The tissue type that exhibits polarity and is avascular is epithelial tissue. Epithelial tissue is characterized by closely packed cells that form continuous sheets, which serve as a protective barrier and are involved in absorption, secretion, and sensation.
Polarity refers to the presence of distinct structural and functional ends in epithelial cells. Each epithelial cell has an apical surface, which faces the external environment or the lumen of an organ, and a basal surface, which is anchored to the underlying connective tissue via a basement membrane. This arrangement allows epithelial tissues to perform their specific functions effectively.
Moreover, epithelial tissue is avascular, meaning it lacks blood vessels. Instead, it receives nutrients and oxygen through diffusion from the underlying connective tissue. This characteristic is important as it helps maintain the integrity of the epithelial layers without the interference that blood vessels would cause.