Final answer:
The true statement about the normal function of the GI tract is that water is reabsorbed in the colon. Protective mechanisms such as Peyer's patches and tight junctions play critical roles in preventing infection and maintaining a healthy GI environment.
Step-by-step explanation:
The accurate statement about the normal function of the gastrointestinal (GI) tract is that water is reabsorbed at the beginning of the colon. The GI tract has a sophisticated system in place to maintain a healthy environment and promote efficient digestion and absorption. The protective mechanisms of the GI tract include the mucosal barrier, the presence of beneficial bacteria, and immune defenses like Peyer's patches and antibodies.
The statement about tight junctions failing to allow bacteria to invade is not accurate as the GI tract has protective measures, such as tight junctions and IgA-mediated immune responses, that prevent harmful bacteria from entering the mucosa. Moreover, the gut possesses many protective mechanisms against infection, contrary to the notion it lacks them. Lastly, nutritional stimulation promoting the health of mucosal villi implies that they do not atrophy in the absence of such stimulation, as their maintenance is linked to a host of factors such as the presence of nutrients, hormones, and neural signals.