Final answer:
Blood cultures are ordered from the microbiology department, where the presence of microorganisms in the blood can be cultured and identified.
Step-by-step explanation:
Blood cultures are typically ordered to detect the presence of microorganisms in a patient's blood. To perform this analysis, blood samples are sent to the microbiology department. In the microbiology lab, the blood is cultured under specific conditions that allow for the growth and identification of bacteria, viruses, and other pathogens. If a pathogen is present, it can be further analyzed to determine its sensitivity to various antibiotics, which aids in the selection of appropriate treatment.