Anatomical localization and histological characteristics of the porcine tonsils. (a) Median section through a porcine head. The pharyngeal tonsil (large oval area) and tubal tonsil (small oval area) in the nasopharynx, the tonsil of the soft palate at the oral side of the soft palate (larger rectangular area, detail shown in upper right insert), and the lingual tonsil (smaller rectangular area) and the paraepiglottic tonsil at the lateral base of the epiglottis (encircled area, detail shown in the lower right insert) are indicated. (b–f) Histological sections through parts of the lingual tonsil (b), the tonsil of the soft palate (c), the pharyngeal tonsil (d), the tubal tonsil (e), and the paraepiglottic tonsil (f), respectively. The encircled areas in (c), (d), and (f) delineate a tonsillar follicle with a central crypt.