Final answer:
The major lymph node groups involved in the spread of pathology from the external genitalia are the inguinal lymph nodes, while for the gonads, it is the para-aortic lymph nodes. The first palpable group of lymph nodes in each of these drainage pathways are the inguinal lymph nodes and the lumbar lymph nodes, respectively.
Step-by-step explanation:
The major lymph node groups that can be involved in the spread of pathology from the external genitalia include the inguinal lymph nodes and the iliac lymph nodes. The inguinal lymph nodes are the first palpable group of lymph nodes in the drainage pathway from the external genitalia. They are located in the groin area and can become enlarged in response to infections or other pathologies.
For the gonads, the major lymph node groups involved in the spread of pathology are the para-aortic lymph nodes. These lymph nodes are located along the aorta, near the kidneys. The first palpable group of lymph nodes in the drainage pathway from the gonads are the lumbar lymph nodes, which are located in the lower back.