This study supports the view that, in cases of tinea capitis due to a Microsporum canis infection, ectothrix arthroconidium formation is extrapilary and arises from intrapilary hyphae. The hyphae of M. canis perforate and digest the hair cuticle to alter its appearance from a normally identifiable structure of imbricated cells with a distal free border, to a grossly altered and pathological layer. Conidium production mainly takes place outside the hair shaft and forms thick clusters between the cuticular tiles. Finally, a shaft of conidia is formed around the hair. The cuticular covering of such a conidium sheath belongs to the root sheath of the hair follicle, and not to the hair structure proper.
Vismer, Hester F.
"Microsporum Canis Scalp Ringworm: Its Primary or Secondary Ectothrix Character,"
Scanning Microscopy: Vol. 7:
2, Article 22.
Available at: https://digitalcommons.usu.edu/microscopy/vol7/iss2/22