroyed and the other half continues to form bone, giving rise to such deformities as knock-knee and club-hand. ”

“ The neural arches are always provided with zygosphenes and zygantra. Many of the vertebrae have strong hypapophyses, and the caudal vertebrae are without chevron bones.
In the skull the cranial cavity extends forwards between the orbits, and is closed in front by downgrowths from the frontals and parietals which meet the well-ossified alisphenoids and orbitosphenoids [82] . The cranium is strongly ossified, and there are no parotic processes or interparietal foramen. There are no temporal arcades and no epipterygoid. The premaxillae if present are very small (fig. 51, 1) and usually toothless. ”

“ It is the magnesia that turns the tissue into perfect, elastic form.
(b) . Osseogen is the composition the constituents of which are necessary to generate perfect bone tissue. How many troubles could easily be prevented by using this cell-food in time!
(c) . This composition becomes an absolute essential in all cases of imperfect bone structure, such as rachitis, or rickets, constitutional disease of children, osteomalacia, tuberculosis of the bones, deformity of bone structure, such as curvature of the spine, etc. ”

“ Syme found that the amputated end of the radius had formed a fresh polished surface, and played both on the humerus and the ulna, a material something like cartilage being interposed. The ends of the bones of the forearm were locked in by two processes projecting downwards from the humerus, and also strong lateral and still stronger anterior and posterior ligaments again bound them fast to the last-named bone.7 It would be easy to bring forward a number of more or less similar cases. The amount of reproduction of lost parts which may take place in many of the lower animals is astonishing. ”

“ A second obstacle, more difficult to be surmounted in the process of reduction, is that arising from the long continuance of the luxation. The head of the bone, having continued for a long time in the bed into which it has been accidentally thrown, forms adhesions to it; the surrounding cellular membrane becomes thickened, and makes, so to speak, a new capsule for the head, which opposes its replacement, and, when the reduction cannot be accomplished, supplies in some measure the office of the old joint, by the movements which it allows to take place. ”

“ But in the case of the true Placoids that analogy is faint indeed. Their skeletons contain true bone;—the vertebral joints of the Sharks and Rays possess each, as has been shown, an osseous nucleus, which retains, when subjected to the heat of a common fire, the complete form of the joint; and their cranial framework has its surface always covered over with hard osseous points. But though their skeletons possess thus their modicum of bone, unlike those of embryonic birds or mammals, they contain, in what is properly their cartilage, no gelatine. ”

“ He lays great stress on the important work performed in such cases by the osteoblasts without whose living and formative action these results could not be obtained. He explains how necessary it is that these living elements should be stimulated into action by work. They thrive only so long as they have work to do. Another surgeon, Ollier, “wondered why the fragments of bone which he had succeeded in raising from slips of periosteum planted beneath the scalp or amongst muscles ceased to grow and tended to disappear. ”

“ Finally, this red zone was covered with a fairly thick layer of 42 white bone: this was the layer formed after the madder had been left off.... We shall have no further difficulty in understanding whence transudes the osseous juice that was thought necessary for the formation of callus and the filling-up of the wounds of the bones, now we see that it is the periosteum that fills up the wounds, or is made thick round the fractures, and afterward becomes of the consistence of cartilage, and at last acquires the hardness of bones. ”