What tissue lines the interior and exterior surfaces, providing protection and enabling absorption and secretion?

• A. Epithelial Tissue
• B. Connective Tissue
• C. Muscle Tissue
• D. Nervous Tissue

Answer: (A)

Epithelial tissue lines interior and exterior surfaces, forming a protective barrier while also specialized for absorption and secretion. The cells form a continuous sheet on a basement membrane, are typically avascular, and show polarity with an apical surface facing the lumen or outside and a basolateral side anchored to underlying tissue. Epithelial tissue comes in different textures and layers—simple epithelia (one cell layer) and stratified epithelia (multiple layers), with shapes that are squamous (flat), cuboidal (cube-like), or columnar (tall). This arrangement allows it to protect body surfaces (as in skin), absorb nutrients (as in the intestinal lining), and secrete substances (as in glandular or mucus-secreting epithelia). Ciliated epithelia in the airways also move mucus along surfaces. Because it directly lines surfaces and handles absorption and secretion, epithelial tissue is the best fit.