The human palatopharyngeus is composed of two divisions: longitudinal and transverse. The longitudinal division originates from the velum, and descends in and along the palatopharyngeal arch to reach the thyroid cartilage and submucosa of the pharynx. It is the portion generally accepted as the palatopharyngeus in standard anatomy textbooks. The transverse division originates from the velum and runs transversely on the lateral to posterior wall of the fauces to reach the pharyngeal raphe. In velopharyngeal closure during swallowing, the lateral and posterior walls of the fauces, opposite to the elevated velum, swell inwards to form Passavant’s ridge, and the pharyngeal isthmus is therefore closed as if strangled. The transverse division occupies the position in which its contraction should produce a ridge and may accordingly be termed the palatopharyngeal sphincter. The transverse division corresponds to the transition muscle bundle (Tr) between the longitudinal division and the superior constrictor of the pharynx (SCP). It remains controversial as to whether the Tr should be regarded as an independent sphincter or as the rostral-most portion of the SCP. In contrast, our previous study clarified that the transverse division was distinct from the SCP, and its contraction may have produced Passavant’s ridge to increase the efficiency of velopharyngeal closure by pressing the salpingopharyngeal fold and musculus uvulae ridge against the elevated velum. In mammals with an intranarial larynx, three muscles radiate from the velum to the tongue, the larynx, and the pharyngeal wall: the palatoglossus, palatothyreoideus (pt), and palatopharyngeus (pp). The latter two collectively correspond to the muscle designated here as the palatopharyngeus and are considered responsible for maintaining the intranarial larynx as follows: the pt draws the larynx near the velum as a retractor while the pp holds the larynx in that position as a sphincter. In humans, however, the larynx is positioned low and is largely separate from the velum, and therefore the anatomical states of the two muscles change as follows: in the pt and lower portion of the pp, the site of insertion descends together with the larynx and the muscles become vertical to form the longitudinal division, whereas the upper portion of the pp, which is not as markedly affected by the descending larynx, retains its primitive position and original sphincter function to form the transverse division.

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In Japan, which has entered a super-aging society, the number of oral cancer patients is expected to increase. According to the 2019 statistics by the National Cancer Center in Japan, the number of patients diagnosed with oral cancer in one year is about 22,000, and the number of patients who died is about 8,000. Thus, the prognosis of oral cancer is not good. Although the incidence of oral cancer in Japan is about 3% of all cancers, oral cancer is one of the most common cancers in the world, because of higher incidence of oral cancer in West Asian countries. As oral cancer is a marked decrease in QOL, the development of novel diagnosis for early detection and prevention of progression and treatment for reducing aesthetic and functional loss is urgently desired. In oral cancer treatment, in addition to conventional surgical and radiotherapy, anticancer drugs such as cisplatin, 5-FU, and paclitaxel are used, but their strong side effects have become a problem. In general, early cancer rarely has severe sequelae after resection, but a wider range of resection in advanced cancer affects speech and feeding. In recent years, molecular-targeted therapies have achieved remarkable results. In oral cancer, only cetuximab targeting the EGF (epidermal growth factor) receptor and immune checkpoint inhibitor, anti-human PD-L1 monoclonal antibody (nivolumab) are approved for oral cancer. There are few effective molecular-targeted therapies compared to other cancers. Recently, in addition to immunotherapy, photoimmunotherapy, superselective arterial injection chemotherapy and differentiation/apoptosis induction therapy, there have been a lot of studies on the molecular and gene therapy. For achieving the development of novel treatment, it is necessary to elucidate the molecular mechanism on the development and progression of oral cancer. The cancer cells that occur on the surface of the oral mucosa invade deeply and metastasize to cervical lymph nodes and other organs. In the process of oral cancer progression, the presence of deep invasion and metastasis is the most important prognostic factor. In this review, I introduce the molecular mechanism of proliferation and invasion in the development and progression of oral cancer including our previous findings.

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Metallic medical devices in the human body cause serious artifacts in magnetic resonance imaging owing to the volume magnetic susceptibility (χ_ν) mismatch between the device and tissue around the device. To reduce artifacts, medical devices produced from alloys with χ_ν values of approximately −9 × 10⁻⁶ are required. Controlling the phase constitution is a basic technique used to control the χ_ν value of an alloy, and the χ_ν value of each phase is a fundamental property. In this study, an α+β-type Ti alloy and two β-type Ti alloys were investigated. The estimated χ_ν values of the α-phase of the alloys were similar to or smaller than that of pure Ti. In contrast, the estimated χ_ν values of the β-phase of the alloys were larger than that of pure Ti. Since the χ_ν value of pure Ti is much larger than −9 × 10⁻⁶, the χ_ν values of the β-phases suggested that increasing the volume fraction of the β-phase was not appropriate for producing a Ti alloy with a lower χ_ν value.

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Metal hypersensitivity, a disorder of the immune system, typically manifests as contact hypersensitivity to metals during daily contact. The molecular mechanism whereby metals enter the body and cause allergic disorders remains elusive. It is thought that eluted metal ions are captured by dendritic cells (DCs) and transferred to the draining lymph nodes to activate T cells. Here, for the first time, we used a metal indicator Newport Green to locate the most common allergenic metal, nickel (Ni) ions, captured by DCs and transferred to lymph nodes. Capturing Ni ions did not affect the activity of DCs. Ni ions entered DCs and showed positive staining in keratinocytes. A time varied quantitative analysis demonstrated that at 1 h, a small amount of Ni ions was observed in the epidermal sheet. After 6 h, the number of Ni ions that entered the epidermal sheet reached a peak and remained constant for a few days and were gradually emitted 48 h later. In the cervical lymph nodes of mice, accumulation of Ni ions reached a peak within 24 h and then gradually decreased. The findings of this study will contribute to the development of effective diagnoses and treatment methods for patients allergic to Ni.

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