Chapter 4, Problem 1CYU

Describe the location of the apical region of an epithelial tissue. How can this region be easily identi�ed in a micrograph?

Summary Introduction

To review:

The apical surface of an epithelial tissue and its identification in a micrograph.

Introduction:

The epithelial tissue is a lining of cells covering body surfaces and cavities. The cells forming the epithelial tissue are closely bound together through specialized intercellular junctions. This tissue performs various functions such as protection, filtration, diffusion, secretion, absorption, and sensory reception. It rests upon a layer of connective tissue that provides nutritional support.

Explanation of Solution

A characteristic feature of epithelial cells is their polarization into apical and basal region which are distinguished on the basis of their position. The protein composition and function of apical and basal membrane varies and the tight junctions prevent the free passage of molecules between adjacent cells.

The apical region of an epithelial tissue is present at the top of the epithelial tissue and is directly exposed to the external environment. In simple epithelial tissue composed of a single layer of cells, the apical region of the cell faces toward the lumen or the external environment and the basal region sits on a layer of connective tissue. The stratified epithelium is composed of multiple layer of cells in which the apical region of topmost layer is exposed to the external environment and the basal region of the bottom layer rests on the connective tissue.

In a micrograph, the apical region of an epithelial tissue is identified as the region exposed to an empty space.