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Central nervous system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The lacrimal system comprises the lacrimal gland, which secretes tears, the lacrimal sac and the ducts through which the tears pass into the nasal cavity (Figs 11.59a–c). The lacrimal gland lies anteriorly in the upper outer quadrant of the orbit and communicates with the lacrimal sac via the lacrimal canaliculi. Tears wash over the surface of the eye and drain through the lacrimal canaliculi into the lacrimal sac through two openings, the puncta lacrimalia, which are situated on the medial aspects of the upper and lower eyelids. The lacrimal sac drains into the nasolacrimal duct, which runs vertically through the lateral nasal wall on the medial aspect of the maxillary antrum. The nasolacrimal duct opens into the nasal cavity below the inferior nasal conchus.
Functional ectodermal organ regeneration based on epithelial and mesenchymal interactions
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
Masamitsu Oshima, Takashi Tsuji
Secretory glands, including salivary glands and lacrimal glands, are important for the protection of appendage organs and the maintenance of physiological functions in the microenvironment of the oral and ocular surfaces. Salivary glands play essential roles in the normal functioning of the upper gastrointestinal tract and oral health via saliva production. There are three major salivary glands: the parotid gland (PG), submandibular gland (SMG), and sublingual gland (SLG). There is also a minor salivary gland. Serous saliva that is produced from the PG and SMG primarily contains amylase proteins for the digestion of foods, whereas mucous saliva that is produced from the SLG contains glycoproteins and mucin proteins for dryness protection in the oral cavity (Avery 2002, Edgar et al. 2004, Tucker and Miletich 2010). Lacrimal glands play multilateral roles in the protection of a healthy ocular surface epithelium through the production of tears from the impairment of air exposure. The lacrimal gland comprises a main gland that secretes aqueous tears and some small accessory glands (Schechter et al. 2010). These mature glands are organized in accordance with a tubuloalveolar scheme: the acini that carry the fluid to the mucosal surface through the lacrimal duct, the myoepithelial cells that envelop the acini, and the early duct elements (Melnick et al. 2009, Schechter et al. 2010). The aqueous layer of the tear is formed by secretion from the lacrimal glands. It contains water and many tear proteins, including lactoferrin, for the expression of biological functions such as moisturizing the ocular surface and antimicrobial activity (Ohashi et al. 2006, Hirayama et al. 2013b).
Tear osmolarity is sensitive to exercise-induced fluid loss but is not associated with common hydration measures in a field setting
Published in Journal of Sports Sciences, 2018
Justin J. Holland, Michelle Ray, Christopher Irwin, Tina L. Skinner, Michael Leveritt, Ben Desbrow
The authors postulate that in field conditions the inability of Tosm to reflect changes in Posm may at least in part be explained by the large standard deviation in tear responses which was almost triple that of Posm post-exercise. When using the TearLab® system the variability of Tosm has previously been reported to be double that of Posm in a laboratory setting (Ungaro et al., 2015). Thus, it appears that this variability may be exacerbated in the field when using the same system. The authors propose that in field conditions the ocular surface of the eye is exposed to a number of environmental factors which may impact the 1) release of tear fluid from the lacrimal gland 2) concentration of various trace elements and 3) evaporation of the tear film. Additionally it is unknown if different environmental conditions lead to changes in blood flow to the tissue around the eye and its subsequent impact on osmolarity. Future research should explore these variables and how they affect tear formation and composition in the field.