Question

Describe the homeostatic mechanisms that create a microbiota free environment in blood and lymph.

Answer 1

The lymphatic and vascular systems work together to maintain homeostasis as well as a microbiota free environment in the body. The lymphatic system plays an integral role in the immune functions of the body. It is the body's first line of defense against diseases. Blood cells, especially the white blood cells, defend the body from unwanted pathogens by either engulfing the germs or by triggering a chain reaction in the immune system which finally overcome the foreign antigen and prevent diseases.

The body has three lines of defense, the first being outer barriers like the skin, the second being non-specific immune cells like macrophages and the third being specific immune cells called lymphocytes which include B-cells and T-cells. These cells are present in the lymphatic system and they recognize the pathogen invading specifically and then initiate a defence reaction in the body that is specific to that particular invader.

So, blood and lymph work together to maintain homeostasis in the following way-

When pathogens breach the first line of defence [skin and mucus membranes] and enter the blood, they have to encounter the second line of defence, that is , the macrophages and dendritic cells. The dendritic cells engulf the invading pathogen and digest it. The dendritic cells select pieces of the invader [antigen] and put them on their surface. The dendritic cells carrying the antigen go back to the lymph nodes and now the lymphocytes, T-cells and B-cells, activating them for full immune response. These cells overpower the pathogen and help the body get free from the disease.