Comprehensive histochemical and stereological study of the parotid and sublingual salivary glands in Caucasian squirrel (Sciurus anomalus)
Graphical abstract
Introduction
The first stage of food digestion in mammals occurs in the oral cavity with the help of teeth, salivary glands, and the tongue. Then other stages occur along the gastrointestinal tract. In the first stage, the major salivary glands, including the parotid, submandibular and sublingual, play an essential role in producing saliva (Amano et al., 2012; Saracco and Crabill, 1993). These glands develop in the late embryonic period from the oral ectoderm and innervate by the parasympathetic and sympathetic nerves (Nordgarden et al., 2001; Proctor and Carpenter, 2007).
Some of the vital functions of saliva are; slippery and sticky chewed food; this helps chewed food to become sticky bolus and move easily toward the stomach without damaging the oesophagus mucosa (Vissink et al., 2010). Furthermore, saliva contains the lysozyme enzyme, which has antibacterial activity and helps clean the oral cavity environment and can change starch to maltose due to its α-amylase enzyme (Jenkins, 1978). Also, saliva helps the sense of taste and has buffering properties due to having bicarbonate.
The literature has shown that there are various differences in the structure of the major salivary glands among the mammalian species (Ribeiro et al., 2001). Squirrels belong to the Sciuridae family. Caucasian squirrel (Sciurus anomalus) is one of the small tree squirrels and can be found in different geographic areas such as Iran, Iraq, Greece and so on (Amr et al., 2006). Therefore, the population of Sciurus anomalus varies according to the difference in the amount of access to food (Kolosov et al., 1965). A caucasian squirrel feeds on acorn, fruits and seeds, so it plays an important role in forest ecosystems as a seed dispenser(Amr et al., 2006; Miyaki, 1987).
Recently, Caucasian squirrel is used as a companion rodent. This triggered the need to provide the baseline data on its organs for further research, especially the pathogenesis of the parotid and sublingual glands tumours (Elwell and Leininger, 1990).
The objective of this research was to determine the histochemical and volumetric properties of the parotid and sublingual salivary glands of Caucasian squirrel and to identify if quantitative or qualitative differences exist between this species and other rodents or mammals.
Section snippets
Samples preparation
Totally, five male Caucasian squirrels with an average weight 255 ± 18 g were used in the study. The animals were referred to private veterinary clinics and dead due to diseases unrelated to the salivary gland lesions such as luxation, trauma and severe bleeding. The animals were dissected immediately after death, and the parotid and sublingual salivary glands were identified, and their topographical position was imaged using a digital camera (Nikon, SR, 250, Japan). Afterwards, the glands were
Topographical observations
Based on the findings, the parotid gland in the Caucasian squirrel had an irregular shape. It originated from the base of the external ear and extended over the caudal border of the mandibular ramus (Fig. 1). The parotid duct had passed over the masseteric muscleو dorsal to the buccal branches of the facial nerve (Fig. 1, Pd). The sublingual glands, as two oval masses, were located in the intermandibular space, and rostral to the mandibular glands (Fig. 1, SLG).
Histological and histochemical observations
Histochemical observations of the
Discussion
In the present work, histological, histochemical and stereological properties of the parotid and sublingual salivary glands in the Caucasian squirrel (Sciurus anomalus), were depicted. Extensive researches has been performed into the structure and configuration of the salivary glands in different animals and the results indicate some similarities and differences between species. According to the observation in the present study on the parotid and sublingual glands of the Caucasian squirrel, in
Conclusion
In the Caucasian squirrel two parotid glands had a unique morphology with seous acini secrating sulphated and a little bit neutral mucins contents and sublingual gland had an oval shaped appearance with mucous acini associated with few seroud demilunes secrating neutral and non-sulfated acidic mucins. For the first time, this study evaluated the parotid gland and sublingual gland in Caucasian squirrel using stereological methods; in most estimations, volumetric features of the parotid glands
Funding
The authors extend their appreciation to the deanship of Scientific Research at King Khalid University, Abha, KSA for supporting this work under grant number (R.G.P1/117/40).
Author statment
Diaa massoud: Conceptualization and Methodology; Diaa Massoud and Fayez shaldoum: Data curation, Software, and Writing- Original draft preparation; Attalla F. El-kott and Diaa Massoud: Visualization, Investigation; Attalla F. El-kott: Supervision; Diaa Massoud: Writing- Reviewing and Editing, Attalla F. El-kott: Funding acquisition.
Declaration of Competing Interest
The authors delare that there is no conflict of interest
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