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Lateral view of the nasopharynx of the camel showing the pharyngeal (PhT, black circle) and the tubal (TT) tonsils. NS nasal septum, ATO auditory tube openning; b–e histological microphotographs of the pharyngeal tonsil (H&E staining). SE squamous epithelium, PF primary follicle, SF secondary follicle, G pharyngeal gland, PT parafollicular tissue
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The tonsils, located around the pharyngeal cavity, constitute the first defence barrier against intruding microorganisms and antigens. The present work aimed to study the anatomical and histological aspects of camel tonsils in order to elucidate their role. The study was carried out on 12 camel heads fixed by infusion with 10 % neutral buffered for...
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Purpose
The adenoids, or pharyngeal tonsils, consist of a pad of lymphoid tissue, located on the posterior pharyngeal wall of the nasopharynx. During childhood, the adenoid pad serves as a contact site for the soft palate to assist with velopharyngeal closure during oral speech. During adenoidal involution, most children are able to maintain approp...
Citations
... Notably, the pharyngeal tonsils are also the main inductive site of intranasal immunization, which can produce antibodies after being stimulated by antigens, thereby preventing respiratory infections [7,8], and can also generate immune responses at the distal mucosal sites through the common mucosal immune system, supplying them with activated memory and effector B cells [8,9]. In recent years, studies on the pharyngeal tonsils have involved many animals, including camelus dromedaries [10], bovine [3,11], goat [12,13], ovine [13,14], porcine [13], equine [15], canine [16] and feline [13]. These studies mainly focused on the anatomical localization, histological features and ultrastructure of the pharyngeal tonsils, but the expression and distribution of immune-related molecules in the pharyngeal tonsils have also been studied. ...
Background: The pharyngeal tonsils, located in the nasopharynx, can effectively defend against invading pathogens of the upper respiratory tract, and play an important role in mucosal immunity of the respiratory tract. IgA and IgG are two important effector molecules of mucosal immunity, and have multiple immune functions. This study aimed to explore the distribution patterns of IgA and IgG antibody-secreting cells (ASCs) in the pharyngeal tonsils of Bactrian camels of different ages. Twelve Alashan Bactrian camels were divided into the following three age groups: young (1-2 years), pubertal (3-5 years) and middle-aged (6-16 years). The structural features of the pharyngeal tonsils were carefully observed by anatomical and histological methods, the age-related distribution of IgA and IgG ASCs in the pharyngeal tonsils was detected and compared using immunohistochemical techniques, and their densities were analyzed using statistical methods.
Results: The results showed that the pharyngeal tonsils of Bactrian camels were located at the posterior wall of the top of the nasopharynx, and mainly composed of epithelium and lamina propria. The epithelium was mainly pseudostratified ciliated columnar epithelium. Interestingly, some of the epithelium was infiltrated by immune cells, forming the reticular epithelium. There were connective tissues and abundant lymphoid tissues in the lamina propria, and a few blood vessels, groups of glands and their excretory ducts were distributed among the connective tissue. In the pharyngeal tonsils of all age groups, IgA and IgG ASCs were mainly clustered or diffusely distributed in the subepithelial regions of reticular epithelium (region A) and around the glands (region C), scattered in the subepithelial regions of nonreticular epithelium (region B), and distributed sporadically in the extrafollicular regions (region D). Their distribution densities in these four regions were significantly decreased in turn (P<0.05). However, the densities of IgA ASCs were significantly higher than IgG ASCs in the same region (P<0.05), and the distribution densities of these two ASCs in each region of the pharyngeal tonsils gradually increased from young to pubertal group, reached a peak in the pubertal group, and then gradually decreased with age.
Conclusions: The results confirmed that IgA and IgG ASCs were distributed in each region of the pharyngeal tonsils of Bactrian camels, which were conducive to forming a complete immune defense barrier in the pharyngeal tonsils, but the subepithelial regions of reticular epithelium and glandular regions in the pharyngeal tonsils were the primary regions for the colonization and exertion of immune function of IgA and IgG ASCs. IgA might be a significant component of mucosal immune responses in the pharyngeal tonsils of Bactrian camels. These findings will provide support for further studies on the immunosenescence and immune response mechanisms of pharyngeal tonsils of Bactrian camels.
... Nevertheless, the available information about the morphology of the soft palate and palatine tonsils of goats are scanty. The palatine tonsil of goat (Indu et al., 2018), sheep (Kumar et al., 2008), buffalo (Girgiri & Kumar, 2018) and camel (Achaaban et al., 2016) has been studied by light microscopy. Moreover, the nasopharyngeal tonsils; tubal and pharyngeal tonsils, of goat (Indu et al., 2015;Indu et al., 2017;Kumar et al., 2006) and buffalo (Girgiri & Kumar, 2019) have been studied by light and SEM. ...
... The palatine tonsil of goat lied in the lateral wall of the oropharynx and was represented by an elevation of the pharyngeal mucosa. In agreement to our results, the palatine tonsils of goat, sheep, bovine, yak and camel are located in the lateral wall of oropharynx between the palatoglossal and the palatopharyngeal arch (Achaaban et al., 2016;Casteleyn et al., 2011;Cocquyt et al., 2005;Habel & Budras, 2003;Sun et al., 2019). This significant position of the palatine tonsils at the entrance of the gastrointestinal tract allows close contact with ingested bacteria and other antigens (Cocquyt et al., 2005). ...
... The palatine tonsil of goat is larger than that in sheep, while that of ox and camel is large, bi-lobed, and contains a central cavity (Achaaban et al., 2016;Casteleyn et al., 2011). In agreement to our findings, the palatine tonsil of goat, bovines and camel has macroscopic crypt openings that lead to the underlying crypts (Achaaban et al., 2016;Casteleyn et al., 2011). ...
The present study was carried out to study the morphology of the goat's soft palate and palatine tonsil by gross anatomy, morphometry, light and scanning electron microscopy (SEM). Twelve heads of normal adult (18–24 months) apparently healthy goats of both sexes were collected from local commercial slaughterhouses in Qena Governorate, Egypt. The oral cavity was dissected, and samples were collected for both light and SEM. The soft palate of the goat formed the caudal continuation of the hard palate. It was relatively short, it extended from the level of the caudal border of the last upper molar tooth to terminate caudally against the base of the epiglottis. The oral mucous membrane of the soft palate was covered by non‐keratinized stratified squamous epithelium. The lamina propria and submucosa contained connective tissue fibers, diffuse and nodular lymphatic tissue, striated muscle fibers, and a large number of mucous and serous palatine glands. By SEM, the ventral surface had several rounded openings occupied by flower‐like structures. These openings represented the entrances to the palatine glands. The palatine tonsil was large and protruded from a fossa in the lateral wall of the oropharynx. It had 2–3 elongated irregular openings that lead to the underlying crypts. These crypts were well‐developed and lined by non‐keratinized stratified squamous epithelium. The epithelium of the tonsillar crypts directly covered lymphoid tissue and was infiltrated by lymphocytes. Tonsillar glands of pure mucous type were demonstrated. In conclusion, the study provides the basic morphological features of soft palate, as well as the palatine tonsil of the goat by gross observation, light and SEM. The palatine tonsils of goat were well‐developed with extensive crypt system, suggesting their essential role in the immunological response against antigens that enter through the oral cavity. The current findings may be useful to understand the role of the palatine tonsil in immunity and disease pathogenesis.
Research Highlights
The study reported the basic morphological features of soft palate and palatine tonsil of goat.
The ventral surface of the soft palate had several rounded openings occupied by flower‐like structures.
The palatine tonsils of goat were well‐developed with extensive crypt system.
The findings might help to understand the role of the palatine tonsil in immunity and disease pathogenesis.
... The dromedary camels (one-humped camels) are important livestock animal and there are various studies including many aspects of sciences (1)(2)(3)(4). There are a lot of literatures about different anatomical structures of camel (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). The camel has two species, one humped camel found in Africa, Arabia, Iran, Afghanistan and India and the twohumped camel found in Central Asia, reaching up to Mongolia and Western part of China (17). ...
The purpose of the current work is to study mucosa of the camel hard palate morphology by gross anatomy, morphometric analysis in addition to light and scanning electron microscopy (SEM). Ten heads of freshly slaughtered camels were collected from Zagazig abattoir. The selected camels were in good general condition, their ages were ranged around three to five years. Anatomically, the hard palate was elongated and it could be divided into a narrow rostral part and a caudal wide part with about 13-14 transverse palatine ridges. The dental pad was a crescentic thick plate at the rostral end of hard palate. The incisive papilla is triangular prominence situated behind the dental pad in the median plane and is surrounded by shallow groove, microscopically, the mucosa of hard palate consisted of a keratinized squamous epithelium. The submucosa comprised from vascularized collagenous connective tissues run in various directions. The soft caudal part of the hard palate is distinguished by lobulated serous acini and it was rich in adipocytes. Scanning electron microscopy demonstrated the stratification of the epithelium; with excessive desquamation and sloughing of the epithelial cells. By high magnification, the microplicae system was inform of irregular surface separated by septae.
... Whereas the mucous membrane of the pharynx has a defense mechanism where the tonsils are different according to their position like the palatine, lingual, tuber-tonsil, and para-epiglottic tonsils that are an aggregation of various tonsils called the Waldeyer's ring (Achaaban et al., 2016;Kumar & Timoney, 2005;Palmer et al., 2009). ...
The study aimed to explore the ultrastructure of the donkeys' palatine tonsils. Palatine tonsils of five male donkeys (5 years old) were investigated macroscopically and microscopically. The tonsils appeared as a dome shape with slight elevation and a circular opening on the surface of the oropharynx. The central tonsillar crypt appeared on the medial side of the palate-pharyngeal folds and the floor of the oropharynx. The external surface of the palatine tonsil had different sizes of mucosal folds, some grooves directed to drainage at the tonsillar opening, and the tonsil crypt opening was a crescentic or irregular oval shape. The outer surface was covered by stratified squamous epithelium and modified to be reticular epithelium invaded by lymphocytes in the crypt called lympho-epithelium. The tonsil crypt had aggregated lymphoid nodules, and the cryptal epithelium has surrounded by diffused lymphocytes and hassles corpuscles-like structures. The lymphocytes infiltrated into different layers of the cryptal epithelium and transformed into reticular or lympho-epithelium. The organized lymphoid nodules were primary and secondary, and the secondary ones had a light germinal center. The interfollicular area had many high endothelial venules and blood capillaries. The endothelial venules were lined by simple cuboidal epithelium and had lymphocytes. The blood capillaries had red blood cells and neutrophils. The tonsil was surrounded incompletely by a connective tissue capsule with mucous glands under that capsule. In conclusion, the epithelial lymphocyte infiltration, crypt epithelium, lymphoid nodules, and intra-follicular area of the donkey's palatine tonsils indicate the humoral and cell-mediated immunological process.
... Tonsils are major components of mucosa-associated lymphoid tissue (MALT) comprised of special lymphoid aggregates integrated into the different parts of pharyngeal mucosa of the upper aero-digestive tract [1]. Their immune specialised cellular architecture, including reticular crypt epithelium, germinal centres in B-cell follicles, and extra-follicular areas rich in T-cells, resembles that of lymph nodes, although the absence of afferent lymphatics implies a reliance on direct interaction with environmental antigens [2]. ...
... The epithelial lining of the paraepiglottic tonsil towards the outer surface was stratified squamous keratinised to non-keratinised type as reported in the sheep [18,23], pig [19,24] and camel [1,25,26]. The stratified squamous keratinised epithelium was comprised of a varying number of rows in strata spinosum, granulosum and corneum as reported in the sheep except for stratum basale [18]. ...
The paraepiglottic tonsil present on either side of the base of the epiglottis constitutes a small portion of the mucosa-associated lymphoid tissue. The present study was conducted on the paraepiglottic tonsils of 12 adult buffaloes of the local mixed breed to explore its basic histomorphological, histochemical, and ultrastructural characteristics and to compare with other tonsils of the oral region to ascribe immunological function. The tonsil mucosa was lined by partly stratified squamous keratinised epithelium towards the outer surface and a stratified squamous non-keratinised epithelium towards the shallow crypts. The non-keratinised epithelium modified into reticular type due to infiltration of underlying lymphoid tissue was characterised by the predominance of the lymphoid cells, interrupting basement membrane and indistinct strata. The reticular epithelium at places presented a spongy appearance. The loose irregular connective tissue of propria-submucosa was mainly comprised of glandular and lymphoid tissue. The lymphoid tissue was mainly in the form of isolated lymphocytes, diffuse aggregations, and lymphoid follicles. The inter-follicular areas showed the presence of high endothelial venules. The sero-mucous type of glandular acini presented a strong reaction for glycogen, acidic mucosubstances, weakly sulfated mucosubstances, mucin, and the presence of more than 4% cysteine in their secretions. The tonsils under scanning electron microscopy presented an undulating appearance due to the presence of crest and folds. Higher magnification revealed squamous cells having various patterns and arrangements of microplicae. Small pits visualised on the mucosal surface represented openings of the glandular ducts. The cells towards the lumen of some glandular ducts appeared whorl-like where typical microplicae were absent. The transmission electron microscopy of different strata of different types of epithelia showed varying cell organelles, especially the mitochondria, endoplasmic reticulum, Golgi apparatus, and few filaments. The structural features of the tonsil were similar to those of other oral tonsils and suggested their immunological role, which might be of importance to local immunity.
... The dromedary, Camelus dromedarius, is well-known for its adaptations to harsh desert conditions. The adaptations include structural (Alsafy et al., 2013;Achaaban et al., 2016), physiological (Adamsons et al., 1956;Schmidt-Nielsen et al., 1956), and behavioral traits (Mitchell et al., 2002;Djazouli Alim et al., 2012). The natural adaptations of the dromedaries were anthropologically exploited via (1) its domestication around 2000-3000 years B.C., (2) the expansion of their uses, and (3) the development of unique populations (i.e., camel-types) (Uerpmann and Uerpmann, 2002;Almathen et al., 2016;Orlando, 2016). ...
Dromedary camels are outstanding livestock that developed efficient abilities to tolerate desert conditions. Many dromedary camel-types (i.e., named populations) exist but lack defined specific breed standards, registries, and breeders’ governing organizations. The breed status of dromedary camel-types can partly be assessed by exploring mitochondrial DNA (mtDNA) variation. Accordingly, this study aimed to examine the breed status and the inter-population relationships of dromedary camel-types by analyzing sequence variation in the mtDNA control region and in three coding genes [cytochrome b, threonine, and proline tRNA, and part of the displacement loop (D-loop)] (867 bp region). Tail hair samples (n = 119) that represent six camel-types from Kuwait were collected, extracted, sequenced, and compared to other publicly available sequences (n = 853). Within the sequenced mitochondrial region, 48 polymorphic sites were identified that contributed to 82 unique haplotypes across 37 camel-types. Haplotype names and identities were updated to avoid previous discrepancies. When all sequences were combined (n = 972), a nucleotide diversity of 0.0026 and a haplotype diversity of 0.725 was observed across the dromedary-types. Two major haplogroups (A and B) were identified and the B1 haplotype was predominant and found in almost all dromedary-types whereas the A haplotypes were more abundant in African regions. Non-metric multidimensional scaling revealed an increased similarity among Arabian Peninsula “Mezayen” camel-types, despite their defining coat colors. The relationships among dromedary camel-types can partly be explained by mtDNA. Future work aimed at a deeper understanding of camel-type breed status should focus on a high number of nuclear markers.
... Despite their importance, Ibrahim and Nakamuta (2018) in a study examining the mucosa of the nasal vestibule of dromedary camel did not refer to the presence of these structures. Similar to humans, camels have been shown to have a full set of tonsils covering most of their oropharyngeal mucosa (Achaaban et al., 2016). The ability of camel tonsils to mediate a strong immune response was suggested by their cellular composition (Zidan and Pabst, 2020). ...
The lining mucosa of the nasal cavity performs important roles for the host adaptation to the external environment. Camels are unique in their adaptation to the lifestyle of nomadic deserts. The present study aimed to evaluate the distribution pattern of T lymphocytes and S-phase proliferating cells within the nasal mucosa of camel using antibodies against CD3 and PCNA, respectively. The mucosa of the rostral, middle, and caudal parts of the nasal cavity was collected and processed for immunohistochemical staining. CD3-immunoreactive (-IR) cells were observed within the epithelium and lamina propria of all examined parts. However, the numbers of these cells were significantly higher in the rostral part of the nasal mucosa compared to its middle and caudal parts (P < 0.05). Such expression of CD3-IR cells within the rostral nasal mucosa was most pronounced within its lamina propria which also revealed aggregations of lymphoid cells. The increased frequency of CD3 expressing cells at the rostral part of the nasal mucosa suggests a potential role of the nasal vestibule in limiting the infection via constant clearance of encountered pathogens. PCNA-IR cells were mainly found within the basal layers of the nasal epithelium at the rostral part of the nasal cavity, though it showed a significant decrease in their frequency on moving caudad. The results of the present work will form a basis for assessment of various nasal pathologies affecting camels particularly those associated with increased rates of T lymphocytes infiltration and/or cell proliferation.
... In a comprehensive study, Achaaban et al. the lingual and the velar tonsils-whereas the group nasopharynx includes the pharyngeal and tubal tonsils, and the final group-the laryngopharynx-is formed of the paraepiglotic tonsil [27]. ...
... This tonsil is formed of a cluster of spheroidal lymphoid masses at the root of the tongue protrusion into the oropharynx ( Figure 2). The lingual tonsil of the dromedary camel is macroscopically visible at the root of the tongue in the form of several spherical macroscopic nodules protruding into the oropharynx [27] [28]. It has been reported that the crypt is not clearly visible in the lingual tonsil of the dromedary camel [27]. ...
... The lingual tonsil of the dromedary camel is macroscopically visible at the root of the tongue in the form of several spherical macroscopic nodules protruding into the oropharynx [27] [28]. It has been reported that the crypt is not clearly visible in the lingual tonsil of the dromedary camel [27]. Zidan and Pabst (2019) described more than one crypt in the dromedary's lingual tonsils [29]. ...
The camel economy is of considerable importance for arid countries. In the last decade, studies about camel immune system and immune responses have recorded increasing interest. However, drawing a comprehensive picture of the camel immune system remains far from reached. A major part of this re- view is to cover the studies of the primary and secondary immune organs and the markers of the camel immune cells and certain lymphoid tissues. At the same time, immune responses to different diseases and the nature of effective immunity were included, with an emphasis on the most important zoonotic diseases in camels such as MERS CoV; brucellosis. New findings on the di- versity mechanisms of camel immunoglobulin genes were addressed. How- ever, detail of the mechanism of MHC-restricted cellular immunity and the mechanism of B lymphocyte activation in camels await further attention. In- terestingly, the gross and the histological structure of the lymphoid tissues of the camel’s thymus, tonsils, and peyer’s patches have indicated significant differences from other animals in terms of structure and function. The most peculiar CD expression, such as LPAM-I, MAdCAM-1 and CX3CR1, in cer- tain camel cells and tissues refers to possible extraordinary mechanisms of immune hemostasis in camel in comparison to other ruminants. The widely applied immunodiagnostic techniques to control camel diseases and to assist in improving the camel resistance were considered. Extensive studies of the camel immune system were greatly hampered by lack of specific reagents to camel markers and low funds in the field of camel immunology.
... Some countries use camel for transport, tourism and camel races (Ahmad et al. 2010). Achaaban et al. (2016) in their study about camel tonsils described limited information about the lingual tonsils; bilobed structure beneath the mucosa of the root of the tongue forming clusters of macroscopic spheroidal lymphoid nodules. They added that the crypts were not clearly visible. ...
... In contrast to the findings of Achaaban et al. (2016), the current work showed that the crypts were prominent in different nodules of the lingual tonsils as documented with light and scanning electron microscopes. The presence of a crypt in each nodule of the lingual tonsil increases the epithelial surface area of the lingual tonsils that are exposed to foreign antigen as explained by Casteleyn et al. (2008). ...
Tonsils are located in the entrance of digestive and respiratory tracts forming Waldeyer’s ring that reacts against ingested or inhaled antigens. On occasion, tonsils may be a site of entry and replication for some pathogens. The lingual tonsils are a main constituent of the Waldeyer’s ring. Despite the immunological importance of the lingual tonsils, there is limited information about their structure in the one-humped camel. The lingual tonsils of 10 clinically healthy male camels (3–25 years) were collected and studied macroscopically and microscopically. Lingual tonsils were localized at the root of the tongue of camels of all ages in the form of several spherical macroscopic nodules protruding into the oropharynx. Each nodule possesses a single central crypt, covered with keratinized stratified squamous epithelium without any M cells and surrounded with an incomplete capsule. Each tonsillar crypt was lined with stratified squamous non-keratinized epithelium with lymphocytic infiltration forming patches of lymphoepithelium or reticular epithelium. Secondary lymphoid nodules extended under the apical epithelium. The interfollicular areas had diffused lymphocytes. Among these lymphocytes, high endothelial venules, macrophages, dendritic cells and plasma cells were observed. The organization of camel lingual tonsils in isolated units with separate crypts increases the surface area exposed to antigen. The present findings indicate a sustained immunological role of the lingual tonsils throughout the life of the one-humped camel.
... The tonsillar crypts reported in bovine lingual tonsil [9,23] have not been identified in sheep [24] and camel [14]. The latter studies in camel, however, differed with the recent findings [25] which reported poorly noticeable crypts. Tonsillar crypts were narrow epithelial diverticula which greatly increased the available surface area for accumulation of foreign antigen and subsequent antigenic stimulation [26]. ...
The study was conducted on lingual tonsil of six adult buffaloes (5-6 years of age) of the local mixed breed to explore histomorphological characteristics with functional significance. The mucosal surface of the lingual tonsil lined by stratified squamous keratinized epithelium was comprised of strata basale, spinosum, granulosum and corneum whereas towards the deeper folds the epithelium was stratified squamous non-keratinized. The latter epithelium modified into reticular epithelium especially toward the deeper portion and was characterized by a reduced number of epithelial cells, loss of distinct strata and heavy infiltration of lymphoid cells. The propria submucosa had loose irregular connective tissue along with glandular and lymphoid tissue. The lymphoid tissue was mainly distributed in the form of lymphoid follicles and diffused arrangement. The follicles of varying shapes and size showed darkly stained corona and lightly stained germinal centre were surrounded by parafollicular areas. The parafollicular areas possessed high endothelial venules (HEVs) with large sized endothelial cells having round to oval nuclei with distinctly visible centric or eccentric nucleoli. These HEVs are involved in trafficking of lymphocytes by transendothelial and interendothelial migration. The mucous glandular acini presented strong reactions for glycogen, acidic mucopolysaccharides, weakly sulfated mucosubstances, hyaluronic acid, sialomucins and mucins as demonstrated by different histochemical techniques. The secretions of acini also showed the presence of more than 4% content of cysteine. The presence of modified reticular epithelium and associated lymphoid tissue suggested that the lingual tonsil may be involved in sampling of oral antigens and transporting them to the underlying mucosal lymphoid tissue for processing and initiation of immune responses. The future microbiological studies may exploit the tonsil as a targeted organ for improved delivery of existing mucosal vaccines and development of new strategies for oral vaccines.
