Which of the following is NOT a main function of epithelial tissue?

• A. Protection
• B. Absorption
• C. Excretion
• D. Nerve impulse conduction

Answer: (D)

Epithelial tissue mainly forms protective barriers and interfaces for selective exchange. It lines surfaces and cavities, shielding underlying tissues from mechanical and chemical stress, and it regulates what enters and leaves the body. It also carries out absorption, as in the lining of the gut, and excretion or secretion in glandular and ductal structures. Some epithelia have sensory roles, but the actual transmission of nerve impulses is performed by nervous tissue, not by epithelial cells. Epithelial cells can respond to stimuli and interact with nerves, but they do not conduct electrical signals the way neurons do. That makes nerve impulse conduction the activity that does not fit as a main function of epithelial tissue.