الفهرس 
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Abstract
The present study was carried out on the lingual tonsils of 15 clinically healthy buffaloes of both sexes. Their age ranged from 40 days to 10 years. The animals were classified into 3 age groups: group 1: of 5 buffalo calves of 40-60 days old, group 2: of five buffalos of 2-3 years old and group 3: of fives buffalos of 5-10 years old. The samples were prepared for histological and ultrastructure examination. This work showed that, the lingual tonsils of the buffalo were localized on the dorsal surface of the pharyngeal part of the tongue as spherical elevated masses each one contained a single crypt. After 5 years old the tonsils regressed and became flattened area with slit like crypt. The buffalo lingual tonsils were formed from surface epithelium of stratified squamous non keratinized epithelium continuous with the cryptal epithelium. These epithelia changed to keratinized after 5 years old. There was a lymphocytic infiltration in the crypt epithelium which was limited in young, highest in middle age forming lymphoepithelium or reticuloepithelium and absent in animals older than 5 years. The parenchyma was enclosed with incomplete capsule and formed from lymphoid follicles and diffused lymohocytes supported with reticular fibers in young age. The lymphoid follicles were formed from lymphocytes with reticular dendretic cells and macrophage. The lymphoid tissue increased in size at 2 years old with clear germinal centers and regressed at 5 years where several apoptotic lymphocytes were observed. This lymphoid tissue disappeared completely at 10 years. The interfollicular areas were rich in high endothelial venules till disappearance of lymphoid tissue. Mucous glands associated with the lingual tonsils in the different ages with their ducts open into the surface epithelium or the top of the crypt. The involution of the lymphoid tissue with age was associated with proliferation of connective tissue. The lingual tonsils showed maximum immunological response at the middle age of 2 years where it may be useful to apply oral vaccination in this age. After 10 years there was a complete involution of the lymphoid tissue and the tonsils lost their function.