The Tonsils Revisited: Review of the Anatomical Localization and Histological Characteristics of the Tonsils of Domestic and Laboratory Animals

Abstract

This paper gives an overview of the anatomical localization and histological characteristics of the tonsils that are present in ten conventional domestic animal species, including the sheep, goat, ox, pig, horse, dog, cat, rabbit, rat, and pigeon. Anatomical macrographs and histological images of the tonsils are shown. Six tonsils can be present in domestic animals, that is, the lingual, palatine, paraepiglottic, pharyngeal, and tubal tonsils and the tonsil of the soft palate. Only in the sheep and goat, all six tonsils are present. Proper tonsils are absent in the rat, and pigeon. In the rabbit, only the palatine tonsils can be noticed, whereas the pig does not present palatine tonsils. The paraepiglottic tonsils lack in the ox, horse, and dog. In addition, the dog and cat are devoid of the tubal tonsil and the tonsil of the soft palate.

Role of Palatine Tonsils as a Prion Entry Site in Classical and Atypical Experimental Sheep Scrapie

“…Indeed, due to their location, PTs play a key role in immunity as the site where vast amounts of antigens enter the body during feeding (17). In this regard, the high efficiency and effectiveness of the low infectivity titers of the scrapie brain homogenate utilized in our study underscore the role likely played by PTs as the entry and first replication site of the scrapie agent; this is also expected to hold true under natural conditions.…”

“…Whether a similar pathogenic behavior may also characterize classical and atypical scrapie under experimental or natural conditions is a matter of speculation, although the documented presence of PrP Sc and/or infectivity in the retina, tongue, and nasal mucosa during scrapie and BSE infection (15,16) would suggest that these highly innervated head districts could represent potential prion entry sites from which neuroinvasion may occur directly through the loco-regional nerve fibers, or after prion replication in the LRS. Furthermore, ruminant PTs, which are not present in rodents (17), exhibit a specialized epithelium, along with B and T lymphocytes, as well as follicular dendritic cells, which are organized into well-defined secondary follicles, thus likely creating a suitable microenvironment for the replication and the subsequent spread of prions, including the sheep scrapie agent (18). With this in mind, the present study had the main objective of defining the role of PTs in prion neuroinvasion from the oral cavity in classical and atypical scrapie.…”

Differential Persistence of Foot-and-Mouth Disease Virus in African Buffalo Is Related to Virus Virulence

“…The tonsil sinuses were swabbed individually by using nylon brushes (Cytotak Transwab) (27). Laryngoscopes used to depress the tongue were disinfected in citric acid and rinsed in PBS.…”

Attachment of Actinobacillus suis H91-0380 and Its Isogenic Adhesin Mutants to Extracellular Matrix Components of the Tonsils of the Soft Palate of Swine

“…Pigs have 5 sets of tonsils located around the oropharyngeal cavity in the so-called Waldeyer's ring, the largest being the tonsils of the soft palate (1), which are thought to be functionally equivalent to the palatine tonsils in humans (2). The tonsils of the soft palate of swine have as many as 200 branching crypts that end blindly within the lymphoid tissue beneath (3).…”

“…The epithelium of the crypts overlays a basement membrane (sometimes fragmented), which in turn is supported by an interstitial extracellular matrix (ECM) of various thickness, depending on the location in the tonsil (3). Despite studies of the ultrastructure and fine structure of the tonsils of swine (1,3) and studies into the ECM components and host cell receptors present in tonsils of other species (6)(7)(8), little has been done to characterize these components in the tonsils of the soft palate of swine.…”