Clarification of the Terminology of the Major Human Salivary Glands: Acinus and Alveolus are not Synonymous

A comprehensive analysis of the tubarial glands

The tubarial glands (TGs) are a collection of salivary glands (SGs) located within the nasopharynx, proximal to the eustachian tube. Currently, there is no quantitative characterization of the TGs. We investigated the histological architecture of the TGs and compared it with the major and minor SGs for categorization. Tubarial, parotid, submandibular, sublingual, buccal, labial, and lingual glands were excised from human donors (8 male and 3 female). Hematoxylin and eosin-stained tissue sections were analyzed to measure the area of the largest lobule, number of ducts, number of mucinous acini, and mean mucinous acini area. Based on our observation, the TGs' histology resembles the minor SGs, while having some unique characteristics that distinguish them from both major and minor SGs. The area of the largest lobule in the TGs and minor SGs was smaller than the major SGs. TGs have a lower number of ducts than the major and minor SGs. TGs contain densely packed clusters of predominantly mucinous acini surrounded by loose connective tissue resembling minor SGs. This density may explain their previously observed high prostate-specific membrane antigen uptake. In our cohort of donors, sex-based differences were observed in the mean mucinous acini area between male and female TGs, submandibular and sublingual glands. Taken together, our findings suggest the histological characteristics of all SGs are better organized on a spectrum rather than discrete groups (major vs. minor) and provide information to open new avenues for research into the TGs' role in head and neck pathologies and sexual dimorphism of the SGs.

Exocrine gland structure-function relationships

Fluid secretion by exocrine glandular organs is essential to the survival of mammals. Each glandular unit within the body is uniquely organized to carry out its own specific functions, with failure to establish these specialized structures resulting in impaired organ function. Here, we review glandular organs in terms of shared and divergent architecture. We first describe the structural organization of the diverse glandular secretory units (the end-pieces) and their fluid transporting systems (the ducts) within the mammalian system, focusing on how tissue architecture corresponds to functional output. We then highlight how defects in development of end-piece and ductal architecture impacts secretory function. Finally, we discuss how knowledge of exocrine gland structure-function relationships can be applied to the development of new diagnostics, regenerative approaches and tissue regeneration.

Morphogenesis and Mucus Production of Epithelial Tissues of Three Major Salivary Glands of Embryonic Mouse in 3D Culture

Embryonic mouse submandibular epithelia initiate branching morphogenesis within two days when embedded in Matrigel and stimulated by members of the epidermal growth factor family. However, it is unknown whether the end buds further branch over longer culture periods, and whether saliva-producing cells differentiate there. In the present study, we cultivated three major (submandibular, sublingual and parotid) salivary epithelia from 13-day embryos for 14 days in mesenchyme-free cultures. All epithelia continued to grow and branch to form numerous acinus-like structures in medium supplemented with neuregulin 1, fibroblast growth factor 1, and insulintransferrin-sodium selenite. Alcian blue staining to detect mucous cells showed that each epithelium differentiated via three distinct modes, as seen in normal development, although the staining intensities were weaker than in normal development. RT-PCR analysis of the amylase gene showed that no epithelia expressed amylase after 14 days of culture, which is inconsistent with the fact that only parotid epithelium does so at postnatal day 7 during normal development. These results suggest that cytodifferentiation progresses to a lesser extent in mesenchyme-free cultures than in vivo.

The Terminologia Histologica after 10years: Inconsistencies, mistakes, and new proposals

This article details our experience with the Terminologia Histologica (TH) and its utility in the teaching of histology, cytology, and clinical medicine (e.g., pathology and hematology). Latin histological nomenclature has been used for 43years, and the latest version of the TH has been in use for 15years (although it was only issued publicly within the past 10years). The following findings and ensuing proposals allow us to discuss key points pertaining to the TH and make important suggestions for potential changes to the TH (such as the exclusion and inclusion of various terms). We classify these changes into six groups: 1.) mistakes in the TH, 2.) discrepancies among various Terminologiae, 3.) discrepancies within the TH, 4.) the repetition of terms, 5.) synonyms in the TH, and 6.) missing terms in the TH. Surprisingly, unlike the anatomical nomenclature, the histological nomenclature has been neglected in the literature. This article addresses this problem by reviewing and summarizing the state of this field, pointing out key discrepancies, offering solutions, and highlighting topics for further discussion.