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Experimental Stomatology
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
Frandsen et al.104 performed a similar experiment in 20 Long-Evans rats maintained on a pantothenic acid-deficient diet from birth. Histologic changes in this series were characterized by marked interference with chondrogenesis and osteogenesis. The late stages of the deficiency were dominated by necrosis of the articular capsule and articular disk, together with fibrous tissue proliferation into the glenoid fossa productive of destruction of the temperomandibular joint. Severity was related more to individual response than to duration of deficiency. Bone resorption was very extensive, leading to almost a complete absence of trabeculae in the head of the condyle and to partial disappearance of the lamina compacta in the ramus. Concurrently, there was osteophytic growth from the periosteal surface of the ramus and squamosal bone. All changes were prevented by the administration of calcium pantothenate.
Head and Neck
Published in Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno, Understanding Human Anatomy and Pathology, 2018
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno
The mandibular cartilage is often called Meckel’s cartilage, because it was first described by the German anatomist Johann Friedrich Meckel. Meckel’s cartilage extends from near the midline of the chin all the way back to the developing middle ear (Figure 3.2), and is a source of genetic instructions to guide ossification by surrounding neural crest cells. In human embryology, the more rostral bar of Meckel’s cartilage is called the palatopterygoquadrate bar. The perichondrial membrane surrounding the middle portion of Meckel’s cartilage becomes the sphenomandibular ligament, which connects the lingula of the mandible to the spine of the sphenoid (Plate 3.28a). In the early evolution of mammals, the lower jaw changed from having two bones (quadrate, articular) between the biting element (dentary) of the lower jaw and the skull (squamosal bone) to having the dentary (the mammalian mandible) articulate directly with the squamosal. Freed of their roles in jaw movement, the quadrate and articular, both derived from the proximal (caudal) end of Meckel’s cartilage, were co-opted to serve as parts of the vibration-transmitting apparatus of the middle ear, the malleus (“hammer”) and incus (“anvil”). All of these elements, including the squamosal, are part of the 1st branchial arch. Prior to these changes, sound was transmitted from the tympanic membrane to the cochlea by a single bone, the columella (mammalian stapes), which is derived from the 2nd branchial arch (Plate 3.45a and c). Despite these evolutionary and developmental changes in human adults, all the muscles that originally form in the mesenchyme of the mandibular and maxillary processes are still innervated by the nerve of this arch: the trigeminal nerve (CN V) (Plate 3.15). That is why, in addition to the masticatory muscles and the anterior digastric, muscles such as the tensor veli palatini (attached to the palatine aponeurosis) and the tensor tympani (attached to the malleus) are also innervated by the trigeminal nerve (Plates 3.36 and 3.45).
The effect of bone vibrator coupling method on the neonate auditory brainstem response
Published in International Journal of Audiology, 2019
Andrew Stuart, Hannah M. Nelson
With regard to bone vibrator placement, Yang, Rupert, and Moushegian (1987) found changes to wave V latency and amplitude with different placements around the cranium of neonates and one-year-old infants: when moving the bone vibrator from a temporal, to an occipital, and to a frontal bone placement, ABR wave V latencies to bone-conducted clicks were prolonged and wave V amplitudes reduced. Similarly, moving the bone vibrator around the temporal bone area from a posterior placement to supero-posterior, and to superior placement significantly prolonged wave V latencies and significantly reduced wave V amplitudes (Stuart, Yang, and Stenstrom 1990). Yang, Rupert, and Moushegian (1987) proposed that membranous sutures surrounding the temporal bone offer greater signal attenuation to frontal and occipital delivered stimuli. Stuart, Yang, and Stenstrom (1990) similarly suggested that movement of the bone vibrator away from the petrosal portion of the temporal bone results in signal energy loss through surrounding sutures, mastoid fontanelle, and parietal, occipital, and squamosal bones.