A hollow organ is one that has a lumen. The lumen may be either large or small or inconspicuous because the edge of the sectioning. One way of recognizing an occult hollow organ is to see if it has a lining of epithelium (red in the diagram above) that is most likely to be an internal lining.
Hollow organs can be recognized as such by a distinct lumen surrounded by definitive epithelium and which is followed by muscle and probably cartilage. They include such tissues as found in the digestive, reproductive, respiratory and urinary systems. It is important to be on the lookout for semicircular specimen (rather than circular, with distinct lumina) especially in those organs that are large and can therefore not be obtained intact in their circular form during tissue processing - e.g. stomach, uterus etc. The distinguishing feature for such specimen will be the distinct epithelial covering which always lies on top of luminal apex.
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