Lymphology Association of North America (LANA) Practice Exam

At what stage of embryological development does the lymphatic system begin to develop?

1. End of the 10th week

2. End of the 5th week

3. End of the 12th week

4. Just before the end of gestation

The correct answer is: End of the 5th week

The lymphatic system begins developing during the end of the 5th week of embryological development. This developmental phase is essential as it marks the onset of important processes that contribute to the formation of lymphatic vessels and structures. During this time, mesenchymal cells differentiate into lymphatic endothelial cells, which are pivotal for forming the lymphatic capillaries and vessels. Understanding this timing is crucial in the study of embryology and lymphatic system pathology because early development impacts the overall structure and function of the lymphatic system later in life. The early formation of lymphatic structures is also linked to the immune system's development, making this knowledge significant in both clinical and educational settings. The other stages mentioned in the choices occur too late in the timeline for primary lymphatic development, as substantial lymphatic structures are already forming by the end of the 5th week. The coordination of development during this embryological period sets the groundwork for the subsequent stages of growth and differentiation of the lymphatic system.