Apical

Definition

In the context of epithelial tissue in anatomy and physiology, "apical" refers to the uppermost layer or surface of cells that is exposed either to the external environment or to an internal body space. It contrasts with the basal side, which faces toward the underlying body structures.

Related terms

Basal: The basal surface refers to the bottom layer of epithelial cells that attach to the basement membrane, anchoring them to underlying tissues.

Epithelial Tissue:

A type of tissue found throughout the body, covering all body surfaces, lining cavities and hollow organs, and forming glands; it serves as a barrier against microbial invasion and fluid loss.

Basement Membrane:

A thin, fibrous extracellular matrix that separates epithelial and endothelial cells from underlying connective tissue, providing support and regulating cell behavior