During which stage of neutrophilic development does the nucleus take on a kidney bean shape with lavender secondary granules?

The stage of neutrophilic development where the nucleus takes on a kidney bean shape and features lavender secondary granules is the metamyelocyte stage. At this point in development, the neutrophilic precursor shows significant morphological changes. The nucleus begins to indent and form a distinctive shape that resembles a kidney bean, which is characteristic of the metamyelocyte.

Additionally, this stage is marked by the appearance of secondary granules that are typically smaller and more diffuse than those found in earlier stages, contributing to the lavender coloration when viewed under a microscope. These secondary granules are important for the future function of the mature neutrophil, as they contain various enzymes and proteins that aid in the immune response.

In contrast, the band stage is when the nucleus is more elongated and still retains a U-shape rather than the kidney bean shape. The myelocyte is earlier in the development process and features a round nucleus with minimal indentation, while the promyelocyte shows large primary granules without the distinct secondary granules associated with the metamyelocyte. Thus, the specific characteristics of the metamyelocyte, including its unique nucleus shape and secondary granule presence, help define this particular stage in neutrophil maturation.