From which layer do the kidney and gonads develop?

The kidney and gonads develop from the mesoderm, which is one of the three primary germ layers in the early embryo. The mesoderm is responsible for forming various structures in the body, including muscles, bones, the circulatory system, and the urogenital system, which encompasses the kidneys and gonads (testes and ovaries).

During embryonic development, the kidney forms from the intermediate mesoderm, while the gonads arise from the genital ridge, which also derives from mesoderm. This particular layer provides the necessary cells and signaling needed for the proper formation of these organs.

In contrast, the ectoderm primarily develops into the nervous system and skin, while the endoderm forms the lining of the digestive tract and associated organs. The term "exoderm" is not recognized in embryological terminology, which further clarifies the mesoderm as the correct answer. Understanding the differentiation of these germ layers is crucial for grasping the developmental biology of the organs.