USA Biology Olympiad (USABO) Practice Exam

Which type of epithelial cells line the inner surface of the urethra?

1. Simple cuboidal epithelia

2. Stratified squamous epithelia

3. Stratified columnar epithelia

4. Simple columnar epithelia

The correct answer is: Stratified columnar epithelia

The inner surface of the urethra is lined by stratified columnar epithelial cells. This type of epithelium is composed of multiple layers of cells, which provides both protection and functionality. The stratified arrangement allows for a robust surface that can withstand the wear and tear associated with urine flow and potential pathogens, while the columnar cell shape is conducive to the secretion and absorption that may occur in the urethral lining. In the urethra, particularly in its prostatic and membranous portions, the stratified columnar epithelium is important because it contributes to the barrier function necessary for maintaining the integrity of the urinary tract, as well as facilitating the passage of urine. The specialized structure of these cells and their arrangement in layers help protect the underlying tissues from irritation and mechanical damage, while also allowing for some flexibility and resiliency during the passage of urine. Understanding the unique characteristics and roles of stratified columnar epithelium can help clarify its function within the context of the urinary system, emphasizing the importance of epithelial tissue types in human biology.