Final answer:
The body uses defecation to eliminate microbes through feces, where peristaltic movements expel both waste and harmful microorganisms as part of the first line of defense.
Step-by-step explanation:
The body eliminates microbes through feces as a part of the first line of defense by a process known as defecation. Feces, which are composed of approximately 25% microbes, also contain sloughed epithelial cells, mucus, and digested or undigested food. While half of the fecal material is bacterial, not all bacteria in the feces are harmful; many are part of the normal gut flora that compete with pathogens, aiding in their removal from the body. Importantly, the movement of the fecal matter through the colon, aided by peristaltic movements, culminates in the elimination of undigested material and microbes. This elimination process not only rids the body of waste but also prevents the proliferation of harmful microorganisms within the digestive system.