There is growing interest in approaching research on language contact and change through an epidemiological, population-based model which takes 'linguistic items' or equivalent as a key unit of analysis. This paper explores a number of elements of such a model, with particular attention to a set of biases which may act as conduits or filters for the transmission of linguistic items in populations. These include a number of such biases introduced in recent models of cultural transmission: a threshold bias, a sociometric bias, a model bias, a conformity bias, and a frequency bias. A further bias is of particular relevance to language, but is argued to be equally important for models of cultural transmission in general. This is a context bias, which takes into account the kind of structural context which a given item or variant presupposes for its function. The presence or absence of a relevant structural context will determine the likelihood that the item will be transmitted, and if so to what degree of faithfulness. These biases may help toward characterising an anatomy of cultural epidemiology which makes explicit the relation between individual cognition, social processes, and population-level structure.