Final answer:
Dendritic cells sample their extracellular environment through phagocytosis and macrophagocytosis.
Step-by-step explanation:
Dendritic cells sample their extracellular environment for molecules and cells through phagocytosis and macrophagocytosis. Phagocytosis is the process by which cells engulf and digest pathogens or cellular debris. Macrophagocytosis refers specifically to the process carried out by macrophages, which are a type of phagocytic immune cell. Dendritic cells, along with macrophages and other phagocytic cells like neutrophils, can engulf and digest pathogens to prevent infection.