Final answer:
A cell with prominent grainlike structures in its cytoplasm is a granulocyte. Granulocytes, which include neutrophils, eosinophils, and basophils, are recognized by their cytoplasmic granules and are part of the immune system's first-responders.
Step-by-step explanation:
The cell that contains prominent grainlike structures in its cytoplasm is a granulocyte. Granulocytes are characterized by their granules, which are cytoplasmic inclusions, and a lobed nucleus. They are part of the immune system and act as first-responders during injury or infection. There are three types of granulocytes: neutrophils, eosinophils, and basophils. Among them, neutrophils have small granules that stain light lilac, eosinophils have granules staining reddish-orange, and basophils have large granules that stain dark blue to purple. In contrast, agranulocytes, which include lymphocytes and monocytes, contain fewer and less visible granules in their cytoplasm.