Please respond to Each Question:

1. Describe the physical, mechanical, and biochemical barriers that provide the first line of defense against damage and infection.

2. All students read the American Cancer Society article on tumor markers available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2902207/ And
Discuss the different uses of tumor markers and share Your opinion on whether tumor markers should be used for general population screening.