Penetration gland functions

Although secretions from the (so-called) penetration glands undoubtedly play a role in penetration, their nature and function are largely unknown. The glands have been particularly studied in H. diminuta and H. nana (205, 888, 889). In most species, glands have been described as syncytial (Fig. 8.16) or multicellular, but in H. nana they appear to be unicellular (205). One or two pairs of ducts may be present and these are supported by microtubules. Secretion has been described as being holocrine in some species (as in trematode miracidia and cercariae) but apocrine and merocrine secretory mechanisms have also been proposed for others (205, 242, 443). 

In the second decade, the researehers were able to relate the growth retardation to lowered funetion of the thyroid. TTiyroid tumors, albeit nonmalignant, were widespread. Clearly thyroid function had been impaired by the ehildren s exposure to the penetrating radiation of fallout particles and the ingested radioiodine that accumulated in their developing thyroid glands. 

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