Morphology of complex lymphoepithelial organs of the anal canal (“anal tonsil”) in the bottlenose dolphin, Tursiops truncatus

Authors

  • Daniel F. Cowan MD, CM,

    Corresponding author
    1. Department of Pathology and The Marine Biomedical Institute, The University of Texas Medical Branch, Galveston, Texas 77555
    2. Texas Marine Mammal Stranding Network, Galveston, Texas 77551
    • Division of Surgical Pathology, Department of Pathology, E88, University of Texas Medical Branch, Galveston, TX 77555–0588
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  • Toby L. Smith

    1. Department of Pathology and The Marine Biomedical Institute, The University of Texas Medical Branch, Galveston, Texas 77555
    2. Texas Marine Mammal Stranding Network, Galveston, Texas 77551
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Abstract

A complex of lymphoepithelial organs, the “anal tonsils,” is a consistent structure in the anal canal of the bottlenose dolphin, Tursiops truncatus. This complex occurs as a circumferential cluster of discrete tonsil like aggregations of lymphoid tissues, together with epithelial ducts (“crypts”) and occasional mucus secretory units in the extreme lower portion of the intestinal tract. These structures are concentrated in the segment lined by stratified squamous epithelium and extend for a variable distance cephalad from the anal aperture. The tonsils appear to be most active, judged by the amount of lymphoid tissue present, in young animals. Depletion of lymphocytes and cystic enlargement of the crypts, probably representing functional as well as morphological involution, is a consistent feature of older animals. © 1995 Wiley-Liss, Inc.

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