Final answer:
Parietal nodes are lymph nodes located in the retroperitoneal space, playing a role in filtering lymphatic fluid and are found near significant blood vessels. They are part of a larger lymphatic system that includes the spleen, which filters blood and responds to pathogens.
Step-by-step explanation:
The parietal nodes mentioned in the question refer to lymph nodes located in the retroperitoneal space, which is the area behind the peritoneum, a membrane that lines the abdominal cavity. These lymph nodes are situated near important blood vessels and serve as filters for lymphatic fluid, trapping harmful substances and facilitating the development of immune responses.
Within the retroperitoneal space, certain organs such as the pancreas, duodenum, and parts of the large intestine like the ascending and descending colon and rectum can be found. The lymph nodes themselves are part of a larger lymphatic system that includes other secondary lymphoid organs such as the spleen. The spleen is also involved in filtering blood and hosting immune responses against blood-borne pathogens.