AAMC FL Practice Exam

Which organ systems are primarily developed from the endoderm?

1. Muscular and skeletal systems

2. Digestive and respiratory systems

3. Circulatory and reproductive systems

4. Nervous and integumentary systems

The correct answer is: Digestive and respiratory systems

The correct answer highlights that the digestive and respiratory systems are primarily developed from the endoderm. During embryonic development, the three primary germ layers formed are ectoderm, mesoderm, and endoderm. The endoderm is specifically responsible for giving rise to structures of the gastrointestinal tract and associated organs, such as the liver and pancreas, as well as the respiratory tract, including the lungs. This understanding stems from the fundamental principles of developmental biology, where each germ layer differentiates into specific tissues and organs. The digestive system, which begins with the foregut, midgut, and hindgut, originates directly from the endoderm. Similarly, the respiratory system develops from the ventral side of the foregut, differentiating into the trachea, bronchi, and lungs. Other options mention systems that arise from different germ layers. For example, muscles and bones (muscular and skeletal systems) arise from the mesoderm, as do components of the circulatory and reproductive systems. The nervous system is derived from the ectoderm, and the integumentary system (skin and related structures) also develops from the ectoderm. Recognizing the embryological origins of these systems is crucial for understanding developmental processes in