Figure 4

Skeletal microstructures of orifice tube structures. (A) Most distal part of the orifice. (B) Enlarged tube wall shown in the white square in (A). (C) Smooth growth edge and rough lower outer side of the tube wall. (D) Enlarged growth edge in the white square in (B). (E) Enlarged outer side of the tube wall in the white square in (A) showing attachment scars of desmocytes in the lower part of the tube wall. (F) Rough surface of the lower outer side of the tube wall comprising irregularly arranged bundles of fibrous crystals.