| Summary: | The morphology of the farmed African catfish distal intestines and rectum was
investigated. The samples were dissected out and the tissue slices were
passed through graded ethanol, cleared in xylene, embedded in paraffin wax,
sectioned and stained for light microscopy. Grossly, the intestine was
subdivided into proximal, middle, distal and rectal regions based on palpable
thickness and diameter of the regions. No intestino-rectal valve was
observed; hence the rectum was not well defined. The histology revealed the
presence of tunica mucosa of simple columnar cells, lamina propria of
collagen fibres and muscularis mucosae of smooth muscle fibres; submucosa of
loose connective tissues and blood vessels; tunica muscularis of smooth
muscles in an inner circular and outer longitudinal arrangement; and a serosa
in all regions except the rectum and anus that presented tunica adventitia.
The mucosal folds were fingerlike to orange leaf shaped ingrowths into the
lumen on a transverse section. They decreased in complexity and height but
increased in width towards the rectum. The lining epithelium of the
intestinal tract was comprised of the absorptive simple columnar cells
containing goblet cells and intraepithelial lymphocytes. Some rectal simple
columnar epithelium contained supranuclear vacuoles while others contained
non-vacuolated cytoplasm. The goblet cells contained neutral and acid mucins,
and increased in number progressively towards the rectum. The anal tunica
muscularis contained mostly skeletal muscles.
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