Simple columnar epithelium is found in which organs?

• A. Lining of the mouth
• B. Stomach, intestines, gallbladder, uterine tubes
• C. Air sacs in the lungs
• D. Kidney tubules

Answer: (B)

Simple columnar epithelium is a single layer of tall, rectangular cells specialized for secretion and absorption; it often has microvilli to increase surface area and goblet cells to produce mucus. This tissue lines organs where nutrients are absorbed and secretions are produced, such as the stomach and intestines for digestion and absorption, the gallbladder for concentrating bile, and the uterine (Fallopian) tubes where ciliated simple columnar cells help move the ovum toward the uterus.

The mouth is lined by stratified squamous epithelium, providing protection against abrasion. The air sacs in the lungs are lined by simple squamous epithelium, which facilitates gas exchange. Kidney tubules are lined by simple cuboidal epithelium, suited to rapid transport and secretion. Therefore, the organs with simple columnar lining are the stomach, intestines, gallbladder, and uterine tubes.