Chapter 21, Problem 1WWTS

Summary Introduction

Introduction:

The human system needs to protect itself from pathogenic microorganism or foreign invaders that can cause serious illness to death. In order to fight against the pathogens, the human system has a well-organized system called the immune system or lymphatic system that consists of a group of cells that inhabit in all organs of our body. Apart from these, our system has some external barriers to fight against the foreign invaders and protect our body. They are mucous membranes and skin; they act as physical barriers to invasion of microbes.