Crossword-Solution: PLEURAE 7 letters, 3 clues 🏆 scrabble score: 9

Foreign bodies ulcerating through may reach the lung without pleural leakage because of the sealing together of the visceral and parietal pleurae.

Correlated with the presence of the genital pleurae there is a pair of vascular folds of the basement membrane proceeding from the dorsal wall of the gut in the post-branchial portion of the branchio-genital region, and from the dorsal angles made by the pleural folds with the body-wall in the pharyngeal region; they pass, in their most fully developed condition, to the free border of the genital pleurae.

Since there are many species which do not possess these genital pleurae, the question arises as to whether their presence or their absence is the more primitive condition.

Without attempting to answer this question categorically, it may be pointed out that within the limits of the family (_Ptychoderidae_) which is especially characterized by their presence there are some species in [v.03 p.0239] which the genital pleurae are quite obsolete, and yet lateral septa occur (_e.g._ _Ptychodera ruficollis_), seeming to indicate that the pleural folds have in such cases been secondarily suppressed.

The _pleurae_ very closely resemble the pericardium except that the fibrous outer coat of the parietal layer is not nearly as strong; it is closely attached to the inner surface of the chest walls and mesially to the outer layer of the pericardium; above it is thickened by a fibrous contribution from the scalene muscles, and this forms the _dome of the pleura_ which fits into the concavity of the first rib and contains the apex of the lung.