This work consists of an approach to the concept of Social Defences, which consolidates one way of applying psychoanalytic thinking to human institutionality. The author briefly describes the path psychoanalytic theory takes towards the outline of this concept, to emphasise later the implications it has for health institutions. There is a statement about the importance of considering the ways in which individual defences tend to collude with the institutionalized group's unconscious mechanisms, where certain conditions will be determined for the containment of primitive states of mind. Emphasis is made about the possibility that these dynamics have concrete effects on the workers' capacities and health, on the patients' treatment, and mainly on the loss of meaning that these people experience in their link with this institution. Two vignettes are included to attempt an illustration of these dynamics.